Negative transcriptional regulation of the interferon-gamma promoter by glucocorticoids and dominant negative mutants of c-Jun

The Psychoneuroimmunological Model of Moral Distress and Health in Healthcare Workers: Toward Individual and System-Level Solutions

Healthcare is presently experiencing a global workforce crisis, marked by the inability of hospitals to retain qualified healthcare workers. Indeed, poor working conditions and staff shortages have contributed to structural collapse and placed a heavy toll on healthcare workers' (HCWs) well-being, with many suffering from stress, exhaustion, demoralization, and burnout. An additional factor driving qualified HCWs away is the repeated experience of moral distress, or the inability to act according to internally held moral values and perceived ethical obligations due to internal and external constraints. Despite general awareness of this crisis, we currently lack an organized understanding of how stress leads to poor health, wellbeing, and performance in healthcare workers. To address this critical issue, we first review the literature on moral distress, stress, and health in HCWs. Second, we summarize the biobehavioral pathways linking occupational and interpersonal stressors to health in this population, focusing on neuroendocrine, immune, genetic, and epigenetic processes. Third, we propose a novel Psychoneuroimmunological Model of Moral Distress and Health in HCWs based on this literature. Finally, we discuss evidence-based individual- and system-level interventions for preventing stress and promoting resilience at work. Throughout this review, we underscore that stress levels in HCWs are a major public health concern, and that a combination of system-level and individual-level interventions are necessary to address preventable health care harm and foster resilience in this population, including new health policies, mental health initiatives, and additional translational research.

Alismol Purified from the Tuber of Alisma orientale Relieves Acute Lung Injury in Mice via Nrf2 Activation

Since the ethanol extract of Alisma orientale Juzepzuk (EEAO) suppresses lung inflammation by suppressing Nuclear Factor-kappa B (NF-κB) and activating Nuclear Factor Erythroid 2-related Factor 2 (Nrf2), we set out to identify chemicals constituting EEAO that suppress lung inflammation. Here, we provide evidence that among the five most abundant chemical constituents identified by Ultra Performance Liquid Chromatography (UPLC) and Nuclear Magnetic Resonance (NMR), alismol is one of the candidate constituents that suppresses lung inflammation in a lipopolysaccharide (LPS)-induced acute lung injury (ALI) mouse model and protects mice from ALI-like symptoms. Alismol did not induce cytotoxicity or reactive oxygen species (ROS). When administered to the lung of LPS-induced ALI mice (n = 5/group), alismol decreased the level of neutrophils and of the pro-inflammatory molecules, including Tumor Necrosis Factor-alpha (TNF-α), Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Monocyte Chemoattractant Protein-1 (MCP-1), Interferon-gamma (IFN-γ), and Cyclooxygenase-2 (COX-2), suggesting an anti-inflammatory activity of alismol. Consistent with these findings, alismol ameliorated the key features of the inflamed lung of ALI, such as high cellularity due to infiltrated inflammatory cells, the development of hyaline membrane structure, and capillary destruction. Unlike EEAO, alismol did not suppress NF-κB activity but rather activated Nrf2. Consequently, alismol induced the expression of prototypic genes regulated by Nrf2, including Heme Oxygenase-1 (HO-1), NAD(P)H: quinine oxidoreductase-1 (NQO-1), and glutamyl cysteine ligase catalytic units (GCLC). Alismol activating Nrf2 appears to be associated with a decrease in the ubiquitination of Nrf2, a key suppressive mechanism for Nrf2 activity. Together, our results suggest that alismol is a chemical constituent of EEAO that contributes at least in part to suppressing some of the key features of ALI by activating Nrf2.

IFN-γ and TGF-β, Crucial Players in Immune Responses: A Tribute to Howard Young

Interferon gamma (IFN-γ) and transforming growth factor beta (TGF-β), both pleiotropic cytokines, have been long studied and described as critical mediators of the immune response, notably in T cells. One of the investigators who made seminal and critical discoveries in the field of IFN-γ biology is Dr. Howard Young. In this review, we provide an overview of the biology of IFN-γ as well as its role in cancer and autoimmunity with an emphasis on Dr. Young's critical work in the field. We also describe how Dr. Young's work influenced our own research studying the role of TGF-β in the modulation of immune responses.

FOXO1 constrains activation and regulates senescence in CD8 T cells

Naive and memory T cells are maintained in a quiescent state, yet capable of rapid response and differentiation to antigen challenge via molecular mechanisms that are not fully understood. In naive cells, the deletion of Foxo1 following thymic development results in the increased expression of multiple AP-1 family members, rendering T cells less able to respond to antigenic challenge. Similarly, in the absence of FOXO1, post-infection memory T cells exhibit the characteristics of extended activation and senescence. Age-based analysis of human peripheral T cells reveals that levels of FOXO1 and its downstream target, TCF7, are inversely related to host age, whereas the opposite is found for AP-1 factors. These characteristics of aging also correlate with the formation of T cells manifesting features of cellular senescence. Our work illustrates a role for FOXO1 in the active maintenance of stem-like properties in T cells at the timescales of acute infection and organismal life span.

BACH2 regulates CD8(+) T cell differentiation by controlling access of AP-1 factors to enhancers

T cell antigen receptor (TCR) signaling drives distinct responses depending on the differentiation state and context of CD8(+) T cells. We hypothesized that access of signal-dependent transcription factors (TFs) to enhancers is dynamically regulated to shape transcriptional responses to TCR signaling. We found that the TF BACH2 restrains terminal differentiation to enable generation of long-lived memory cells and protective immunity after viral infection. BACH2 was recruited to enhancers, where it limited expression of TCR-driven genes by attenuating the availability of activator protein-1 (AP-1) sites to Jun family signal-dependent TFs. In naive cells, this prevented TCR-driven induction of genes associated with terminal differentiation. Upon effector differentiation, reduced expression of BACH2 and its phosphorylation enabled unrestrained induction of TCR-driven effector programs.

Retinoic acid modulates interferon-γ production by hepatic natural killer T cells via phosphatase 2A and the extracellular signal-regulated kinase pathway

Retinoic acid (RA), an active metabolite converted from vitamin A, plays an active role in immune function, such as defending against infections and immune regulation. Although RA affects various types of immune cells, including antigen-presenting cells, B lymphocytes, and T lymphocytes, whether it affects natural killer T (NKT) cells remain unknown. In this study, we found that RA decreased interferon (IFN)-γ production by activated NKT cells through T-cell receptor (TCR) and CD28. We also found that RA reduced extracellular signal-regulated kinase (ERK) phosphorylation, but increased phosphatase 2A (PP2A) activity in TCR/CD28-stimulated NKT cells. The increased PP2A activity, at least partly, contributed to the reduction of ERK phosphorylation. Since inhibition of ERK activation decreases IFN-γ production by TCR/CD28-stimulated NKT cells, RA may downregulate IFN-γ production by TCR/CD28-stimulated NKT cells through the PP2A-ERK pathway. Our results demonstrated a novel function of RA in modulating the IFN-γ expression by activated NKT cells.

Glucocorticoids regulate natural killer cell function epigenetically

Although glucocorticoids are well known for their capacity to suppress the immune response, glucocorticoids can also promote immune responsiveness. It was the purpose of this investigation to evaluate the molecular basis for this apparent dichotomous immunologic effect. Glucocorticoid treatment of natural killer cells (NK) was shown to reduce NK cell cytolytic activity by reduction of histone promoter acetylation for perforin and granzyme B, which corresponded with reduced mRNA and protein for each. In contrast, glucocorticoid treatment increased histone acetylation at regulatory regions for interferon gamma and IL-6, as well as chromatin accessibility for each. This increase in histone acetylation was associated with increased proinflammatory cytokine mRNA and protein production upon cellular stimulation. These immunologic effects were evident at the level of the individual cell and demonstrate glucocorticoids to epigenetically reduce NK cell cytolytic activity while at the same time to prime NK cells for proinflammatory cytokine production.

