Discrete roles for histone acetylation in human T helper 1 cell-specific gene expression

Histone deacetylase inhibitors: targeting epigenetic regulation in the treatment of acute leukemia

Acute leukemia (AL) is a rare yet perilous malignancy. Currently, the primary treatment for AL involves combination chemotherapy as the cornerstone of comprehensive measures, alongside hematopoietic stem cell transplantation as a radical approach. However, despite these interventions, mortality rates remain high, particularly among refractory/recurrent patients or elderly individuals with a poor prognosis. Acetylation, a form of epigenetic regulation, has emerged as a promising therapeutic avenue for treating AL. Recent studies have highlighted the potential of acetylation regulation as a novel treatment pathway. Histone deacetylase inhibitors (HDACis) play a pivotal role in modulating the differentiation and development of tumor cells through diverse pathways, simultaneously impacting the maturation and function of lymphocytes. HDACis demonstrate promise in enhancing survival rates and achieving a complete response in both acute myeloid leukemia and acute T-lymphoblastic leukemia patients. This article provides a comprehensive review of the advancements in HDACi therapy for AL, shedding light on its potential implications for clinical practice.

Gut microbiota and epigenetics in colorectal cancer: implications for carcinogenesis and therapeutic intervention

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. The occurrence of CRC is associated with various genetic and epigenetic mutations in intestinal epithelial cells that transform them into adenocarcinomas. There is increasing evidence indicating the gut microbiota plays a crucial role in the regulation of host physiological processes. Alterations in gut microbiota composition are responsible for initiating carcinogenesis through diverse epigenetic modifications, including histone modifications, ncRNAs and DNA methylation. This work was designed to comprehensively review recent findings to provide insight into the associations between the gut microbiota and CRC at an epigenetic level. These scientific insights can be used in the future to develop effective strategies for early detection and treatment of CRC.

Epigenetics in T-cell driven inflammation and cancer

For decades, scientists have been investigating how processes such as gene expression, stem cell plasticity, and cell differentiation can be modulated. The discovery of epigenetics helped unravel these processes and enabled the identification of major underlying mechanisms that, for example, are central for T cell maturation. T cells go through various stages in their development evolving from progenitor cells into double positive CD4/CD8 T cells that finally leave the thymus as naïve T cells. One major mechanism driving T cell maturation is the modulation of gene activity by temporally sequenced transcription of spatially exposed gene loci. DNA methylation, demethylation, and acetylation are key processes that enable a sequenced gene expression required for T cell differentiation. In vivo, differentiated T cells are subjected to enormous pressures originating from the microenvironment. Signals from this environment, particularly from an inflammatory or a tumor microenvironment, can push T cells to differentiate into specific effector and memory T cells, and even prompt T cells to adopt a state of dysfunctional exhaustion, en route of an epigenetically controlled mechanism. Fundamentals of these processes will be discussed in this review highlighting potential therapeutic interventions, in particular those beneficial to revive exhausted T cells.

Nuclear and chromatin rearrangement associate to epigenome and gene expression changes in a model of in vitro adipogenesis and hypertrophy

Hypertrophy of adipocytes represents the main cause of obesity. We investigated in vitro the changes associated with adipocyte differentiation and hypertrophy focusing on the nuclear morphometry and chromatin epigenetic remodelling. The 3 T3-L1 pre-adipocytes were firstly differentiated into mature adipocytes, then cultured with long-chain fatty acids to induce hypertrophy. Confocal and super-resolution stimulation emission depletion (STED) microscopy combined with ELISA assays allowed us to explore nuclear architecture, chromatin distribution and epigenetic modifications. In each condition, we quantified the triglyceride accumulation, the mRNA expression of adipogenesis and dysfunction markers, the release of five pro-inflammatory cytokines. Confocal microscopy revealed larger volume and less elongated shape of the nuclei in both mature and hypertrophic cells respect to pre-adipocytes, and a trend toward reduced chromatin compaction. Compared to mature adipocytes, the hypertrophic phenotype showed larger triglyceride content, increased PPARγ expression reduced IL-1a release, and up-regulation of a pool of genes markers for adipose tissue dysfunction. Moreover, a remodelling of both epigenome and chromatin organization was observed in hypertrophic adipocytes, with an increase in the average fluorescence of H3K9 acetylated domains in parallel with the increase in KAT2A expression, and a global hypomethylation of DNA. These findings making light on the nuclear changes during adipocyte differentiation and hypertrophy might help the strategies for treating obesity and metabolic complications.

Diabetes and Its Cardiovascular Complications: Potential Role of the Acetyltransferase p300

Diabetes has been shown to accelerate vascular senescence, which is associated with chronic inflammation and oxidative stress, both implicated in the development of endothelial dysfunction. This condition represents the initial alteration linking diabetes to related cardiovascular (CV) complications. Recently, it has been hypothesised that the acetyltransferase, p300, may contribute to establishing an early vascular senescent phenotype, playing a relevant role in diabetes-associated inflammation and oxidative stress, which drive endothelial dysfunction. Specifically, p300 can modulate vascular inflammation through epigenetic mechanisms and transcription factors acetylation. Indeed, it regulates the inflammatory pathway by interacting with nuclear factor kappa-light-chain-enhancer of activated B cells p65 subunit (NF-κB p65) or by inducing its acetylation, suggesting a crucial role of p300 as a bridge between NF-κB p65 and the transcriptional machinery. Additionally, p300-mediated epigenetic modifications could be upstream of the activation of inflammatory cytokines, and they may induce oxidative stress by affecting the production of reactive oxygen species (ROS). Because several in vitro and in vivo studies shed light on the potential use of acetyltransferase inhibitors, a better understanding of the mechanisms underlying the role of p300 in diabetic vascular dysfunction could help in finding new strategies for the clinical management of CV diseases related to diabetes.

Targeting Epigenetic Mechanisms: A Boon for Cancer Immunotherapy

Immunotherapy is rapidly emerging as a promising approach against cancer. In the last decade, various immunological mechanisms have been targeted to induce an increase in the immune response against cancer cells. However, despite promising results, many patients show partial response, resistance, or serious toxicities. A promising way to overcome this is the use of immunotherapeutic approaches, in combination with other potential therapeutic approaches. Aberrant epigenetic modifications play an important role in carcinogenesis and its progression, as well as in the functioning of immune cells. Thus, therapeutic approaches targeting aberrant epigenetic mechanisms and the immune response might provide an effective antitumor effect. Further, the recent development of potent epigenetic drugs and immunomodulators gives hope to this combinatorial approach. In this review, we summarize the synergy mechanism between epigenetic therapies and immunotherapy for the treatment of cancer, and discuss recent advancements in the translation of this approach.

