A collection of mRNA species that are inducible in the RAW 264.7 mouse macrophage cell line by gamma interferon and other agents

Fine-tuning of regulatory T cells is indispensable for the metabolic steatosis-related hepatocellular carcinoma: A review

The majority of chronic hepatic diseases are caused by nutritional imbalance. These nutritional inequities include excessive intake of alcohol and fat, which causes alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD), respectively. The pathogenesis of hepatic diseases is mainly dependent on oxidative stress, autophagy, DNA damage, and gut microbiota and their metabolites. These factors influence the normal physiology of the liver and impact the hepatic microenvironment. The hepatic microenvironment contains several immune cells and inflammatory cytokines which interact with each other and contribute to the progression of chronic hepatic diseases. Among these immune cells, Foxp3⁺ CD4⁺ regulatory T cells (Tregs) are the crucial subset of CD4⁺ T cells that create an immunosuppressive environment. This review emphasizes the function of Tregs in the pathogenesis of ALD and NAFLD and their role in the progression of NAFLD-associated hepatocellular carcinoma (HCC). Briefly, Tregs establish an immunosuppressive landscape in the liver by interacting with the innate immune cells and gut microbiota and their metabolites. Meanwhile, with the advancement of steatosis, these Tregs inhibit the proliferation, activation and functions of other cytotoxic T cells and support the progression of simple steatosis to HCC. Briefly, it can be suggested that targeting Tregs can act as a favourable prognostic indicator by modulating steatosis and insulin resistance during the pathogenesis of hepatic steatosis and NAFLD-associated HCC.

Capsule carbohydrate structure determines virulence in Acinetobacter baumannii

Acinetobacter baumannii is a highly antibiotic-resistant bacterial pathogen for which novel therapeutic approaches are needed. Unfortunately, the drivers of virulence in A. baumannii remain uncertain. By comparing genomes among a panel of A. baumannii strains we identified a specific gene variation in the capsule locus that correlated with altered virulence. While less virulent strains possessed the intact gene gtr6, a hypervirulent clinical isolate contained a spontaneous transposon insertion in the same gene, resulting in the loss of a branchpoint in capsular carbohydrate structure. By constructing isogenic gtr6 mutants, we confirmed that gtr6-disrupted strains were protected from phagocytosis in vitro and displayed higher bacterial burden and lethality in vivo. Gtr6+ strains were phagocytized more readily and caused lower bacterial burden and no clinical illness in vivo. We found that the CR3 receptor mediated phagocytosis of gtr6+, but not gtr6-, strains in a complement-dependent manner. Furthermore, hypovirulent gtr6+ strains demonstrated increased virulence in vivo when CR3 function was abrogated. In summary, loss-of-function in a single capsule assembly gene dramatically altered virulence by inhibiting complement deposition and recognition by phagocytes across multiple A. baumannii strains. Thus, capsular structure can determine virulence among A. baumannii strains by altering bacterial interactions with host complement-mediated opsonophagocytosis.

Toll-like receptors in sepsis-associated cytokine storm and their endogenous negative regulators as future immunomodulatory targets

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Sepsis infects more than 48.9 million people world-wide, with 19.7 million deaths.

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Cytokine storm plays a significant role in sepsis, along with severe COVID-19.

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TLR signaling pathways plays a crucial role in generating the cytokine storm.

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Endogenous negative regulators of TLR signaling are crucial to regulate cytokine storm.

Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.

IFN-γR -/- mice show an enhanced liver and brain metallothionein I+II response to endotoxin but not to immobilization stress

