Opposing roles of STAT4 and Dnmt3a in Th1 gene regulation

Intrinsic sexual dimorphism in the placenta determines the differential response to benzene exposure

Maternal immune activation (MIA) by environmental challenges is linked to severe developmental complications, such as neurocognitive disorders, autism, and even fetal/maternal death. Benzene is a major toxic compound in air pollution that affects the mother as well as the fetus and has been associated with reproductive complications. Our objective was to elucidate whether benzene exposure during gestation triggers MIA and its impact on fetal development. We report that benzene exposure during pregnancy leads MIA associated with increased fetal resorptions, fetal growth, and abnormal placenta development. Furthermore, we demonstrate the existence of a sexual dimorphic response to benzene exposure in male and female placentas. The sexual dimorphic response is a consequence of inherent differences between male and female placenta. These data provide crucial information on the origins or sexual dimorphism and how exposure to environmental factors can have a differential impact on the development of male and female offspring.

A new risk factor associated with cardiovascular disease: clonal hematopoiesis of indeterminate potential

Clonal hematopoiesis is a prevalent disease associated with all-cause death. Not only because it can be a precancerous lesion of blood system diseases but also has a strong association with cardiovascular disease. A narrow term, clonal hematopoiesis of indeterminate potential (CHIP), was proposed by Steensma et al. [1] to describe individuals with detectable somatic clonal mutations in their genes in blood or bone marrow but without a diagnosis of hematological disease or unexplained cytopenia. Recently, studies have suggested that CHIP is associated with adverse cardiovascular disease progression, particularly in patients with ten-eleven translocation 2 (TET2) mutations or DNA methyltransferase 3 alpha (DNMT3A) mutations. Age is the most crucial factor which is associated with increased CHIP prevalence. The underlying mechanisms appear to be related to inflammatory status. However, new evidence suggests that genetic factors, lifestyle and environmental factors such as smoking, obesity, and diet also play essential roles in developing CHIP. More research needs to be done on the potential genetic mechanisms driving CHIP and the environmental factors that modulate CHIP risk. This review summarizes the latest research on CHIP, discusses in detail the strong association between clonal hematopoiesis and accelerated cardiovascular disease, and rationalizes the intervention of CHIP in combination with existing evidence, which may be beneficial for future treatment.

Emerging Role of Acquired Mutations and Clonal Hematopoiesis in Atherosclerosis - Beyond Conventional Cardiovascular Risk Factors

Accumulating evidence suggests that conventional cardiovascular risk factors are incompletely predictive of cardiovascular disease, as a substantial risk remains even when these factors are apparently managed well. In this context, clonal hematopoiesis has emerged as a new and potent risk factor for atherosclerotic cardiovascular disease and other cardiometabolic conditions. Clonal hematopoiesis typically arises from somatic mutations that confer a competitive advantage to a mutant hematopoietic stem cell, leading to its clonal expansion in the stem cell population and its progeny of blood leukocytes. Human sequencing studies and experiments in mice suggest that clonal hematopoiesis, at least when driven by certain mutations, contributes to accelerated atherosclerosis development. However, the epidemiology, biology and clinical implications of this phenomenon remain incompletely understood. Here, we review the current understanding of the connection between clonal hematopoiesis and atherosclerosis, and highlight knowledge gaps in this area of research.

Clonal hematopoiesis, somatic mosaicism, and age-associated disease

Somatic mosaicism, the occurrence of multiple genetically distinct cell clones within the same tissue, is an evitable consequence of human aging. The hematopoietic system is no exception to this, where studies have revealed the presence of expanded blood cell clones carrying mutations in preleukemic driver genes and/or genetic alterations in chromosomes. This phenomenon is referred to as clonal hematopoiesis and is remarkably prevalent in elderly individuals. While clonal hematopoiesis represents an early step toward a hematological malignancy, most individuals will never develop blood cancer. Somewhat unexpectedly, epidemiological studies have found that clonal hematopoiesis is associated with an increase in the risk of all-cause mortality and age-related disease, particularly in the cardiovascular system. Studies using murine models of clonal hematopoiesis have begun to shed light on this relationship, suggesting that driver mutations in mature blood cells can causally contribute to aging and disease by augmenting inflammatory processes. Here we provide an up-to-date review of clonal hematopoiesis within the context of somatic mosaicism and aging and describe recent epidemiological studies that have reported associations with age-related disease. We will also discuss the experimental studies that have provided important mechanistic insight into how driver mutations promote age-related disease and how this knowledge could be leveraged to treat individuals with clonal hematopoiesis.