Epigenetic regulation by gut microbiota

The gastrointestinal tract is continuously exposed to trillions of commensal microbes, collectively termed the microbiota, which are environmental stimuli that can direct health and disease within the host. In addition to well-established bacterial sensing pathways, microbial signals are also integrated through epigenetic modifications that calibrate the transcriptional program of host cells without altering the underlying genetic code. Microbiota-sensitive epigenetic changes include modifications to the DNA or histones, as well as regulation of non-coding RNAs. While microbiota-sensitive epigenetic mechanisms have been described in both local intestinal cells and as well in peripheral tissues, further research is required to fully decipher the complex relationship between the host and microbiota. This Review highlights current understandings of epigenetic regulation by gut microbiota and important implications of these findings in guiding therapeutic approaches to prevent or combat diseases driven by impaired microbiota-host interactions.

Epigenetic Reprogramming of CD4+ Helper T Cells as a Strategy to Improve Anticancer Immunotherapy

Evidences highlight the role of various CD4⁺ helper T cells (CD4⁺ Th) subpopulations in orchestrating the immune responses against cancers. Epigenetics takes an important part in the regulation of CD4⁺ Th polarization and plasticity. In this review, we described the epigenetic factors that govern CD4⁺ T cells differentiation and recruitment in the tumor microenvironment and their subsequent involvement in the antitumor immunity. Finally, we discussed how to manipulate tumor reactive CD4⁺ Th responses by epigenetic drugs to improve anticancer immunotherapy.

Comparative Analysis of Global Proteome and Lysine Acetylome Between Naive CD4+ T Cells and CD4+ T Follicular Helper Cells

As a subgroup of CD4⁺ T helper cells, follicular helper T (Tfh) cells provide help to germinal center B cells and mediate the development of long-lived humoral immunity. Dysregulation of Tfh cells is associated with several major autoimmune diseases. Although recent studies showed that Tfh cell differentiation is controlled by the transcription factor Bcl6, cytokines, and cell-cell signals, limited information is available on the proteome and post-translational modifications (PTMs) of proteins in human Tfh cells. In the present study, we investigated quantitative proteome and acetylome in human naive CD4⁺ T cells and in vitro induced Tfh (iTfh) cells using the tandem mass tag (TMT) labeling technique, antibody-based affinity enrichment, and high-resolution liquid chromatography-mass spectrometry (LC-MS)/mass spectrometry (MS) analysis. In total, we identified 802 upregulated proteins and 598 downregulated proteins at the threshold of 1.5-fold in iTfh cells compared to naive CD4⁺ T cells. With the aid of intensive bioinformatics, the biological process, the cellular compartment, the molecular function, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein–protein interaction of these differentially expressed proteins were revealed. Moreover, the acetylome data showed that 22 lysine (K) acetylated proteins are upregulated and 26 K acetylated proteins are downregulated in iTfh cells compared to the naive CD4⁺ T cells, among which 11 differentially acetylated K residues in core histones were identified, indicating that protein acetylation and epigenetic mechanism are involved in regulating Tfh cell differentiation. The study provides some important clues for investigating T cell activation and Tfh cell differentiation.

Lamin A/C and the Immune System: One Intermediate Filament, Many Faces

Nuclear envelope lamin A/C proteins are a major component of the mammalian nuclear lamina, a dense fibrous protein meshwork located in the nuclear interior. Lamin A/C proteins regulate nuclear mechanics and structure and control cellular signaling, gene transcription, epigenetic regulation, cell cycle progression, cell differentiation, and cell migration. The immune system is composed of the innate and adaptive branches. Innate immunity is mediated by myeloid cells such as neutrophils, macrophages, and dendritic cells. These cells produce a rapid and nonspecific response through phagocytosis, cytokine production, and complement activation, as well as activating adaptive immunity. Specific adaptive immunity is activated by antigen presentation by antigen presenting cells (APCs) and the cytokine microenvironment, and is mainly mediated by the cellular functions of T cells and the production of antibodies by B cells. Unlike most cell types, immune cells regulate their lamin A/C protein expression relatively rapidly to exert their functions, with expression increasing in macrophages, reducing in neutrophils, and increasing transiently in T cells. In this review, we discuss and summarize studies that have addressed the role played by lamin A/C in the functions of innate and adaptive immune cells in the context of human inflammatory and autoimmune diseases, pathogen infections, and cancer.

Effects of glycerol-esters of saturated short- and medium chain fatty acids on immune, health and growth variables in veal calves

In veal and dairy beef production systems, Holstein bull calves experience many stressors and excessive pathogen exposure, necessitating the use of antimicrobials for welfare and production reasons. The aim of this randomized clinical trial was to explore the effects of esterified fatty acids used as feed supplement on health, production and immune variables in veal calves. Different glycerol-esters of fatty acids were used: short chain fatty acid (SCFA)-based glycerol-mono- (C4) and tributyrate (C4), and medium chain fatty acid (MCFA)-based glycerol-monocaprylate/monocaprinate (C8/C10) and glycerol-monolaurate (C12) in two different doses. One hundred sixty eight calves (2-to 4-week-old) were randomly assigned to 6 treatment groups; tributyrate (0.5 g/animal/day); monobutyrate (1 g/animal/day); low C8/C10 (7 g/animal/day) and high C8/C10 (10 g/animal/day); low C12 (4 g/animal/day) and high C12 (6 g/animal/day) and a control group (CON). Duration of in-feed supplementation was 14 weeks. Average daily gain, bodyweight at 14 weeks on feed and slaughter weight were determined. Health monitoring consisted of clinical signs and repeated thoracic ultrasonography. After 4, 8 and 12 weeks of supplementation, the function of neutrophils, monocytes and peripheral blood mononuclear cells (PBMCs) was evaluated ex vivo by measuring reactive oxygen species (ROS) production by neutrophils and monocytes, proliferation of and cytokine release by PBMCs. Study power was based upon ROS production by neutrophils and treatment groups were too limited to detect significant differences in growth and health variables. Glycerol-ester supplementation resulted in different effects on immune cell function, depending on the type and dose of the glycerol-ester as well as duration of supplementation. Our main findings were increased secretion of interleukin IL-17A by PBMCs at 4 weeks of feed supplementation in high C8/C10 (P< 0.01), low C12 (P < 0.01) and monobutyrate (P< 0.01) groups, combined with decreased ROS production in neutrophils (P < 0.001) and monocytes (P < 0.05) in the high C8/C10 and monocytes (P < 0.05) in low C12 groups compared to the control animals. After 12 weeks on feed, ROS production by neutrophils (P < 0.001) and monocytes (P < 0.01) of monobutyrate and by monocytes (P < 0.01) of tributyrate groups was decreased compared to control calves. In summary, supplementation of glycerol-esters of MCFAs resulted in immune-modulatory effects, which did not manifest themselves in improved health and growth of calves under the conditions and limitations of this study. Especially doses of high C8/C10 and low C12 show potential to promote an early, robust pro-inflammatory response with diminished ROS production. This might be beneficial for clearance of pathogens in young calves in periods of stress and high pathogen load.

