Cell-type-specific regulation of the human tumor necrosis factor alpha gene in B cells and T cells by NFATp and ATF-2/JUN

Human γδ T Cell Function Is Impaired Upon Mevalonate Pathway Inhibition

Vδ2 T cells, a predominant human peripheral γδ T cell population, are a promising candidate for the development of immunotherapies against cancer and infected cells. Aminobisphosphonate drugs, such as zoledronate, are commonly used to expand Vδ2 T cells. Yet, such in vitro generated cells have limited efficacy in the clinic. We found that despite inducing excessive proliferation of Vδ2 T cells, zoledronate impaired their effector function and caused the upregulation of the inhibitory receptor TIM3. This effect was due to the inhibition of mevalonate metabolism and dysregulation of downstream biological processes such as protein prenylation and intracellular signalling. In vitro and in vivo inhibition of mevalonate metabolism with zoledronate, statins, and 6-fluoromevalonate, as well as genetic deficiency of the mevalonate kinase, all resulted in compromised cytokine and cytotoxic molecule production by Vδ2 T cells. Impaired Vδ2 T cell function was accompanied by transcriptome and kinome changes. Our findings reveal the importance of mevalonate metabolism for the proper functioning of Vδ2 T cells. This observation provides important considerations for improving their therapeutic use and has repercussions for patients with statin or aminobisphosphonate treatments.

Inhibition of ATM promotes PD-L1 expression by activating JNK/c-Jun/TNF-α signaling axis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of breast cancer. Anti-PD-1/PD-L1 treatment for advanced TNBC is still limited to PD-L1-positive patients. Ataxia telangiectasia mutated (ATM) is a switch molecule for homologous recombination and repair. In this study, we found a significant negative correlation between ATM and PD-L1 in 4 TNBC clinical specimens by single-cell RNA sequencing (scRNA-seq), which was confirmed by immunochemical staining in 86 TNBC specimens. We then established ATM knockdown TNBC stable cell lines to perform in vitro studies and animal experiments, proving the negative regulation of PD-L1 by ATM via suppression of tumor necrosis factor-alpha (TNF-α), which was confirmed by cytokine array analysis of TNBC cell line and analysis of clinical specimens. We further found that ATM inhibits TNF-α via inactivating JNK/c-Jun by scRNA-seq, Western blot and luciferase reporter assays. Finally, we identified a negative correlation between changes in phospho-ATMS1981 and PD-L1 levels in TNBC post- and pre-neoadjuvant therapy. This study reveals a novel mechanism by which ATM negatively regulates PD-L1 by downregulating JNK/c-Jun/TNF-α in TNBC, shedding light on the wide application of immune checkpoint blockade therapy for treating multi-line-resistant TNBC.

The dichotomous outcomes of TNFα signaling in CD4+ T cells

TNFa blocking agents were the first-in-class biologic drugs used for the treatment of autoimmune disease. Paradoxically, however, exacerbation of autoimmunity was observed in some patients. TNFa is a pleiotropic cytokine that has both proinflammatory and regulatory effects on CD4+ T cells and can influence the adaptive immune response against autoantigens. Here, we critically appraise the literature and discuss the intricacies of TNFa signaling that may explain the controversial findings of previous studies. The pleiotropism of TNFa is based in part on the existence of two biologically active forms of TNFa, soluble and membrane-bound, with different affinities for two distinct TNF receptors, TNFR1 and TNFR2, leading to activation of diverse downstream molecular pathways involved in cell fate decisions and immune function. Distinct membrane expression patterns of TNF receptors by CD4+ T cell subsets and their preferential binding of distinct forms of TNFα produced by a diverse pool of cellular sources during different stages of an immune response are important determinants of the differential outcomes of TNFa-TNF receptor signaling. Targeted manipulation of TNFa-TNF receptor signaling on select CD4+ T cell subsets may offer specific therapeutic interventions to dampen inflammation while fortifying immune regulation for the treatment of autoimmune diseases.

Rocaglamide Prolonged Allograft Survival by Inhibiting Differentiation of Th1/Th17 Cells in Cardiac Transplantation

BACKGROUND

Aglaia (Meliaceae) species are used for treating autoimmune disorders and allergic diseases in Asian countries. Rocaglamide, an extract obtained from Aglaia species, exhibits suppressive effect by regulating the T cell subset balance and cytokine network in cancer. However, whether it can be used in organ transplantation is unknown. In this study, we investigated the antirejection effect and mechanism of action of rocaglamide in a mouse cardiac allograft model.

METHODS

Survival studies were performed by administering mice with phosphate-buffered saline (PBS) (n = 6) and rocaglamide (n = 8). Heart grafts were monitored until they stopped beating. After grafting, the mice were sacrificed on day 7 for histological, mixed lymphocyte reaction (MLR), enzyme-linked immunosorbent assay (ELISA), and flow cytometric analyses.

RESULTS

Rocaglamide administration significantly prolonged the median survival of the grafts from 7 to 25 days compared with PBS treatment (P < 0.001). On posttransplantation day 7, the rocaglamide-treated group showed a significant decrease in the percentage of Th1 cells (7.9 ± 0.9% vs. 1.58 ± 0.5%, P < 0.001) in the lymph nodes and spleen (8.0 ± 2.5% vs. 2.4 ± 1.3%, P < 0.05). Rocaglamide treatment also significantly inhibited the production of Th17 cells (6.4 ± 1.0% vs. 1.8 ± 0.4%, P < 0.01) in the lymph nodes and spleen (5.9 ± 0.3% vs. 2.9 ± 0.8%, P < 0.01). Furthermore, the prolonged survival of the grafts was associated with a significant decrease in IFN-γ and IL-17 levels. Our results also showed that NF-AT activation was inhibited by rocaglamide, which also induced p38 and Jun N-terminal kinase (JNK) phosphorylation in Jurkat T cells. Furthermore, by using inhibitors that suppressed p38 and JNK phosphorylation, rocaglamide-mediated reduction in NF-AT protein levels was prevented.

CONCLUSION

We identified a new immunoregulatory property of rocaglamide, wherein it was found to regulate oxidative stress response and reduce inflammatory cell infiltration and organ injury, which have been associated with the inhibition of NF-AT activation in T cells.

Association between nuclear factor of activated T cells C2 polymorphisms and treatment response in rheumatoid arthritis patients receiving tumor necrosis factor-alpha inhibitors

OBJECTIVES

Nuclear factor of activated T cells C2 (NFATC2) is known as a member of the transcription family and enhances tumor necrosis factor-alpha (TNF-α) synthesis in human T cells at the gene transcription level. Although NFATC2 has a potential role in rheumatoid arthritis (RA) progression and treatment, no study has investigated the association between NFATC2 gene polymorphisms and response status in RA patients receiving TNF-α inhibitors. This study aimed to examine the effects of polymorphisms in NFATC2, a TNF-α transcription factor, on response to TNF-α inhibitors.

METHODS

This prospective observational study was performed in two centers. Seven single nucleotide polymorphisms (SNPs) were investigated. Good responders were defined as patients with disease activity score (DAS)28 ≤3.2 after 6 months of treatment. Logistic regression analyses were used to investigate the association between genetic polymorphisms and response to the treatment. To test the model's goodness of fit, a Hosmer-Lemeshow test was performed.

RESULTS

This study included 98 patients, among whom 46 showed favorable responses to the treatment. Patients with hypertension revealed an approximately three-fold lower response to TNF-α inhibitors compared to those without hypertension (23.5 vs. 76.5%; P = 0.049). After adjusting for covariates, C allele carriers of NFATC2 rs3787186 exhibited approximately three-fold lower rates of treatment response compared to those with TT genotype (P = 0.037). The Hosmer-Lemeshow test showed that the fitness of the multivariable analysis model was satisfactory (χ2 = 9.745; 8 degrees of freedom; P = 0.283).

CONCLUSION

This study suggested an association between the C allele of rs3787186 and treatment response in RA patients receiving TNF-α inhibitors.