JUNB/AP-1 controls IFN-γ during inflammatory liver disease

Understanding the molecular pathogenesis of inflammatory liver disease is essential to design efficient therapeutic approaches. In hepatocytes, the dimeric transcription factor c-JUN/AP-1 is a major mediator of cell survival during hepatitis, although functions for other JUN proteins in liver disease are less defined. Here, we found that JUNB was specifically expressed in human and murine immune cells during acute liver injury. We analyzed the molecular function of JUNB in experimental models of hepatitis, including administration of concanavalin A (ConA) or α-galactosyl-ceramide, which induce liver inflammation and injury. Mice specifically lacking JUNB in hepatocytes displayed a mild increase in ConA-induced liver damage. However, targeted deletion of Junb in immune cells and hepatocytes protected against hepatitis in experimental models that involved NK/NKT cells. The absence of JUNB in immune cells decreased IFN-γ expression and secretion from NK and NKT cells, leading to reduced STAT1 pathway activation. Systemic IFN-γ treatment or adenovirus-based IRF1 delivery to Junb-deficient mice restored hepatotoxicity, and we demonstrate that Ifng is a direct transcriptional target of JUNB. These findings demonstrate that JUNB/AP-1 promotes cell death during acute hepatitis by regulating IFN-γ production in NK and NKT cells and thus functionally antagonizes the hepatoprotective function of c-JUN/AP-1 in hepatocytes.

STAT4 and T-bet are required for the plasticity of IFN-γ expression across Th2 ontogeny and influence changes in Ifng promoter DNA methylation

CD4(+) T cells developing toward a Th2 fate express IL-4, IL-5, and IL-13 while inhibiting production of cytokines associated with other Th types, such as the Th1 cytokine IFN- γ. IL-4-producing Th2 effector cells give rise to a long-lived memory population committed to reactivation of the Th2 cytokine gene expression program. However, reactivation of these effector-derived cells under Th1-skewing conditions leads to production of IFN-γ along with IL-4 in the same cell. We now show that this flexibility ("plasticity") of cytokine expression is preceded by a loss of the repressive DNA methylation of the Ifng promoter acquired during Th2 polarization yet requires STAT4 along with T-box expressed in T cells. Surprisingly, loss of either STAT4 or T-box expressed in T cells increased Ifng promoter CpG methylation in both effector and memory Th2 cells. Taken together, our data suggest a model in which the expression of IFN-γ by Th2-derived memory cells involves attenuation of epigenetic repression in memory Th2 cells, combined with Th1-polarizing signals after their recall activation.

Phosphorylation of mitogen-activated protein kinases contributes to interferon γ production in response to Mycobacterium tuberculosis

Immune control of Mycobacterium tuberculosis depends on interferon γ (IFN-γ)-producing CD4(+) lymphocytes. Previous studies have shown that T cells from patients with tuberculosis produce less IFN-γ, compared with healthy donors, in response to mycobacterial antigens, although IFN-γ responses to mitogens are preserved. In this work, we found that M. tuberculosis-induced IFN-γ production by human T cells correlated with phosphorylation of the mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), and p38. Moreover, the majority of IFN-γ-producing T cells expressed signaling lymphocyte activation molecule (SLAM), and SLAM activation further increased ERK phosphorylation. Interestingly, patients with tuberculosis had delayed activation of ERK and p38, and this was most marked in patients with the poorest IFN-γ responses (ie, low responders). Besides, SLAM signaling failed to phosphorylate ERK in low responders. Our findings suggest that activation of p38 and ERK, in part through SLAM, mediates T-cell IFN-γ production in response to M. tuberculosis, a pathway that is defective in patients with tuberculosis.

Glucocorticoid receptor mediated suppression of natural killer cell activity: identification of associated deacetylase and corepressor molecules

Physical and psychological stressors reduce natural killer cell function. This reduction in cellular function results from stress-induced release of glucocorticoids. Glucocorticoids act upon natural killer cells to deacetylate and transrepress immune response genes through epigenetic processes. However, other than the glucocorticoid receptor, the proteins that participate in this process are not well described in natural killer cells. The purpose of this study was to identify the proteins associated with the glucocorticoid receptor that are likely epigenetic participants in this process. Treatment of natural killer cells with the synthetic glucocorticoid, dexamethasone, produced a significant time dependent reduction in natural killer cell activity as early as 8h post treatment. This reduction in natural killer cell activity was preceded by nuclear localization of the glucocorticoid receptor with histone deacetylase 1 and the corepressor, SMRT. Other class I histone deacetylases were not associated with the glucocorticoid receptor nor was the corepressor NCoR. These results demonstrate histone deacetylase 1 and SMRT to associate with the ligand activated glucocorticoid receptor within the nuclei of natural killer cells and to be the likely participants in the histone deacetylation and transrepression that accompanies glucocorticoid mediated reductions in natural killer cell function.

Changes in epigenetic regulation of CD4+ T lymphocytesin biliary atresia

Biliary atresia (BA) is a virus-induced autoimmune disease associated with abnormal DNA methylation patterns that contribute to disease presentation. This study examined DNA methylation patterns, changes to genes associated with methylation regulation, and changes to the autoimmune-related gene interferon gamma (IFN-γ) in CD4+ T cells from BA patients. We demonstrated that genomic DNA isolated from CD4+ T cells harvested from infants presenting with BA were hypomethylated relative to healthy controls. In addition, DNA methyltransferase (DNMT1) and DNMT3a mRNA levels were significantly lower in BA CD4+ T cells compared with controls and methyl-DNA-binding domain proteins (MBD1) mRNA expression (but not MBD4 detected at higher levels in BA patients), which was significantly lower in CD4+ T cells from BA infants than in controls. DNMT1 expression positively correlated with global DNA methylation in BA CD4+ T cells. IFN-γ mRNA expression levels in BA patients were also significantly increased, and the IFN-γ gene promoter region was hypomethylated in BA CD4+ T cells compared with controls and negatively correlated with DNA methylation. These data suggest that methylation changes in CD4+ cells may contribute to BA disease presentation and progression by affecting the expression of genes associated with autoimmunity.

Epigenetic patterns associated with the immune dysregulation that accompanies psychosocial distress

The molecular basis for psychosocial-distress mediated immune-dysregulation is not well understood. The purpose of this study was to determine whether peripheral blood mononuclear cell (PBMC) epigenetic pattern associates with this form of immune dysregulation. Women newly diagnosed with early stage breast cancer were enrolled into the study and psychosocial, immunological and epigenetic assessments were made at diagnosis and four months later, after completion of cancer treatment. At diagnosis women reported increased perceived stress, anxiety, and mood disturbance and the PBMC of these women exhibited reduced natural killer cell activity and reduced production of interferon gamma, which contrasted with results, obtained after completion of treatment. At the epigenetic level, a PBMC subset derived from women at diagnosis exhibited a distinct epigenetic pattern, with reduced nuclear acetylation of histone residues H4-K8 and H4-K12, as well as reduced phosphorylation of H3-S10, when compared to similar cells derived after the completion of treatment. Natural killer cell activity and interferon-gamma production were associated with nuclear acetylation and phosphorylation status of these histone residues. These findings demonstrate associations among nuclear epigenetic pattern and the immune dysregulation that accompanies psychosocial distress.