Immunoepigenetics Combination Therapies: An Overview of the Role of HDACs in Cancer Immunotherapy

Long-standing efforts to identify the multifaceted roles of histone deacetylase inhibitors (HDACis) have positioned these agents as promising drug candidates in combatting cancer, autoimmune, neurodegenerative, and infectious diseases. The same has also encouraged the evaluation of multiple HDACi candidates in preclinical studies in cancer and other diseases as well as the FDA-approval towards clinical use for specific agents. In this review, we have discussed how the efficacy of immunotherapy can be leveraged by combining it with HDACis. We have also included a brief overview of the classification of HDACis as well as their various roles in physiological and pathophysiological scenarios to target key cellular processes promoting the initiation, establishment, and progression of cancer. Given the critical role of the tumor microenvironment (TME) towards the outcome of anticancer therapies, we have also discussed the effect of HDACis on different components of the TME. We then have gradually progressed into examples of specific pan-HDACis, class I HDACi, and selective HDACis that either have been incorporated into clinical trials or show promising preclinical effects for future consideration. Finally, we have included examples of ongoing trials for each of the above categories of HDACis as standalone agents or in combination with immunotherapeutic approaches.

Regulation of the effector function of CD8+ T cells by gut microbiota-derived metabolite butyrate

The gut microbiota produces metabolites such as short-chain fatty acids (SCFAs) that regulate the energy homeostasis and impact on immune cell function of the host. Recently, innovative approaches based on the oral administration of SCFAs have been discussed for therapeutic modification of inflammatory immune responses in autoimmune diseases. So far, most studies have investigated the SCFA-mediated effects on CD4⁺ T cells and antigen presenting cells. Here we show that butyrate and, to a lesser degree, propionate directly modulate the gene expression of CD8⁺ cytotoxic T lymphocytes (CTLs) and Tc17 cells. Increased IFN-γ and granzyme B expression by CTLs as well as the molecular switch of Tc17 cells towards the CTL phenotype was mediated by butyrate independently of its interaction with specific SCFA-receptors GPR41 and GPR43. Our results indicate that butyrate strongly inhibited histone-deacetylases (HDACs) in CD8⁺ T cells thereby affecting the gene expression of effector molecules. Accordingly, the pan-HDAC inhibitors trichostatin A (TSA) and sodium valproate exerted similar influence on CD8⁺ T cells. Furthermore, higher acetate concentrations were also able to increase IFN-γ production in CD8⁺ T lymphocytes by modulating cellular metabolism and mTOR activity. These findings might have significant implications in adoptive immunotherapy of cancers and in anti-viral immunity.

The Microbial Metabolite Butyrate Induces Expression of Th1-Associated Factors in CD4+ T Cells

Short-chain fatty acids (SCFAs), which are generated by the bacterial fermentation of dietary fibers, promote expansion of regulatory T cells (Tregs). Potential therapeutic value of SCFAs has been recently highlighted in the experimental models of T cell-mediated autoimmunity and allergic inflammation. These studies suggest that physiological intestinal concentrations of SCFAs within the millimolar range are crucial for dampening inflammation-mediated processes. Here, we describe opposing effects of SCFAs on T cell-mediated immune responses. In accordance with published data, lower butyrate concentrations facilitated differentiation of Tregs in vitro and in vivo under steady-state conditions. In contrast, higher concentrations of butyrate induced expression of the transcription factor T-bet in all investigated T cell subsets resulting in IFN-γ-producing Tregs or conventional T cells. This effect was mediated by the inhibition of histone deacetylase activity and was independent of SCFA-receptors FFA2 and FFA3 as well as of Na⁺-coupled SCFA transporter Slc5a8. Importantly, while butyrate was not able to induce the generation of Tregs in the absence of TGF-β1, the expression of T-bet and IFN-γ was triggered upon stimulation of CD4⁺ T cells with this SCFA alone. Moreover, the treatment of germ-free mice with butyrate enhanced the expression of T-bet and IFN-γ during acute colitis. Our data reveal that, depending on its concentration and immunological milieu, butyrate may exert either beneficial or detrimental effects on the mucosal immune system.

Epigenetic regulation of immune checkpoints: another target for cancer immunotherapy?

Epigenetic changes in oncogenes and tumor-suppressor genes contribute to carcinogenesis. Understanding the epigenetic and genetic components of tumor immune evasion is crucial. Few cancer genetic mutations have been linked to direct correlations with immune evasion. Studies on the epigenetic modulation of the immune checkpoints have revealed a critical interaction between epigenetic and immune modulation. Epigenetic modifiers can activate many silenced genes. Some of them are immune checkpoints regulators that turn on immune responses and others turn them off resulting in immune evasion. Many forms of epigenetic inheritance mechanisms may play a role in regulation of immune checkpoints including: covalent modifications, noncoding RNA and histone modifications. In this review, we will show how the potential interaction between epigenetic and immune modulation may lead to new approaches for specific epigenome/immunome-targeted therapies for cancer.

Epi-drugs in combination with immunotherapy: a new avenue to improve anticancer efficacy

Immune checkpoint factors, such as programmed cell death protein-1/2 (PD-1, PD-2) or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) receptors, are targets for monoclonal antibodies (MAbs) developed for cancer immunotherapy. Indeed, modulating immune inhibitory pathways has been considered an important breakthrough in cancer treatment. Although immune checkpoint blockade therapy used to treat malignant diseases has provided promising results, both solid and haematological malignancies develop mechanisms that enable themselves to evade the host immune system. To overcome some major limitations and ensure safety in patients, recent strategies have shown that combining epigenetic modulators, such as inhibitors of histone deacetylases (HDACi) or DNA methyltransferases (DNMTi), with immunotherapeutics can be useful. Preclinical data generated using mouse models strongly support the feasibility and effectiveness of the proposed approaches. Indeed, co-treatment with pan- or class I-selective HDACi or DNMTi improved beneficial outcomes in both in vitro and in vivo studies. Based on the evidence of a pivotal role for HDACi and DNMTi in modulating various components belonging to the immune system, recent clinical trials have shown that both HDACi and DNMTi strongly augmented response to anti-PD-1 immunotherapy in different tumour types. This review describes the current strategies to increase immunotherapy responses, the effects of HDACi and DNMTi on immune modulation, and the advantages of combinatorial therapy over single-drug treatment.