MicroRNA-mediated calcineurin signaling activation induces CCL2, CCL3, CCL5, IL8, and chemotactic activities in 4,4'-methylene diphenyl diisocyanate exposed macrophages

Occupational exposure to 4,4'-methylene diphenyl diisocyanate (MDI), the most widely used monomeric diisocyanate, is one of the leading causes of occupational asthma (OA). Previously, we identified microRNA (miR)-206-3p/miR-381-3p-mediated PPP3CA/calcineurin signalling regulated iNOS transcription in macrophages and bronchoalveolar lavage cells (BALCs) after acute MDI exposure; however, whether PPP3CA/calcineurin signalling participates in regulation of other asthma-associated mediators secreted by macrophages/BALCs after MDI exposure is unknown.Several asthma-associated, macrophage-secreted mediator mRNAs from MDI exposed murine BALCs and MDI-glutathione (GSH) conjugate treated differentiated THP-1 macrophages were analysed using RT-qPCR.Endogenous IL1B, TNF, CCL2, CCL3, CCL5, and TGFB1 were upregulated in MDI or MDI-GSH conjugate exposed BALCs and macrophages, respectively. Calcineurin inhibitor tacrolimus (FK506) attenuated the MDI-GSH conjugate-mediated induction of CCL2, CCL3, CCL5, and CXCL8/IL8 but not others. Transfection of either miR-inhibitor-206-3p or miR-inhibitor-381-3p in macrophages induced chemokine CCL2, CCL3, CCL5, and CXCL8 transcription, whereas FK506 attenuated the miR-inhibitor-206-3p or miR-inhibitor-381-3p-mediated effects. Finally, MDI-GSH conjugate treated macrophages showed increased chemotactic ability to various immune cells, which may be attenuated by FK506.In conclusion, these results indicate that MDI exposure to macrophages/BALCs may recruit immune cells into the airway via induction of chemokines by miR-206-3p and miR-381-3p-mediated calcineurin signalling activation.

Perspectives for immunotherapy in noninfectious immune mediated uveitis

Introduction: Noninfectious uveitis (NIU) is one of the leading causes of blindness worldwide. In adult patients, anterior NIU is usually managed with topical corticosteroids. In intermediate, posterior uveitis. and panuveitis, systemic corticosteroids are used especially in case of bilaterality or association with systemic disease. Biotherapies are recommended in case of inefficacy or intolerance to corticosteroids or conventional immunosuppressive drugs. Anti-TNF-α agents are by far the most widely used biotherapies. In case of failure or poor tolerance to anti-TNF-α, new targeted therapies can be proposed.Areas covered: We present and discuss an updated overview on biologics and biotherapies in NIU.Expert opinion: In case of dependency to systemic or intravitreal steroids, sight-threatening disease, and/or failure of conventional immunosuppressive drugs, anti-TNF-α are used as first-line biologics to achieve quiescence of inflammation. Anti-interleukin-6 is another option that may be proposed as first-line biologic or in case of poor efficacy of anti-TNF-α. Interferon can be directly proposed in specific indications (e.g. refractory macular edema, sight-threatening Behçet's uveitis). In the rare cases that remain unresponsive to traditional biotherapies, novel molecules, such as Janus-associated-kinase and anti-phosphodiesterase-4-inhibitors can be used. Therapeutic response must always be evaluated by clinical and appropriate ancillary investigations.

Harnessing Tumor Necrosis Factor Alpha to Achieve Effective Cancer Immunotherapy

Tumor necrosis factor alpha (TNFα) is a pleiotropic cytokine known to have contradictory roles in oncoimmunology. Indeed, TNFα has a central role in the onset of the immune response, inducing both activation and the effector function of macrophages, dendritic cells, natural killer (NK) cells, and B and T lymphocytes. Within the tumor microenvironment, however, TNFα is one of the main mediators of cancer-related inflammation. It is involved in the recruitment and differentiation of immune suppressor cells, leading to evasion of tumor immune surveillance. These characteristics turn TNFα into an attractive target to overcome therapy resistance and tackle cancer. This review focuses on the diverse molecular mechanisms that place TNFα as a source of resistance to immunotherapy such as monoclonal antibodies against cancer cells or immune checkpoints and adoptive cell therapy. We also expose the benefits of TNFα blocking strategies in combination with immunotherapy to improve the antitumor effect and prevent or treat adverse immune-related effects.

Identification of a Distal Locus Enhancer Element That Controls Cell Type-Specific TNF and LTA Gene Expression in Human T Cells

The human TNF/LT locus genes TNF, LTA, and LTB are expressed in a cell type-specific manner. In this study, we show that a highly conserved NFAT binding site within the distal noncoding element hHS-8 coordinately controls TNF and LTA gene expression in human T cells. Upon activation of primary human CD4⁺ T cells, hHS-8 and the TNF and LTA promoters display increased H3K27 acetylation and nuclease sensitivity and coordinate induction of TNF, LTA, and hHS-8 enhancer RNA transcription occurs. Functional analyses using CRISPR/dead(d)Cas9 targeting of the hHS-8-NFAT site in the human T cell line CEM demonstrate significant reduction of TNF and LTA mRNA synthesis and of RNA polymerase II recruitment to their promoters. These studies elucidate how a distal element regulates the inducible cell type-specific gene expression program of the human TNF/LT locus and provide an approach for modulation of TNF and LTA transcription in human disease using CRISPR/dCas9.

Tumor Necrosis Factor α Blockade: An Opportunity to Tackle Breast Cancer

Breast cancer is the most frequently diagnosed cancer and the principal cause of mortality by malignancy in women and represents a main problem for public health worldwide. Tumor necrosis factor α (TNFα) is a pro-inflammatory cytokine whose expression is increased in a variety of cancers. In particular, in breast cancer it correlates with augmented tumor cell proliferation, higher malignancy grade, increased occurrence of metastasis and general poor prognosis for the patient. These characteristics highlight TNFα as an attractive therapeutic target, and consequently, the study of soluble and transmembrane TNFα effects and its receptors in breast cancer is an area of active research. In this review we summarize the recent findings on TNFα participation in luminal, HER2-positive and triple negative breast cancer progression and metastasis. Also, we describe TNFα role in immune response against tumors and in chemotherapy, hormone therapy, HER2-targeted therapy and anti-immune checkpoint therapy resistance in breast cancer. Furthermore, we discuss the use of TNFα blocking strategies as potential therapies and their clinical relevance for breast cancer. These TNFα blocking agents have long been used in the clinical setting to treat inflammatory and autoimmune diseases. TNFα blockade can be achieved by monoclonal antibodies (such as infliximab, adalimumab, etc.), fusion proteins (etanercept) and dominant negative proteins (INB03). Here we address the different effects of each compound and also analyze the use of potential biomarkers in the selection of patients who would benefit from a combination of TNFα blocking agents with HER2-targeted treatments to prevent or overcome therapy resistance in breast cancer.

IL12 Abrogates Calcineurin-Dependent Immune Evasion during Leukemia Progression

Exploitation of the immune system has emerged as an important therapeutic strategy for acute lymphoblastic leukemia (ALL). However, the mechanisms of immune evasion during leukemia progression remain poorly understood. We sought to understand the role of calcineurin in ALL and observed that depletion of calcineurin B (CnB) in leukemia cells dramatically prolongs survival in immune-competent but not immune-deficient recipients. Immune-competent recipients were protected from challenge with leukemia if they were first immunized with CnB-deficient leukemia, suggesting robust adaptive immunity. In the bone marrow (BM), recipients of CnB-deficient leukemia harbored expanded T-cell populations as compared with controls. Gene expression analyses of leukemia cells extracted from the BM identified Cn-dependent significant changes in the expression of immunoregulatory genes. Increased secretion of IL12 from CnB-deficient leukemia cells was sufficient to induce T-cell activation ex vivo, an effect that was abolished when IL12 was neutralized. Strikingly, recombinant IL12 prolonged survival of mice challenged with highly aggressive B-ALL. Moreover, gene expression analyses from children with ALL showed that patients with higher expression of either IL12A or IL12B exhibited prolonged survival. These data suggest that leukemia cells are dependent upon calcineurin for immune evasion by restricting the regulation of proinflammatory genes, particularly IL12. SIGNIFICANCE: This report implicates calcineurin as an intracellular signaling molecule responsible for immune evasion during leukemia progression and raises the prospect of re-examining IL12 as a therapeutic in leukemia.

