Distinct requirements for the naturally occurring splice forms Stat4alpha and Stat4beta in IL-12 responses

STAT4 gene polymorphisms in human diseases

Signal transducer and activator of transcription 4 (STAT4) is a member of the STAT family, which is a group of transcription factors that regulate cytokine signaling. Genetic polymorphisms in STAT4 strongly influence immune responses and disease outcomes, especially in cancer and autoimmune diseases. Several studies have indicated that certain STAT4 gene variants are associated with alterations in STAT4 expression and/or activity and that there is a close relationship between STAT4 polymorphisms and drug efficacy. However, the underlying mechanisms are complex, and the roles of these polymorphisms in disease acquisition, progression, and severity are of widespread concern. Therefore, we provide an overview of the clinical significance of polymorphisms in STAT4 and the mechanisms by which these STAT4 variants are involved in various diseases.

STAT4 and STAT6, their role in cellular and humoral immunity and in diverse human diseases

Signal transducer and activator of transcription (STAT) 4 and STAT6 play a crucial role in immune cells by transducing signals from specific cytokine receptors, and inducing transcription of genes involved in cell-mediated and humoral immunity. These two different defense mechanisms against pathogens are regulated by two specific CD4+ T helper (Th) cells known as Th1 and Th2 cells. Many studies have shown that several diseases including cancer, inflammatory, autoimmune and allergic diseases are associated with a Th1/Th2 imbalance caused by increased or decreased expression/activity of STAT4 or STAT6 often due to genetic and epigenetic aberrances. An altered expression of STAT4 has been observed in different tumors and autoimmune diseases, while a dysregulation of STAT6 signaling pathway is frequently observed in allergic conditions, such as atopic dermatitis, allergic asthma, food allergy, and tumors such as Hodgkin and non-Hodgkin lymphomas. Recently, dysregulations of STAT4 and STAT6 expression have been observed in SARS-CoV2 and monkeypox infections, which are still public health emergencies in many countries. SARS-CoV-2 can induce an imbalance in Th1 and Th2 responses with a predominant activation of STAT6 in the cytosol and nuclei of pneumocytes that drives Th2 polarization and cytokine storm. In monkeypox infection the virus can promote an immune evasion by inducing a Th2 response that in turn inhibits the Th1 response essential for virus elimination. Furthermore, genetic variations of STAT4 that are associated with an increased risk of developing systemic lupus erythematosus seem to play a role in defense against SARS-CoV-2 infection.

The Role of STATs in Ovarian Cancer: Exploring Their Potential for Therapy

Ovarian cancer (OvCa) is a deadly gynecologic malignancy that presents many clinical challenges due to late-stage diagnoses and the development of acquired resistance to standard-of-care treatment protocols. There is an increasing body of evidence suggesting that STATs may play a critical role in OvCa progression, resistance, and disease recurrence, and thus we sought to compile a comprehensive review to summarize the current state of knowledge on the topic. We have examined peer reviewed literature to delineate the role of STATs in both cancer cells and cells within the tumor microenvironment. In addition to summarizing the current knowledge of STAT biology in OvCa, we have also examined the capacity of small molecule inhibitor development to target specific STATs and progress toward clinical applications. From our research, the best studied and targeted factors are STAT3 and STAT5, which has resulted in the development of several inhibitors that are under current evaluation in clinical trials. There remain gaps in understanding the role of STAT1, STAT2, STAT4, and STAT6, due to limited reports in the current literature; as such, further studies to establish their implications in OvCa are necessitated. Moreover, due to the deficiency in our understanding of these STATs, selective inhibitors also remain elusive, and therefore present opportunities for discovery.

The implications of alternative pre-mRNA splicing in cell signal transduction

Cells produce multiple mRNAs through alternative splicing, which ensures proteome diversity. Because most human genes undergo alternative splicing, key components of signal transduction pathways are no exception. Cells regulate various signal transduction pathways, including those associated with cell proliferation, development, differentiation, migration, and apoptosis. Since proteins produced through alternative splicing can exhibit diverse biological functions, splicing regulatory mechanisms affect all signal transduction pathways. Studies have demonstrated that proteins generated by the selective combination of exons encoding important domains can enhance or attenuate signal transduction and can stably and precisely regulate various signal transduction pathways. However, aberrant splicing regulation via genetic mutation or abnormal expression of splicing factors negatively affects signal transduction pathways and is associated with the onset and progression of various diseases, including cancer. In this review, we describe the effects of alternative splicing regulation on major signal transduction pathways and highlight the significance of alternative splicing.

Differential regulation of lineage-determining transcription factor expression in innate lymphoid cell and adaptive T helper cell subsets

CD4 T helper (Th) cell subsets, including Th1, Th2 and Th17 cells, and their innate counterparts innate lymphoid cell (ILC) subsets consisting of ILC1s, ILC2s and ILC3s, display similar effector cytokine-producing capabilities during pro-inflammatory immune responses. These lymphoid cell subsets utilize the same set of lineage-determining transcription factors (LDTFs) for their differentiation, development and functions. The distinct ontogeny and developmental niches between Th cells and ILCs indicate that they may adopt different external signals for the induction of LDTF during lineage commitment. Increasing evidence demonstrates that many conserved cis-regulatory elements at the gene loci of LDTFs are often preferentially utilized for the induction of LDTF expression during Th cell differentiation and ILC development at different stages. In this review, we discuss the functions of lineage-related cis-regulatory elements in inducing T-bet, GATA3 or RORγt expression based on the genetic evidence provided in recent publications. We also review and compare the upstream signals involved in LDTF induction in Th cells and ILCs both in vitro and in vivo. Finally, we discuss the possible mechanisms and physiological importance of regulating LDTF dynamic expression during ILC development and activation.

Activation pathways that drive CD4+ T cells to break tolerance in autoimmune diseases. Immunol Rev 2022;307:161-190. [PMID: 35142369 PMCID: PMC9255211 DOI: 10.1111/imr.13071]

Autoimmune diseases are characterized by dysfunctional immune systems that misrecognize self as non-self and cause tissue destruction. Several cell types have been implicated in triggering and sustaining disease. Due to a strong association of major histocompatibility complex II (MHC-II) proteins with various autoimmune diseases, CD4+ T lymphocytes have been thoroughly investigated for their roles in dictating disease course. CD4+ T cell activation is a coordinated process that requires three distinct signals: Signal 1, which is mediated by antigen recognition on MHC-II molecules; Signal 2, which boosts signal 1 in a costimulatory manner; and Signal 3, which helps to differentiate the activated cells into functionally relevant subsets. These signals are disrupted during autoimmunity and prompt CD4+ T cells to break tolerance. Herein, we review our current understanding of how each of the three signals plays a role in three different autoimmune diseases and highlight the genetic polymorphisms that predispose individuals to autoimmunity. We also discuss the drawbacks of existing therapies and how they can be addressed to achieve lasting tolerance in patients.