T cells lacking HDAC11 have increased effector functions and mediate enhanced alloreactivity in a murine model

Histone acetylation and the families of enzymes responsible for controlling these epigenetic marks have been implicated in regulating T-cell maturation and phenotype. Here, we demonstrate a previously undefined role of histone deacetylase 11 (HDAC11) in regulating T-cell effector functions. Using EGFP-HDAC11 transgenic reporter mice, we found that HDAC11 expression was lower in effector relative to naive and central memory T-cell populations, and activation of resting T cells resulted in its decreased expression. Experiments using HDAC11 knockout (KO) mice revealed that T cells from these mice displayed enhanced proliferation, proinflammatory cytokine production, and effector molecule expression. In addition, HDAC11KO T cells had increased expression of Eomesodermin (Eomes) and TBX21 (Tbet), transcription factors previously shown to regulate inflammatory cytokine and effector molecule production. Conversely, overexpression of HDAC11 resulted in decreased expression of these genes. Chromatin immunoprecipitation showed the presence of HDAC11 at the Eomes and Tbet gene promoters in resting T cells, where it rapidly disassociated following T-cell activation. In vivo, HDAC11KO T cells were refractory to tolerance induction. HDAC11KO T cells also mediated accelerated onset of acute graft-versus-host disease (GVHD) in a murine model, characterized by increased proliferation of T cells and expression of interferon-γ, tumor necrosis factor, and EOMES. In addition, adoptive transfer of HDAC11KO T cells resulted in significantly reduced tumor burden in a murine B-cell lymphoma model. Taken together, these data demonstrate a previously unknown role of HDAC11 as a negative epigenetic regulator of T-cell effector phenotype and function.

Effects of alcohol on H3K9 acetylation in mouse pre-implantation embryos

It is well known that excessive long-term alcohol consumption is harmful, especially in pregnant women. In the present study, the Kunming white mouse was used as an animal model and indirect immunofluorescence was performed to analyze the toxic effects of alcohol on early pre-implantation embryos. H3K9 acetylation immunofluorescence could not be detected in MII oocytes. H3K9 acetylation levels in the treatment group were higher than in the control group during the morula stage, and contrary to results during the blastocyst stage. Other stages showed no obvious differences for in vivo embryos. For in vitro embryos, almost no difference was found between the two experimental groups across all stages, and both groups showed increasing H3K9 acetylation levels (except at the 2-cell stage). This study shows that H3K9 acetylation levels in early pre-implantation embryos are notably impacted by excessive alcohol ingestion by females. These data are the first step in understanding the epigenetic mechanism of alcohol toxicity in early pre-implantation mouse embryos.

Cell cycle progression is regulated by intertwined redox oscillators

The different phases of the eukaryotic cell cycle are exceptionally well-preserved phenomena. DNA decompaction, RNA and protein synthesis (in late G1 phase) followed by DNA replication (in S phase) and lipid synthesis (in G2 phase) occur after resting cells (in G0) are committed to proliferate. The G1 phase of the cell cycle is characterized by an increase in the glycolytic metabolism, sustained by high NAD+/NADH ratio. A transient cytosolic acidification occurs, probably due to lactic acid synthesis or ATP hydrolysis, followed by cytosolic alkalinization. A hyperpolarized transmembrane potential is also observed, as result of sodium/potassium pump (NaK-ATPase) activity. During progression of the cell cycle, the Pentose Phosphate Pathway (PPP) is activated by increased NADP+/NADPH ratio, converting glucose 6-phosphate to nucleotide precursors. Then, nucleic acid synthesis and DNA replication occur in S phase. Along with S phase, unpublished results show a cytosolic acidification, probably the result of glutaminolysis occurring during this phase. In G2 phase there is a decrease in NADPH concentration (used for membrane lipid synthesis) and a cytoplasmic alkalinization occurs. Mitochondria hyperfusion matches the cytosolic acidification at late G1/S transition and then triggers ATP synthesis by oxidative phosphorylation. We hypothesize here that the cytosolic pH may coordinate mitochondrial activity and thus the different redox cycles, which in turn control the cell metabolism.

Epigenetics of inflammation, maternal infection, and nutrition

Studies have demonstrated that epigenetic changes such as DNA methylation, histone modification, and chromatin remodeling are linked to an increased inflammatory response as well as increased risk of chronic disease development. A few studies have begun to investigate whether dietary nutrients play a beneficial role by modifying or reversing epigenetically induced inflammation. Results of these studies show that nutrients modify epigenetic pathways. However, little is known about how nutrients modulate inflammation by regulating immune cell function and/or immune cell differentiation via epigenetic pathways. This overview will provide information about the current understanding of the role of nutrients in the epigenetic control mechanisms of immune function.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Long Intergenic Non-Coding RNAs: Novel Drivers of Human Lymphocyte Differentiation

Upon recognition of a foreign antigen, CD4(+) naïve T lymphocytes proliferate and differentiate into subsets with distinct functions. This process is fundamental for the effective immune system function, as CD4(+) T cells orchestrate both the innate and adaptive immune response. Traditionally, this differentiation event has been regarded as the acquisition of an irreversible cell fate so that memory and effector CD4(+) T subsets were considered terminally differentiated cells or lineages. Consequently, these lineages are conventionally defined thanks to their prototypical set of cytokines and transcription factors. However, recent findings suggest that CD4(+) T lymphocytes possess a remarkable phenotypic plasticity, as they can often re-direct their functional program depending on the milieu they encounter. Therefore, new questions are now compelling such as which are the molecular determinants underlying plasticity and stability and how the balance between these two opposite forces drives the cell fate. As already mentioned, in some cases, the mere expression of cytokines and master regulators could not fully explain lymphocytes plasticity. We should consider other layers of regulation, including epigenetic factors such as the modulation of chromatin state or the transcription of non-coding RNAs, whose high cell-specificity give a hint on their involvement in cell fate determination. In this review, we will focus on the recent advances in understanding CD4(+) T lymphocytes subsets specification from an epigenetic point of view. In particular, we will emphasize the emerging importance of non-coding RNAs as key players in these differentiation events. We will also present here new data from our laboratory highlighting the contribution of long non-coding RNAs in driving human CD4(+) T lymphocytes differentiation.