Constitutive and inducible in vivo protein-DNA interactions at the tumor necrosis factor-alpha promoter in primary human T lymphocytes

Tumor necrosis factor-alpha (TNF-alpha) is a key cytokine of lymphocytes with major regulatory functions in immunomodulation, chronic inflammation, and septic shock. However, only limited information on TNF promoter regulation in vivo in primary lymphocytes is available. To determine and compare protein-DNA interactions at the native TNF locus in primary lymphocytes, we analyzed the human TNF-alpha promoter by ligation-mediated polymerase chain reaction (LM-PCR) techniques. Accordingly, primary CD4+ T lymphocytes from peripheral blood were cultured in the presence of various stimuli and analyzed by LM-PCR. Inducible in vivo protein-DNA interactions at the TNF promoter were detected between -120 and -70 bp of the human TNF promoter relative to the transcriptional start site. This area includes binding sites for transcription factors such as ETS-1, NFAT, ATF-2/c-jun, SP-1/Egr-1, and NF-kappaB. In contrast, no protein-DNA interactions were observed at various binding sites with reported regulatory function in tumor cell lines such as the k2 element, the NFAT site at -160, the AP1 site at -50, and the SP1 site at -65. Additional mutagenesis and transfection studies demonstrated that NF-kappaB and CREB/AP-1 are important regulators of inducible TNF promoter activity in primary human T lymphocytes. These results provide novel insights into the complex regulation of TNF gene transcription in primary T lymphocytes in vivo by constitutive and inducible protein-DNA interactions that appear to be at least partially different compared to previously characterized tumor cell lines.

Cell cycle and apoptosis regulation by NFAT transcription factors: new roles for an old player

The NFAT (nuclear factor of activated T cells) family of transcription factors consists of four Ca²⁺-regulated members (NFAT1–NFAT4), which were first described in T lymphocytes. In addition to their well-documented role in T lymphocytes, where they control gene expression during cell activation and differentiation, NFAT proteins are also expressed in a wide range of cells and tissue types and regulate genes involved in cell cycle, apoptosis, angiogenesis and metastasis. The NFAT proteins share a highly conserved DNA-binding domain (DBD), which allows all NFAT members to bind to the same DNA sequence in enhancers or promoter regions. The same DNA-binding specificity suggests redundant roles for the NFAT proteins, which is true during the regulation of some genes such as IL-2 and p21. However, it has become increasingly clear that different NFAT proteins and even isoforms can have unique functions. In this review, we address the possible reasons for these distinct roles, particularly regarding N- and C-terminal transactivation regions (TADs) and the partner proteins that interact with these TADs. We also discuss the genes regulated by NFAT during cell cycle regulation and apoptosis and the role of NFAT during tumorigenesis.

Widespread JNK-dependent alternative splicing induces a positive feedback loop through CELF2-mediated regulation of MKK7 during T-cell activation

In this study, Martinez et al. find a positive feedback loop in the JNK signaling pathway through the alternative splicing of MKK7, identify the RNA-binding protein CELF2 as a major regulator of MKK7 splicing, and show that ∼25% of T-cell receptor-mediated alternative splicing events are dependent on JNK signaling. This study provides insight into a novel paradigm for the reciprocal interplay of signaling and splicing.

Alternative splicing is prevalent among genes encoding signaling molecules; however, the functional consequence of differential isoform expression remains largely unknown. Here we demonstrate that, in response to T-cell activation, the Jun kinase (JNK) kinase MAP kinase kinase 7 (MKK7) is alternatively spliced to favor an isoform that lacks exon 2. This isoform restores a JNK-docking site within MKK7 that is disrupted in the larger isoform. Consistently, we show that skipping of MKK7 exon 2 enhances JNK pathway activity, as indicated by c-Jun phosphorylation and up-regulation of TNF-α. Moreover, this splicing event is itself dependent on JNK signaling. Thus, MKK7 alternative splicing represents a positive feedback loop through which JNK promotes its own signaling. We further show that repression of MKK7 exon 2 is dependent on the presence of flanking sequences and the JNK-induced expression of the RNA-binding protein CELF2, which binds to these regulatory elements. Finally, we found that ∼25% of T-cell receptor-mediated alternative splicing events are dependent on JNK signaling. Strikingly, these JNK-dependent events are also significantly enriched for responsiveness to CELF2. Together, our data demonstrate a widespread role for the JNK–CELF2 axis in controlling splicing during T-cell activation, including a specific role in propagating JNK signaling.

Identification of genetic variants in the TNF promoter associated with COPD secondary to tobacco smoking and its severity

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease that arises in response to noxious particles or gases. Associations of genetic polymorphisms in TNF have been reported in Asians and Caucasians, but not in Mestizo populations. A case-control study was conducted in two stages: in the first stage, patients with COPD (COPD group, n=165) and smokers without disease (SNC group, n=165) were included and the TNF promoter sequence was determined using direct sequencing. In the second stage, the identified polymorphisms were validated by real-time polymerase chain reaction (PCR) in COPD (n=260) and SNC (n=506). In the first stage, 11 different sets of “contig” alignments were determined, of which contig 10 was found to be associated with susceptibility (P=5.0E-04, OR [odds ratio] =3.64) and contig 1 with Global Initiative for COPD (GOLD) greater grade (P=1.0E-02, OR =3.82). The single nucleotide polymorphisms found in this region were individually identified; the GA genotypes of rs1800629 (P=0.038, OR =2.07), rs56036015 (P=0.0082, OR =3.18), and rs361525 (P=1.0E-02, OR =4.220) were higher in the COPD group vs the SNC group; after second-stage validation, rs1800629 (P=6.00E-03, OR =2.26) and rs56036015 (P=1.10E-03, OR =2.54) are maintained. There are genetic variants in the TNF promoter associated with increased risk of COPD secondary to smoking and with a higher GOLD grade in the Mexican Mestizo population.

Glucose, insulin, and oxygen interplay in placental hypervascularisation in diabetes mellitus

The placental vasculature rapidly expands during the course of pregnancy in order to sustain the growing needs of the fetus. Angiogenesis and vascular growth are stimulated and regulated by a variety of growth factors expressed in the placenta or present in the fetal circulation. Like in tumors, hypoxia is a major regulator of angiogenesis because of its ability to stimulate expression of various proangiogenic factors. Chronic fetal hypoxia is often found in pregnancies complicated by maternal diabetes as a result of fetal hyperglycaemia and hyperinsulinemia. Both are associated with altered levels of hormones, growth factors, and proinflammatory cytokines, which may act in a proangiogenic manner and, hence, affect placental angiogenesis and vascular development. Indeed, the placenta in diabetes is characterized by hypervascularisation, demonstrating high placental plasticity in response to diabetic metabolic derangements. This review describes the major regulators of placental angiogenesis and how the diabetic environment in utero alters their expression. In the light of hypervascularized diabetic placenta, the focus was placed on proangiogenic factors.

TNF and TNF-receptors: From mediators of cell death and inflammation to therapeutic giants - past, present and future

Tumor Necrosis Factor (TNF), initially known for its tumor cytotoxicity, is a potent mediator of inflammation, as well as many normal physiological functions in homeostasis and health, and anti-microbial immunity. It also appears to have a central role in neurobiology, although this area of TNF biology is only recently emerging. Here, we review the basic biology of TNF and its normal effector functions, and discuss the advantages and disadvantages of therapeutic neutralization of TNF - now a commonplace practice in the treatment of a wide range of human inflammatory diseases. With over ten years of experience, and an emerging range of anti-TNF biologics now available, we also review their modes of action, which appear to be far more complex than had originally been anticipated. Finally, we highlight the current challenges for therapeutic intervention of TNF: (i) to discover and produce orally delivered small molecule TNF-inhibitors, (ii) to specifically target selected TNF producing cells or individual (diseased) tissue targets, and (iii) to pre-identify anti-TNF treatment responders. Although the future looks bright, the therapeutic modulation of TNF now moves into the era of personalized medicine with society's challenging expectations of durable treatment success and of achieving long-term disease remission.

