The function role of GATA-3 in Th1 and Th2 differentiation

A network model for the control of the differentiation process in Th cells

T helper cells differentiate from a precursor type, Th0, to either the Th1 or Th2 phenotypes. While a number of molecules are known to participate in this process, it is not completely understood how they regulate each other to ensure differentiation. This article presents the core regulatory network controlling the differentiation of Th cells, reconstructed from published molecular data. This network encompasses 17 nodes, namely IFN-gamma, IL-4, IL-12, IL-18, IFN-beta, IFN-gammaR, IL-4R, IL-12R, IL-18R, IFN-betaR, STAT-1, STAT-6, STAT-4, IRAK, SOCS-1, GATA-3, and T-bet, as well as their cross-regulatory interactions. The reconstructed network was modeled as a discrete dynamical system, and analyzed in terms of its constituent feedback loops. The stable steady states of the Th network model are consistent with the stable molecular patterns of activation observed in wild type and mutant Th0, Th1 and Th2 cells.

Introduction to immune cell signalling

The dynamic interaction of cells of the immune system with other cells, antigens and secreted factors determines the nature of an immune response. The response of individual cells is governed by the sequence of intracellular signalling events triggered following the association of cell surface molecules during cell-cell contact or the detection of soluble molecules of host or pathogen origin. In this review we will first outline the general principles of intracellular signal transduction. We will then describe the signalling pathways triggered following the recognition of antigen, as well as the detection of cytokines, and discuss how the signalling pathways activated regulate the effector response.

LMCD1/Dyxin is a novel transcriptional cofactor that restricts GATA6 function by inhibiting DNA binding

The activity of GATA factors is regulated, in part, at the level of protein-protein interactions. LIM domain proteins, first defined by the zinc finger motifs found in the Lin11, Isl-1, and Mec-3 proteins, act as coactivators of GATA function in both hematopoietic and cardiovascular tissues. We have identified a novel GATA-LIM interaction between GATA6 and LMCD1/dyxin. The LIM domains and cysteine-rich domains in LMCD1/dyxin and the carboxy-terminal zinc finger of GATA6 mediate this interaction. Expression of LMCD1/dyxin is remarkably similar to that of GATA6, with high-level expression observed in distal airway epithelium of the lung, vascular smooth muscle, and myocardium. In contrast to other GATA-LIM protein interactions, LMCD1/dyxin represses GATA6 activation of both lung and cardiac tissue-specific promoters. Electrophoretic mobility shift and chromatin immunoprecipitation assays show that LMCD1/dyxin represses GATA6 function by inhibiting GATA6 DNA binding. These data reveal an interaction between GATA6 and LMCD1/dyxin and demonstrate a novel mechanism through which LIM proteins can assert their role as transcriptional cofactors of GATA proteins.

Novel signal transduction modulators for the treatment of airway diseases

Multiple signal transduction pathways are involved in the inflammatory process in the airways of patients with asthma and chronic obstructive pulmonary disease (COPD), hence modulators of these pathways may result in novel anti-inflammatory treatments. The advantage of this approach is that these pathways are activated in many inflammatory and structural cells of the airways, hence a broad spectrum of anti-inflammatory effects may be possible. However, this also makes it more likely that side effects may be limiting, but this may not be a problem if the signal transduction pathway is selectively activated in disease and the therapeutic index may be increased by inhaled delivery. Phosphodiesterase-4 (PDE4) inhibitors are the most advanced treatment in this category as anti-inflammatory treatment for asthma and COPD, although side effects are dose limiting. Other promising approaches are inhibitors of p38 mitogen-activated protein (MAP) kinase, inhibitor of nuclear factor-kappaB kinase-2 (IKK2), and Syk kinase, all of which are in clinical development. Several other kinases and transcription factors are also targets for novel drug development. It is likely that modulators of signal transduction pathways may lead to the development of several novel anti-inflammatory treatments for asthma and COPD in the future.

Transcription factor GATA-1 potently represses the expression of the HIV-1 coreceptor CCR5 in human T cells and dendritic cells

CC chemokine receptor 5 (CCR5) is the major HIV-1 coreceptor and its expression levels are a critical determinant of HIV-1 infection. However, the molecular mechanisms of CCR5 regulation in primary targets of HIV-1 remain unknown. Despite binding to conserved DNA elements, we show that the transcription factors GATA binding protein 1 (GATA-1) and GATA-3 differentially suppress the expression of CCR5 in stem-cell-derived dendritic cells and primary human T-cell subsets. In addition, GATA-1 expression was also more potent than GATA-3 in suppressing T helper 1 (Th1)-associated genes, interferon-gamma (IFNgamma), and CXC chemokine receptor-3 (CXCR3). GATA-1, but not GATA-3, potently suppressed CCR5 transcription, thereby rendering human T cells resistant to CCR5-tropic HIV-1 infection. However, GATA-1 could also serve as a surrogate for GATA-3 in its canonic role of programming Th2 gene expression. These findings provide insight into GATA-3-mediated gene regulation during T-cell differentiation. Importantly, decoding the mechanisms of GATA-1-mediated repression of CCR5 may offer an opportunity to develop novel approaches to inhibit CCR5 expression in T cells.