Epigenetic Regulation of Immunological Alterations Following Prenatal Exposure to Marijuana Cannabinoids and its Long Term Consequences in Offspring

Use of marijuana during pregnancy is fairly commonplace and can be expected increase in frequency as more states legalize its recreational use. The cannabinoids present in marijuana have been shown to be immunosuppressive, yet the effect of prenatal exposure to cannabinoids on the immune system of the developing fetus, its long term consequences during adult stage of life, and transgenerational effects have not been well characterized. Confounding factors such as co-existing drug use make the impact of cannabis use on progeny inherently difficult to study in a human population. Data from various animal models suggests that in utero exposure to cannabinoids results in profound T cell dysfunction and a greatly reduced immune response to viral antigens. Furthermore, evidence from animal studies indicates that the immunosuppressive effects of cannabinoids can be mediated through epigenetic mechanisms such as altered microRNA, DNA methylation and histone modification profiles. Such studies support the hypothesis that that parental or prenatal exposure to cannabis can trigger epigenetic changes that could have significant immunological consequences for offspring as well as long term transgenerational effects.

Comparative epigenetics: relevance to the regulation of production and health traits in cattle

With the development of genomic, transcriptomic and bioinformatic tools, recent advances in molecular technologies have significantly impacted bovine bioscience research and are revolutionising animal selection and breeding. Integration of epigenetic information represents yet another challenging molecular frontier. Epigenetics is the study of biochemical modifications to DNA and to histones, the proteins that provide stability to DNA. These epigenetic changes are induced by environmental stimuli; they alter gene expression and are potentially heritable. Epigenetics research holds the key to understanding how environmental factors contribute to phenotypic variation in traits of economic importance in cattle including development, nutrition, behaviour and health. In this review, we discuss the potential applications of epigenetics in bovine research, using breakthroughs in human and murine research to signpost the way.

Histone modifications are associated with Δ9-tetrahydrocannabinol-mediated alterations in antigen-specific T cell responses

Marijuana is one of the most abused drugs due to its psychotropic effects. Interestingly, it is also used for medicinal purposes. The main psychotropic component in marijuana, Δ(9)-tetrahydrocannabinol (THC), has also been shown to mediate potent anti-inflammatory properties. Whether the immunomodulatory activity of THC is mediated by epigenetic regulation has not been investigated previously. In this study, we employed ChIP-Seq technology to examine the in vivo effect of THC on global histone methylation in lymph node cells of mice immunized with a superantigen, staphylococcal enterotoxin B. We compared genome-wide histone H3 Lys-4, Lys-27, Lys-9, and Lys-36 trimethylation and histone H3 Lys-9 acetylation patterns in such cells exposed to THC or vehicle. Our results showed that THC treatment leads to the association of active histone modification signals to Th2 cytokine genes and suppressive modification signals to Th1 cytokine genes, indicating that such a mechanism may play a critical role in the THC-mediated switch from Th1 to Th2. At the global level, a significant portion of histone methylation and acetylation regions were altered by THC. However, the overall distribution of these histone methylation signals among the genomic features was not altered significantly by THC, suggesting that THC activates the expression of a subset of genes while suppressing the expression of another subset of genes through histone modification. Functional classification of these histone marker-associated genes showed that these differentially associated genes were involved in various cellular functions, from cell cycle regulation to metabolism, suggesting that THC had a pleiotropic effect on gene expression in immune cells. Altogether, the current study demonstrates for the first time that THC may modulate immune response through epigenetic regulation involving histone modifications.

Loss of methylation at the IFNG promoter and CNS-1 is associated with the development of functional IFN-γ memory in human CD4(+) T lymphocytes

Cytokine memory for IFN-γ production by effector/memory Th1 cells plays a key role in both protective and pathological immune responses. To understand the epigenetic mechanism determining the ontogeny of effector/memory Th1 cells characterized by stable effector functions, we identified a T-cell-specific methylation pattern at the IFNG promoter and CNS-1 in ex vivo effector/memory Th1 cells, and investigated methylation dynamics of these regions during the development of effector/memory Th1 cells. During Th1 differentiation, demethylation occurred at both the promoter and CNS-1 regions of IFNG as early as 16 h, and this process was independent of cell proliferation and DNA synthesis. Using an IFN-γ capture assay, we found early IFN-γ-producing cells from 2-day differentiating cultures acquired "permissive" levels of demethylation and developed into effector/memory Th1 cells undergoing progressive demethylation at the IFNG promoter and CNS-1 when induced by IL-12. Methylation levels of these regions in effector/memory Th1 cells of peripheral blood from rheumatoid arthritis patients correlated inversely with reduced frequencies of IFN-γ-producers, coincident with recruitment of effector/memory Th1 cells to the site of inflammation. Thus, after termination of TCR stimulation, IL-12 signaling potentiates the stable functional IFN-γ memory in effector/memory Th1 cells characterized by hypomethylation at the IFNG promoter and CNS-1.

Inhibition of histone acetylation by curcumin reduces alcohol-induced expression of heart development-related transcription factors in cardiac progenitor cells

Alcohol exposure during pregnancy may cause congenital heart disease (CHD). In our previous studies, we found that alcohol selectively increased acetylation of histone H3 at lysine 9 (H3K9) and enhanced the expression of heart development-related genes in cardiac progenitor cells. The objective of this study is to investigate the protective effects of histone acetyltransferases (HATs) inhibitor, curcumin, on histone hyperacetylation and the over-expression of heart development genes induced by alcohol. Western blot analysis was employed to detect the acetylation levels of histone H3K9 and real-time PCR was applied to measure the expressions of heart development-related transcription factors, GATA4, Mef2c and Tbx5 (GMT). Our results showed that alcohol increased the acetylation of H3K9 by 2.76-fold (P<0.05) and significantly enhanced the expression of GATA4 and Mef2c (P<0.05). When cells were treated with alcohol plus 25 μM curcumin, the hyperacetylation of H3K9 and over-expression of GATA4 and Mef2c by alcohol was reversed. These data indicate that curcumin can correct the over-expression of cardiac genes by reversing the alcohol induced hyperacetylation of histone H3 at lysine 9 in cardiac progenitor cells, suggesting that curcumin is protective against alcohol-induced cardiac gene over-expression that may result in heart malformations.

Acetylation of retinal histones in diabetes increases inflammatory proteins: effects of minocycline and manipulation of histone acetyltransferase (HAT) and histone deacetylase (HDAC)

Histone acetylation was significantly increased in retinas from diabetic rats, and this acetylation was inhibited in diabetics treated with minocycline, a drug known to inhibit early diabetic retinopathy in animals. Histone acetylation and expression of inflammatory proteins that have been implicated in the pathogenesis of diabetic retinopathy were increased likewise in cultured retinal Müller glia grown in a diabetes-like concentration of glucose. Both the acetylation and induction of the inflammatory proteins in elevated glucose levels were significantly inhibited by inhibitors of histone acetyltransferase (garcinol and antisense against the histone acetylase, p300) or activators of histone deacetylase (theophylline and resveratrol) and were increased by the histone deacetylase inhibitor, suberolylanilide hydroxamic acid. We conclude that hyperglycemia causes acetylation of retinal histones (and probably other proteins) and that the acetylation contributes to the hyperglycemia-induced up-regulation of proinflammatory proteins and thereby to the development of diabetic retinopathy.