β-Caryophyllene inhibits dextran sulfate sodium-induced colitis in mice through CB2 receptor activation and PPARγ pathway

Cannabinoid receptor 2 (CB2) activation is suggested to trigger the peroxisome proliferator-activated receptor-γ (PPARγ) pathway, and agonists of both receptors improve colitis. Recently, the plant metabolite (E)-β-caryophyllene (BCP) was shown to bind to and activate CB2. In this study, we examined the anti-inflammatory effect of BCP in dextran sulfate sodium (DSS)-induced colitis and analyzed whether this effect was mediated by CB2 and PPARγ. Oral treatment with BCP reduced disease activity, colonic macro- and microscopic damage, myeloperoxidase and N-acetylglucosaminidase activities, and levels and mRNA expression of colonic tumor necrosis factor-α, IL-1β, interferon-γ, and keratinocyte-derived chemokine. BCP treatment also inhibited the activation of extracellular signal-regulated kinase 1/2, nuclear factor κB, IκB-kinase α/β, cAMP response element binding and the expression of caspase-3 and Ki-67. Moreover, BCP enhanced IL-4 levels and forkhead box P3 mRNA expression in the mouse colon and reduced cytokine levels (tumor necrosis factor-α, keratinocyte-derived chemokine, and macrophage-inflammatory protein-2) in a culture of macrophages stimulated with lipopolysaccharide. The use of the CB2 antagonist AM630 or the PPARγ antagonist GW9662 significantly reversed the protective effect of BCP. Confirming our results, AM630 reversed the beneficial effect of BCP on pro-inflammatory cytokine expression in IEC-6 cells. These results demonstrate that the anti-inflammatory effect of BCP involves CB2 and the PPARγ pathway and suggest BCP as a possible therapy for the treatment of inflammatory bowel disease.

Glucocorticoid dysregulation of natural killer cell function through epigenetic modification

It is well-established that psychological distress reduces natural killer cell activity (NKCA) and dysregulates cytokine balance. This may be mediated by stress-induced release of glucocorticoids, which have broad effects on the immune system, including the suppression of NKCA and alteration of cytokine production. The purpose of this study was to evaluate epigenetic mechanisms that may underlie the effect of glucocorticoids on NK cells, using the human NK cell line, NK92. Treatment of NK92 cells with the synthetic glucocorticoid, dexamethasone, at a concentration of 10⁻⁷M, produced a significant reduction in NKCA. Glucocorticoid inhibition was a consequence of not only a reduced capacity of the NK cells to bind to tumor targets but also a reduced production of granule constituents (perforin and granzyme B) with no detectable effect on granule exocytosis. Glucocorticoids also reduced the constitutive and the stimulated production of the cytokines, IL-6, TNF alpha and IFN gamma, and reduced the surface expression of LFA-1. Glucocorticoid treatment also reduced global histone acetylation, the acetylation of histone 4 lysine position 8, and the accessibility of the proximal promoters of perforin, interferon gamma and granzyme B. Histone acetylation was recovered by treatment of the NK cells with a histone deacetylase inhibitor, which also restored NKCA and IFN gamma production. These results demonstrate glucocorticoids to dysregulate NK cell function at least in part through an epigenetic mechanism, which reduces promoter accessibility through modification of histone acetylation status. This epigenetic modification decreases the expression of effector proteins necessary to the full functional activity of NK cells.

Surgery as a double-edged sword: a clinically feasible approach to overcome the metastasis-promoting effects of surgery by blunting stress and prostaglandin responses

Surgery remains an essential therapeutic approach for most solid malignancies, including breast cancer. However, surgery also constitutes a risk factor for promotion of pre-existing micrometastases and the initiation of new metastases through several mechanisms, including the release of prostaglandins and stress hormones (e.g., catecholamines and glucocorticoids). However, the perioperative period also presents an opportunity for cell mediated immunity (CMI) and other mechanisms to eradicate or control minimal residual disease, provided that the deleterious effects of surgery are minimized. Here, we discuss the key role of endogenous stress hormones and prostaglandins in promoting the metastatic process through their direct impact on malignant cells, and through their deleterious impact on anti-cancer CMI. We further discuss the effects of anesthetic techniques, the extent of surgery, pain alleviation, and timing within the menstrual cycle with respect to their impact on tumor recurrence and physiological stress responses. Last, we suggest an attractive perioperative drug regimen, based on a combination of a cyclooxygenase (COX)-2 inhibitor and a β-adrenergic blocker, which we found effective in attenuating immune suppression and the metastasis-promoting effects of surgery in several tumor models. This regimen is clinically applicable, and could potentially promote disease free survival in patients operated for breast and other types of cancer.

Phosphodiesterase type 4 inhibitors: potential in the treatment of multiple sclerosis?

Phosphodiesterases (PDEs) are involved in the regulation of intracellular levels of the second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). These enzymes hydrolyse the cyclic nucleotides to the corresponding nucleoside 5'-monophosphates. Nine PDE subtypes have been identified; these differ in their substrate specificity and mode of activation. The type 4 PDE (PDE(4)) hydrolyses cAMP, is activated by elevated levels of cAMP, and is inhibited by rolipram. Inhibition of enzyme activity has been shown to modulate the activity of cells of the immune system. The production of tumour necrosis factor (TNF)(alpha) by activated monocytes and macrophages is inhibited, and cytokine secretion and proliferation of type 1 T helper cells are suppressed. Both immune cell activation and their concomitant induction of cytokine secretion are implicated in multiple sclerosis (MS), which is the major demyelinating disease of the central nervous system. Studies with the selective PDE(4) inhibitor rolipram in experimental autoimmune encephalomyelitis (an animal model of MS) in mice, rats and nonhuman primates have demonstrated the efficacy of the compound in this disease model, suggesting that PDE(4) inhibitors could ameliorate the clinical course of MS. Unfortunately, clinical trials with PDE(4) inhibitors revealed the major adverse effects of these drugs, namely nausea and vomiting. However, novel PDE(4) inhibitors, which target only a subpopulation of PDE(4) enzymes, may provoke fewer adverse effects. The efficacy of a PDE(4) inhibitor in MS still needs to be demonstrated in a well designed clinical trial.

ESAT-6 inhibits production of IFN-gamma by Mycobacterium tuberculosis-responsive human T cells

The Mycobacterium tuberculosis early secreted Ag of 6 kDa (ESAT-6) is a potent Ag for human T cells and is a putative vaccine candidate. However, ESAT-6 also contributes to virulence in animal models, mediates cellular cytolysis, and inhibits IL-12 production by mononuclear phagocytes. We evaluated the effects of ESAT-6 and its molecular chaperone, culture filtrate protein of 10 kDa (CFP10), on the capacity of human T cells to produce IFN-gamma and proliferate in response to TCR activation. Recombinant ESAT-6, but not CFP10, markedly inhibited IFN-gamma production by T cells stimulated with M. tuberculosis or with the combination of anti-CD3 and anti-CD28, in a dose-dependent manner. ESAT-6 also inhibited T cell production of IL-17 and TNF-alpha but not IL-2. Preincubation of ESAT-6 with CFP10 under conditions that favor dimer formation did not affect inhibition of IFN-gamma. ESAT-6 decreased IFN-gamma transcription and reduced expression of the transcription factors, ATF-2 and c-Jun, which normally bind to the IFN-gamma proximal promoter and stimulate mRNA expression. ESAT-6 inhibited T cell IFN-gamma secretion through mechanisms that did not involve cellular cytotoxicity or apoptosis. ESAT-6, but not CFP10, bound to T cells and inhibited expression of early activation markers without reducing activation of ZAP70. We conclude that ESAT-6 directly inhibits human T cell responses to mycobacterial Ags by affecting TCR signaling pathways downstream of ZAP70.

Glucocorticoids inhibit GATA-3 phosphorylation and activity in T cells

Glucocorticoid (GC) immunosuppression and anti-inflammatory action involve the regulation of several transcription factors (TFs). GCs inhibit the acute production of T-helper (Th) 1 and Th2 cytokines but ultimately favor a shift toward Th2 phenotype. GCs inhibit the transcriptional activity of T-bet Th1 TF by a transrepression mechanism. Here we analyze GC regulation of GATA-3, the master driver of Th2 differentiation. We found that GCs inhibit GATA-3 transcriptional activity. We demonstrate that this mechanism does not involve physical interaction between the glucocorticoid receptor (GR) and GATA-3 or reduction of GATA-3 binding to DNA, as described previously for T-bet. Instead, GCs inhibit GATA-3 activity by inhibition of p38 mitogen-activated protein kinase induced GATA-3 phosphorylation. GCs also inhibit GATA-3 mRNA and protein expression. Finally, GATA-3 inhibition affects the interleukin-5 gene, a central Th2 cytokine. The IC(50) of dexamethasone is 10 nM with a maximum effect at 100 nM. All inhibitory actions were blocked by the GR antagonist RU38486 (1 uM), proving the specificity of GR action. In view of the crucial role of GATA-3 in T-cell differentiation and inflammation, we propose that the mechanism of GATA-3 inhibition compared with that in T-bet may have relevant implications in understanding and modulating the anti-inflammatory and Th-regulatory properties of GCs.