Regulatory mechanisms and their therapeutic implications of interleukin-12 production in immune cells

Studies with neutralizing anti-interleukin (IL)-12 antibodies and IL-12-deficient mice have suggested that endogenous IL-12 plays an important role in the normal host defense against infection by a variety of intracellular microorganisms. However, IL-12 also appears to play a central role in the pathogenesis of autoimmune diseases such as multiple sclerosis or rheumatic arthritis. Therefore, it is crucial to understand how IL-12 is produced and its production is regulated at the molecular level. IL-12 production is differentially regulated through multiple pathways, which can be classified as follows: nuclear factor-kappaB (NF-kappaB) and other transcription factors, p38 mitogen-activated protein (MAP) kinase, cyclic adenosine monophosphate (cyclic AMP)-modulating molecules, cell membrane ion channels and pumps, nitric oxide (NO), and receptors. In this review we describe the regulatory mechanisms of IL-12 production in immune cells and also some agents to control IL-12 production for the treatment of immune-related diseases.

A Leishmania major response locus identified by interval-specific congenic mapping of a T helper type 2 cell bias-controlling quantitative trait locus

The propensity of naive CD4 T cells to become T helper (Th) type 2 cells correlates with susceptibility to infection by the protozoal parasite Leishmania major. Using genetic linkage analysis, we earlier identified Dice1 as a Th2 cell bias-controlling quantitative trait locus on chromosome 16. Using interval-specific congenic mapping, we now resolve Dice1 into two independent genetic loci, Dice1.1 and Dice1.2, which control Il4 expression from naive Th cells and thereby indirectly control Th2 cell bias. Interestingly, only one of the two congenic intervals containing Dice1.1 and Dice1.2, respectively, also contained an L. major response locus, indicating that L. major responsiveness can be insensitive to determinants that influence Th2 cell bias by controlling naive T cell Il4 expression. These results lay the groundwork for identifying the Dice1.1 and Dice1.2 genes controlling naive T cell Il4 expression and L. major responses, and for testing whether these control other Th2 cell–dependent processes such as worm expulsion, allergic asthma, and dermatitis.

The interaction between GATA proteins and activator protein-1 promotes the transcription of IL-13 in mast cells

IL-13 is considered to be a key modulator in the pathogenesis of Th2-induced allergic inflammation, although little is known about the regulation of IL-13 transcription in mast cells. In T cells, involvement of GATA-3 in cell type-specific expression of the IL-13 gene has been reported. However, the mechanisms that induce rapid transactivation of the IL-13 gene in response to various types of stimulation have hitherto remained unknown. In this report, we describe our investigation of the promoter region necessary for IL-13 transcription; we have found that both AP-1 and GATA proteins are indispensable for IL-13 transcription in mouse mast cells. In our investigation, we focused on the functional interaction between GATA and AP-1 in the IL-13 promoter context. Transfection experiments have revealed that GATA-1 and GATA-2 proteins are able to associate with AP-1 proteins. We have also shown that overexpression of GATA-1 induced excess AP-1 binding to the IL-13 promoter as well as a significant increase in IL-13 production in mast cells. The results of the present study have shown that direct interaction between AP-1 and GATA proteins plays an important role in IL-13 transcription in mast cells.

New drugs for asthma

Asthma is a major and increasing global health problem and, despite major advances in therapy, many patients' symptoms are not adequately controlled. Treatment with combination inhalers, which contain a corticosteroid and long-acting beta(2) adrenoceptor agonist, is the most effective current therapy. There is therefore a search for new therapies, particularly safe and effective oral treatments and those that are more efficacious in severe asthma. New therapies in development include mediator antagonists and inhibitors of cytokines, although these therapies might be too specific to be very effective. New anti-inflammatory therapies include corticosteroids and inhibitors of phosphodiesterase-4, p38 mitogen-activated protein kinase and nuclear factor-kappaB. The prospects for a curative treatment are on the horizon.

Immunomodulatory Effect of Astragali Radix Extract on Murine Th1/Th2 Cell Lineage Development

Astragali Radix (AR), is a popular herbal medicine used to treat allergic diseases in Korea, Japan and China. Our study examined the effect of an AR ethanol extract on both in vitro and in vivo murine CD4 T cells' differentiation into Th1 and Th2 subsets. CD4 T cells from Balb/c mice were activated with anti-CD3/anti-CD28 mAb in the presence of AR for 2 d. AR treated cells showed an elevated level of IL-4 but a reduced level of IFN-gamma secretion. In addition, in vitro Th1/Th2 polarization experiments revealed that AR enhanced the levels of IL-4 in Th2 cells but reduced the levels of IFN-gamma in Th1 cells. To elucidate the effects of AR in Th1/Th2 lineage development during the in vivo condition, AR was administrated orally to BALB/c mice. The results demonstrated that AR administration significantly increased IL-4 production in both the serum and supernatant of splenocyte culture, while IFN-gamma secretion was diminished upon in vivo activation with anti-CD3 antibody. Our data clearly indicates that AR selectively alters Th1/Th2 cytokine secretion patterns and provides the pharmacological basis for AR's clinical applications.