DNMT3A mutations define a unique biological and prognostic subgroup associated with cytotoxic T cells in PTCL-NOS

Peripheral T-cell lymphomas (PTCLs) are heterogenous T-cell neoplasms often associated with epigenetic dysregulation. We investigated de novo DNA methyltransferase 3A (DNMT3A) mutations in common PTCL entities, including angioimmunoblastic T-cell lymphoma and novel molecular subtypes identified within PTCL-not otherwise specified (PTCL-NOS) designated as PTCL-GATA3 and PTCL-TBX21. DNMT3A-mutated PTCL-TBX21 cases showed inferior overall survival (OS), with DNMT3A-mutated residues skewed toward the methyltransferase domain and dimerization motif (S881-R887). Transcriptional profiling demonstrated significant enrichment of activated CD8+ T-cell cytotoxic gene signatures in the DNMT3A-mutant PTCL-TBX21 cases, which was further validated using immunohistochemistry. Genomewide methylation analysis of DNMT3A-mutant vs wild-type (WT) PTCL-TBX21 cases demonstrated hypomethylation in target genes regulating interferon-γ (IFN-γ), T-cell receptor signaling, and EOMES (eomesodermin), a master transcriptional regulator of cytotoxic effector cells. Similar findings were observed in a murine model of PTCL with Dnmt3a loss (in vivo) and further validated in vitro by ectopic expression of DNMT3A mutants (DNMT3A-R882, -Q886, and -V716, vs WT) in CD8+ T-cell line, resulting in T-cell activation and EOMES upregulation. Furthermore, stable, ectopic expression of the DNMT3A mutants in primary CD3+ T-cell cultures resulted in the preferential outgrowth of CD8+ T cells with DNMT3AR882H mutation. Single-cell RNA sequencing(RNA-seq) analysis of CD3+ T cells revealed differential CD8+ T-cell subset polarization, mirroring findings in DNMT3A-mutated PTCL-TBX21 and validating the cytotoxic and T-cell memory transcriptional programs associated with the DNMT3AR882H mutation. Our findings indicate that DNMT3A mutations define a cytotoxic subset in PTCL-TBX21 with prognostic significance and thus may further refine pathological heterogeneity in PTCL-NOS and suggest alternative treatment strategies for this subset.

JMJD family proteins in cancer and inflammation

The occurrence of cancer entails a series of genetic mutations that favor uncontrollable tumor growth. It is believed that various factors collectively contribute to cancer, and there is no one single explanation for tumorigenesis. Epigenetic changes such as the dysregulation of enzymes modifying DNA or histones are actively involved in oncogenesis and inflammatory response. The methylation of lysine residues on histone proteins represents a class of post-translational modifications. The human Jumonji C domain-containing (JMJD) protein family consists of more than 30 members. The JMJD proteins have long been identified with histone lysine demethylases (KDM) and histone arginine demethylases activities and thus could function as epigenetic modulators in physiological processes and diseases. Importantly, growing evidence has demonstrated the aberrant expression of JMJD proteins in cancer and inflammatory diseases, which might serve as an underlying mechanism for the initiation and progression of such diseases. Here, we discuss the role of key JMJD proteins in cancer and inflammation, including the intensively studied histone lysine demethylases, as well as the understudied group of JMJD members. In particular, we focused on epigenetic changes induced by each JMJD member and summarized recent research progress evaluating their therapeutic potential for the treatment of cancer and inflammatory diseases.

DNA methyltransferase 3 alpha and TET methylcytosine dioxygenase 2 restrain mitochondrial DNA-mediated interferon signaling in macrophages

Deleterious somatic mutations in DNA methyltransferase 3 alpha (DNMT3A) and TET mehtylcytosine dioxygenase 2 (TET2) are associated with clonal expansion of hematopoietic cells and higher risk of cardiovascular disease (CVD). Here, we investigated roles of DNMT3A and TET2 in normal human monocyte-derived macrophages (MDM), in MDM isolated from individuals with DNMT3A or TET2 mutations, and in macrophages isolated from human atherosclerotic plaques. We found that loss of function of DNMT3A or TET2 resulted in a type I interferon response due to impaired mitochondrial DNA integrity and activation of cGAS signaling. DNMT3A and TET2 normally maintained mitochondrial DNA integrity by regulating the expression of transcription factor A mitochondria (TFAM) dependent on their interactions with RBPJ and ZNF143 at regulatory regions of the TFAM gene. These findings suggest that targeting the cGAS-type I IFN pathway may have therapeutic value in reducing risk of CVD in patients with DNMT3A or TET2 mutations.

Somatic Mutations of Hematopoietic Cells Are an Additional Mechanism of Body Aging, Conducive to Comorbidity and Increasing Chronification of Inflammation

It is known that the development of foci of chronic inflammation usually accompanies body aging. In these foci, senescent cells appear with a pro-inflammatory phenotype that helps maintain inflammation. Their removal with the help of senolytics significantly improves the general condition of the body and, according to many indicators, contributes to rejuvenation. The cells of the immune system participate in the initiation, development, and resolution of inflammation. With age, the human body accumulates mutations, including the cells of the bone marrow, giving rise to the cells of the immune system. We assume that a number of such mutations formed with age can lead to the appearance of “naive” cells with an initially pro-inflammatory phenotype, the migration of which to preexisting foci of inflammation contributes not to the resolution of inflammation but its chronicity. One of such cell variants are monocytes carrying mitochondrial mutations, which may be responsible for comorbidity and deterioration in the prognosis of the course of pathologies associated with aging, such as atherosclerosis, arthritis, osteoporosis, and neurodegenerative diseases.