CREB, ATF, and AP-1 transcription factors regulate IFN-gamma secretion by human T cells in response to mycobacterial antigen

IFN-gamma production by T cells is pivotal for defense against many pathogens, and the proximal promoter of IFN-gamma, -73 to -48 bp upstream of the transcription start site, is essential for its expression. However, transcriptional regulation mechanisms through this promoter in primary human cells remain unclear. We studied the effects of cAMP response element binding protein/activating transcription factor (CREB/ATF) and AP-1 transcription factors on the proximal promoter of IFN-gamma in human T cells stimulated with Mycobacterium tuberculosis. Using EMSA, supershift assays, and promoter pulldown assays, we demonstrated that CREB, ATF-2, and c-Jun, but not cyclic AMP response element modulator, ATF-1, or c-Fos, bind to the proximal promoter of IFN-gamma upon stimulation, and coimmunoprecipitation indicated the possibility of interaction among these transcription factors. Chromatin immunoprecipitation confirmed the recruitment of these transcription factors to the IFN-gamma proximal promoter in live Ag-activated T cells. Inhibition of ATF-2 activity in T cells with a dominant-negative ATF-2 peptide or with small interfering RNA markedly reduced the expression of IFN-gamma and decreased the expression of CREB and c-Jun. These findings suggest that CREB, ATF-2, and c-Jun are recruited to the IFN-gamma proximal promoter and that they up-regulate IFN-gamma transcription in response to microbial Ag. Additionally, ATF-2 controls expression of CREB and c-Jun during T cell activation.

NF-kappaB activation by the viral oncoprotein StpC enhances IFN-gamma production in T cells

Interferon-gamma (IFN-gamma) is an essential regulator of innate and adaptive immune responses and a hallmark of the Th1 T-cell subset. It is produced at high levels by human T lymphocytes upon transformation with Herpesvirus saimiri, which depends on the expression of the viral oncoproteins saimiri transformation-associated protein of subgroup C (StpC) and tyrosine kinase-interacting protein (Tip). Here, we show that IFN-gamma production was induced by Tip in Jurkat T cells. StpC by itself did not affect IFN-gamma expression, but enhanced the effect of Tip. Our results substantiated the findings that StpC induces NF-kappaB activation and demonstrated that other transcription factors, including NFAT, AP-1 and serum response element regulators, were not activated by StpC in unstimulated T cells. Studies using StpC mutants deficient in NF-kappaB activation, dominant negative IkappaBalpha and constitutively active IKK2, established the importance of NF-kappaB in StpC-mediated upregulation of IFN-gamma production. These observations suggest that NF-kappaB induction by StpC contributes to the Th1-like phenotype of virus-transformed human T cells.

The excitotoxic effect of NMDA on human lymphocyte immune function

N-Methyl-d-aspartate (NMDA)-activated glutamate receptors are expressed in lymphocytes, but their roles have not yet been defined. We show that incubation of human peripheral blood lymphocytes with NMDA resulted in increased intracellular calcium and reactive oxygen species (ROS) levels through effects on NMDA-activated glutamate receptors. In terms of ROS production, T cells were most affected, followed by NK cells, whereas B cell ROS levels were not increased. In unstimulated T and NK cells, interferon-gamma (IFN-gamma) production was unaffected by NMDA, whereas interleukin-2 stimulation of IFN-gamma production was significantly suppressed by NMDA. Simultaneous incubation of the cells with NMDA and IL-2 resulted in a dramatic increase in the amount of cells expressing the NR1 subunit of the NMDA-activated receptors. We conclude that NMDA-activated glutamate receptor activation, accompanied by the changes in intracellular calcium and ROS levels, may be involved in the modification of immune functions of human T and NK cells.

BOB.1/OBF.1 controls the balance of TH1 and TH2 immune responses

BOB.1/OBF.1 is a transcriptional coactivator essential at several stages of B-cell development. In T cells, BOB.1/OBF.1 expression is inducible by co-stimulation. However, a defined role of BOB.1/OBF.1 for T-cell function had not been discovered so far. Here, we show that BOB.1/OBF.1 is critical for T helper cell function. BOB.1/OBF.1(-/-) mice showed imbalanced immune responses, resulting in increased susceptibility to Leishmania major infection. Functional analyses revealed specific defects in TH1 and TH2 cells. Whereas expression levels of TH1 cytokines were reduced, the secretion of TH2 cytokines was increased. BOB.1/OBF.1 directly contributes to the IFNgamma and IL2 promoter activities. In contrast, increased TH2 cytokine production is controlled indirectly, probably via the transcription factor PU.1, the expression of which is regulated by BOB.1/OBF.1. Thus, BOB.1/OBF.1 regulates the balance of TH1 versus TH2 mediated immunity.

Glucocorticoids in the regulation of transcription factors that control cytokine synthesis

The interaction at different levels between intracellular signals elicited by cytokines and activated glucocorticoid receptors (GR) is essential for the regulation of immune responses. We describe different levels of interaction between glucocorticoids and cytokines which result in the induction or repression of gene transcription. These include the regulation of cytokine receptor expression, the molecular cross-talk between the GR and transcription factors (TFs) activated by cytokine signaling, the interaction with several signaling pathways and also posttranslational modifications of both GR and TFs. Also, an overview of the implications of chromatin remodeling in this interplay is discussed. The complexity of the intricate network involved in the interaction between GR and TFs is pivotal for the final outcome of cytokines biological action.

The activated glucocorticoid receptor inhibits the transcription factor T-bet by direct protein-protein interaction

Glucocorticoids (GCs) immunosuppression acts via regulation of several transcription factors (TF), including activating protein (AP)-1, NF-kappaB, and NFAT. GCs inhibit Th1 cytokines and promote a shift toward Th2 differentiation. Th1 phenotype depends on TF T-bet. In this study, we examined GC regulation of T-bet. We found that GCs inhibit T-bet transcriptional activity. We show that glucocorticoid receptor (GR) physically interacts with T-bet both in transfected cell lines and in primary splenocyte cultures with endogenous GR and T-bet. This interaction also blocks GR-dependent transcription. We show both in vitro and in vivo at endogenous binding sites that the mechanism underlying T-bet inhibition further involves reduction of T-bet binding to DNA. Using specific mutations of GR, we demonstrate that the first zinc finger region of GR is required for T-bet inhibition. GCs additionally inhibit T-bet both at mRNA and protein expression levels, revealing another layer of GR action on T-bet. Finally, we examined the functional consequences of GR/T-bet interaction on IFN-gamma, showing that GCs inhibit transcriptional activity of T-bet on its promoter. In view of the crucial role of T-bet in T cell differentiation and inflammation, we propose that GR inhibitory interaction with T-bet may be an important mechanism underlying the immunosuppressive properties of GCs.

A functional SNP of interferon-gamma gene is important for interferon-alpha-induced and spontaneous recovery from hepatitis C virus infection

Cytokine polymorphisms are associated with disease outcome and interferon (IFN) treatment response in hepatitis C virus (HCV) infection. We genotyped eight SNPs spanning the entire IFN-gamma gene in two cohorts and assessed the association between those polymorphisms and treatment response or spontaneous viral clearance. The first cohort was composed of 284 chronically HCV-infected patients who had received IFN-alpha-based therapy and the second was 251 i.v. drug users who had either spontaneously cleared HCV or become chronically infected. A SNP variant located in the proximal IFN-gamma promoter region next to the binding motif of heat shock transcription factor (HSF), -764G, was significantly associated with sustained virological response [P = 0.01, odds ratio (OR) = 2.66 [corrected] (confidence interval 1.3-5.6)[corrected]]. The association was independently significant in multiple logistic regression (P = 0.04) along with race, viral titer, and genotype. This variant was also significantly associated with spontaneous recovery [P = 0.04, OR = 3.51 (1.0-12.5)] in the second cohort. Functional analyses show that the G allele confers a two- to three-fold higher promoter activity and stronger binding affinity to HSF1 than the C allele. Our study suggests that the IFN-gamma promoter SNP -764G/C is functionally important in determining viral clearance and treatment response in HCV-infected patients and may be used as a genetic marker to predict sustained virological response in HCV-infected patients.