Impact of STAT Proteins in Tumor Progress and Therapy Resistance in Advanced and Metastasized Prostate Cancer

Signal transducers and activators of transcription (STATs) are a family of transcription factors involved in several biological processes such as immune response, cell survival, and cell growth. However, they have also been implicated in the development and progression of several cancers, including prostate cancer (PCa). Although the members of the STAT protein family are structurally similar, they convey different functions in PCa. STAT1, STAT3, and STAT5 are associated with therapy resistance. STAT1 and STAT3 are involved in docetaxel resistance, while STAT3 and STAT5 are involved in antiandrogen resistance. Expression of STAT3 and STAT5 is increased in PCa metastases, and together with STAT6, they play a crucial role in PCa metastasis. Further, expression of STAT3, STAT5, and STAT6 was elevated in advanced and high-grade PCa. STAT2 and STAT4 are currently less researched in PCa. Since STATs are widely involved in PCa, they serve as potential therapeutic targets. Several inhibitors interfering with STATs signaling have been tested unsuccessfully in PCa clinical trials. This review focuses on the respective roles of the STAT family members in PCa, especially in metastatic disease and provides an overview of STAT-inhibitors evaluated in clinical trials.

IL-35: A Novel Immunomodulator in Hepatitis B Virus-Related Liver Diseases

Chronic hepatitis B virus (HBV) infection is a risk factor for liver cirrhosis (LC) and hepatocellular carcinoma (HCC), however, little is known about the mechanisms involved in the progression of HBV-related diseases. It has been well acknowledged that host immune response was closely related to the clinical outcomes of patients with HBV infection. As the factors closely related to the immunomodulatory process, cytokines are crucial in the cell-cell communication and the host responses to HBV infection. Recently, a newly discovered cytokine, designated as interleukin-35 (IL-35), has been proved to be essential for the progression of chronic HBV infection, the development of cirrhosis, the transformation of cirrhosis to HCC, and the metastasis of HCC. Specifically, it showed various biological activities such as inhibiting the HBV-specific cytotoxic T lymphocyte (CTL) proliferation and cytotoxicity, deactivating the immature effector T-cells (Teffs), as well as delaying the proliferation of dendritic cells. It regulated the immune responses by acting as a “brake” on the activation of Teffs, which subsequently played important roles in the pathogenesis of various inflammatory diseases and malignancies. In this review, we focused on the most recent data on the relationship between IL-35 and chronic HBV infection, LC and HCC.

STAT1 Isoforms Differentially Regulate NK Cell Maturation and Anti-tumor Activity

Natural killer (NK) cells are important components of the innate immune defense against infections and cancers. Signal transducer and activator of transcription 1 (STAT1) is a transcription factor that is essential for NK cell maturation and NK cell-dependent tumor surveillance. Two alternatively spliced isoforms of STAT1 exist: a full-length STAT1α and a C-terminally truncated STAT1β isoform. Aberrant splicing is frequently observed in cancer cells and several anti-cancer drugs interfere with the cellular splicing machinery. To investigate whether NK cell-mediated tumor surveillance is affected by a switch in STAT1 splicing, we made use of knock-in mice expressing either only the STAT1α (Stat1α/α) or the STAT1β (Stat1β/β ) isoform. NK cells from Stat1α/α mice matured normally and controlled transplanted tumor cells as efficiently as NK cells from wild-type mice. In contrast, NK cells from Stat1β/β mice showed impaired maturation and effector functions, albeit less severe than NK cells from mice that completely lack STAT1 (Stat1-/- ). Mechanistically, we show that NK cell maturation requires the presence of STAT1α in the niche rather than in NK cells themselves and that NK cell maturation depends on IFNγ signaling under homeostatic conditions. The impaired NK cell maturation in Stat1β/β mice was paralleled by decreased IL-15 receptor alpha (IL-15Rα) surface levels on dendritic cells, macrophages and monocytes. Treatment of Stat1β/β mice with exogenous IL-15/IL-15Rα complexes rescued NK cell maturation but not their effector functions. Collectively, our findings provide evidence that STAT1 isoforms are not functionally redundant in regulating NK cell activity and that the absence of STAT1α severely impairs, but does not abolish, NK cell-dependent tumor surveillance.

Glutathione S-Transferase Mu-3 Predicts a Better Prognosis and Inhibits Malignant Behavior and Glycolysis in Pancreatic Cancer

Background: Pancreatic cancer (PC) is a lethal malignancy with an extremely unfavorable 5-year survival rate and a high mortality rate. Glutathione S-transferase mu-3 (GSTM3) has been shown to exert different functions in the progression and development of various cancers, except for PC. This study aimed to explore the role of GSTM3 in the malignant behavior and metabolic aspects of PC, its clinical significance, and its possible molecular mechanism in pancreatic cancer.

Methods: Tumor microarrays of pancreatic ductal adenocarcinoma (PDAC) were used to evaluate the clinicopathological variables and GSTM3 expression by immunohistochemical staining. Kaplan–Meier survival and Cox regression analyses were further performed to assess the prognosis. The effect of GSTM3 on PC aggressiveness was detected using overexpressing and silencing transfection methods. Western blot, RT-qPCR, CCK-8, and cell cycle assay were applied to evaluate the expression level and proliferation. A xenograft animal model was assessed. Reactive oxygen species (ROS) were measured using the laser confocal scanner and glycolysis was detected using an Agilent Seahorse kit. RNA sequencing was used to assess the underlying mechanism and the signaling pathway involved.

Results: GSTM3 was relatively poorly expressed in PDAC tissues compared to para-tumoral tissues and a high level of GSTM3 indicated good overall survival. Functionally, overexpression of GSTM3 could significantly inhibit cell proliferation by delaying the G0/G1 transition, whereas the opposite results were found in the GSTM3 downregulation group. In addition, xenograft animal models further confirmed the effect on proliferation. Moreover, silencing of GSTM3 induced ROS accumulation and promoted glycolysis in PC, indicating its tumor suppressive effect, and vice versa when GSTM3 was upregulated. Finally, RNA sequencing results demonstrated that GSTM3 facilitates anti-tumorigenicity partly via the JAK-STAT signaling pathway in PC.

Conclusion: GSTM3 inhibited tumor progression and altered the metabolic pattern in PC. This may be a potential predictive biomarker in PC and a prospective therapeutic target.

STAT4: an immunoregulator contributing to diverse human diseases

Signal transducer and activator of transcription 4 (STAT4) is a member of the STAT family and localizes to the cytoplasm. STAT4 is phosphorylated after a variety of cytokines bind to the membrane, and then dimerized STAT4 translocates to the nucleus to regulate gene expression. We reviewed the essential role played by STAT4 in a wide variety of cells and the pathogenesis of diverse human diseases, especially many kinds of autoimmune and inflammatory diseases, via activation by different cytokines through the Janus kinase (JAK)-STAT signaling pathway.