Histone/protein deacetylases and T-cell immune responses

Clinical and experimental studies show that inhibition of histone/protein deacetylases (HDAC) can have important anti-neoplastic effects through cytotoxic and proapoptotic mechanisms. There are also increasing data from nononcologic settings that HDAC inhibitors (HDACi) can exhibit useful anti-inflammatory effects in vitro and in vivo, unrelated to cytotoxicity or apoptosis. These effects can be cell-, tissue-, or context-dependent and can involve modulation of specific inflammatory signaling pathways as well as epigenetic mechanisms. We review recent advances in the understanding of how HDACi alter immune and inflammatory processes, with a particular focus on the effects of HDACi on T-cell biology, including the activation and functions of conventional T cells and the unique T-cell subset, composed of Foxp3(+) T-regulatory cells. Although studies are still needed to tease out details of the various biologic roles of individual HDAC isoforms and their corresponding selective inhibitors, the anti-inflammatory effects of HDACi are already promising and may lead to new therapeutic avenues in transplantation and autoimmune diseases.

Transcriptional and epigenetic control of T helper cell specification: molecular mechanisms underlying commitment and plasticity

T helper cell differentiation occurs in the context of the extracellular cytokine milieu evoked by diverse microbes and other pathogenic stimuli along with T cell receptor stimulation. The culmination of these signals results in specification of T helper lineages, which occurs through the combinatorial action of multiple transcription factors that establish distinctive transcriptomes. In this manner, inducible, but constitutively active, master regulators work in conjunction with factors such as the signal transducer and activator of transcriptions (STATs) that sense the extracellular environment. The acquisition of a distinctive transcriptome also depends on chromatin modifications that impact key cis elements as well as the changes in global genomic organization. Thus, signal transduction and epigenetics are linked in these processes of differentiation. In this review, recent advances in understanding T helper lineage specification and deciphering the action of transcription factors are summarized with emphasis on comprehensive views of the dynamic T cell epigenome.

cAMP-responsive element modulator (CREM)α protein induces interleukin 17A expression and mediates epigenetic alterations at the interleukin-17A gene locus in patients with systemic lupus erythematosus

IL-17A is a proinflammatory cytokine that is produced by specialized T helper cells and contributes to the development of several autoimmune diseases such as systemic lupus erythematosus (SLE). Transcription factor cAMP-responsive element modulator (CREM)α displays increased expression levels in T cells from SLE patients and has been described to account for aberrant T cell function in SLE pathogenesis. In this report, we provide evidence that CREMα physically binds to a cAMP-responsive element, CRE (-111/-104), within the proximal human IL17A promoter and increases its activity. Chromatin immunoprecipitation assays reveal that activated naïve CD4(+) T cells as well as T cells from SLE patients display increased CREMα binding to this site compared with T cells from healthy controls. The histone H3 modification pattern at the CRE site (-111/-104) and neighboring conserved noncoding sequences within the human IL17A gene locus suggests an accessible chromatin structure (H3K27 hypomethylation/H3K18 hyperacetylation) in activated naïve CD4(+) T cells and SLE T cells. H3K27 hypomethylation is accompanied by decreased cytosine phosphate guanosine (CpG)-DNA methylation in these regions in SLE T cells. Decreased recruitment of histone deacetylase (HDAC)1 and DNA methyltransferase (DNMT)3a to the CRE site (-111/-104) probably accounts for the observed epigenetic alterations. Reporter studies confirmed that DNA methylation of the IL17A promoter indeed abrogates its inducibility. Our findings demonstrate an extended role for CREMα in the immunopathogenesis of SLE because it contributes to increased expression of IL-17A.

Helper T-cell differentiation and plasticity: insights from epigenetics

CD4(+) T cells have critical roles in orchestrating immune responses to diverse microbial pathogens. This is accomplished through the differentiation of CD4(+) T helper cells to specialized subsets in response to microbial pathogens, which evoke a distinct cytokine milieu. Signal transducer and activator of transcription family transcription factors sense these cytokines and they in turn regulate expression of lineage-defining master regulators that programme selective gene expression, resulting in distinctive phenotypes. However, phenotype and restricted gene expression are determined not only by the action of transcription factors; chromatin accessibility is required for these factors to exert their effect. Technical advances have greatly expanded our understanding of transcription factor action and dynamic changes in the epigenome that accompany cellular differentiation. In this review, we will discuss recent progress in the understanding of how cytokines influence gene expression and epigenetic modifications, and the impact of these findings on our views of helper cell lineage commitment and plasticity.

Tipifarnib-mediated suppression of T-bet-dependent signaling pathways

Large granular lymphocyte (LGL) leukemia is a chronic lymphoproliferative disease in which T-bet [T-box transcription factor 21 gene (tbx21)] overexpression may play a pathogenic role. T-bet orchestrates the differentiation of mature peripheral T-cells into interferon-γ (IFN-γ) and tumor necrosis factor-α producing CD4+ T-helper type I (Th1) and CD8+ T cytotoxic cells that are necessary for antiviral responses. When IL-12 is produced by antigen-presenting cells, T-bet expression is induced, causing direct stimulation of ifng gene transcription while simultaneously acting as a transcriptional repressor of the IL4 gene, which then leads to Th1 dominance and T-helper type 2 differentiation blockade. Additionally, T-bet has been shown to regulate histone acetylation of the ifng promoter and enhancer to loosen condensed DNA, creating greater accessibility for other transcription factor binding, which further amplifies IFNγ production. We found that treatment with a farnesyltransferase inhibitor tipifarnib reduced Th1 cytokines in LGL leukemia patient T-cells and blocked T-bet protein expression and IL-12 responsiveness in T-cells from healthy donors. The mechanism of suppression was based on modulation of histone acetylation of the ifng gene, which culminated in Th1 blockade.