IFN-gamma and T-bet expression in human dendritic cells from normal donors and cancer patients is controlled through mechanisms involving ERK-1/2-dependent and IL-12-independent pathways

Dendritic cells (DC) play a major role in priming naive T cells and modulating the immune response. We have previously reported that bryostatin-1, a potent immune modulator with antitumor activity, activates monocytes and lymphocytes to produce cytokines. Studies have shown that tumor-bearing hosts have a Th1/Th2 cytokine pattern that is associated with decreased production of IFN-gamma. We investigated the expression of IFN-gamma in bryostatin-1-treated human DC. Bryostatin-1 induced both IFN-gamma and T-bet mRNA expression in a dose- and time-dependent manner. As little as 1 ng/ml bryostatin-1 induced IFN-gamma and T-bet transcripts within 3 h and protein at 12 h. Treatment of DC with cycloheximide revealed that bryostatin-1-induced T-bet expression requires de novo protein synthesis, but bryostatin-1-induced IFN-gamma expression is independent of protein synthesis. Furthermore, dexamethasone inhibits bryostatin-1-induced IFN-gamma mRNA expression but increases bryostatin-1-induced T-bet mRNA expression. Experiments with ERK-1/2 inhibitors demonstrated that bryostatin-1 induction of IFN- gamma and T-bet was ERK-dependent and IL-12-independent. Similar results were obtained from both normal donors and cancer patients. In summary, our results suggest that bryostatin-1-induced IFN-gamma expression is T-bet independent. They also suggest for the first time that IFN- gamma and T-bet can be induced in human DC through an ERK-dependent pathway. Bryostatin-1-induced IFN- gamma may play a crucial role in the initiation of the immune response, before specific recognition by T cells that could be beneficial in the treatment of cancer.

The antineoplastic agent bryostatin-1 differentially regulates IFN-gamma receptor subunits in monocytic cells: transcriptional and posttranscriptional control of IFN-gamma R2

Bryostatin-1 (Bryo-1) is a potent ligand and modulator of protein kinase C that exerts antineoplastic and immunomodulatory activities both in vitro and in vivo. We have previously reported that Bryo-1 synergized with IFN-gamma to induce NO synthase and NO by macrophages. To determine whether this effect was associated with changes in levels of IFN-gammaR, we investigated the effects of Bryo-1 on the expression and regulation of IFN-gammaR chains in monocytic cells. Northern blot analysis revealed that Bryo-1 treatment of the human monocytic cell lines MonoMac6 and THP-1 and human monocytes enhanced the expression of IFN-gammaR2 mRNA but did not affect IFN-gammaR1 mRNA expression. Bryo-1 increased IFN-gammaR2 mRNA in a dose-dependent manner as early as 3 h posttreatment. Bryo-1-induced up-regulation of IFN-gammaR2 mRNA levels is not dependent on de novo protein synthesis as shown by cell treatment with the protein-synthesis inhibitor cycloheximide. Bryo-1 treatment increased the IFN-gammaR2 mRNA half-life by 2 h. EMSA analysis from Bryo-1-treated MonoMac6 cells showed an increased nuclear protein binding to the NF-kappaB motif present in the 5' flanking region of the human IFN-gammaR2 promoter that was markedly decreased by pretreatment with the NF-kappaB inhibitor SN50. These results show for the first time that Bryo-1 up-regulates IFN-gammaR2 expression in monocytic cells. Given the pivotal role that IFN-gamma exerts on monocyte activation and in the initiation and outcome of the immune response, the induction of IFN-gammaR2 by Bryo-1 has significant implications in immunomodulation and could overcome some of the immune defects observed in cancer patients.

T-box proteins differentially activate the expression of the endogenous interferon γ gene versus transfected reporter genes in non-immune cells

The T-box transcription factor T-bet is expressed in a number of hematopoetic cell types and plays an essential role in the lineage determination of Th1 T-helper cells. In the absence of T-bet, CD4(+) T-cells fail to induce IFNgamma, the cytokine whose expression characterizes Th1 cells. Here we show that, surprisingly, T-bet induces the expression of endogenous IFNgamma in non-immune human cells, including 293 and other cell lines. Thus T-bet can induce IFNgamma expression independently of its role in T-cell lineage determination. In addition, mutations in T-bet, and chimeras of T-bet with other transcription factors including the T-box transcription factor, TBX2, differentially affect the ability of T-bet to activate expression of endogenous IFNgamma versus a T-site regulated reporter gene. A truncated T-betVp16 fusion protein strongly activates the T-site reporter but fails to activate endogenous IFNgamma. Conversely, native T-bet strongly activates endogenous IFNgamma expression but only weakly activates the reporter gene. Fusion of the Vp16 activation domain to full-length T-bet greatly increases its activation of both endogenous IFNgamma and transfected T-site reporter gene expression. In contrast, TBX2Vp16 potently activates the T-site reporter but has a negligible effect on endogenous IFNgamma expression. Butyrate treatment of T-bet expressing cells potentiates the expression of endogenous IFNgamma but weakly represses expression of the T-site reporter gene. These data indicate that induction of endogenous IFNgamma can be uncoupled from differentiation into the Th1 lineage and that the expression of endogenous IFNgamma versus a T-site reporter gene is differentially regulated by T-bet and other T-box proteins.

An IFNG SNP with an estrogen-like response element selectively enhances promoter expression in peripheral but not lamina propria T cells

This study examines mucosa-specific regulatory pathways involved in modulation of interferon-gamma (IFN-gamma) in lamina propria T cells. Previous studies identified mucosa-specific CD2 cis-elements within the -204 to -108 bp IFNG promoter. Within this region, a single-site nucleotide polymorphism, -179G/T, imparts tumor necrosis factor-alpha stimulation of IFNG in peripheral blood lymphocytes, and is linked with accelerated AIDS progression. We discovered a putative estrogen response element (ERE) introduced by the -179T, which displays selective activation in peripheral blood mononuclear cells (PBMC) vs lamina propria mononuclear cells (LPMC). Transfection of PBMC with constructs containing the -179G or -179T site revealed CD2-mediated enhancement of the -179T compared to -179G allele, although, in LPMC, a similar level of expression was detected. Electrophoretic mobility shift assay (EMSA) analysis demonstrated CD2-mediated nucleoprotein binding to the -179T but not the -179G in PBMC. In LPMC, binding is constitutive to both -179G and -179T regions. Sequence and EMSA analysis suggests that the -179T allele creates an ERE-like binding site capable of binding recombinant estrogen receptor. Estrogen response element transactivation is enhanced by CD2 signaling, but inhibited by estrogen in PBMC but not in LPMC, although expression of estrogen receptor was similar. This is the first report to describe a potential molecular mechanism responsible for selectively controlling IFN-gamma production in LPMC.

Inhibition of IFN-gamma transcription by site-specific methylation during T helper cell development

Polarization of naïve CD4 T cells into T helper type 2 (TH2) cells is characterized by expression of IL-4 and silencing of IFN-gamma. Here we show that during TH2 polarization, the DNA methyltransferase Dnmt3a is recruited to the IFN-gamma promoter and correspondingly the promoter undergoes progressive de novo methylation. Notably, the CpG located at the -53 position becomes methylated rapidly and this methylation inhibits ATF2/c-Jun and CREB transcription factor binding in vitro. In vivo, the same factors bind to the unmethylated IFN-gamma promoter in T helper type 1 (TH1) cells but not the methylated IFN-gamma promoter in TH2 cells. Furthermore, methylation at the -53 CpG alone is sufficient to inhibit the IFN-gamma promoter-driven reporter gene expression in a TH1 cell line. These findings suggest that rapid methylation of the evolutionarily conserved -53 CpG by Dnmt3a may suppress IFN-gamma transcription in developing TH2 cells by directly inhibiting transcription factor binding.