STAT Signaling in Glioma Cells

STAT (signal transducers and activators of transcription) are latent cytoplasmic transcription factors that function as downstream effectors of cytokine and growth factor receptor signaling. The canonical JAK/STAT signaling pathway involves the activation of Janus kinases (JAK) or growth factors receptor kinases, phosphorylation of STAT proteins, their dimerization and translocation into the nucleus where STATs act as transcription factors with pleiotropic downstream effects. STAT signaling is tightly controlled with restricted kinetics due to action of its negative regulators. While STAT1 is believed to play an important role in growth arrest and apoptosis, and to act as a tumor suppressor, STAT3 and 5 are involved in promoting cell cycle progression, cellular transformation, and preventing apoptosis. Aberrant activation of STATs, in particular STAT3 and STAT5, have been found in a large number of human tumors, including gliomas and may contribute to oncogenesis. In this chapter, we have (1) summarized the mechanisms of STAT activation in normal and malignant signaling; (2) discussed evidence for the critical role of constitutively activated STAT3 and STAT5 in glioma pathobiology; (3) disclosed molecular and pharmacological strategies to interfere with STAT signaling for potential therapeutic intervention in gliomas.

Transcriptional Programs Underlying Cd4 T Cell Differentiation and Functions

Understanding the basis of cellular differentiation is a fundamental issue in developmental biology but also for the comprehension of pathological processes. In fact, the palette of developmental decisions for naive CD4 T cells is a critical aspect of the development of appropriate immune responses which could control infectious processes or cancer growth. However, the current accumulation of data on CD4 T cells biology reveals a complex world with different helper populations. Naive CD4 T cells can differentiate into different subtypes in response to cytokine stimulation. This stimulation involves a complex transcriptional network implicating the activation of Signal Transducer and Activator of Transcription but also master regulator transcription factors allowing the functions of each helper T lymphocyte subtype. In this review, we will present an overview of the transcriptional regulation which controls process of helper T cells differentiation. We will focus on the role of initiator transcriptional factors and on master regulators but also on other nonspecific transcriptional factors which refine the T helper polarization to stabilize or modulate the differentiation program.

Interplay between Janus Kinase/Signal Transducer and Activator of Transcription Signaling Activated by Type I Interferons and Viral Antagonism

Interferons (IFNs), which were discovered a half century ago, are a group of secreted proteins that play key roles in innate immunity against viral infection. The major signaling pathway activated by IFNs is the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, which leads to the expression of IFN-stimulated genes (ISGs), including many antiviral effectors. Viruses have evolved various strategies with which to antagonize the JAK/STAT pathway to influence viral virulence and pathogenesis. In recent years, notable progress has been made to better understand the JAK/STAT pathway activated by IFNs and antagonized by viruses. In this review, recent progress in research of the JAK/STAT pathway activated by type I IFNs, non-canonical STAT activation, viral antagonism of the JAK/STAT pathway, removing of the JAK/STAT antagonist from viral genome for attenuation, and the potential pathogenesis roles of tyrosine phosphorylation-independent non-canonical STATs activation during virus infection are discussed in detail. We expect that this review will provide new insight into the understanding the complexity of the interplay between JAK/STAT signaling and viral antagonism.

STAT4-associated natural killer cell tolerance following liver transplantation

OBJECTIVE

Natural killer (NK) cells are important mediators of liver inflammation in chronic liver disease. The aim of this study was to investigate why liver transplants (LTs) are not rejected by NK cells in the absence of human leukocyte antigen (HLA) matching, and to identify a tolerogenic NK cell phenotype.

DESIGN

Phenotypic and functional analyses on NK cells from 54 LT recipients were performed, and comparisons made with healthy controls. Further investigation was performed using gene expression analysis and donor:recipient HLA typing.

RESULTS

NK cells from non-HCV LT recipients were hypofunctional, with reduced expression of NKp46 (p<0.05) and NKp30 (p<0.001), reduced cytotoxicity (p<0.001) and interferon (IFN)-γ secretion (p<0.025). There was no segregation of this effect with HLA-C, and these functional changes were not observed in individuals with HCV. Microarray and RT-qPCR analysis demonstrated downregulation of STAT4 in NK cells from LT recipients (p<0.0001). Changes in the expression levels of the transcription factors Helios (p=0.06) and Hobit (p=0.07), which control NKp46 and IFNγ expression, respectively, were also detected. Hypofunctionality of NK cells was associated with impaired STAT4 phosphorylation and downregulation of the STAT4 target microRNA-155. Conversely in HCV-LT NK cell tolerance was reversed, consistent with the more aggressive outcome of LT for HCV.

CONCLUSIONS

LT is associated with transcriptional and functional changes in NK cells, resulting in reduced activation. NK cell tolerance occurs upstream of major histocompatibility complex (MHC) class I mediated education, and is associated with deficient STAT4 phosphorylation. STAT4 therefore represents a potential therapeutic target to induce NK cell tolerance in liver disease.

Role of STAT3 in Genesis and Progression of Human Malignant Gliomas

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in glioblastoma and has been identified as a relevant therapeutic target in this disease and many other human cancers. After two decades of intensive research, there is not yet any approved STAT3-based glioma therapy. In addition to the canonical activation by tyrosine 705 phosphorylation, concordant reports described a potential therapeutic relevance of other post-translational modifications including mainly serine 727 phosphorylation. Such reports reinforce the need to refine the strategy of targeting STAT3 in each concerned disease. This review focuses on the role of serine 727 and tyrosine 705 phosphorylation of STAT3 in glioma. It explores their contribution to glial cell transformation and to the mechanisms that make glioma escape to both immune control and standard treatment.

STAT4-mediated transcriptional repression of the IL5 gene in human memory Th2 cells

Type I interferon (IFN-α/β) plays a critical role in suppressing viral replication by driving the transcription of hundreds of interferon-sensitive genes (ISGs). While many ISGs are transcriptionally activated by the ISGF3 complex, the significance of other signaling intermediates in IFN-α/β-mediated gene regulation remains elusive, particularly in rare cases of gene silencing. In human Th2 cells, IFN-α/β signaling suppressed IL5 and IL13 mRNA expression during recall responses to T-cell receptor (TCR) activation. This suppression occurred through a rapid reduction in the rate of nascent transcription, independent of de novo expression of ISGs. Further, IFN-α/β-mediated STAT4 activation was required for repressing the human IL5 gene, and disrupting STAT4 dimerization reversed this effect. This is the first demonstration of STAT4 acting as a transcriptional repressor in response to IFN-α/β signaling and highlights the unique activity of this cytokine to acutely block the expression of an inflammatory cytokine in human T cells.