Distinct roles of transforming growth factor-beta-activated kinase 1 (TAK1)-c-Rel and interferon regulatory factor 4 (IRF4) pathways in human T cell lymphotropic virus 1-transformed T helper 17 cells producing interleukin-9

Investigation of helper T cell markers in HTLV-1-transformed cell lines demonstrated that HuT-102 has an IL-9-producing Th17 phenotype. We confirmed the vital role of retinoic acid-related orphan receptor C, a Th17 transcription factor, in the expression of IL-17. Interferon regulatory factor 4 (IRF4), a transcription factor overexpressed in all HTLV-1-infected cells, regulated IL-17 and IL-9 concomitantly. We further demonstrated a novel pathway for the regulation of Tax-induced cytokines, IL-9 and IL-6, through TAK1-mediated nuclear accumulation of c-Rel. A microarray analysis for IRF4 knocked down HuT-102 cells showed a significant up-regulation in the set of genes related to Th1, mainly IFN-γ and several transcription factors. T-bet and IRF1, but not STAT1 and IRF9, participated in counteracting the inhibitory effect of IRF4 on the production of IFN-γ. Finally, suppression of both IRF4 and c-Rel resulted in the reduced proliferation. Collectively, these findings indicate that TAK1-c-Rel and IRF4 pathways play distinct roles in the maintenance of IL-9-producing Th17 phenotype of HTLV-1-transformed cells.

Ethanol and its metabolites induce histone lysine 9 acetylation and an alteration of the expression of heart development-related genes in cardiac progenitor cells

Alcohol exposure during pregnancy may cause congenital heart disease (CHD), but the underlying mechanisms are not clear. Recent evidence suggests that ethanol and its metabolites can selectively increase histone H3 acetylation at lysine 9 (H3AcK9) residue in rat hepatocytes. This may be a mechanism by which ethanol alters gene expression. The goal of current study is to investigate the effect of ethanol and its metabolites on H3AcK9 acetylation and the mRNA expression of heart development-related genes (GATA4, Mef2c, and Tbx5) in cardiac progenitor cells. We used mitochondrial activity (MTT) assay to assess the viability of cardiac progenitor cells. Western blotting and real-time PCR were employed to determine H3AcK9 acetylation and gene expression. Low levels of ethanol (50 mM), acetaldehyde (4 mM), and acetate (4 mM) had no effect on cell proliferation. However, high concentrations of ethanol (200 mM), acetaldehyde (12 mM), and acetate (16 mM) reduced cell viability by 30%, respectively (P < 0.05). Low levels of ethanol and acetate increased the acetylation of H3 lysine 9 by 2.4- and 2.2-fold, respectively (P < 0.05), but did not significantly change the expression of the heart development-related genes. High concentrations of ethanol and acetate increased H3 lysine 9 acetylation by 5.3- and 5.6-fold, respectively (P < 0.05). Moreover, high levels of ethanol and acetate significantly augmented the expression of GATA4 and Mef2c. Conversely, acetaldehyde (4 or 12 mM) had little effect on H3 lysine 9 acetylation or the expression of the heart development-related genes. Our studies demonstrate that high levels of ethanol or its metabolites induce H3AcK9 acetylation and impair cardiac progenitor cells. The altered histone H3 acetylation at lysine 9 has an important impact on the expression of the heart development-related genes, which may be one of the mechanisms underlying the alcohol-induced CHD.

Evidence for the role of oxidative stress in the acetylation of histone H3 by ethanol in rat hepatocytes

The relationship between ethanol-induced oxidative stress and acetylation of histone H3 at lysine 9 (H3AcK9) remains unknown and was therefore investigated in primary cultures of rat hepatocytes. Cells were treated with ethanol, and a select group of pharmacological agents and the status of H3AcK9 and reactive oxygen species (ROS) were monitored. Pretreatment of hepatocytes with N-acetyl cystein (ROS reducer), or dietary antioxidants (quercetin, reserveratrol), or NADPH (reduced nicotinamide adenine dinucleotide phosphate) oxidase inhibitor apocynin, significantly reduced ethanol (50 mM, 24 h) induced increases in ROS and H3AcK9. In contrast, l-buthionine sulfoximine (ROS inducer) and inhibitor of mitochondrial complexes I (rotenone) and III (antimycin) increased ethanol-induced H3AcK9 (P<.01). Oxidative stress also affected ethanol-induced alcohol dehydrogenase 1 mRNA expression. These results demonstrate for the first time that oxidative stress is involved in the ethanol-induced histone H3 acetylation in hepatocytes.

T-bet expression is regulated by EGR1-mediated signaling in activated T cells

T-bet is a Th1-specific transcription factor that is directly involved in three important pathways for Th1 cell differentiation, namely TCR signaling, and the IFN-gamma-STAT1 and IL-12-STAT4 pathways. A recent study also showed that T-bet plays a vital role in innate immunity. However, the molecular mechanism responsible for transcriptional activation of T-bet during T cell development is not yet known. Here, we characterize the essential human T-bet promoter elements and show that binding of EGR1 to this promoter induces T-bet transcription. Notably, overexpression of EGR1 transactivates and, synergistically in concert with TCR signaling, induces T-bet expression in activated T cells. In contrast, depletion of EGR1 significantly decreases T-bet induction. Finally, we report a positive correlation between EGR1 and T-bet expression during T helper cell differentiation. Collectively, these findings provide molecular insight into T-bet transcription and suggest that EGR1 is an upstream regulator of T-bet induction.

Cutting edge: Ikaros is a regulator of Th2 cell differentiation

Ikaros, a hematopoietic transcription factor, has well defined effects on early lymphocyte development in the bone marrow and thymus. In this study we demonstrate that Ikaros is a positive regulator of Th2 cytokine gene expression in peripheral T cells. CD4+ T cells from naive Ikaros(null) mice cultured under Th2-skewing conditions express the Th1 cytokine IFN-gamma and have reduced IL-4, IL-5, and IL-13 expression. Ikaros directly associates with several Th2 locus regulatory regions in naive CD4+ T cells. The decreased ability to express Th2 cytokines in Ikaros(null)T cells corresponds with histone 3 hypoacetylation across the Th2 cytokine locus as well as decreased GATA3 and cMaf and increased T-bet and STAT1 expression. These data support a model whereby Ikaros directly activates Th2 gene expression by promoting local chromatin accessibility during CD4+ T cell differentiation and also acts indirectly to regulate expression of Th2- and Th1-specific transcription factors.

Tpl2 kinase regulates T cell interferon-gamma production and host resistance to Toxoplasma gondii

Tpl2 (Tumor progression locus 2), also known as Cot/MAP3K8, is a hematopoietically expressed serine-threonine kinase. Tpl2 is known to have critical functions in innate immunity in regulating tumor necrosis factor–α, Toll-like receptor, and G protein–coupled receptor signaling; however, our understanding of its physiological role in T cells is limited. We investigated the potential roles of Tpl2 in T cells and found that it was induced by interleukin-12 in human and mouse T cells in a Stat4-dependent manner. Deficiency of Tpl2 was associated with impaired interferon (IFN)-γ production. Accordingly, Tpl2^−/− mice had impaired host defense against Toxoplasma gondii with reduced parasite clearance and decreased IFN-γ production. Furthermore, reconstitution of Rag2^−/− mice with Tpl2-deficient T cells followed by T. gondii infection recapitulated the IFN-γ defect seen in the Tpl2-deficient mice, confirming a T cell–intrinsic defect. CD4⁺ T cells isolated from Tpl2^−/− mice showed poor induction of T-bet and failure to up-regulate Stat4 protein, which is associated with impaired TCR-dependent extracellular signal-regulated kinase activation. These data underscore the role of Tpl2 as a regulator of T helper cell lineage decisions and demonstrate that Tpl2 has an important functional role in the regulation of Th1 responses.