LXR activation reduces proinflammatory cytokine expression in human CD4-positive lymphocytes

BACKGROUND

CD4-positive lymphocytes, the major T-cell population in human atheroma, mainly secrete Th-1-type proinflammatory cytokines, like interferon (IFN)gamma, tumor necrosis factor (TNF)alpha, and interleukin (IL)-2, thus promoting atherogenesis. Recent data suggest that the nuclear transcription factors liver X receptor-alpha and liver X receptor-beta (LXRalpha and LXRbeta) limit plaque formation in animal models by modulating macrophage function. Still, the role of LXRs in CD4-positive lymphocytes is currently unexplored.

METHODS AND RESULTS

Human CD4-positive lymphocytes express LXRalpha and LXRbeta mRNA and protein. Activation of CD4-positive cells by anti-CD3 mAbs, anti-CD3/CD28 mAbs, as well as PMA/ionomycin significantly increased Th1-cytokine mRNA and protein expression. Treatment with the LXR activator T0901317 reduced this increase of IFNgamma, TNFalpha, and IL-2 in a concentration-dependent manner with a maximum at 1 micromol/L T0901317. Transient transfection assays revealed an inhibition of IFNgamma promoter activity by T0901317 as the underlying molecular mechanism. Such anti-inflammatory actions were also evident in cell-cell interactions with medium conditioned by T0901317-treated CD4-positive cells attenuating human monocyte CD64 expression.

CONCLUSIONS

Human CD4-positive lymphocytes express both LXRalpha and LXRbeta, and LXR activation can reduce Th-1 cytokine expression in these cells. These data provide new insight how LXR activators might modulate the inflammatory process in atherogenesis and as such influence lesion development.

Circadian Oscillations of Clock Genes, Cytolytic Factors, and Cytokines in Rat NK Cells

A growing body of knowledge is revealing the critical role of circadian physiology in the development of specific pathological entities such as cancer. NK cell function participates in the immune response against infection and malignancy. We have reported previously the existence of a physiological circadian rhythm of NK cell cytolytic activity in rats, suggesting the existence of circadian mechanisms subjacent to NK cell function. At the cellular level, circadian rhythms are originated by the sustained transcriptional-translational oscillation of clock genes that form the cellular clock apparatus. Our aim in this study was to investigate the presence of molecular clock mechanisms in NK cells as well as the circadian expression of critical factors involved in NK cell function. For that purpose, we measured the circadian changes in the expression of clock genes (Per1, Per2, Bmal1, Clock), Dbp (a clock-controlled output gene), CREB (involved in clock signaling), cytolytic factors (granzyme B and perforin), and cytokines (IFN-gamma and TNF-alpha) in NK cells enriched from the rat spleen. The results obtained from this study demonstrate for the first time the existence of functional molecular clock mechanisms in NK cells. Moreover, the circadian expression of cytolytic factors and cytokines in NK cells reported in this study emphasizes the circadian nature of NK cell function.

Cyclic AMP Response Element-Binding Protein Positively Regulates Production of IFN-γ by T Cells in Response to a Microbial Pathogen

IFN-gamma is essential for resistance to many intracellular pathogens, including Mycobacterium tuberculosis. Transcription of the IFN-gamma gene in activated T cells is controlled by the proximal promoter element (-73 to -48 bp). CREB binds to the IFN-gamma proximal promoter, and binding is enhanced by phosphorylation of CREB. Studies in human T cell lines and in transgenic mice have yielded conflicting results about whether CREB is a positive or a negative regulator of IFN-gamma transcription. To determine the role of CREB in mediating IFN-gamma production in response to a microbial pathogen, we evaluated the peripheral blood T cell response to M. tuberculosis in healthy tuberculin reactors. EMSAs, chromatin immunoprecipitation, and Western blotting demonstrated that stimulation of PBMC with M. tuberculosis induced phosphorylation and enhanced binding of CREB to the IFN-gamma proximal promoter. Neutralization of CREB with intracellular Abs or down-regulation of CREB levels with small interfering RNA decreased M. tuberculosis-induced production of IFN-gamma and IFN-gamma mRNA expression. In addition, M. tuberculosis-stimulated T cells from tuberculosis patients, who have ineffective immunity, showed diminished IFN-gamma production, reduced amounts of CREB binding to the IFN-gamma proximal promoter, and absence of phosphorylated CREB. These findings demonstrate that CREB positively regulates IFN-gamma production by human T cells that respond to M. tuberculosis.

DIM stimulates IFNgamma gene expression in human breast cancer cells via the specific activation of JNK and p38 pathways

3,3'-Diindolylmethane (DIM) is a promising anticancer agent derived from Brassica vegetables, but the mechanisms of DIM action are largely unknown. We have shown that DIM can upregulate the expression and stimulate the secretion of interferon-gamma (IFNgamma) in the human MCF-7 breast cancer cell line. This novel effect may provide important clues to explain the anticancer effects of DIM because it is well known that IFNgamma plays an important role in preventing the development of primary and transplanted tumors. Utilizing promoter deletions, we show here that the region between -108 and -36 bp in the IFNgamma promoter, which contains two conserved and essential regulatory elements, is required for DIM-induced IFNgamma expression. DIM activates both JNK and p38 pathways, induces the phosphorylation of c-Jun and ATF-2, and increases the binding of the homodimer or heterodimer of c-Jun/ATF-2 to the proximal AP-1.CREB-ATF-binding element. Moreover, studies with specific enzyme inhibitors showed that up-stream Ca2+-dependent kinase(s) is required for the inducing effects of DIM in MCF-7 cells. These results establish that DIM-induced IFNgamma expression in human breast tumor cells is mediated by activation of both JNK and p38 pathways, which is ultimately dependent on intracellular calcium signaling.

Repression of IFN-gamma expression by peroxisome proliferator-activated receptor gamma

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors expressed in a wide variety of cells. Our studies and others have demonstrated that both human and murine T cells express PPARgamma and that expression can be augmented over time in mitogen-activated splenocytes. PPARgamma ligands decrease proliferation and IL-2 production, and induce apoptosis in both B and T cells. PPARgamma ligands have also been shown to be anti-inflammatory in multiple models of inflammatory disease. In the following study, we demonstrate for the first time that PPARgamma is expressed in both murine CD4 and CD8 cells and that PPARgamma ligands directly decrease IFN-gamma expression by murine and transformed T cell lines. Unexpectedly, GW9662, a PPARgamma antagonist, increases lymphocyte IFN-gamma expression. Transient transfection studies reveal that PPARgamma ligands, in a PPARgamma-dependent manner, potently repress an IFN-gamma promoter construct. Repression localizes to the distal conserved sequence of the IFN-gamma promoter. Our studies also demonstrate that PPARgamma acts on the IFN-gamma promoter by interfering with c-Jun activation. These studies suggest that many of the observed anti-inflammatory effects of PPARgamma ligands may be related to direct inhibition of IFN-gamma by PPARgamma.

Chromatin-mediated regulation of nucleolar structure and RNA Pol I localization by TOR

The target of rapamycin (TOR) protein is a conserved regulator of ribosome biogenesis, an important process for cell growth and proliferation. However, how TOR is involved remains poorly understood. In this study, we find that rapamycin and nutrient starvation, conditions inhibiting TOR, lead to significant nucleolar size reduction in both yeast and mammalian cells. In yeast, this morphological change is accompanied by release of RNA polymerase I (Pol I) from the nucleolus and inhibition of ribosomal DNA (rDNA) transcription. We also present evidence that TOR regulates association of Rpd3-Sin3 histone deacetylase (HDAC) with rDNA chromatin, leading to site-specific deacetylation of histone H4. Moreover, histone H4 hypoacetylation mutations cause nucleolar size reduction and Pol I delocalization, while rpd3Delta and histone H4 hyperacetylation mutations block the nucleolar changes as a result of TOR inhibition. Taken together, our results suggest a chromatin-mediated mechanism by which TOR modulates nucleolar structure, RNA Pol I localization and rRNA gene expression in response to nutrient availability.