Dynamic changes in chromatin conformation at the TNF transcription start site in T helper lymphocyte subsets

Tumor necrosis factor (TNF) is one of the key primary response genes in the immune system that can be activated by a variety of stimuli. Previous analysis of chromatin accessibility to DNaseI demonstrated open chromatin conformation of the TNF proximal promoter in T cells. Here, using chromatin probing with restriction enzyme EcoNI and micrococcal nuclease we show that in contrast to the proximal promoter, the TNF transcription start site remains in a closed chromatin configuration in primary T helper (Th) cells, but acquires an open state after activation or polarization under Th1 and Th17 conditions. We further demonstrate that transcription factor c-Jun plays a pivotal role in the maintenance of open chromatin conformation at the transcription start site of the TNF gene.

Epigenetic control of cytokine gene expression: regulation of the TNF/LT locus and T helper cell differentiation

Epigenetics encompasses transient and heritable modifications to DNA and nucleosomes in the native chromatin context. For example, enzymatic addition of chemical moieties to the N-terminal "tails" of histones, particularly acetylation and methylation of lysine residues in the histone tails of H3 and H4, plays a key role in regulation of gene transcription. The modified histones, which are physically associated with gene regulatory regions that typically occur within conserved noncoding sequences, play a functional role in active, poised, or repressed gene transcription. The "histone code" defined by these modifications, along with the chromatin-binding acetylases, deacetylases, methylases, demethylases, and other enzymes that direct modifications resulting in specific patterns of histone modification, shows considerable evolutionary conservation from yeast to humans. Direct modifications at the DNA level, such as cytosine methylation at CpG motifs that represses promoter activity, are another highly conserved epigenetic mechanism of gene regulation. Furthermore, epigenetic modifications at the nucleosome or DNA level can also be coupled with higher-order intra- or interchromosomal interactions that influence the location of regulatory elements and that can place them in an environment of specific nucleoprotein complexes associated with transcription. In the mammalian immune system, epigenetic gene regulation is a crucial mechanism for a range of physiological processes, including the innate host immune response to pathogens and T cell differentiation driven by specific patterns of cytokine gene expression. Here, we will review current findings regarding epigenetic regulation of cytokine genes important in innate and/or adaptive immune responses, with a special focus upon the tumor necrosis factor/lymphotoxin locus and cytokine-driven CD4+ T cell differentiation into the Th1, Th2, and Th17 lineages.

Curcumin: an orally bioavailable blocker of TNF and other pro-inflammatory biomarkers

TNFs are major mediators of inflammation and inflammation-related diseases, hence, the United States Food and Drug Administration (FDA) has approved the use of blockers of the cytokine, TNF-α, for the treatment of osteoarthritis, inflammatory bowel disease, psoriasis and ankylosis. These drugs include the chimeric TNF antibody (infliximab), humanized TNF-α antibody (Humira) and soluble TNF receptor-II (Enbrel) and are associated with a total cumulative market value of more than $20 billion a year. As well as being expensive ($15 000-20 000 per person per year), these drugs have to be injected and have enough adverse effects to be given a black label warning by the FDA. In the current report, we describe an alternative, curcumin (diferuloylmethane), a component of turmeric (Curcuma longa) that is very inexpensive, orally bioavailable and highly safe in humans, yet can block TNF-α action and production in in vitro models, in animal models and in humans. In addition, we provide evidence for curcumin's activities against all of the diseases for which TNF blockers are currently being used. Mechanisms by which curcumin inhibits the production and the cell signalling pathways activated by this cytokine are also discussed. With health-care costs and safety being major issues today, this golden spice may help provide the solution.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

The transcription factor NFATp plays a key role in susceptibility to TB in mice

In T cells, the transcription factor nuclear factor of activated T cells p (NFATp) is a key regulator of the cytokine genes tumor necrosis factor (TNF) and interferon-γ (IFN-γ). Here, we show that NFATp-deficient (NFATp(-/-)) mice have a dramatic and highly significant increase in mortality after Mycobacterium tuberculosis (MTb) infection as compared to mortality of control animals after MTb infection. Animals deficient in NFATp have significantly impaired levels of TNF and IFN-γ transcription and protein expression in naïve or total CD4(+) T cells, but display wild-type levels of TNF mRNA or protein from MTb-stimulated dendritic cells (DC). The rapid mortality and disease severity observed in MTb-infected NFATp(-/-) mice is associated with dysregulated production of TNF and IFN-γ in the lungs, as well as with increased levels of TNF, in their serum. Furthermore, global blocking of TNF production by injection of a TNF neutralizaing agent at 6 weeks, but not 12 weeks, post-MTb-infection further decreased the survival rate of both wild-type and NFATp(-/-) mice, indicating an early role for TNF derived from cells from the monocyte lineage in containment of infection. These results thus demonstrate that NFATp plays a critical role in immune containment of TB disease in vivo, through the NFATp-dependent expression of TNF and IFN-γ in T cells.

Alternative splicing networks regulated by signaling in human T cells

The formation and execution of a productive immune response requires the maturation of competent T cells and a robust change in cellular activity upon antigen challenge. Such changes in cellular function depend on regulated alterations to protein expression. Previous research has focused on defining transcriptional changes that regulate protein expression during T-cell maturation and antigen stimulation. Here, we globally analyze another critical process in gene regulation during T-cell stimulation, alternative splicing. Specifically, we use RNA-seq profiling to identify 178 exons in 168 genes that exhibit robust changes in inclusion in response to stimulation of a human T-cell line. Supporting an important role for the global coordination of alternative splicing following T-cell stimulation, these signal-responsive exons are significantly enriched in genes with functional annotations specifically related to immune response. The vast majority of these genes also exhibit differential alternative splicing between naive and activated primary T cells. Comparison of the responsiveness of splicing to various stimuli in the cultured and primary T cells further reveals at least three distinct networks of signal-induced alternative splicing events. Importantly, we find that each regulatory network is specifically associated with distinct sequence features, suggesting that they are controlled by independent regulatory mechanisms. These results thus provide a basis for elucidating mechanisms of signal pathway-specific regulation of alternative splicing during T-cell stimulation.

A cell permeable peptide inhibitor of NFAT inhibits macrophage cytokine expression and ameliorates experimental colitis

Nuclear factor of activated T cells (NFAT) plays a critical role in the development and function of immune and non-immune cells. Although NFAT is a central transcriptional regulator of T cell cytokines, its role in macrophage specific gene expression is less defined. Previous work from our group demonstrated that NFAT regulates Il12b gene expression in macrophages. Here, we further investigate NFAT function in murine macrophages and determined the effects of a cell permeable NFAT inhibitor peptide 11R-VIVIT on experimental colitis in mice. Treatment of bone marrow derived macrophages (BMDMs) with tacrolimus or 11R-VIVIT significantly inhibited LPS and LPS plus IFN-γ induced IL-12 p40 mRNA and protein expression. IL-12 p70 and IL-23 secretion were also decreased. NFAT nuclear translocation and binding to the IL-12 p40 promoter was reduced by NFAT inhibition. Experiments in BMDMs from IL-10 deficient (Il10^−/−) mice demonstrate that inhibition of IL-12 expression by 11R-VIVIT was independent of IL-10 expression. To test its therapeutic potential, 11R-VIVIT was administered systemically to Il10^−/− mice with piroxicam-induced colitis. 11R-VIVIT treated mice demonstrated significant improvement in colitis compared to mice treated with an inactive peptide. Moreover, decreased spontaneous secretion of IL-12 p40 and TNF in supernatants from colon explant cultures was demonstrated. In summary, NFAT, widely recognized for its role in T cell biology, also regulates important innate inflammatory pathways in macrophages. Selective blocking of NFAT via a cell permeable inhibitory peptide is a promising therapeutic strategy for the treatment of inflammatory bowel diseases.