Altered STAT4 Isoform Expression in Patients with Inflammatory Bowel Disease

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are the major forms of inflammatory bowel disease, and pathogenesis involves a complex interplay among genetic, environmental, and immunological factors. We evaluated isoform expression of the IL-12-activated transcription factor STAT4 in children with CD and UC.

METHODS

We collected biopsy samples from both patients newly diagnosed with CD and with UC. We further collected blood samples from patients newly diagnosed with CD and with UC as well as from patients who had a flare-up after being in clinical remission, and we examined the ratios of STAT4β/STAT4α mRNA. In addition to STAT4 isoforms, we measured the expression of the cytokines TNFα, IFNγ, granulocyte macrophage-colony stimulating factor, and IL-17 using polymerase chain reaction of biopsy samples and multiplex analysis of patient serum samples.

RESULTS

Ratios of STAT4β/STAT4α were increased in specific gastrointestinal tract segments in both patients with CD and those with UC that correlate with the location and severity of inflammation. In contrast, we did not observe changes in STAT4β/STAT4α ratios in biopsy specimens from patients with eosinophilic esophagitis. We also observed increased STAT4β/STAT4α ratios in the peripheral blood mononuclear cells of patients with UC and those with CD, compared with healthy controls. Ratios were normalized after patients were treated with steroids.

CONCLUSIONS

Collectively, these data indicate that STAT4 isoforms could be an important noninvasive biomarker in the diagnosis and treatment of inflammatory bowel disease and that expression of these isoforms might provide further insight into the pathogenesis of IBD.

Super-enhancers: Asset management in immune cell genomes

Super-enhancers (SEs) are regions of the genome consisting of clusters of regulatory elements bound with very high amounts of transcription factors, and this architecture appears to be the hallmark of genes and noncoding RNAs linked with cell identity. Recent studies have identified SEs in CD4(+) T cells and have further linked these regions to single nucleotide polymorphisms (SNPs) associated with immune-mediated disorders, pointing to an important role for these structures in the T cell differentiation and function. Here we review the features that define SEs, and discuss their function within the broader understanding of the mechanisms that define immune cell identity and function. We propose that SEs present crucial regulatory hubs, coordinating intrinsic and extrinsic differentiation signals, and argue that delineating these regions will provide important insight into the factors and mechanisms that define immune cell identity.

Transcriptional regulatory networks for CD4 T cell differentiation

CD4(+) T cells play a central role in controlling the adaptive immune response by secreting cytokines to activate target cells. Naïve CD4(+) T cells differentiate into at least four subsets, Th1Th1 , Th2Th2 , Th17Th17 , and inducible regulatory T cellsregulatory T cells , each with unique functions for pathogen elimination. The differentiation of these subsets is induced in response to cytokine stimulation, which is translated into Stat activation, followed by induction of master regulator transcription factorstranscription factors . In addition to these factors, multiple other transcription factors, both subset specific and shared, are also involved in promoting subset differentiation. This review will focus on the network of transcription factors that control CD4(+) T cell differentiation.

Integration of genome-wide of Stat3 binding and epigenetic modification mapping with transcriptome reveals novel Stat3 target genes in glioma cells

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in many human tumors, including gliomas, and regulates the expression of genes implicated in proliferation, survival, apoptosis, angiogenesis and immune regulation. Only a small fraction of those genes has been proven to be direct STAT3 targets. In gliomas, STAT3 can play tumor suppressive or oncogenic roles depending on the tumor genetic background with target genes being largely unknown.

RESULTS

We used chromatin immunoprecipitation, promoter microarrays and deep sequencing to assess the genome-wide occupancy of phospho (p)-Stat3 and epigenetic modifications of H3K4me3 and H3ac in C6 glioma cells. This combined assessment identified a list of 1200 genes whose promoters have both Stat3 binding sites and epigenetic marks characteristic for actively transcribed genes. The Stat3 and histone markings data were also intersected with a set of microarray data from C6 glioma cells after inhibition of Jak2/Stat3 signaling. Subsequently, we found 284 genes characterized by p-Stat3 occupancy, activating histone marks and transcriptional changes. Novel genes were screened for their potential involvement in oncogenesis, and the most interesting hits were verified by ChIP-PCR and STAT3 knockdown in human glioma cells.

CONCLUSIONS

Non-random association between silent genes, histone marks and p-Stat3 binding near transcription start sites was observed, consistent with its repressive role in transcriptional regulation of target genes in glioma cells with specific genetic background.

Association between STAT4 gene polymorphisms and autoimmune thyroid diseases in a Chinese population

The STAT4 gene encodes a transcriptional factor that transmits signals induced by several key cytokines which play important roles in the development of autoimmune diseases. The aim of this study was to explore the association of STAT4 polymorphism with Graves’ disease (GD) and Hashimoto’s thyroiditis (HT). A total of 1048 autoimmune thyroid diseases (AITDs) patients (693 with GD and 355 with HT) and 909 age- and gender-matched controls were examined. STAT4 polymorphisms (rs7574865/rs10181656/rs7572482) were genotyped by multiplex polymerase chain reaction (PCR) and ligase detection reaction (LDR). The results indicated that the frequencies of rs7574865 genotypes in patients with GD differed significantly from the controls (p = 0.028), the T allele frequency of GD patients was also significantly higher than the controls (p = 0.020). The genotypes of rs10181656 differed significantly in GD patients from controls (p = 0.012); G allele frequencies were significantly higher in AITD patients than the controls (p = 0.014 and 0.031, respectively). The frequencies of haplotype GC with GD and HT patients were significantly lower than their controls (p = 0.015 and 0.030, respectively). In contrast, the frequencies of haplotype TG with GD and HT patients were significantly higher than their controls (p = 0.016 and 0.048, respectively). These findings strongly suggest that STAT4 rs7574865/rs10181656 polymorphisms increase the risk of AITD in a Chinese population.

Therapeutic potential of STAT4 in autoimmunity

INTRODUCTION

STAT4, which acts as the major signaling transducing STATs in response to IL-12, is a central mediator in generating inflammation during protective immune responses and immune-mediated diseases.

AREAS COVERED

This review summarizes that STAT4 is essential for the differentiation and function of a wide variety of immune cells, including natural killer cells, mast cells, dendritic cells and T helper cells. In addition, STAT4-mediated signaling promoted the production of autoimmune-associated components, which are implicated in the pathogenesis of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and psoriasis.

EXPERT OPINION

Due to its crucial roles in inflammation and autoimmunity, STAT4 may have promise as an effective therapeutic target for autoimmune diseases. Understanding the molecular mechanisms driving STAT4, together with knowledge on the ability of current immunosuppressive treatment to target this process, may open an avenue to novel therapeutic options.