Effect of promoter methylation on the regulation of IFN-gamma gene during in vitro differentiation of human peripheral blood T cells into a Th2 population

The carefully orchestrated events that result in a protective immune response are coordinated to a large extent by cytokines produced by Th1 and Th2 cell subsets. Th1 cells preferentially produce IL-2 and IFN-gamma, resulting in a cellular response that helps to eliminate infected cells. In contrast, Th2 cells produce IL-4, IL-5, IL-6, and IL-10, stimulating an Ab response that attacks extracellular pathogens, thereby preventing the cells from becoming infected. To elucidate the mechanisms of differential regulation of cytokine genes by these two different subsets of T cells, we established an in vitro differentiation model of freshly isolated human peripheral blood T cells in which IFN-gamma was used as an index gene to study the transcriptional regulation. The data presented here demonstrate that the IFN-gamma promoter undergoes differential methylation during in vitro differentiation: the promoter becomes hypermethylated in Th2 cells, whereas it is hypomethylated in Th1 cells. Hypermethylation in Th2 cells results in chromatin condensation and exclusion of CREB proteins from the IFN-gamma promoter. Treatment with 5-azacytidine, a demethylating agent, causes Th2 cells to reverse histone condensation and enables CREB recruitment to the hypomethylated promoter. This results in the increased production of IFN-gamma. These data indicate the importance of promoter methylation in the regulation of the IFN-gamma gene during differentiation.

The interplay between the glucocorticoid receptor and nuclear factor-kappaB or activator protein-1: molecular mechanisms for gene repression

The inflammatory response is a highly regulated physiological process that is critically important for homeostasis. A precise physiological control of inflammation allows a timely reaction to invading pathogens or to other insults without causing overreaction liable to damage the host. The cellular signaling pathways identified as important regulators of inflammation are the signal transduction cascades mediated by the nuclear factor-kappaB and the activator protein-1, which can both be modulated by glucocorticoids. Their use in the clinic includes treatment of rheumatoid arthritis, asthma, allograft rejection, and allergic skin diseases. Although glucocorticoids have been widely used since the late 1940s, the molecular mechanisms responsible for their antiinflammatory activity are still under investigation. The various molecular pathways proposed so far are discussed in more detail.

Overexpression of Id-1 is associated with poor clinical outcome in node negative breast cancer

Id-1 is an important regulator of cellular growth and differentiation and controls malignant progression of breast cancer cells. The aim of our study was to assess the clinical impact of Id-1 expression in breast cancer, i.e., its potential impact on prognosis and prediction of treatment response. Id-1 protein expression was determined immunohistochemically in 191 patients with lymph-node negative breast cancer, and univariate and multivariate survival analysis was carried out. Fifteen (7.9%) specimens showed strong expression, 75 (39.3%) moderate, 55 (28.8%) weak expression and 46 (24.1%) cases no expression of Id-1. Patients with strong or moderate Id-1 expression had a significant shorter overall (p = 0.003, Cox regression) and disease-free survival (p = 0.01, Cox regression) compared to those with absent or low expression. Progesterone receptor density was significantly higher in breast cancers with absent/low Id-1 expression compared to those with moderate/strong expression (p < 0.001, t-test). Id-1 expression was significantly stronger in cases positive for p16(INK4a) expression compared to those negative for p16 (p = 0.049, Mann-Whitney test). The influence of Id-1 on clinical outcome seems much stronger in patients with negative estrogen receptor status compared to those with positive status, who received receptor antagonists as adjuvant therapy in most cases. Overexpression of Id-1 protein represents a strong independent prognostic marker in node negative breast cancer, and future therapies inhibiting Id-1 expression might be beneficial for these patients. Our results also suggest that due to the apparent interaction of Id-1 with the steroid-receptor system in breast cancer, hormonal therapies might influence Id-1 expression and its impact on clinical outcome.

The cyclopentenone-type prostaglandin 15-deoxy-delta 12,14-prostaglandin J2 inhibits CD95 ligand gene expression in T lymphocytes: interference with promoter activation via peroxisome proliferator-activated receptor-gamma-independent mechanisms

15-Deoxy-delta(12,14)-PGJ(2) (15d-PGJ(2)) is a cyclopentenone-type PG endowed with anti-inflammatory properties and produced by different cells, including those of the immune system. 15d-PGJ(2) is a natural ligand of the peroxisome proliferator-activated receptor (PPAR)-gamma nuclear receptor, but relevant PPARgamma-independent actions mediated by this prostanoid have been described. Fas (APO-1/CD95) and its ligand (Fas-L) are cell surface proteins whose interaction activates apoptosis of Fas-expressing targets. In T cells, the Fas-Fas-L system regulates activation-induced cell death and has been implicated in diseases in which lymphocyte homeostasis is compromised. Moreover, several studies have described the pathogenic functions of Fas and Fas-L in vivo, particularly in the induction-progression of organ-specific autoimmune diseases. In this study we describe the effect of 15d-PGJ(2) on the activation of the fas-L gene in T lymphocytes. We show that 15d-PGJ(2) inhibits fas-L mRNA expression, activation-induced cell death, and fas-L promoter activity by mechanisms independent of PPARgamma and mediated by its chemically reactive cyclopentenone moiety. Our data indicate that 15d-PGJ(2) may repress fas-L activation by interfering with the expression and/or transcriptional activity of different transcription factors (early growth response types 3 and 1, NF-kappaB, AP-1, c-Myc, Nur77) whose altered balancing and transactivation may contribute for overall repression of this gene. In addition, the activation/expression of the heat shock response genes HSF-1 and HSP70 is not directly involved in the repression, and the electrophilic molecule cyclopentenone (2-cyclopenten-1-one) may reproduce the effects mediated by 15d-PGJ(2). These results suggest that modulation of Fas-L by 15d-PGJ(2) in T cells may represent an additional tool to consider for treatment of specific autoimmune and inflammatory disorders.

CD40 ligand trimer enhances the response of CD8+ T cells to Mycobacterium tuberculosis

We investigated the effect of recombinant CD40 ligand trimer (CD40LT) on the functional capacity of peripheral blood CD8(+) T cells from healthy tuberculin reactors that were cultured with Mycobacterium tuberculosis-infected autologous monocytes. CD40LT enhanced the capacity of M. tuberculosis-responsive CD8(+) T cells to produce IFN-gamma by increasing the number of IFN-gamma-producing CD8(+) T cells and the amount of IFN-gamma produced per cell. CD40LT-induced IFN-gamma production was dependent on production of IL-12 and IL-18, but did not require IL-15. CD40LT up-regulated expression of the transcription factors phosphorylated CREB and c-Jun, both of which have been previously shown to stimulate IFN-gamma mRNA transcription by binding to the IFN-gamma promoter. CD40LT also enhanced the capacity of CD8(+) T cells to lyse M. tuberculosis-infected monocytes, and increased CTL activity was associated with higher expression of perforin and granulysin, but not of Fas ligand. We conclude that CD40LT can enhance CD8(+) T cell effector function in response to M. tuberculosis.

Epigenetic control during lymphoid development and immune responses: aberrant regulation, viruses, and cancer

Methylation of cytosines controls a number of biologic processes such as imprinting and X chromosomal inactivation. DNA hypermethylation is closely associated with transcriptional silencing, while DNA hypomethylation is associated with transcriptional activation. Hypoacetylation of histones leads to compact chromatin with reduced accessibility to the transcriptional machinery. Methyl-CpG binding proteins can recruit corepressors and histone deacetylases; thus, the interplay between these epigenetic mechanisms regulates gene activation. Methylation has been implicated as an important mechanism during immune development, controlling VDJ recombination, lineage-specific expression of cell surface antigens, and transcriptional regulation of cytokine genes during immune responses. Aberrations in epigenetic machinery, either by genetic mutations or by somatic changes such as viral infections, are associated with early alterations in chronic diseases such as immunodeficiency and cancer.