Interferon-γ (IFN-γ) is known for its important antiviral activity and other immunomodulatory actions. In in vitro studies, this cytokine has also been involved in the control of metallothionein (MT) synthesis. MT is a low molecular weight protein comprised of several isoforms called MT-I to MT-IV; of these, MT-1+11 are widely expressed, whereas MT-III and MT-IV are rather tissue specific. In the present report, we have studied in vivo the role of IFN-γ for a normal liver and brain MT-I+II response to immobilization stress and to an inflammatory process caused by bacterial lipopolysaccharide (LPS, endotoxin), using mice carrying a null mutation in the IFN-γ receptor gene (IFN-γR-/-). Liver MT-I mRNA and MT-(I+II) protein levels during stress of IFN-γR-/- mice were similar to those of the two parental mouse strains used to generate them, namely C57BU6 and 129/Sv mice, and that of the F1 C57BU6 x 129/Sv offspring mice. In contrast, liver MT response to LPS was significantly higher in the IFN-γR-/- mice than in the other strains. MT-I+II response to LPS was also higher in IFN-γR-/- mice in medulla plus pons and tended to in hypothalamus, hippocampus, and cerebellum, but not in the remaining brain. These results suggest that a role of IFN-γ on liver and brain MT-I+II response to stress is unlikely, but that this cytokine exerts an inhibitory effect on the signaling pathways activated by LPS involved in MT-I+II regulation. In situ hybridization analysis for MT-I and MT-III mRNAs of control mice revealed significant effects of the functional IFN-γ deficiency on MT-I but not MT-III mRNA levels in the dentate gyrus and the habenula, while no effects were observed in the remaining brain areas studied.

Activating transcription factor 3 represses inflammatory responses by binding to the p65 subunit of NF-κB

Activating transcription factor 3 (ATF3) is induced by inflammatory responses, cell death, cytokines, and oxidative stress conditions. ATF3 is a negative regulator in the Toll-like receptor 4 signalling pathway. The principal molecule in this pathway is nuclear factor κB (NF-κB) that translocates into the nucleus to initiate the transcription of inflammatory mediators. However, scarce data are available regarding the interaction of ATF3 and p65, a part of the NF-κB dimer. Therefore, we studied the mechanism of regulation of p65 by ATF3 in RAW 264.7 cells. First, LPS-mediated NF-κB activation was confirmed, and then the direct interaction of ATF3 and p65 was observed through immunoprecipitation (IP). The presence of histone deacetylase 1 (HDAC1) was also detected in the complex. In ATF3 deficient cells, NF-κB activity was up-regulated and HDAC1 was not detected by IP. These observations suggest that p65 is attenuated by ATF3 such that ATF3 recruits HDAC1 to the ATF3/p65 complex and facilitates the deacetylation of p65. Likewise, inflammatory response genes were induced by translocated NF-κB in ATF3-deficient cells. Cumulatively, we uncovered a novel mechanism for the negative regulation of NF-κB by ATF3 via direct interaction with p65.

IP-10/CXCL10 and MIG/CXCL9 as novel markers for the diagnosis of lymphoma-associated hemophagocytic syndrome

Lymphoma-associated hemophagocytic syndrome (LAHS) is a serious disorder, and its early diagnosis and treatment with appropriate chemotherapy are very important. However, reliable markers for early diagnosis of LAHS have not been identified. We screened serum cytokines using a newly introduced assay system, cytometric bead array (CBA), and identified interferon-inducible protein 10 (IP-10)/CXCL10 and monokine induced by interferon gamma (MIG)/CXCL9 as useful markers. Serum concentrations of IP-10 and MIG at the time of LAHS diagnosis were greater than 500 and 5,000 pg/ml, respectively. The sensitivity and specificity for LAHS diagnosis were 100 and 95 %, respectively, when we set the above values as the cut-off levels. Serum levels of these two chemokines were already elevated at the time of admission and significantly decreased after successful treatment, indicating their usefulness for both the diagnosis and therapeutic outcomes for LAHS. IP-10 and MIG were also useful in distinguishing severe from moderate/mild LAHS, and B-cell-type LAHS from T-cell/natural killer cell-type LAHS. Furthermore, IP-10 and MIG were of use to distinguish LAHS from sepsis in patients with hematologic malignancies. Rapid measurement of IP-10 and MIG by CBA appeared to be important for early diagnosis and treatment of LAHS.

A whole blood monokine-based reporter assay provides a sensitive and robust measurement of the antigen-specific T cell response

BACKGROUND

The ability to measure T-cell responses to antigens is proving critical in the field of vaccine development and for understanding immunity to pathogens, allergens and self-antigens. Although a variety of technologies exist for this purpose IFNγ-ELISpot assays are widely used because of their sensitivity and simplicity. However, ELISpots cannot be performed on whole blood, and require relatively large volumes of blood to yield sufficient numbers of peripheral blood mononuclear cells. To address these deficiencies, we describe an assay that measures antigen-specific T cell responses through changes in monokine gene transcription. The biological amplification of the IFNγ signal generated by this assay provides sensitivity comparable to ELISpot, but with the advantage that responses can be quantified using small volumes of whole blood.