STAT1β is not dominant negative and is capable of contributing to gamma interferon-dependent innate immunity

The transcription factor STAT1 is essential for interferon (IFN)-mediated immunity in humans and mice. STAT1 function is tightly regulated, and both loss- and gain-of-function mutations result in severe immune diseases. The two alternatively spliced isoforms, STAT1α and STAT1β, differ with regard to a C-terminal transactivation domain, which is absent in STAT1β. STAT1β is considered to be transcriptionally inactive and to be a competitive inhibitor of STAT1α. To investigate the functions of the STAT1 isoforms in vivo, we generated mice deficient for either STAT1α or STAT1β. As expected, the functions of STAT1α and STAT1β in IFN-α/β- and IFN-λ-dependent antiviral activity are largely redundant. In contrast to the current dogma, however, we found that STAT1β is transcriptionally active in response to IFN-γ. In the absence of STAT1α, STAT1β shows more prolonged IFN-γ-induced phosphorylation and promoter binding. Both isoforms mediate protective, IFN-γ-dependent immunity against the bacterium Listeria monocytogenes, although with remarkably different efficiencies. Our data shed new light on the potential contributions of the individual STAT1 isoforms to STAT1-dependent immune responses. Knowledge of STAT1β's function will help fine-tune diagnostic approaches and help design more specific strategies to interfere with STAT1 activity.

Association of STAT4 polymorphisms with susceptibility to type-1 autoimmune hepatitis in the Japanese population

Background/Aims

Recent studies demonstrated an association of STAT4 polymorphisms with autoimmune diseases including systemic lupus erythematosus and rheumatoid arthritis, indicating multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 polymorphisms on the susceptibility and phenotype of type-1 autoimmune hepatitis in a Japanese National Hospital Organization (NHO) AIH multicenter cohort study.

Methodology/Principal Findings

Genomic DNA from 460 individuals of Japanese origin including 230 patients with type-1 autoimmune hepatitis and 230 healthy controls was analyzed for two single nucleotide polymorphisms in the STAT4 gene (rs7574865, rs7582694). The STAT4 rs7574865T allele conferred risk for type-1 autoimmune hepatitis (OR = 1.61, 95% CI = 1.23–2.11; P = 0.001), and patients without accompanying autoimmune diseases exhibited an association with the rs7574865T allele (OR = 1.50, 95%CI = 1.13–1.99; P = 0.005). Detailed genotype-phenotype analysis of type-1 autoimmune hepatitis patients with (n = 44) or without liver cirrhosis (n = 186) demonstrated that rs7574865 was not associated with the development of liver cirrhosis and phenotype (biochemical data and the presence of auto-antibodies).

Conclusions/Significance

This is the first study to show a positive association between a STAT4 polymorphism and type-1 autoimmune hepatitis, suggesting that autoimmune hepatitis shares a gene commonly associated with risk for other autoimmune diseases.

Tissue inhibitor of metalloproteinase 1 is preferentially expressed in Th1 and Th17 T-helper cell subsets and is a direct STAT target gene

CD4(+) T helper (Th) cells differentiate into distinct effector subsets that are critical for host defense, but are also implicated in the pathogenesis of autoimmune disorders. Thelper17 (Th17) cells in particular are emerging as important drivers of multiple diseases including psoriasis, spondyloarthropathy and multiple sclerosis. To gain insight into the function of Th17 cells, we performed transcriptional profiling in hopes of elucidating products not previously recognized as being functionally relevant in these T cells. Herein, we demonstrate that tissue inhibitor of metalloproteinase 1 (TIMP1), a secreted protein with pleiotropic effects on cellular growth, survival and integrity of the extracellular matrix, is preferentially produced by Th17 and Th1 cells. We further show that Th1 and Th17 cell TIMP1 regulation follows separate mechanisms with a requirement for STAT4 in the former and STAT3 in the latter. Finally, we demonstrate that when restricted to T cells, expression of TIMP1 promotes neuropathology in experimental allergic encephalomyelitis.

Helper T-cell identity and evolution of differential transcriptomes and epigenomes

CD4(+) T cells are critical for the elimination of an immense array of microbial pathogens. Among the ways they accomplish this task is to generate progeny with specialized, characteristic patterns of gene expression. From this perspective, helper cells can be viewed as pluripotent precursors that adopt distinct cell fates. Although there are aspects of helper cell differentiation that can be modeled as a classic cell fate commitment, CD4(+) T cells also maintain considerable flexibility in their transcriptional program. This makes sense in terms of host defense, but raises the question of how these remarkable cells balance both these requirements, a high degree of specific gene expression and the capacity for plasticity. In this review, we discuss recent advances in our understanding of CD4(+) T-cell specification, focusing on how genomic perspectives have influenced our views of these processes. The relative contributions of sensors of the cytokine milieu, especially the signal transducer and activator of transcription family transcription factors, 'master regulators', and other transcription factors are considered as they relate to the helper cell transcriptome and epigenome.

Decreased signal transducers and activators of transcription (STAT) protein expression in lymphatic organs during EAE development in mice

Experimental autoimmune encephalomyelitis (EAE) is mediated by myelin-specific CD4+ T cells secreting Th1 and/or Th17 cytokines. Signal transducer and activator of transcription (STAT) family proteins have essential roles in transmitting Th1 and/or Th17 cytokine-mediated signals. However, most studies demonstrating the importance of the STAT signaling system in EAE have focused on distinct members of this family, often looking at their role specifically in the central nervous system, or in vitro. There is limited information available regarding the temporal and spatial expression patterns of each STAT protein and interplay between STAT proteins over the course of EAE development in critical lymphatic organs in vivo. In the present study, we demonstrate dramatic and progressive decrease of all six STAT family members (STAT1, STAT2, STAT3, STAT4, STAT5, STAT6) in the spleen and lymph nodes through the course of EAE development in SJL/J mice, in contrast with almost steady expression of thymic STAT proteins. Decreased splenic and lymphatic STAT expression was accompanied by significant enlargement of the spleen and lymph nodes, and histological proliferation of T cell areas with remodeling of the splenic microstructure in EAE mice. All STAT family members except STAT2 were mainly confined in T cell areas in spleen, whereas they were distributed in a protein specific manner in thymus. We present here a comprehensive analysis of all six members of the STAT family in spleen, lymph nodes and thymus through the development phase of EAE. Results suggest that EAE induced inflammatory T cells may develop distinct biological features different from normal splenic T cells due to altered STAT signaling.

Mechanisms of Signal Transduction from Receptors of Type I and Type II Cytokines

Cytokines play pivotal roles in regulation of immune responses. Signaling proteins involved in cytokine signal transduction pathways can be potential targets of toxins causing aberrant immune responses. Binding of cytokines to their specific receptors induces activation of signal transduction pathways. In this review, an overview of the cytokine/cytokine receptor system, signaling pathways activated by cytokine receptors, their regulation mechanisms, pathological conditions caused by aberrant cytokine signaling, and issues to be elucidated in the near future is provided.