A minimal IFN-gamma promoter confers Th1 selective expression

Th1 and Th2 cells differentiate from naive precursors to effector cells that produce either IFN-gamma or IL-4, respectively. To identify transcriptional paths leading to activation and silencing of the IFN-gamma gene, we analyzed transgenic mice that express a reporter gene under the control of the 5' IFN-gamma promoter. We found that as the length of the promoter is increased, -110 to -225 to -565 bp, the activity of the promoter undergoes a transition from Th1 nonselective to Th1 selective. This is due, at least in part, to a T box expressed in T cells-responsive unit within the -565 to -410 region of the IFN-gamma promoter. The -225 promoter is silent when compared with the -110 promoter and silencing correlates with Yin Yang 1 binding to the promoter. The p38 mitogen-activated protein kinase signaling pathway, which also regulates IFN-gamma gene transcription, regulates the -70- to -44-bp promoter element. Together, the results demonstrate that a minimal IFN-gamma promoter contains a T box expressed in T cells responsive unit and is sufficient to confer Th1 selective expression upon a reporter.

Reduced expression of nuclear cyclic adenosine 5'-monophosphate response element-binding proteins and IFN-gamma promoter function in disease due to an intracellular pathogen

Mycobacterium tuberculosis-induced IFN-gamma protein and mRNA expression have been shown to be reduced in tuberculosis patients, compared with healthy tuberculin reactors. To determine whether this decrease was associated with reduced activity of the IFN-gamma promoter, we first studied binding of nuclear proteins to the radiolabeled proximal IFN-gamma promoter (-71 to -40 bp), using EMSAs with nuclear extracts of freshly isolated peripheral blood T cells. Nuclear extracts of T cells from most tuberculosis patients showed markedly reduced expression of proteins that bind to the proximal IFN-gamma promoter, compared with findings in nuclear extracts of T cells from healthy tuberculin reactors. These DNA-binding complexes contained CREB proteins, based on competitive EMSAs, supershift assays, and Western blotting with an anti-CREB Ab. Transient transfection of PBLs with a luciferase reporter construct under the control of the IFN-gamma promoter revealed reduced IFN-gamma promoter activity in tuberculosis patients. Transient transfection of Jurkat cells with a dominant-negative CREB repressor plasmid reduced IFN-gamma promoter activity. These data suggest that reduced expression of CREB nuclear proteins in tuberculosis patients results in decreased IFN-gamma promoter activity and reduced IFN-gamma production.

Regulation of nuclear gamma interferon gene expression by interleukin 12 (IL-12) and IL-2 represents a novel form of posttranscriptional control

Posttranscriptional control of gamma interferon (IFN-gamma) gene expression has not been extensively studied and is poorly understood. Our work describes a posttranscriptional mechanism that modulates IFN-gamma mRNA expression in stimulated natural killer (NK) cells through nuclear retention of the IFN-gamma mRNA. This is evidenced by the elevated and sustained nuclear accumulation of both precursor and processed IFN-gamma mRNAs in NK cells stimulated with interleukin-12 (IL-12). The elevated nuclear mRNA accumulation persists long after transcriptional activity has subsided and the rate of cytoplasmic IFN-gamma mRNA accumulation has dropped. The IL-12-induced nuclear retention of the IFN-gamma mRNA prevails until a secondary cytokine stimulus is received. The secondary stimulus, which is initiated by IL-2, mediates transcription-independent movement of the nuclear IFN-gamma mRNA. Concurrent with the nucleocytoplasmic movement of the IFN-gamma mRNA, we have observed increases in the amount of processed nuclear IFN-gamma mRNA that are greater than that seen for the unprocessed IFN-gamma mRNA. The increase in processed IFN-gamma mRNA appears to be due to increased mRNA stability which then promotes increased nucleocytoplasmic shuttling of the mature IFN-gamma mRNA. These data support a model whereby mobilization of nuclear IFN-gamma mRNA stores allows NK cells to rapidly and robustly respond to secondary cytokine activators in a transcription-independent manner, thus shortening the time for overall cellular response to inflammatory signals.

Negative regulation of CD95 ligand gene expression by vitamin D3 in T lymphocytes

Fas (APO-1/CD95) and its ligand (FasL/CD95L) are cell surface proteins whose interaction activates apoptosis of Fas-expressing targets. In T lymphocytes, the Fas/FasL system regulates activation-induced cell death, a fundamental mechanism for negative selection of immature T cells in the thymus and for maintenance of peripheral tolerance. Aberrant expression of Fas and FasL has also been implicated in diseases in which the lymphocyte homeostasis is compromised, and several studies have described the pathogenic functions of Fas and FasL in vivo, particularly in the induction/regulation of organ-specific autoimmune diseases. The 1,25(OH)(2)D(3) is a secosteroid hormone that activates the nuclear receptor vitamin D(3) receptor (VDR), whose immunosuppressive activities have been well studied in different models of autoimmune disease and in experimental organ transplantation. We and others have recently described the molecular mechanisms responsible for the negative regulation of the IFN-gamma and IL-12 genes by 1,25(OH)(2)D(3) in activated T lymphocytes and macrophages/dendritic cells. In this study, we describe the effect of 1,25(OH)(2)D(3) on the activation of the fasL gene in T lymphocytes. We show that 1,25(OH)(2)D(3) inhibits activation-induced cell death, fasL mRNA expression, and that 1,25(OH)(2)D(3)-activated VDR represses fasL promoter activity by a mechanism dependent on the presence of a functional VDR DNA-binding domain and ligand-dependent transcriptional activation domain (AF-2). Moreover, we identified a minimal region of the promoter containing the transcription start site and a noncanonical c-Myc-binding element, which mediates this repression. These results place FasL as a novel target for the immunoregulatory activities of 1,25(OH)(2)D(3), and confirm the interest for a possible pharmacological use of this molecule and its derivatives.

Human lymphocyte growth hormone stimulates interferon gamma production and is inhibited by cortisol and norepinephrine

Lymphocyte growth hormone (L-GH) is distributed throughout the human immune system; however, its biologic role has not been defined. In order to clarify this issue, we determined if Candida, commonly used as a recall antigen, and IL-12, an important monocyte cytokine that stimulates the TH1 cytokine pathway, could stimulate L-GH mRNA synthesis in cultured human peripheral blood mononuclear cells (PBMCs). Both Candida and IL-12 produced significant (p<0.01) stimulation of L-GH mRNA synthesis and the TH1 cytokine, gamma interferon (IFN-gamma). These effects on IFN-gamma production were significantly (p<0.001) inhibited by a GH antagonist, suggesting that L-GH was acting by an autocrine or paracrine mechanism to enhance IFN-gamma production in these serum-free cultured cells. Concentrations of norepinephrine and cortisol achievable in humans during stress were able to significantly (p<0.001) decrease L-GH synthesis in the PBMCs. They also diminished IFN-gamma significantly (p<0.001), but not the TH2 cytokine, IL-10, in the supernatants of the cultured PBMLs. These studies suggest that L-GH plays a role in cellular immune function mediated via the TH-1 pathway.

Transcriptional reprogramming during T helper cell differentiation

Our laboratory employs reporter transgenic mice as model systems to study the transcriptional reprogramming that accompanies T helper cell differentiation. These studies demonstrate that changes in the activity of simple transcriptional elements associated with the IFN-gamma gene can recapitulate alterations in gene expression. In addition, our studies have revealed a key role for the transcription factor, CAMP response element binding protein (CREB), in the protection of differentiating T cells from apoptosis. Together, these findings further our understanding of the logic employed by T cells to alter gene expression profiles in response to differentiation signals.