Potent anti-inflammatory activity of ursolic acid, a triterpenoid antioxidant, is mediated through suppression of NF-κB, AP-1 and NF-AT

BACKGROUND

Ursolic acid (UA), a pentacyclic triterpenoid carboxylic acid, is the major component of many plants including apples, basil, cranberries, peppermint, rosemary, oregano and prunes and has been reported to possess antioxidant and anti-tumor properties. These properties of UA have been attributed to its ability to suppress NF-κB (nuclear factor kappa B) activation. Since NF-κB, in co-ordination with NF-AT (nuclear factor of activated T cells) and AP-1(activator protein-1), is known to regulate inflammatory genes, we hypothesized that UA might exhibit potent anti-inflammatory effects.

METHODOLOGY/PRINCIPAL FINDINGS

The anti-inflammatory effects of UA were assessed in activated T cells, B cells and macrophages. Effects of UA on ERK, JNK, NF-κB, AP-1 and NF-AT were studied to elucidate its mechanism of action. In vivo efficacy of UA was studied using mouse model of graft-versus-host disease. UA inhibited activation, proliferation and cytokine secretion in T cells, B cells and macrophages. UA inhibited mitogen-induced up-regulation of activation markers and co-stimulatory molecules in T and B cells. It inhibited mitogen-induced phosphorylation of ERK and JNK and suppressed the activation of immunoregulatory transcription factors NF-κB, NF-AT and AP-1 in lymphocytes. Treatment of cells with UA prior to allogenic transplantation significantly delayed induction of acute graft-versus-host disease in mice and also significantly reduced the serum levels of pro-inflammatory cytokines IL-6 and IFN-γ. UA treatment inhibited T cell activation even when added post-mitogenic stimulation demonstrating its therapeutic utility as an anti-inflammatory agent.

CONCLUSIONS/SIGNIFICANCE

The present study describes the detailed mechanism of anti-inflammatory activity of UA. Further, UA may find application in the treatment of inflammatory disorders.

Toll-like receptor triggering in cord blood mesenchymal stem cells

Recently, the antagonizing effect on the differentiation of mesenchymal stem cells (MSCs) by toll-like receptor (TLR) ligands, was described. Our study shows that on more primitive cord blood derived MSCs, the expression of TLRs and ligand-induced triggering differs from that of bone marrow derived MSCs. At the RNA level, cord blood MSCs (unrestricted somatic stem cells; USSCs) express low levels of TLR1,3,5,9 and high levels of TLR4 and TLR6. At the protein level expression of TLR5 and very low expression of TLR4 was observed. NF-κB translocation studies revealed that both TLR4 and TLR5 are functional, although signalling kinetics induced by the individual ligands differed. Stimulation of USSCs with either lipopolysaccharide (LPS) or flagellin resulted in a marked increase of interleukin (IL)-6 and/or IL-8 production although levels differed significantly between both stimuli. Interestingly, tumour necrosis factor (TNF)-α was undetectable after TLR stimulation, which appeared to be due to an inactivated TNF-α promoter in USSCs. Moreover, osteoblastic differentiation was enhanced after triggering USSCs with LPS and flagellin. In summary, TLR4 and 5 signalling in USSCs is slow and results in the up-regulation of a restricted number of pro-inflammatory cytokines and enhanced osteoblastic differentiation. Apparently, the outcome of TLR signalling depends on the cell type that expresses them.

Monocyte-specific accessibility of a matrix attachment region in the tumor necrosis factor locus

Regulation of TNF gene expression is cell type- and stimulus-specific. We have previously identified highly conserved noncoding regulatory elements within DNase I-hypersensitive sites (HSS) located 9 kb upstream (HSS-9) and 3 kb downstream (HSS+3) of the TNF gene, which play an important role in the transcriptional regulation of TNF in T cells. They act as enhancers and interact with the TNF promoter and with each other, generating a higher order chromatin structure. Here, we report a novel monocyte-specific AT-rich DNase I-hypersensitive element located 7 kb upstream of the TNF gene (HSS-7), which serves as a matrix attachment region in monocytes. We show that HSS-7 associates with topoisomerase IIα (Top2) in vivo and that induction of endogenous TNF mRNA expression is suppressed by etoposide, a Top2 inhibitor. Moreover, Top2 binds to and cleaves HSS-7 in in vitro analysis. Thus, HSS-7, which is selectively accessible in monocytes, can tether the TNF locus to the nuclear matrix via matrix attachment region formation, potentially promoting TNF gene expression by acting as a Top2 substrate.

Arc of a vicious circle: pathways activated by Mycobacterium tuberculosis that target the HIV-1 long terminal repeat

In this review, we examine how a subset of signal transduction cascades initiated by Mycobacterium tuberculosis (Mtb) infection modulates transcription mediated by the human immunodeficiency virus type 1 long terminal repeat (HIV-1 LTR). We describe two distinct phases of signaling that target transcription factors known to bind the HIV-1 LTR, and thus drive viral transcription and replication, in cells of the Mtb-infected host. First, Mtb-derived molecules, including cell wall components and DNA, interact with a number of host pattern recognition receptors. Second, cytokines and chemokines secreted in response to Mtb infection initiate signal transduction cascades through their cognate receptors. Given the variation in cell wall components among distinct clinical Mtb strains, the initial pattern recognition receptor interaction leading to direct LTR activation and differential cytokine and chemokine production is likely to be an important aspect of Mtb strain-specific regulation of HIV-1 transcription and replication. Improved understanding of these molecular mechanisms in the context of bacterial and host genetics should provide key insights into the accelerated viral replication and disease progression characteristic of HIV/TB coinfection.

Early c-Jun N-terminal kinase-dependent phosphorylation of activating transcription factor-2 is associated with degeneration of retinal ganglion cells

Neuron death due to deprivation of target-derived neurotrophic factors depends on protein synthesis regulated by transcription factor activity. We investigated the content and phosphorylation of activating transcription factor 2 (ATF-2) in axon-damaged retinal ganglion cells of neonatal rats. In the retina of neonatal rats, the ATF-2 protein is predominantly located in the nucleus of the ganglion cells. A gradual loss of the immunoreactivity for ATF-2 occurred after explantation. ATF-2 is phosphorylated early after explantation, with a peak within 3 hours, preceding the peak of cell death that occurs at 18 hours. Both the phosphorylation of ATF-2 and ganglion cell death were blocked by treatment with an inhibitor of c-Jun N-terminal kinase (JNK), whereas an inhibitor of p38 reduced only slightly the rate of ganglion cell death with no effect upon phosphorylation of ATF-2. Inhibitors of phosphatidyl inositol 3 kinase (PI-3K), protein kinase C (PKC) or extracellular regulated kinase (ERK) had no effect. Finally, the inhibitor of JNK blocked the upregulation of both c-Jun and Hrk in the GCL after retinal explantation. The data show that phosphorylation of ATF-2 by JNK is associated with retinal ganglion cell death after axon damage.

Effects of the black tea polyphenol theaflavin-2 on apoptotic and inflammatory pathways in vitro and in vivo

SCOPE

Theaflavin-2 (TF-2), a major component of black tea extract, induces apoptosis of human colon cancer cells and suppresses serum-induced cyclooxygenase-2 (COX-2) expression 1. Here, we explored the mechanisms for activation of apoptosis, evaluated the impact on inflammatory genes in a broader panel of cells and tested whether topical anti-inflammatory effects could be observed in vivo.

METHODS AND RESULTS

TF-2 triggered apoptosis in five other transformed cancer cell lines, inducing cell shrinkage, membrane blebbing, and mitochondrial clustering within 3 h of treatment. Among a set of pro-apoptotic genes, TF-2 quickly induced the up-regulation of P53 and BAX, suggesting mitochondria as the primary target. Using a cell model for inflammatory response, we showed that TF-2 suppressed the 12-O-tetradecanoylphorbol-13-acetate-induced COX-2 gene expression, and also down-regulated TNF-α, iNOS, ICAM-1, and NFκB. A reporter gene assay showed that TF-2 down-regulated COX-2 at the transcriptional level. We also demonstrated that TF-2 exhibited anti-inflammatory activity in two mouse models of inflammation. Topical application with TF-2 significantly reduced ear edema and produced a pattern of gene down-regulation similar to that observed in the cell model.