Association of STAT4 rs7574865 polymorphism with autoimmune diseases: a meta-analysis

The association between the signal transducer and activator of transcription 4 (STAT4) gene rs7574865 single nucleotide polymorphism and different autoimmune diseases remains controversial and ambiguous. We conducted this study to investigate whether combined evidence shows the association between STAT4 rs7574865 polymorphism and autoimmune diseases. Comprehensive Medline search and review of the references were used to get the relevant reports published before September 2011. Meta-analysis was conducted for genotype T/T (recessive effect), T/T + G/T (dominant effect) and T allele in random effects models. 40 studies with 90 comparisons including 32 systemic lupus erythematosus (SLE), 19 rheumatoid arthritis (RA), 3 type 1 diabetes (T1D), 11 Systemeric Sclerosis (SSc), 4 inflammatory bowed diseases (IBD), 3 Primary Sjogren's syndrome (pSS), 4 juvenile idiopathic arthritis (JIA), 2 Primary antiphospholipid syndrome (APS), 1 Autoimmune thyroid diseases, 1 multiple sclerosis, 1 Psoriasis, 1 Wegener's granulomatosis, 1 Type 2 diabetes, and 1 giant cell arteritis disease were available for this meta-analysis. The overall odds ratios for rs7574865 T-allele significantly increased in SLE, RA, T1D, SSc, JIA, and APS (OR = 1.56, 1.25, 1.13, 1.34, 1.25, and 2.15, respectively, P < 0.00001) and in IBD-UC and pSS (OR = 1.11 and 1.33, respectively, P < 0.05). This meta-analysis demonstrates that the STAT4 rs7574865 T allele confers susceptibility to SLE, RA, T1D, SSc, JIA, APS, IBD-UC, and pSS patients, supporting the hypothesis of association between STAT4 gene polymorphism and subgroup of autoimmune diseases.

Biology and significance of the JAK/STAT signalling pathways

Since its discovery two decades ago, the activation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway by numerous cytokines and growth factors has resulted in it becoming one of the most well-studied intracellular signalling networks. The field has progressed from the identification of the individual components to high-resolution crystal structures of both JAK and STAT, and an understanding of the complexities of the molecular activation and deactivation cycle which results in a diverse, yet highly specific and regulated pattern of transcriptional responses. While there is still more to learn, we now appreciate how disruption and deregulation of this pathway can result in clinical disease and look forward to adoption of the next generation of JAK inhibitors in routine clinical treatment.

Acquired STAT4 deficiency as a consequence of cancer chemotherapy

Signal Transducer and Activator of Transcription 4 (STAT4) is a transcription factor that is activated by IL-12 signaling and promotes Th1-cell differentiation and IFN-γ production. Defective IFN-γ production because of STAT4 mRNA and protein deficiency occurs after autologous stem cell transplantation for lymphoma. In the present study, we investigated the mechanisms of STAT4 deficiency in lymphoma patients. The tumor-bearing state is not responsible, because STAT4 levels were not significantly different in PBMCs obtained from healthy control subjects compared with those from lymphoma patients before treatment. STAT4 protein levels were significantly decreased in PBMCs and T cells obtained from lymphoma patients after standard-dose chemotherapy. Furthermore, treatment of control PBMC cultures or a natural killer cell line with chemotherapy drugs in vitro also resulted in reduced STAT4 protein and diminished, IL-12-induced IFN-γ production. Translation of STAT4 protein was not impaired in chemotherapy-treated cells, whereas the STAT4 protein half-life was significantly reduced. Chemotherapy drugs promoted the ubiquitination and proteasomal degradation of STAT4. Treatment with the proteasome inhibitor bortezomib reversed chemotherapy-induced STAT4 deficiency and defective IFN-γ production. We conclude that acquired STAT4 deficiency in lymphoma patients is a consequence of treatment with chemotherapy, results that have important implications for the design of optimal immunotherapy for lymphoma.

Genomic views of STAT function in CD4+ T helper cell differentiation

Signal transducer and activator of transcription (STAT) proteins are well known for their essential roles in transmitting cytokine-mediated signals and specifying T helper (T(H)) cell differentiation. Recent technological advances have revealed that STAT proteins have broad and complex roles in gene regulation and epigenetic control, including important roles as functional repressors. However, the challenge of how to link signal transduction, nucleosome biology and gene regulation remains. The relevance of tackling this problem is highlighted by genome-wide association studies that link cytokine signalling and STATs to various autoimmune or immune deficiency disorders. Defining exactly how extrinsic signals control the specification and plasticity of T(H) cells will provide important insights and perhaps therapeutic opportunities in these diseases.

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

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

STAT4 is a confirmed genetic risk factor for Sjögren's syndrome and could be involved in type 1 interferon pathway signaling

Signal transducer and activator of transcription 4 (STAT4) is a transcription factor mainly activated by interleukin 12, which promotes the secretion of type 2 interferon (IFN) by T-helper 1 cells. We assessed the association of STAT4 gene polymorphism and primary Sjögren's syndrome (pSS) and its functional relevance. We analyzed STAT4 rs7582694 polymorphism in an exploratory cohort of 186 pSS patients and 152 controls, and in a replication cohort of 192 pSS patients and 483 controls, all Caucasian. mRNA levels of STAT4alpha, STAT4beta, STAT1, and the type 1 IFN-induced genes PKR, MX1 and IFITM1 were assessed in peripheral blood mononuclear cells (PBMCs) from 30 pSS patients. STAT4 rs7582694 C allele was associated with pSS in both cohorts (odds ratio (OR) 1.57, 95% confidence interval (CI) 1.27-1.93, P=2.3 x 10(-5)). The association was increased for homozygous subjects, which suggests a recessive effect of the STAT4 at-risk allele. STAT4alpha, STAT4beta and STAT1 mRNA levels in PBMCs were not significantly associated with rs7582694 genotypes, however the mRNA levels of STAT4alpha and type 1 IFN-induced genes were strongly correlated: PKR (P=4 x 10(-3), r=0.51), MX1 (P=2 x 10(-4), r=0.63) and IFITM1 (P=8 x 10(-3), r=0.47), suggesting that STAT4 might be involved in not only type 2 IFN production but also in type 1 IFN-mediated effects.