Clonal hematopoiesis driven by DNMT3A and TET2 mutations: role in monocyte and macrophage biology and atherosclerotic cardiovascular disease

PURPOSE OF REVIEW

Clonal hematopoiesis of indeterminate potential (CHIP), defined by the presence of somatic mutations in hematopoietic cells, is associated with advanced age and increased mortality due to cardiovascular disease. Gene mutations in DNMT3A and TET2 are the most frequently identified variants among patients with CHIP and provide selective advantage that spurs clonal expansion and myeloid skewing. Although DNMT3A and TET2 appear to have opposing enzymatic influence on DNA methylation, mounting data has characterized convergent inflammatory pathways, providing insights to how CHIP may mediate atherosclerotic cardiovascular disease (ASCVD).

RECENT FINDINGS

We review a multitude of studies that characterize aberrant inflammatory signaling as result of DNMT3A and TET2 deficiency in monocytes and macrophages, immune cells with prominent roles in atherosclerosis. Although specific DNA methylation signatures associated with these known epigenetic regulators have been identified, many studies have also characterized diverse modulatory functions of DNTM3A and TET2 that urge cell and context-specific experimental studies to further define how DNMT3A and TET2 may nonenzymatically activate inflammatory pathways with clinically meaningful consequences.

SUMMARY

CHIP, common in elderly individuals, provides an opportunity understand and potentially modify age-related chronic inflammatory ASCVD risk.

Histone 3 Lysine 27 Trimethylation Signature in Breast Cancer

Cancer development and progression rely on complicated genetic and also epigenetic changes which regulate gene expression without altering the DNA sequence. Epigenetic mechanisms such as DNA methylation, histone modifications, and regulation by lncRNAs alter protein expression by either promoting gene transcription or repressing it. The presence of so-called chromatin modification marks at various gene promoters and gene bodies is associated with normal cell development but also with tumorigenesis and progression of different types of cancer, including the most frequently diagnosed breast cancer. This review is focused on the significance of one of the abundant post-translational modifications of histone 3- trimethylation of lysine 27 (H3K27me3), which was shown to participate in tumour suppressor genes' silencing. Unlike other reviews in the field, here the overview of existing evidence linking H3K27me3 status with breast cancer biology and the tumour outcome is presented especially in the context of diverse breast cancer subtypes. Moreover, the potential of agents that target H3K27me3 for the treatment of this complex disease as well as H3K27 methylation in cross-talk with other chromatin modifications and lncRNAs are discussed.

A feedback loop: Interactions between Inflammatory Signals and Clonal Hematopoiesis in Cardiovascular Disease

Age and inflammation are powerful drivers of cardiovascular disease. With the growing recognition that traditional cardiovascular risk factors are not fully accurate predictors of cardiovascular disease, recent studies have revealed the prevalence of positive selection of somatic cell mutations in hematopoietic stem cells in the elderly population, which can cause clonal hematopoiesis. Interestingly, clonal hematopoiesis is not only associated with cancer and death, but also closely related to the risk of increased cardiovascular disease due to mutations in TET2, DNMT3A, ASXL1, and JAK2. However, the mechanism of the interaction of clonal hematopoiesis and cardiovascular disease is only partially understood. In mice, somatic mutations have led to significantly increased expression of inflammatory genes in innate immune cells, which may explain the relationship between mutations and cardiovascular disease. Here, we further discuss the association between inflammatory signaling, clonal hematopoiesis, and cardiovascular disease,and using two hypotheses to propose a feedback loop between inflammatory signaling and clonal hematopoiesis for getting insight into the pathogenesis of cardiovascular diseases in depth. Therapies targeting mutant clones or increased inflammatory mediators may be useful for ameliorating the risk of cardiovascular disease.

DNA Methylation in T-Cell Acute Lymphoblastic Leukemia: In Search for Clinical and Biological Meaning

Distinct DNA methylation signatures, related to different prognosis, have been observed across many cancers, including T-cell acute lymphoblastic leukemia (T-ALL), an aggressive hematological neoplasm. By global methylation analysis, two major phenotypes might be observed in T-ALL: hypermethylation related to better outcome and hypomethylation, which is a candidate marker of poor prognosis. Moreover, DNA methylation holds more than a clinical meaning. It reflects the replicative history of leukemic cells and most likely different mechanisms underlying leukemia development in these T-ALL subtypes. The elucidation of the mechanisms and aberrations specific to (epi-)genomic subtypes might pave the way towards predictive diagnostics and precision medicine in T-ALL. We present the current state of knowledge on the role of DNA methylation in T-ALL. We describe the involvement of DNA methylation in normal hematopoiesis and T-cell development, focusing on epigenetic aberrations contributing to this leukemia. We further review the research investigating distinct methylation phenotypes in T-ALL, related to different outcomes, pointing to the most recent research aimed to unravel the biological mechanisms behind differential methylation. We highlight how technological advancements facilitated broadening the perspective of the investigation into DNA methylation and how this has changed our understanding of the roles of this epigenetic modification in T-ALL.