CONCLUSION

These results suggest that the anti-inflammatory and pro-apoptotic activity of TF-2 may be exploited therapeutically in cancer and other diseases associated with inflammation.

Inhibition of tumor progression locus 2 protein kinase decreases lipopolysaccharide-induced tumor necrosis factor alpha production due to the inhibition of the tip-associated protein induction in RAW264.7 cells

The activation of mitogen-activated protein kinases (MAPKs) is critically involved in inflammatory events through mediation of the production of various inflammatory cytokines. The Tpl2 (tumor progression locus 2)-MEK (MAPK/ERK kinase)-ERK (extracellular signal-regulated kinase) signaling pathway plays an essential role in the production of tumor necrosis factor alpha (TNFalpha) in macrophages stimulated with lipopolysaccharide (LPS). Here, we studied the molecular mechanisms of Tpl2-mediated TNFalpha production using a potent Tpl2 kinase inhibitor, 1,7-naphtyridine-3-carbonitrile, and LPS-stimulated RAW264.7 cells. This inhibitor was effective in suppressing the in vitro Tpl2 kinase activity, and caused a significant reduction in TNFalpha production via specific suppression of the phosphorylation of MEK and ERK but not that of p38 and c-Jun N-terminal kinase (JNK). A p38 inhibitor, SB203580, also inhibited the TNFalpha production dose-dependently. Although the TNFalpha mRNA level was not altered by either inhibitor, the Tpl2 inhibitor increased the nuclear TNFalpha mRNA level, while decreasing that in the cytoplasm. Tip-associated protein (TAP), a key molecule in the nucleocytoplasmic transport of TNFalpha mRNA, was up-regulated by LPS, but this increase was impaired by the Tpl2 inhibitor. In all cases, SB203580 was without effect in the presence of LPS. These results suggest that the LPS-induced TNFalpha production via the Tpl2-MEK-ERK signaling pathway is regulated by changing the TAP level at the nucleocytoplasmic transport level. These results improve understanding of TNFalpha regulatory mechanisms and might provide a new therapeutic strategy against inflammatory diseases.

Calcineurin/nuclear factor of activated T cells and MAPK signaling induce TNF-{alpha} gene expression in pancreatic islet endocrine cells

Cytokines contribute to pancreatic islet inflammation, leading to impaired glucose homeostasis and diabetic diseases. A plethora of data shows that proinflammatory cytokines are produced in pancreatic islets by infiltrating mononuclear immune cells. Here, we show that pancreatic islet α cells and β cells express tumor necrosis factor-α (TNF-α) and other cytokines capable of promoting islet inflammation when exposed to interleukin-1β (IL-1β). Cytokine expression by β cells was dependent on calcineurin (CN)/nuclear factor of activated T cells (NFAT) and MAPK signaling. NFAT associated with the TNF-α promoter in response to stimuli and synergistically activated promoter activity with ATF2 and c-Jun. In contrast, the β-cell-specific transcriptional activator MafA could repress NFAT-mediated TNF-α gene expression whenever C/EBP-β was bound to the promoter. NFAT differentially regulated the TNF-α gene depending upon the expression and MAPK-dependent activation of interacting basic leucine zipper partners in β cells. Both p38 and JNK were required for induction of TNF-α mRNA and protein expression. Collectively, the data show that glucose and IL-1β can activate signaling pathways, which control induction and repression of cytokines in pancreatic endocrine cells. Thus, by these mechanisms, pancreatic β cells themselves may contribute to islet inflammation and their own immunological destruction in the pathogenesis of diabetes.

Association of tumor necrosis factor-alpha gene promoter polymorphisms with acute viral hepatitis in the Indian population

The key elements that determine the host response to either the self-limited or a severe fulminant form of liver disease are unclear. We have investigated the potential association of single nucleotide polymorphisms (SNPs) in the promoter region of tumor necrosis factor-alpha (TNFalpha) in their susceptibility to acute viral hepatitis (AVH) and fulminant hepatic failure (FHF) patients exhibiting specific viral etiology. A total of 124 individuals including 64 cases comprising 27 FHF, 37 AVH, and 60 healthy controls were recruited. SNPs at -238 (G/A), -308 (G/A), -857 (C/T), and -863 (C/A) of TNFalpha were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by direct sequencing. Serum levels of TNFalpha were determined at admission and death or recovery. Association between the TNFalpha genotype and susceptibility to FHF was not evident; however, carrier genotypes in relation to the -308 (GA/AA) and -857 (CT/TT) loci were found to be significantly (P < or = 0.05) associated with susceptibility to AVH in relation to controls. The mean TNFalpha serum levels at admission were significantly higher (P < 0.001) in FHF than AVH patients, but no marked difference was observed between FHF-E (expired; n = 17) and FHF-S (survivors; n = 10), though the former were comparatively higher. This study suggests that SNPs at -308 and -857 of the TNFalpha promoter may represent an increased risk for the development of AVH but not for FHF in the Indian population.

cAMP/CREB-mediated transcriptional regulation of ectonucleoside triphosphate diphosphohydrolase 1 (CD39) expression

CD39 is a transmembrane enzyme that inhibits platelet reactivity and inflammation by phosphohydrolyzing ATP and ADP to AMP. Cyclic AMP (cAMP), an essential second messenger, is particularly important in regulating genes controlling vascular homeostasis. These experiments test the hypothesis that cAMP might positively regulate the expression of CD39 and thereby modulate important vascular homeostatic properties. Cd39 mRNA was induced by 13.8- fold in RAW cells treated with a membrane-permeant cAMP analogue (8-bromo-cyclic AMP; 8-Br-cAMP), stimulation of adenylate cyclase, or prostanoids known to drive cAMP response. Fluorescence-activated cell sorting, immunofluorescence, and TLC assays demonstrated that both CD39 protein expression and enzymatic activity were increased in cells treated with 8-Br-cAMP but not in cells transfected with short hairpin RNA against CD39. This analogue drove a significant increase in transcriptional activity at the Cd39 promoter although not when the promoter's cAMP-response element sites were mutated. Pretreatment with cAMP-dependent protein kinase (PKA), phosphoinositide 3-kinase (PI3K), or ERK inhibitors nearly obliterated the cAMP-driven increase in Cd39 mRNA, protein expression, and promoter activity. 8-Br-cAMP greatly increased the phosphorylation of CREB1 (Ser(133)) and ATF2 (Thr(71)) in a PKA-, PI3K-, and ERK-dependent fashion. Chromatin immunoprecipitation assays demonstrated that binding of phosphorylated CREB1 and ATF2 to cAMP-response element-like sites was significantly increased with 8-Br-cAMP treatment and that binding was reduced with PKA, PI3K, and ERK inhibition, whereas transfection of Creb1 and Atf2 overexpression constructs enhanced cAMP-driven Cd39 mRNA expression. Transfection of RAW cells with mutated Creb1 (S133A) reduced cAMP-driven Cd39 mRNA expression. Furthermore, the cAMP-mediated induction of Cd39 mRNA, protein, and phosphohydrolytic activity was replicated in primary peritoneal macrophages. These data identify cAMP as a crucial regulator of macrophage CD39 expression and demonstrate that cAMP acts through the PKA/CREB, PKA/PI3K/ATF2, and PKA/ERK/ATF2 pathways to control a key vascular homeostatic mediator.