Functional genomics of endothelial cells treated with anti-angiogenic or angiopreventive drugs

Angiogenesis is a highly regulated physiological process that has been studied in considerable detail given its importance in several chronic pathologies. Many endogenous factors and hormones intervene in the regulation of angiogensis and classical as well as targeted drugs have been developed for its control. Angiogenesis inhibition has come off the bench and entered into clinical application for cancer therapy, particularly for metastatic disease. While the clinical benefit is currently in terms of months, preclinical data suggest that novel drugs and drug combinations could lead to substantial improvement. The many targets of endogenous angiogenesis inhibitors reflect the complexity of the process; in contrast, current clinical therapies mainly target the vascular endothelial growth factor system. Cancer chemopreventive compounds can retard tumor insurgence and delay or prevent metastasis and many of these molecules hinder angiogenesis, a mechanism that we termed angioprevention. Angiopreventive drugs appear to prevalently act through the inhibition of the pro-inflammatory and anti-apoptotic player NFkappaB, thus contrasting inflammation dependent angiogenesis. Relatively little is known concerning the effects of these angiogenesis inhibitors on gene expression of endothelial cells, the main target of many of these molecules. Here we provide an exhaustive list of anti-angiogenic molecules, and summarize their effects, where known, on the transcriptome and functional genomics of endothelial cells. The regulation of specific genes can be crucial to preventive or therapeutic intervention. Further, novel targets might help to circumvent resistance to anti-angiogenic therapy. The studies we review are relevant not only to cancer but also to other chronic degenerative diseases involving endothelial cells, such as cardiovascular disorders, diabetes, rheumatoid arthritis and retinopaties, as well as vessel aging.

The intestinal antiinflammatory agent glycomacropeptide has immunomodulatory actions on rat splenocytes

Bovine glycomacropeptide (GMP) is an immunologically active milk peptide that is a part of the normal human diet. GMP has therapeutic value in preclinical models of intestinal inflammation, and its mechanism may be related to effects on lymphocytes. This study focuses on the actions of GMP on rat splenocytes in vitro and in vivo. Bovine serum albumin and lactoferrin were used for comparative purposes. GMP (0.01-0.1mgmL(-1)) enhanced Concanavalin A (ConA) evoked but not basal splenocyte proliferation. At 1mgmL(-1) GMP lost this effect but augmented basal TNF-alpha secretion and also iNOS and COX2 expression. IFN-gamma, IL-2 and IL-17 were not affected by GMP in quiescent splenocytes, but IL-10 was augmented at all concentrations tested. On the other hand, GMP produced a marked inhibitory effect (70%) on IFN-gamma secretion and to a lower extent (50%) also on TNF-alpha. GMP was shown to block STAT4 but not IkappaB-alpha phosphorylation. The Treg marker Foxp3 was markedly upregulated by GMP. Bovine serum albumin had some effects on splenocyte function which were of lower magnitude and not entirely coincidental, while lactoferrin had a strong antiproliferative effect, as expected, indicating a specific effect of GMP. When administered for 3 days to normal Wistar rats, GMP reproduced the Foxp3 induction effect observed previously in vitro. This was observed in splenocytes but not in thymocytes, and only when administered by the oral rather than the intraperitoneal route. Thus our results support the hypothesis that GMP may limit intestinal inflammation acting at least in part on lymphocytes.

Enteric pathogens and gut function: Role of cytokines and STATs

The gut harbors the largest immune system in the body. The mucosa is considered to be the initial site of interaction with commensal and pathogenic organisms; therefore, it is the first line of defense against the pathogens. In response to the invasion of various pathogens, naïve CD4(+) cells differentiate into subsets of T helper (Th) cells that are characterized by different cytokine profiles. Cytokines bind to cell surface receptors on both immune and non-immune cells leading to activation of JAK-STAT signaling pathway and influence gut function by upregulating the expression of specific target genes. This review considers the roles of cytokines and receptor-mediated activation of STATs on pathogen-induced changes in gut function. The focus on STAT4 and STAT6 is because of their requirement for the full development of Th1 and Th2 cytokine profiles.

STAT4 associates with systemic lupus erythematosus through two independent effects that correlate with gene expression and act additively with IRF5 to increase risk

OBJECTIVES

To confirm and define the genetic association of STAT4 and systemic lupus erythematosus (SLE), investigate the possibility of correlations with differential splicing and/or expression levels, and genetic interaction with IRF5.

METHODS

30 tag SNPs were genotyped in an independent set of Spanish cases and controls. SNPs surviving correction for multiple tests were genotyped in five new sets of cases and controls for replication. STAT4 cDNA was analysed by 5'-RACE PCR and sequencing. Expression levels were measured by quantitative PCR.

RESULTS

In the fine mapping, four SNPs were significant after correction for multiple testing, with rs3821236 and rs3024866 as the strongest signals, followed by the previously associated rs7574865, and by rs1467199. Association was replicated in all cohorts. After conditional regression analyses, two major independent signals, represented by SNPs rs3821236 and rs7574865, remained significant across the sets. These SNPs belong to separate haplotype blocks. High levels of STAT4 expression correlated with SNPs rs3821236, rs3024866 (both in the same haplotype block) and rs7574865 but not with other SNPs. Transcription of alternative tissue-specific exons 1, indicating the presence of tissue-specific promoters of potential importance in the expression of STAT4, was also detected. No interaction with associated SNPs of IRF5 was observed using regression analysis.

CONCLUSIONS

These data confirm STAT4 as a susceptibility gene for SLE and suggest the presence of at least two functional variants affecting levels of STAT4. The results also indicate that the genes STAT4 and IRF5 act additively to increase the risk for SLE.

Increase of NADPH-diaphorase expression in hypothalamus of stat4 knockout mice

Signal transducer and activator of transcription 4 (STAT4), a STAT family member, mediates interleukin 12 (IL12) signal transduction. IL12 is known to be related to calorie-restricted status. In the central nervous system, IL12 also enhances the production of nitric oxide (NO), which regulates food intake. In this study, the expression of neuronal NO synthase (Nos1), which is also related to food intake, was investigated in the hypothalamic areas of Stat4 knockout (KO) mice using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry, a marker for neurons expressing Nos1 enzyme. Western blots were also performed to evaluate Nos1 and Fos expression. Wild-type Balb/c (WT group, n=10 male) and Stat4 KO mice (Stat4 KO group, n=8 male) were used. The body weight and daily food intake in the WT group were 22.4+/-0.3 and 4.4 g per day, while those in the Stat4 KO group were 18.7+/-0.4 and 1.8 g per day, respectively. Stat4 mice had lower body weight and food intake than Balb/c mice. Optical intensities of NADPH-d-positive neurons in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA) of the Stat4 KO group were significantly higher than those of the WT group. Western blotting analysis revealed that the hypothalamic Nos1 and Fos expression of the Stat4 KO group was up-regulated, compared to that in the WT group. These results suggest that Stat4 may be related to the regulation of food intake and expression of Nos1 in the hypothalamus.