AP-1 activity induced by co-stimulation is required for chromatin opening during T cell activation

Activation of T cells is dependent on the organized and timely opening and closing of chromatin. Herein, we identify AP-1 as the transcription factor that directs most of this remodeling. Chromatin accessibility profiling showed quick opening of closed chromatin in naive T cells within 5 h of activation. These newly opened regions were strongly enriched for the AP-1 motif, and indeed, ChIP-seq demonstrated AP-1 binding at >70% of them. Broad inhibition of AP-1 activity prevented chromatin opening at AP-1 sites and reduced the expression of nearby genes. Similarly, induction of anergy in the absence of co-stimulation during activation was associated with reduced induction of AP-1 and a failure of proper chromatin remodeling. The translational relevance of these findings was highlighted by the substantial overlap of AP-1-dependent elements with risk loci for multiple immune diseases, including multiple sclerosis, inflammatory bowel disease, and allergic disease. Our findings define AP-1 as the key link between T cell activation and chromatin remodeling.

IL-12 Signaling Contributes to the Reprogramming of Neonatal CD8+ T Cells

Neonates are highly susceptible to intracellular pathogens, leading to high morbidity and mortality rates. CD8⁺ T lymphocytes are responsible for the elimination of infected cells. Understanding the response of these cells to normal and high stimulatory conditions is important to propose better treatments and vaccine formulations for neonates. We have previously shown that human neonatal CD8⁺ T cells overexpress innate inflammatory genes and have a low expression of cytotoxic and cell signaling genes. To investigate the activation potential of these cells, we evaluated the transcriptome of human neonatal and adult naïve CD8⁺ T cells after TCR/CD28 signals ± IL-12. We found that in neonatal cells, IL-12 signals contribute to the adult-like expression of genes associated with cell-signaling, T-cell cytokines, metabolism, and cell division. Additionally, IL-12 signals contributed to the downregulation of the neutrophil signature transcription factor CEBPE and other immaturity related genes. To validate the transcriptome results, we evaluated the expression of a series of genes by RT-qPCR and the promoter methylation status on independent samples. We found that in agreement with the transcriptome, IL-12 signals contributed to the chromatin closure of neutrophil-like genes and the opening of cytotoxicity genes, suggesting that IL-12 signals contribute to the epigenetic reprogramming of neonatal lymphocytes. Furthermore, high expression of some inflammatory genes was observed in naïve and stimulated neonatal cells, in agreement with the high inflammatory profile of neonates to infections. Altogether our results point to an important contribution of IL-12 signals to the reprogramming of the neonatal CD8⁺ T cells.

Jumonji domain containing-3 (JMJD3) inhibition attenuates IL-1β-induced chondrocytes damage in vitro and protects osteoarthritis cartilage in vivo

OBJECTIVES

This study aimed to explore the effects and relative mechanism of JMJD3 on knee osteoarthritis (OA).

METHODS

In this study, we first analyzed the expression of JMJD3 in OA cartilage using western blot and immunohistochemistry. In an in vitro study, the effects of GSK-J4, JMJD3 inhibitor, on ATDC-5 chondrocytes were evaluated by CCK-8 assay. Real-time PCR and western blot were used to examine the inhibitory effect of GSK-J4 on the inflammation and ECM degradation of chondrocytes. NF-κB p65 phosphorylation and nuclear translocation were measured by western blot and immunofluorescence. In the animal study, twenty mice were randomized into four experimental groups: sham group, DMM-induced OA + DMSO group, OA + low-dose GSK-J4 group, and OA + high-dose GSK-J4 group. After the treatment, hematoxylin-eosin and safranin O/fast green staining were used to evaluate cartilage degradation of knee joint, with OARSI scores for quantitative assessment of cartilage damage.

RESULTS

Our results revealed that JMJD3 was overexpressed in OA cartilage and GSK-J4 could suppress the IL-1β-induced production of pro-inflammatory cytokines and catabolic enzymes, including IL-6, IL-8, MMP-9 and ADAMTS-5. Consistent with these findings, GSK-J4 could inhibit IL-1β-induced degradation of collagen II and aggrecan. Mechanistically, GSK-J4 dramatically suppressed IL-1β-stimulated NF-κB signal pathway activation. In vivo, GSK-J4 prevented cartilage damage in mouse DMM-induced OA model.

CONCLUSIONS

This study elucidates the important role of JMJD3 in cartilage degeneration in OA, and our results indicate that JDJM3 may become a novel therapeutic target in OA therapy.