Janus-kinase-3-dependent signals induce chromatin remodeling at the Ifng locus during T helper 1 cell differentiation

Differentiation of naive CD4+ T cells into T helper type 1 (Th1) effector cells requires both T cell receptor (TCR) signaling and cytokines such as interleukin-12 and interferon gamma (IFN-gamma). Here, we report that a third cytokine signal, mediated by the Janus family tyrosine kinase 3 (Jak3) and signal transducer and activator of transcription 5 (STAT5) pathway, is also required for Th1 cell differentiation. In the absence of Jak3-dependent signals, naive CD4+ T cells proliferate robustly but produce little IFN-gamma after Th1 cell polarization in vitro. This defect is not due to reduced activation of STAT1 or STAT4 or to impaired upregulation of the transcription factor T-bet. Instead, we find that T-bet binding to the Ifng promoter is greatly diminished in the absence of Jak3-dependent signals, correlating with a decrease in Ifng promoter accessibility and histone acetylation. These data indicate that Jak3 regulates epigenetic modification and chromatin remodeling of the Ifng locus during Th1 cell differentiation.

Hematopoietic-specific Stat5-null mice display microcytic hypochromic anemia associated with reduced transferrin receptor gene expression

Iron is essential for all cells but is toxic in excess, so iron absorption and distribution are tightly regulated. Serum iron is bound to transferrin and enters erythroid cells primarily via receptor-mediated endocytosis of the transferrin receptor (Tfr1). Tfr1 is essential for developing erythrocytes and reduced Tfr1 expression is associated with anemia. The transcription factors STAT5A/B are activated by many cytokines, including erythropoietin. Stat5a/b(-/-) mice are severely anemic and die perinatally, but no link has been made to iron homeostasis. To study the function of STAT5A/B in vivo, we deleted the floxed Stat5a/b locus in hematopoietic cells with a Tie2-Cre transgene. These mice exhibited microcytic, hypochromic anemia, as did lethally irradiated mice that received a transplant of Stat5a/b(-/-) fetal liver cells. Flow cytometry and RNA analyses of erythroid cells from mutant mice revealed a 50% reduction in Tfr1 mRNA and protein. We detected STAT5A/B binding sites in the first intron of the Tfr1 gene and found that expression of constitutively active STAT5A in an erythroid cell line increased Tfr1 levels. Chromatin immunoprecipitation experiments confirmed the binding of STAT5A/B to these sites. We conclude that STAT5A/B is an important regulator of iron update in erythroid progenitor cells via its control of Tfr1 transcription.

An insight into molecular mechanisms of human T helper cell differentiation

Selective activation of T helper (Th) cell subsets plays an important role in immune response to pathogens as well as in the pathogenesis of human allergy and inflammatory diseases. Th1 cells along with the recently discovered Th17 cells play a role in the pathogenesis of autoimmune diseases. Th2 cytokines lead to series of inflammatory processes characteristic for asthma and other atopic diseases. To understand the pathogenesis of immune-mediated diseases it is crucial to dissect pathways and regulatory networks leading to the development of distinct Th subsets. Such knowledge may lead to better strategies for developing diagnostics and therapies for these diseases. The differentiation of Th1, Th2, and Th17 effector cells is driven by signals originating from T cell and costimulatory receptors as well as cytokines in the surroundings of activated naive T helper cells. There are several proteins involved in the regulation of this differentiation process. Most of the data on T helper cell differentiation have been acquired using mouse. In this review, we have summarized what is known about human T helper differentiation. In addition, selected differences between human and mouse will be discussed.

Nonredundant roles for Stat5a/b in directly regulating Foxp3

Stats (signal transducers and activators of transcription) regulate multiple aspects of T-cell fate. T regulatory (Treg) cells are a critical subset that limits immune responses, but the relative importance of Stat5a/b versus Stat3 for Treg cell development has been contentious. We observed that peripheral CD25(+)CD4(+) T cells were reduced in Stat5(DeltaN) mice; however, the levels of Foxp3, a transcription factor that is critical for Treg cells, were normal in splenic CD4(+) T cells even though they were reduced in the thymus. In contrast, complete deletion of Stat5a/b (Stat5(-/-)) resulted in dramatic reduction in CD25- or Foxp3-expressing CD4(+) T cells. An intrinsic requirement was demonstrated by reduction of Stat5a/b in CD4-expressing cells and by stem cell transplantation using Stat5(-/-) fetal liver cells. Stat5a/b were also required for optimal induction of Foxp3 in vitro and bound directly to the Foxp3 gene. Reduction of Stat3 in T cells did not reduce the numbers of Treg cells in the thymus or spleen; however, Stat3 was required for IL-6-dependent down-regulation of Foxp3. Therefore, we conclude that Stat5a/b have an essential, nonredundant role in regulating Treg cells, and that Stat3 and Stat5a/b appear to have opposing roles in the regulation of Foxp3.

Stat4 limits DNA methyltransferase recruitment and DNA methylation of the IL-18Ralpha gene during Th1 differentiation

Stat4 is required for Th1 development, although how a transiently activated factor generates heritable patterns of gene expression is still unclear. We examined the regulation of IL-18Ralpha expression to define a mechanism for Stat4-dependent genetic programming of a Th1-associated gene. Although Stat4 binds the Il18r1 promoter following IL-12 stimulation and transiently increases acetylated histones H3 and H4, patterns of histone acetylation alone in Th1 cells may not be sufficient to explain cell-type-specific patterns of gene expression. The level of DNA methylation and recruitment of Dnmt3a to Il18r1 inversely correlate with IL-18Ralpha expression, and blocking DNA methylation increases IL-18Ralpha expression. Moreover, there was decreased Il18r1-Dnmt3a association and DNA methylation following transient trichostatin A-induced histone hyperacetylation in Stat4-/-Th1 cultures. Increased association of Dnmt3a and the Dnmt3a cofactor Dnmt3L with the promoters of several Stat4-dependent genes was found in Stat4-/- Th1 cultures, providing a general mechanism for Stat4-dependent gene programming. These data support a mechanism wherein the transient hyperacetylation induced by Stat4 prevents the recruitment of DNA methyltransferases and the subsequent repression of the Il18r1 locus.