Signal transducer and activator of transcription 4 limits the development of adaptive regulatory T cells

T-cell responses to a cytokine milieu instruct the development of multiple effector phenotypes. While transforming growth factor-beta(1) (TGF-beta(1)) inhibits the development of T helper type 1 (Th1) and Th2 cells, we demonstrate that like interleukin-6 (IL-6) and IL-4, IL-12 can inhibit the development of TGF-beta(1)-induced Foxp3-expressing adaptive T regulatory (aTreg) cells. Signal transducer and activator of transcription 4 (STAT4) is critical for the response to IL-12, although there is a parallel pathway involving T box expressed in T cells (T-bet), and cells from mice double-deficient in STAT4 and T-bet are refractory to the inhibition of aTreg-cell development by IL-12. While the ability of these cytokines to promote Th differentiation may contribute to this effect, we observe that culture with IL-12, or other instructive cytokines, results in an increase in repressive chromatin modifications at the Foxp3 locus that limit STAT5 binding to Foxp3, without observed effects on IL-2 signalling pathways. In a model of allergic lung inflammation there are increased percentages of Treg cells in the lungs of Stat4(-/-) mice, compared with wild-type mice, and increases in Treg cells correlate with decreased allergic inflammation. Overall, these results suggest an important role for STAT4 in regulating Treg-cell development.

Temporal induction pattern of STAT4 target genes defines potential for Th1 lineage-specific programming

STAT4 is a critical component in the development of inflammatory adaptive immune responses. It has been extensively characterized as a lineage-determining factor in Th1 development. However, the genetic program activated by STAT4 that results in an inflammatory cell type is not well defined. In this report, we use DNA isolated from STAT4-chromatin immunoprecipitation to perform chromatin immunoprecipitation-on-chip analysis of over 28,000 mouse gene promoters to identify STAT4 targets. We demonstrate that STAT4 binds multiple gene-sets that program distinct components of the Th1 lineage. Although many STAT4 target genes display STAT4-dependent IL-12-inducible expression, other genes displayed IL-12-induced histone modifications but lack induction, possibly due to high relative basal expression. In the subset of genes that STAT4 programs for expression in Th1 cells, IL-12-induced mRNA levels remain increased for a longer time than mRNA from genes that are not programmed. This suggests that STAT4 binding to target genes, while critical, is not the only determinant for STAT4-dependent gene programming during Th1 differentiation.

Association of STAT4 polymorphism with rheumatoid arthritis and systemic lupus erythematosus: a meta-analysis

STAT4 is a transcription factor that has been implicated in the pathogenesis of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Recently, several reports has documented that a STAT4 haplotype is associated with RA, SLE and Sjogren's syndrome. To summarize and review these findings, we conducted a meta-analysis of all relevant reports published before September 2008. Studies on STAT4 rs7574865 single nucleotide polymorphism (SNP) of RA and SLE were identified using PubMed. Meta-analyses were performed for 15,609 patients with RA and 15,793 controls from 14 published studies and for 2,478 patients with SLE and 5,058 controls from 8 published studies. Meta-odds ratios (ORs) and 95% confidence intervals (CIs) based on random effects models were calculated for all available studies. The overall ORs for the minor T allele of STAT4 rs7574865 SNP were 1.27 (95% CI 1.20-1.34) in RA and 1.57 (95% CI 1.44-1.71) in SLE. Asian controls have significantly higher allele frequency (32%) for the minor T allele of STAT4 rs7574865 SNP than population of European origin (22%), however, there was no significant difference of ORs for RA and SLE by ethnicity. No apparent effect of anti-CCP positivity was found in stratified analysis. The risk of STAT4 genotype for SLE was significantly higher than for RA in populations of European origin and Asian. The results of our meta-analysis demonstrated that STAT4 rs7574865 SNP is significantly associated with RA and SLE. In addition to specific alleles of HLA-DRB1, the minor T allele of STAT4 rs7574865 SNP is a common RA risk factor in populations of European origin and Asian.

Impaired development of human Th1 cells in patients with deficient expression of STAT4

IL-12 activates STAT4, which is a critical regulator of inflammation and T helper type I (Th1) lineage development in murine systems. The requirement for STAT4 in the generation of human Th1 cells has not been examined thoroughly. Compared with control Th1 cultures, expression of the Th1 genes IFNgamma, IL-12Rbeta2, and TNFalpha is greatly reduced in Th1 cultures of CD4 T cells isolated from lymphoma patients after autologous stem cell transplantation who have acquired STAT4 deficiency. Moreover, IL-4 and IL-5 production is increased in patient Th1 cultures though there are no defects in the development of Th2 cells. Reconstitution of STAT4 in patient T cells allowed recovery of IFNgamma and IL-12Rbeta2 expression, whereas ectopic expression of IL-12Rbeta2 did not rescue STAT4 expression, and increased IFNgamma production only to levels intermediate between control and patient samples. These results demonstrate that, as in murine systems, STAT4 is required for optimal human Th1 lineage development.

Signal transducer and activation of transcription (STAT) 4beta, a shorter isoform of interleukin-12-induced STAT4, is preferentially activated by estrogen

Estrogen, a natural immunomodulatory compound, has been shown to promote the induction of a prototype T helper 1 cytokine, interferon (IFN)-gamma, as well as to up-regulate IFNgamma-mediated proinflammatory molecules (nitric oxide, cyclooxygenase 2, monocyte chemoattractant protein 1). Because IL-12 is a major IFNgamma-inducing cytokine, in this study we investigated whether estrogen treatment of wild-type C57BL/6 mice alters IL-12-mediated signaling pathways. A recent study has shown that IL-12 activates two isoforms of signal transducer and activation of transcription (STAT) 4, a normal-sized (full-length STAT4alpha) and a truncated form (STAT4beta). Interestingly, we found that estrogen treatment preferentially up-regulates the phosphorylation of STAT4beta in splenic lymphoid cells. Time kinetic data showed the differential activation of STAT4beta in splenic lymphoid cells from estrogen-treated mice, but not in cells from placebo controls. The activation of STAT4beta was mediated by IL-12 and not IFNgamma because deliberate addition or neutralization of IL-12, but not IFNgamma, affected the activation of STAT4beta. In contrast to IL-12-induced activation of STAT4beta in cells from estrogen-treated mice, STAT4alpha was not increased, rather it tended to be decreased. In this context, STAT4alpha-induced p27(kip1) protein was decreased in concanavalin A + IL-12-activated lymphocytes from estrogen-treated mice only. By using the in vitro DNA binding assay, we confirmed the ability of pSTAT4beta to bind to the IFNgamma-activated sites (IFNgamma activation sequences)/STAT4-binding sites in estrogen-treated mice. Our data are the first to show that estrogen apparently has selective effects on IL-12-mediated signaling by preferentially activating STAT4beta. These novel findings are likely to provide new knowledge with regard to estrogen regulation of inflammation.