METHODS

Whole blood or peripheral blood mononuclear cells (PBMCs) from healthy controls and immunosuppressed recipients of solid organ transplants were incubated with peptide pools covering viral and control antigens or mitogen for 20 hours. Total RNA was extracted and reverse transcribed before amplification in a TaqMan qPCR reaction using primers and probes specific for MIG (CXCL9), IP-10 (CXCL10) and HPRT. The induction of MIG and IP-10 in response to stimuli was analysed and the results were compared with those obtained by ELISpot.

RESULTS

Antigen-specific T cell responses can be measured through the induction of MIG or IP-10 gene expression in PBMCs or whole blood with results comparable to those achieved in ELISpot assays. The biological amplification generated by IFNγ-R signaling allows responses to be detected in as little as 25 uL of whole blood and enables the assay to retain sensitivity despite storage of samples for up to 48 hours prior to processing.

CONCLUSIONS

A monokine-based reporter assay provides a sensitive measure of antigen-specific T cell activation. Assays can be performed on small volumes of whole blood and remain accurate despite delays in processing. This assay may be a useful tool for studying T cell responses, particularly when samples are limited in quantity or when storage or transportation are required before processing.

Negative Regulation of TLR-Signaling Pathways by Activating Transcription Factor-3

Activating transcription factor-3 (ATF3) is rapidly induced by LPS in mouse macrophages and regulates TLR4 responses. We show that ATF3 is rapidly induced by various TLRs in mouse macrophages and plasmacytoid dendritic cells (DCs), as well as plasmacytoid and myeloid subsets of human DCs. In primary macrophages from mice with a targeted deletion of the atf3 gene (ATF3-knockout (KO)), TLR-stimulated levels of IL-12 and IL-6 were elevated relative to responses in wild-type macrophages. Similarly, targeted deletion of atf3 correlated with enhanced responsiveness of myeloid DCs to TLR activation as measured by IL-12 secretion. Ectopic expression of ATF3 antagonized TLR-stimulated IL-12p40 activation in a reporter assay. In vivo, CpG-oligodeoxynucleotide, a TLR9 agonist, given i.p. to ATF3-KO mice resulted in enhanced cytokine production from splenocytes. Furthermore, while ATF3-KO mice challenged with a sublethal dose of PR8 influenza virus were delayed in body weight recovery in comparison to wild type, the ATF3-KO mice showed higher titers of serum neutralizing Ab against PR8 5 mo postinfection. Thus, ATF3 behaves as a negative regulatory transcription factor in TLR pathways and, accordingly, deficiency in atf3 alters responses to immunological challenges in vivo. ATF3 dysregulation merits further exploration in diseases such as type I diabetes and cancer, where altered innate immunity has been implicated in their pathogenesis.

Macrophage activation increases the invasive properties of hepatoma cells by destabilization of the adherens junction

Tumor-associated macrophages play an important role in tumor progression, but whether they exert a tumor-progressive effect remains controversial. Here, we demonstrated that activated macrophage-conditioned medium (AMCM) obtained from RAW macrophages (RAW/AMCM) induced epithelial-mesenchymal transition (EMT) and stimulated the migratory and invasive activities of HepG2 cells, whereas control conditioned media had no effect. Epithelial-cadherin (E-cadherin) and beta-catenin staining patterns were altered at the adherens junctions by RAW/AMCM treatment, with an approximately 50% decrease in E-cadherin and beta-catenin in the cell membrane. Importantly, levels of beta-catenin-associated E-cadherin were also decreased. Following RAW/AMCM treatment, enhanced activation of c-Src was seen prior to increased tyrosine phosphorylation of beta-catenin, and this led to the destabilization of adherens junctions. Pretreatment of HepG2 cells with the Src kinase inhibitor, PP2, completely abolished the effects of RAW/AMCM on the EMT, migration, invasion, and expression and association of E-cadherin and beta-catenin. AMCMs obtained from human THP-1 monocytes and mouse peritoneal macrophages also caused disassembly of the adherens junctions and migration of HepG2 cells. Furthermore, inhibition of the epidermal growth factor receptor (EGFR) with gefitinib partially prevented the downregulation of E-cadherin and beta-catenin at the adherens junctions and migration behavior induced by RAW/AMCM. Our results suggest that activated macrophages have a tumor-progressive effect on HepG2 cells which involves the c-Src- and EGFR-dependent signaling cascades.