Transcriptional control of the TNF gene

The cytokine TNF is a critical mediator of immune and inflammatory responses. The TNF gene is an immediate early gene, rapidly transcribed in a variety of cell types following exposure to a broad range of pathogens and signals of inflammation and stress. Regulation of TNF gene expression at the transcriptional level is cell type- and stimulus-specific, involving the recruitment of distinct sets of transcription factors to a compact and modular promoter region. In this review, we describe our current understanding of the mechanisms through which TNF transcription is specifically activated by a variety of extracellular stimuli in multiple cell types, including T cells, B cells, macrophages, mast cells, dendritic cells, and fibroblasts. We discuss the role of nuclear factor of activated T cells and other transcription factors and coactivators in enhanceosome formation, as well as the contradictory evidence for a role for nuclear factor kappaB as a classical activator of the TNF gene. We describe the impact of evolutionarily conserved cis-regulatory DNA motifs in the TNF locus upon TNF gene transcription, in contrast to the neutral effect of single nucleotide polymorphisms. We also assess the regulatory role of chromatin organization, epigenetic modifications, and long-range chromosomal interactions at the TNF locus.

Exogenous Nef is an inhibitor of Mycobacterium tuberculosis-induced tumor necrosis factor-alpha production and macrophage apoptosis

Human immunodeficiency virus-1 (HIV-1) impairs tumor necrosis factor-alpha (TNF-alpha)-mediated macrophage apoptosis induced by Mycobacterium tuberculosis (Mtb). HIV Nef protein plays an important role in the pathogenesis of AIDS. We have tested the hypothesis that exogenous Nef is a factor that inhibits TNF-alpha production/apoptosis in macrophages infected with Mtb. We demonstrate that Mtb and Nef individually trigger TNF-alpha production in macrophages. However, TNF-alpha production is dampened when the two are present simultaneously, probably through cross-regulation of the individual signaling pathways leading to activation of the TNF-alpha promoter. Mtb-induced TNF-alpha production is abrogated upon mutation of the Ets, Egr, Sp1, CRE, or AP1 binding sites on the TNF-alpha promoter, whereas Nef-mediated promoter activation depends only on the CRE and AP1 binding sites, pointing to differences in the mechanisms of activation of the promoter. Mtb-dependent promoter activation depends on the mitogen-activated kinase (MAPK) kinase kinase ASK1 and on MEK/ERK signaling. Nef inhibits ASK1/p38 MAPK-dependent Mtb-induced TNF-alpha production probably by inhibiting binding of ATF2 to the TNF-alpha promoter. It also inhibits MEK/ERK-dependent Mtb-induced binding of FosB to the promoter. Nef-driven TNF-alpha production occurs in an ASK1-independent, Rac1/PAK1/p38 MAPK-dependent, and MEK/ERK-independent manner. The signaling pathways used by Mtb and Nef to trigger TNF-alpha production are therefore distinctly different. In addition to attenuating Mtb-dependent TNF-alpha promoter activation, Nef also reduces Mtb-dependent TNF-alpha mRNA stability probably through its ability to inhibit ASK1/p38 MAPK signaling. These results provide new insight into how HIV Nef probably exacerbates tuberculosis infection by virtue of its ability to dampen Mtb-induced TNF-alpha production.

Comparative analyses of single-nucleotide polymorphisms in the TNF promoter region provide further validation for the vervet monkey model of obesity

Tumor necrosis factor is a cytokine that plays critical roles in inflammation, the innate immune response, and a variety of other physiologic and pathophysiologic processes. In addition, TNF has recently been shown to mediate an intersection of chronic, low-grade inflammation and concurrent metabolic dysregulation associated with obesity and its comorbidities. As part of an ongoing initiative to further characterize vervet monkeys originating from St Kitts as an animal model of obesity and inflammation, we sequenced and genotyped the human ortholog vervet TNF gene and approximately 1 kb of the flanking 3' and 5' regions from 265 monkeys in a closed, pedigreed colony. This process revealed a total of 11 single-nucleotide polymorphisms (SNPs) and a single 4-bp insertion-deletion, with minor allele frequencies of 0.08 to 0.39. Many of these polymorphisms were in strong or complete linkage disequilibrium with each other, and all but 1 were contained within a single haplotype block, comprising 5 haplotypes with frequencies of 0.075 to 0.298. Using sequences from humans, chimpanzees, vervets, baboons, and rhesus macaques, phylogenetic shadowing of the TNF promoter region revealed that vervet SNPs, like the SNPs in related species, were clustered nonrandomly and nonuniformly around conserved transcription factor binding sites. These data, combined with previously defined heritable phenotypes, permit future association analyses in this nonhuman primate model and have great potential to help dissect the genetic and nongenetic contributions to complex diseases like obesity. More broadly, the sequence data and comparative analyses reported herein facilitates study of the evolution of regulatory sequences of inflammatory and immune-related genes.

Mesenchymal stem cells respond to TNF but do not produce TNF

Previously, we demonstrated that several TLRs are expressed on cord blood-derived USSC. Stimulation of USSC with TLR agonists resulted in a marked increase of IL-6 and IL-8 production. Interestingly, TNF was undetectable after TLR stimulation, which appeared to be a result of an inactivated TNF promoter in USSC. Here, we elaborate this study by demonstrating that although USSC do not produce TNF, they are susceptible to TNF stimulation, resulting in NF-kappaB translocation and cytokine production. Additionally, we compared different stem cell sources for their ability to produce TNF. Interestingly, we found that the TNF promoter in BM-MSC is inactivated as well. Like USSC, they are able to respond to TNF stimulation, but they are not able to produce TNF, even not after LPS stimulation. This limited cytokine response in combination with the well-studied immunosuppressive properties of MSC makes these cells ideal for immune-suppressive treatment modalities such as graft-versus-host disease.

cJun modulates Ggamma-globin gene expression via an upstream cAMP response element

The upstream Ggamma-globin gene cAMP response element (G-CRE) was previously shown to play a role in drug-mediated fetal hemoglobin induction. This effect is achieved via p38 mitogen activated protein kinase (MAPK)-dependent CREB1 and ATF-2 phosphorylation and G-CRE transactivation. Since this motif is also a predicted consensus binding site for cJun we extended our analysis to determine the ability of cJun to transactivate gamma-globin through the G-CRE. Using chromatin immunoprecipitation assays we showed comparable in vivo cJun and CREB1 binding to the G-CRE region. Protein-protein interactions were confirmed between cJun/ATF-2 and CREB1/ATF-2 but not between CREB1 and cJun. However, we observed cJun and CREB1 binding to the G-CRE in vitro by electrophoretic mobility shift assay. Promoter pull-down assay followed by sequential western blot analysis confirmed co-localization of cJun, CREB1, and ATF-2 on the G-CRE. To show functional relevance, enforced expression studies with pLen-cJun and a Ggamma-promoter (-1500 to +36) luciferase reporter were completed; we observed a concentration-dependent increase in luciferase activity with pLen-cJun similar to that produced by CREB1 enforced expression. Moreover, the G/A mutation at -1225 in the G-CRE abolished cJun transactivation. Finally, enforced cJun expression in K562 cells and normal primary erythroid progenitors enhanced endogenous gamma-globin gene expression. We conclude that these data indicate that cJun activates the Ggamma-globin promoter via the G-CRE in a manner comparable with CREB1 and propose a model for gamma-globin activation based on DNA-protein interactions in the G-CRE.

Regulation of proinflammatory cytokine expression in primary mouse astrocytes by coronavirus infection

Previous studies have shown that proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6), are differentially induced in primary mouse astrocytes by mouse hepatitis virus strain A59 (MHV-A59) and MHV-2. However, the signaling events that trigger TNF-alpha and IL-6 induction in these cells upon MHV infection remain unknown. In this study, we explored the potential signaling events. We found that induction of TNF-alpha and IL-6 occurred as early as 2 h postinfection and was completely dependent on viral replication. Using inhibitors specific for three mitogen-activated protein kinases, we showed that induction of TNF-alpha and IL-6 by MHV-A59 infection was mediated through activation of the Janus N-terminal kinase signaling pathway, but not through the extracellular signal-regulated kinase or p38 signaling pathway. This finding was further confirmed with knockdown experiments using small interfering RNAs specific for Janus N-terminal kinase. Interestingly, while nuclear factor kappaB (NF-kappaB), a key transcription factor required for the expression of proinflammatory cytokines in most cell types, was activated in astrocytes during MHV-A59 infection, disruption of the NF-kappaB pathway by peptide inhibitors did not significantly inhibit TNF-alpha and IL-6 expression. Furthermore, experiments using chimeric viruses demonstrated that the viral spike and nucleocapsid proteins, which play important roles in MHV pathogenicity in mice, are not responsible for the differential induction of the cytokines. These results illustrate the complexity of the regulatory mechanism by which MHV induces proinflammatory cytokines in primary astrocytes.