Clonal hematopoiesis driven by somatic mutations: A new player in atherosclerotic cardiovascular disease

The accumulation of acquired mutations is an inevitable consequence of the aging process, but its pathophysiological relevance has remained largely unexplored beyond cancer. Most of these mutations have little or no functional consequences, but in a few rare instances, a mutation may arise that confers a competitive advantage to a stem cell, leading to its clonal expansion. When such a mutation occurs in hematopoietic stem cells, it leads to a situation of clonal hematopoiesis, which has the potential to affect multiple tissues beyond the bone marrow, as the clonal expansion of the mutant stem cell is extended to circulating blood cells and tissue-infiltrating immune cells. Recent genomics and experimental studies have provided support to the notion that this somatic mutation-driven clonal hematopoiesis contributes to vascular inflammation and the development of atherosclerosis and related cardiovascular and cerebrovascular ischemic events. Here, we review our current understanding of this emerging cardiovascular risk modifier and the mechanisms underlying its connection to atherosclerosis development.

Upregulation of H3K27 Demethylase KDM6 During Respiratory Syncytial Virus Infection Enhances Proinflammatory Responses and Immunopathology

Severe disease following respiratory syncytial virus (RSV) infection has been linked to enhanced proinflammatory cytokine production that promotes a Th2-type immune environment. Epigenetic regulation in immune cells following viral infection plays a role in the inflammatory response and may result from upregulation of key epigenetic modifiers. In this study, we show that RSV-infected bone marrow-derived dendritic cells (BMDC) as well as pulmonary dendritic cells (DC) from RSV-infected mice upregulated the expression of Kdm6b/Jmjd3 and Kdm6a/Utx, H3K27 demethylases. KDM6-specific chemical inhibition (GSK J4) in BMDC led to decreased production of chemokines and cytokines associated with the inflammatory response during RSV infection (i.e., CCL-2, CCL-3, CCL-5, IL-6) as well as decreased MHC class II and costimulatory marker (CD80/86) expression. RSV-infected BMDC treated with GSK J4 altered coactivation of T cell cytokine production to RSV as well as a primary OVA response. Airway sensitization of naive mice with RSV-infected BMDCs exacerbate a live challenge with RSV infection but was inhibited when BMDCs were treated with GSK J4 prior to sensitization. Finally, in vivo treatment with the KDM6 inhibitor, GSK J4, during RSV infection reduced inflammatory DC in the lungs along with IL-13 levels and overall inflammation. These results suggest that KDM6 expression in DC enhances proinflammatory innate cytokine production to promote an altered Th2 immune response following RSV infection that leads to more severe immunopathology.

JMJD3 in the regulation of human diseases

In recent years, many studies have shown that histone methylation plays an important role in maintaining the active and silent state of gene expression in human diseases. The Jumonji domain-containing protein D3 (JMJD3), specifically demethylate di- and trimethyl-lysine 27 on histone H3 (H3K27me2/3), has been widely studied in immune diseases, infectious diseases, cancer, developmental diseases, and aging related diseases. We will focus on the recent advances of JMJD3 function in human diseases, and looks ahead to the future of JMJD3 gene research in this review.

Cardiovascular Disease, Aging, and Clonal Hematopoiesis

Traditional risk factors are incompletely predictive of cardiovascular disease development, a leading cause of death in the elderly. Recent epidemiological studies have shown that human aging is associated with an increased frequency of somatic mutations in the hematopoietic system, which provide a competitive advantage to a mutant cell, thus allowing for its clonal expansion, a phenomenon known as clonal hematopoiesis. Unexpectedly, these mutations have been associated with a higher incidence of cardiovascular disease, suggesting a previously unrecognized connection between somatic mutations in hematopoietic cells and cardiovascular disease. Here, we provide an up-to-date review of clonal hematopoiesis and its association with aging and cardiovascular disease. We also give a detailed report of the experimental studies that have been instrumental in understanding the relationship between clonal hematopoiesis and cardiovascular disease and have shed light on the mechanisms by which hematopoietic somatic mutations contribute to disease pathology.

Somatic Mutations and Clonal Hematopoiesis: Unexpected Potential New Drivers of Age-Related Cardiovascular Disease

Increasing evidence shows that conventional cardiovascular risk factors are incompletely predictive of cardiovascular disease, particularly in elderly individuals, suggesting that there may still be unidentified causal risk factors. Although the accumulation of somatic DNA mutations is a hallmark of aging, its relevance in cardiovascular disease or other age-related conditions has been, with the exception of cancer, largely unexplored. Here, we review recent clinical and preclinical studies that have identified acquired mutations in hematopoietic stem cells and subsequent clonal hematopoiesis as a new cardiovascular risk factor and a potential major driver of atherosclerosis. Understanding the mechanisms underlying the connection between somatic mutation-driven clonal hematopoiesis and cardiovascular disease will be highly relevant in the context of personalized medicine, as it may provide key information for the design of diagnostic, preventive, or therapeutic strategies tailored to the effects of specific somatic mutations.

Regulation of T cell differentiation and function by epigenetic modification enzymes

Peripheral naive CD4⁺ and CD8⁺ cells are developed in the thymus and proliferate and differentiate into various specialized T cell subsets upon activation by peptide-major histocompatibility complexes in periphery to execute different functions during immune responses. Cytokines, transcription factors, and a large number of intracellular molecules have been shown to affect T cell development, activation, and function. In addition, epigenetic modifications, such as histone modification and DNA methylation, regulate T cell biology. The epigenetic modifications are regulated by a range of DNA methyltransferases, DNA demethylation enzymes, and histone modification enzymes. Dysregulations of epigenetic modifications are closely associated with autoimmune diseases and tumorigenesis. Here, we review the current literature about the functions of DNA and histone modification enzymes in T cell development, activation, differentiation, and function.

Role of IL-18 induced Amphiregulin expression on virus induced ocular lesions

This report deals with the possible mechanism by which IL-18 can contribute to the control and resolution of inflammatory lesions in the cornea caused by herpes simplex virus infection. Our results demonstrate that the expression of the IL-18R by both regulatory T cells (Treg) and effector T cells was a pivotal event that influenced lesion pathogenesis. The engagement of IL-18R on Treg with its cytokine ligand resulted in Amphiregulin expression a molecule associated with tissue repair. In support of this scheme of events, lesion severity became more severe in animals unable to express the IL-18R because of gene knockout and was reduced in severity when IL-18 was overexpressed in the cornea. These changes in lesion severity correlated with the frequency and number of both Treg and Teff that expressed Amphiregulin. Additional experiments indicated that IL-12 and IL-18 acted synergistically to enhance Amphiregulin expression in Treg, an event partly dependent on P38 MAPK activity. Finally, sub-conjunctival administration of Amphiregulin resulted in resolution of both developing and developed lesions. Thus, overall our results imply that IL-18 may participate in controlling the severity of SK and contribute to tissue repair by converting both Treg and effector T cells into those that produce Amphiregulin.

Notch-effector CSL promotes squamous cell carcinoma by repressing histone demethylase KDM6B

Notch 1/2 genes play tumor-suppressing functions in squamous cell carcinoma (SCC), a very common malignancy in skin and internal organs. In contrast with Notch, we show that the transcription factor CSL (also known as RBP-Jκ), a key effector of canonical Notch signaling endowed with intrinsic transcription-repressive functions, plays a tumor-promoting function in SCC development. Expression of this gene decreased in upper epidermal layers and human keratinocytes (HKCs) undergoing differentiation, while it increased in premalignant and malignant SCC lesions from skin, head/neck, and lung. Increased CSL levels enhanced the proliferative potential of HKCs and SCC cells, while silencing of CSL induced growth arrest and apoptosis. In vivo, SCC cells with increased CSL levels gave rise to rapidly expanding tumors, while cells with silenced CSL formed smaller and more differentiated tumors with enhanced inflammatory infiltrate. Global transcriptomic analysis of HKCs and SCC cells with silenced CSL revealed major modulation of apoptotic, cell-cycle, and proinflammatory genes. We also show that the histone demethylase KDM6B is a direct CSL-negative target, with inverse roles of CSL in HKC and SCC proliferative capacity, tumorigenesis, and tumor-associated inflammatory reaction. CSL/KDM6B protein expression could be used as a biomarker of SCC development and indicator of cancer treatment.

Expression of the p66Shc protein adaptor is regulated by the activator of transcription STAT4 in normal and chronic lymphocytic leukemia B cells

p66Shc attenuates mitogenic, prosurvival and chemotactic signaling and promotes apoptosis in lymphocytes. Consistently, p66Shc deficiency contributes to the survival and trafficking abnormalities of chronic lymphocytic leukemia (CLL) B cells. The mechanism of p66shc silencing in CLL B cells is methylation-independent, at variance with other cancer cell types. Here we identify STAT4 as a novel transcriptional regulator of p66Shc in B cells. Chromatin immunoprecipitation and reporter gene assays showed that STAT4 binds to and activates the p66shc promoter. Silencing or overexpression of STAT4 resulted in a co-modulation of p66Shc. IL-12-dependent STAT4 activation caused a coordinate increase in STAT4 and p66Shc expression, which correlated with enhanced B cell apoptosis. Treatment with the STAT4 inhibitor lisofylline reverted partly this effect, suggesting that STAT4 phosphorylation is not essential for but enhances p66shc transcription. Additionally, we demonstrate that CLL B lymphocytes have a STAT4 expression defect which partly accounts for their p66Shc deficiency, as supported by reconstitution experiments. Finally, we show that p66Shc participates in a positive feedback loop to promote STAT4 expression. These results provide new insights into the mechanism of p66Shc expression in B cells and its defect in CLL, identifying the STAT4/IL-12 pathway as a potential therapeutic target in this neoplasia.