Systems biology evaluation of immune responses induced by human host defence peptide LL-37 in mononuclear cells

The immune system is very complex, it involves the integrated regulation and expression of hundreds of proteins. To understand in greater detail how the human host defence immunomodulatory peptide LL-37 interacts with innate immunity, a systems approach was pursued. Polychromatic flow cytometry was employed to demonstrate that within human peripheral blood mononuclear cells, CD14+ monocytes, myeloid and plasmocytoid dendritic cells and T- and B-lymphocytes, all responded to LL-37, with the differential production of intracellular cytokines. Microarray analyses with CD14+ monocytes indicated the differential expression of 475 genes in response to stimulation with LL-37. To understand this complex response, bioinformatic interrogation, using InnateDB, of the gene ontology, signalling pathways and transcription factor binding sites was undertaken. Activation of the IkappaBalpha/NFkappaB, mitogen-activated protein kinases p38, ERK1/2 and JNK, and PI3K signalling pathways in response to LL-37 was demonstrated by pathway and ontology over-representation analyses, and confirmed experimentally by inhibitor studies. Computational analysis of the predicted transcription factor binding sites upstream of the genes that were regulated by LL-37 predicted the involvement of several transcription factors including NFkappaB and five novel factors, AP-1, AP-2, SP-1, E2F1, and EGR, which were experimentally confirmed to respond to LL-37 by performing transcription factor array studies on nuclear extracts from LL-37 treated mononuclear cells. These data are discussed as reflecting the integration of several responsive signalling pathways through the involvement of transcription factor complexes in gene expression activated by LL-37 in human mononuclear cells.

Suppression of acute lung inflammation by intracellular peptide delivery of a nuclear import inhibitor

Acute lung inflammation is a potentially life-threatening complication of infections due to community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), a worldwide emerging pathogen, which causes necrotizing pneumonia and acute respiratory distress syndrome (ARDS). MRSA virulence factors encompass immunotoxins termed superantigens that contribute to lung inflammation. In this study, we demonstrate that staphylococcal enterotoxin B (SEB)-induced lung inflammation is attenuated by a cell-penetrating peptide nuclear import inhibitor of nuclear factor (NF)-kappaB and other stress-responsive transcription factors (SRTFs). This inhibitor suppressed production of a wide spectrum of cytokines and chemokines induced by direct SEB airway exposure. Consequently, trafficking of neutrophils, monocytes/macrophages, and lymphocytes to the bronchoalveolar space was significantly reduced while vascular injury, manifested by increased permeability and protein leakage, was attenuated. Moreover, induction of systemic proinflammatory cytokines and chemokines in response to direct SEB airway exposure was reduced. Thus, intracellular delivery of a nuclear import inhibitory peptide suppresses respiratory and systemic expression of key mediators of lung inflammation evoked by SEB.

Molecular Basis of Pulmonary Disease

Pulmonary pathology includes a large spectrum of both neoplastic and non-neoplastic diseases that affect the lung. Many of these are a result of the unusual relationship of the lung with the outside world. Every breath that a human takes brings the outside world into the body in the form of infectious agents, organic and inorganic particles, and noxious agents of all types. Although the lung has many defense mechanisms to protect itself from these insults, these are not infallible; therefore, lung pathology arises. Damage to the lung is particularly important given the role of the lung in the survival of the organism. Any impairment of lung function has widespread effects throughout the body, since all organs depend on the lungs for the oxygen they need. Pulmonary pathology catalogs the changes in the lung tissues and the mechanisms through which these occur. This chapter presents a review of lung pathology and the current state of knowledge about the pathogenesis of each disease. It suggests that a clear understanding of both morphology and mechanism is required for the development of new therapies and preventive measures.

Regulation of T-cell function by endogenously produced angiotensin II

The adaptive immune response and, in particular, T cells have been shown to be important in the genesis of hypertension. In the present study, we sought to determine how the interplay between ANG II, NADPH oxidase, and reactive oxygen species modulates T cell activation and ultimately causes hypertension. We determined that T cells express angiotensinogen, the angiotensin I-converting enzyme, and renin and produce physiological levels of ANG II. AT1 receptors were primarily expressed intracellularly, and endogenously produced ANG II increased T-cell activation, expression of tissue homing markers, and production of the cytokine TNF-alpha. Inhibition of T-cell ACE reduced TNF-alpha production, indicating endogenously produced ANG II has a regulatory role in this process. Studies with specific antagonists and T cells from AT1R and AT2R-deficient mice indicated that both receptor subtypes contribute to TNF-alpha production. We found that superoxide was a critical mediator of T-cell TNF-alpha production, as this was significantly inhibited by polyethylene glycol (PEG)-SOD, but not PEG-catalase. Thus, T cells contain an endogenous renin-angiotensin system that modulates T-cell function, NADPH oxidase activity, and production of superoxide that, in turn, modulates TNF-alpha production. These findings contribute to our understanding of how ANG II and T cells enhance inflammation in cardiovascular disease.

A dimer-specific function of the transcription factor NFATp

The transcription factor NFATp integrates multiple signal transduction pathways through coordinate binding with basic-region leucine zipper (bZIP) proteins and other transcription factors. The NFATp monomer, even in the absence of its activation domains, recruits bZIP proteins to canonical NFAT-bZIP composite DNA elements. By contrast, the NFATp dimer and its bZIP partner bind noncooperatively to the NFAT-bZIP element of the tumor necrosis factor (TNF) gene promoter. This observation raises the possibility that the function of the activation domains of NFATp is dimer-specific. Here, we determine the consensus DNA binding site of the NFATp dimer, describe monomer- and dimer-specific NFATp-DNA contact patterns, and demonstrate that NFATp dimerization and dimer-specific activation subdomains are required for transcriptional activation from the TNF NFAT-bZIP element. We also show that these NFATp subdomains interact with the coactivator CBP (CREB-binding protein), which is required for NFATp-dependent TNF gene transcription. Thus, the context-specific function of the activation domains of NFAT can be potentiated by DNA-directed dimerization.

Genome-wide transcriptional response of primary alveolar macrophages following infection with porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome is a major cause of economic loss for the swine industry worldwide. Porcine reproductive and respiratory syndrome virus (PRRSV) triggers weak and atypical innate immune responses, but key genes and mechanisms by which the virus interferes with the host innate immunity have not yet been elucidated. In this study, genes that control the response of the main target of PRRSV, porcine alveolar macrophages (PAMs), were profiled in vitro with a time-course experiment spanning the first round of virus replication. PAMs were obtained from six piglets and challenged with the Lelystad PRRSV strain, and gene expression was investigated using Affymetrix microarrays and real-time PCR. Of the 1409 differentially expressed transcripts identified by analysis of variance, two, five, 25, 16 and 100 differed from controls by a minimum of 1.5-fold at 1, 3, 6, 9 and 12 h post-infection (p.i.), respectively. A PRRSV infection effect was detectable between 3 and 6 h p.i., and was characterized by a consistent downregulation of gene expression, followed by the start of the host innate immune response at 9 h p.i. The expression of beta interferon 1 (IFN-β), but not of IFN-α, was strongly upregulated, whilst few genes commonly expressed in response to viral infections and/or induced by interferons were found to be differentially expressed. A predominance of anti-apoptotic transcripts (e.g. interleukin-10), a shift towards a T-helper cell type 2 response and a weak upregulation of tumour necrosis factor-α expression were observed within 12 h p.i., reinforcing the hypotheses that PRRSV has developed sophisticated mechanisms to escape the host defence.