Connections Between Metabolism and Epigenetics in Programming Cellular Differentiation

Researchers are intensifying efforts to understand the mechanisms by which changes in metabolic states influence differentiation programs. An emerging objective is to define how fluctuations in metabolites influence the epigenetic states that contribute to differentiation programs. This is because metabolites such as S-adenosylmethionine, acetyl-CoA, α-ketoglutarate, 2-hydroxyglutarate, and butyrate are donors, substrates, cofactors, and antagonists for the activities of epigenetic-modifying complexes and for epigenetic modifications. We discuss this topic from the perspective of specialized CD4⁺ T cells as well as effector and memory T cell differentiation programs. We also highlight findings from embryonic stem cells that give mechanistic insight into how nutrients processed through pathways such as glycolysis, glutaminolysis, and one-carbon metabolism regulate metabolite levels to influence epigenetic events and discuss similar mechanistic principles in T cells. Finally, we highlight how dysregulated environments, such as the tumor microenvironment, might alter programming events.

Bcl6 promotes follicular helper T-cell differentiation and PD-1 expression in a Blimp1-independent manner in mice

The transcription factors Bcl6 and Blimp1 have opposing roles in the development of the follicular helper T (T_FH ) cells: Bcl6 promotes and Blimp1 inhibits T_FH -cell differentiation. Similarly, Bcl6 activates, while Blimp1 represses, expression of the T_FH -cell marker PD-1. However, Bcl6 and Blimp1 repress each other's expression, complicating the interpretation of the regulatory network. Here we sought to clarify the extent to which Bcl6 and Blimp1 independently control T_FH -cell differentiation by generating mice with T-cell specific deletion of both Bcl6 and Blimp1 (double conditional KO [dcKO] mice). Our data indicate that Blimp1 does not control T_FH -cell differentiation independently of Bcl6. However, a population of T follicular regulatory (T_FR ) cells developed independently of Bcl6 in dcKO mice. We have also analyzed regulation of IL-10 and PD-1, two genes controlled by both Bcl6 and Blimp1, and observed that Bcl6 regulates both genes independently of Blimp1. We found that Bcl6 positively regulates PD-1 expression by inhibiting the ability of T-bet/Tbx21 to repress Pdcd1 transcription. Our data provide a novel mechanism for positive control of gene expression by Bcl6, and illuminate how Bcl6 and Blimp1 control T_FH -cell differentiation.

The transcription factor network in Th9 cells

The development of T helper cell subsets requires activated T cells that respond to a polarizing cytokine environment resulting in the activation and expression of transcription factors. The subset-specific transcription factors bind and induce the production of specific effector cytokines. Th9 cells express IL-9 and develop in the presence of TGFβ, IL-4, and IL-2. Each of these cytokines activates signaling pathways that are required for Th9 differentiation and IL-9 production. In this review, I summarize what is currently understood about the signaling pathways and transcription factors that promote the Th9 genetic program, providing some perspective for the integration of the signals in regulating the Il9 gene and dictating the expression of other Th9-associated genes. I highlight how experiments in mouse cells have established a transcriptional network that is conserved in human T cells and set the stage toward defining the next important questions for a more detailed understanding of Th9 cell development and function.

The histone demethylase inhibitor GSK-J4 limits inflammation through the induction of a tolerogenic phenotype on DCs

As it has been established that demethylation of lysine 27 of histone H3 by the lysine-specific demethylase JMJD3 increases immune responses and thus elicits inflammation, we hypothesize that inhibition of JMJD3 may attenuate autoimmune disorders. We found that in vivo administration of GSK-J4, a selective inhibitor of JMJD3 and UTX, ameliorates the severity of experimental autoimmune encephalomyelitis (EAE). In vitro experiments revealed that the anti-inflammatory effect of GSK-J4 was exerted through an effect on dendritic cells (DCs), promoting a tolerogenic profile characterized by reduced expression of costimulatory molecules CD80/CD86, an increased expression of tolerogenic molecules CD103 and TGF-β1, and reduced secretion of proinflammatory cytokines IL-6, IFN-γ, and TNF. Adoptive transfer of GSK-J4-treated DCs into EAE mice reduced the clinical manifestation of the disease and decreased the extent of inflammatory CD4+ T cells infiltrating the central nervous system. Notably, Treg generation, stability, and suppressive activity were all exacerbated by GSK-J4-treated DCs without affecting Th1 and Th17 cell production. Our data show that GSK-J4-mediated modulation of inflammation is achieved by a direct effect on DCs and that systemic treatment with GSK-J4 or adoptive transfer of GSK-J4-treated DCs ex vivo may be promising approaches for the treatment of inflammatory and autoimmune disorders.

TWIST and ovarian cancer stem cells: implications for chemoresistance and metastasis

The transcription factor TWIST1 is a highly evolutionally conserved basic Helix-Loop-Helix (bHLH) transcription factor that functions as a master regulator of gastrulation and mesodermal development. Although TWIST1 was initially associated with embryo development, an increasing number of studies have shown TWIST1 role in the regulation of tissue homeostasis, primarily as a regulator of inflammation. More recently, TWIST1 has been found to be involved in the process of tumor metastasis through the regulation of Epithelial Mesenchymal Transition (EMT). The objective of this review is to examine the normal functions of TWIST1 and its role in tumor development, with a particular focus on ovarian cancer. We discuss the potential role of TWIST1 in the context of ovarian cancer stem cells and its influence in the process of tumor formation.

STAT4 controls GM-CSF production by both Th1 and Th17 cells during EAE

BACKGROUND

In experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis, mice genetically deficient in the transcription factor signal transducer and activator of transcription 4 (STAT4) are resistant to disease. In contrast, deletion or inhibition of the Th1-associated cytokines IL-12 or IFNγ which act upstream and downstream of STAT4, respectively, does not ameliorate disease. These discordant findings imply that STAT4 may act in a non-canonical role during EAE. Recently, STAT4 has been shown to regulate GM-CSF production by CD4 T cells and this cytokine is necessary for the induction of EAE. However, it is not known if STAT4 controls GM-CSF production by both Th1 and Th17 effector CD4 T cells.

METHODS

This study utilized the MOG(35-55) peptide immunization model of EAE. Intracellular cytokine staining and novel mixed bone marrow chimeric mice were used to study the CD4 T cell-intrinsic role of STAT4 during disease. STAT4 chromatin-immunoprecipitation (ChIP-PCR) experiments were performed to show STAT4 directly interacts with the Csf2 gene loci.

RESULTS

Herein, we demonstrate that STAT4 controls CD4 T cell-intrinsic GM-CSF production by both Th1 and Th17 CD4 T cells during EAE as well as in vitro. Importantly, we show that STAT4 interacts with the Csf2 locus in MOG(35-55)-activated effector CD4 T cells demonstrating direct modulation of GM-CSF.

CONCLUSIONS

Overall, these studies illustrate a previously unrecognized role of STAT4 to regulate GM-CSF production by not only Th1 cells, but also Th17 effector CD4 T cell subsets during EAE pathogenesis. Critically, these data highlight for the first time that STAT4 is able to modulate the effector profile of Th17 CD4 T cell subsets, which redefines our current understanding of STAT4 as a Th1-centric factor.

The development and in vivo function of T helper 9 cells

The specialized cytokine secretion profiles of T helper (TH) cells are the basis for a focused and efficient immune response. On the twentieth anniversary of the first descriptions of the cytokine signals that promote the differentiation of interleukin-9 (IL-9)-secreting T cells, this Review focuses on the extracellular signals and the transcription factors that promote the development of what we now term TH9 cells, which are characterized by the production of this cytokine. We summarize our current understanding of the contribution of TH9 cells to both effective immunity and immunopathological disease, and we propose that TH9 cells could be targeted for the treatment of allergic and autoimmune disease.

Critical role of histone demethylase Jmjd3 in the regulation of CD4+ T-cell differentiation

Epigenetic factors have been implicated in the regulation of CD4⁺ T cell differentiation. Jmjd3 plays a role in many biological processes, but its in vivo function in T cell differentiation remains unknown. Here, we report that Jmjd3 ablation promotes CD4⁺ T cell differentiation into Th2 and Th17 cells in the small intestine and colon, and inhibits T cell differentiation into Th1 cells under different cytokine-polarizing conditions and in a Th1-dependent colitis model. Jmjd3 deficiency also restrains the plasticity of the conversion of Th2, Th17 or Treg cells to Th1 cells. The skewing of T cell differentiation is concomitant with changes in the expression of key transcription factors and cytokines. H3K27me3 and H3K4me3 levels in Jmjd3-deficient cells are correlated with altered gene expression through interactions with specific transcription factors. Our results identify Jmjd3 as an epigenetic factor in T cell differentiation via changes in histone methylation and target gene expression.

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.

Protein kinase C θ regulates the phenotype of murine CD4+ Th17 cells

Protein kinase C θ (PKCθ) is involved in signaling downstream of the T cell antigen receptor (TCR) and is important for shaping effector T cell functions and inflammatory disease development. Acquisition of Th1-like effector features by Th17 cells has been linked to increased pathogenic potential. However, the molecular mechanisms underlying Th17/Th1 phenotypic instability remain largely unknown. In the current study, we address the role of PKCθ in differentiation and function of Th17 cells by using genetic knock-out mice. Implementing in vitro (polarizing T cell cultures) and in vivo (experimental autoimmune encephalomyelitis model, EAE) techniques, we demonstrated that PKCθ-deficient CD4⁺ T cells show normal Th17 marker gene expression (interleukin 17A/F, RORγt), accompanied by enhanced production of the Th1-typical markers such as interferon gamma (IFN-γ) and transcription factor T-bet. Mechanistically, this phenotype was linked to aberrantly elevated Stat4 mRNA levels in PKCθ^−/− CD4⁺ T cells during the priming phase of Th17 differentiation. In contrast, transcription of the Stat4 gene was suppressed in Th17-primed wild-type cells. This change in cellular effector phenotype was reflected in vivo by prolonged neurological impairment of PKCθ-deficient mice during the course of EAE. Taken together, our data provide genetic evidence that PKCθ is critical for stabilizing Th17 cell phenotype by selective suppression of the STAT4/IFN-γ/T-bet axis at the onset of differentiation.