Gene transcription profile in mice vaccinated with ultraviolet-attenuated cercariae of Schistosoma japonicum reveals molecules contributing to elevated IFN-gamma levels

Vaccination with ultraviolet-attenuated cercariae of Schistosoma japonicum induced protective immunity against challenge infection in experimental animal models. Our preliminary study on the transcription levels of IFN-gamma and IL-4 in splenic CD4+ T cells revealed that attenuated cercariae elicited predominantly a Th1 response in mice at the early stage, whereas normal cercariae stimulated primarily Th2-dependent responses. Further analysis on the gene profile of the skin-draining lymph nodes demonstrated that the levels of IFN-gamma were significantly higher in vaccinated mice than those in infected mice at day 4, 7 and 14 post-vaccination or post-infection. However, for IL-12 and IL-4, the potent inducers of Th1 and Th2 responses, respectively, as well as IL-10, there were no differences over the course of the experiment between the infected and vaccinated mice. To explore the underlying factors that may potentially contribute to elevated IFN-gamma in vaccinated mice, the mRNA profiles of the skin-draining lymph nodes at day 4 post-exposure were compared using oligonucleotide microarrays. Within the 847 probe sets with increased signal values, we focused on chemokines, cytokines and relevant receptors, which were validated by semi-quantitative RT-PCR. A comprehensive understanding of the immune mechanisms of attenuated cercariae-induced protection may contribute to developing efficient vaccination strategies against S. japonicum, especially during the early stage of infection.

The development of COX2 inhibitors

Aspirin, arguably the world's favourite drug, has been around since the late nineteenth century, but it wasn't until the late 1970s that its ability to inhibit prostaglandin production by the cyclooxygenase enzyme was identified as the basis of its therapeutic action. Early hints of a second form of the cyclooxygenase that was differentially sensitive to other aspirin-like drugs ultimately ushered in an exciting era of drug discovery, culminating in the introduction of an entirely new generation of anti-inflammatories. This article reviews the story of this discovery and looks at the future of cyclooxygenase pharmacology.

Interferon regulatory factor-1 (IRF-1) is a mediator for interferon-gamma induced attenuation of telomerase activity and human telomerase reverse transcriptase (hTERT) expression

Constitutive activation of the telomerase is a key step in the development of human cancers. Interferon-gamma (IFN-gamma) signaling induces growth arrest in many tumors through multiple regulatory mechanisms. In this study, we show that IFN-gamma signaling represses telomerase activity and human telomerase reverse transcriptase (hTERT) transcription, and suggest that this signaling is mediated by IRF-1. Ectopic expression of IRF-1 attenuated hTERT promoter activity. Murine embryonic fibroblasts (MEFs) genetically deficient in IRF-1 (IRF-1(-/-)) showed an elevated level (>15 times) of hTERT promoter activity as compared to the hTERT promoter activity of wild-type MEFs. The telomerase activity and hTERT expression in IRF-1(-/-) MEFs were downregulated by IRF-1 transfection. Interestingly, less extent of telomerase repression was observed in HPV E6 and E7 negative, p53 mutant HT-3 cells than in HPV 18 E6 and E7 positive HeLa cells (intact p53). These findings provide evidence that IRF-1 is a potential mediator of IFN-gamma-induced attenuation of telomerase activity and hTERT expression.

In vivo evidence for interferon-gamma-mediated homeostatic mechanisms in small intestine of the NHE3 Na+/H+ exchanger knockout model of congenital diarrhea

Mice lacking NHE3, the major absorptive Na(+)/H(+) exchanger in the intestine, are the only animal model of congenital diarrhea. To identify molecular changes underlying compensatory mechanisms activated in chronic diarrheas, cDNA microarrays and Northern blot analyses were used to compare global mRNA expression patterns in small intestine of NHE3-deficient and wild-type mice. Among the genes identified were members of the RegIII family of growth factors, which may contribute to the increased absorptive area, and a large number of interferon-gamma-responsive genes. The latter finding is of particular interest, since interferon-gamma has been shown to regulate ion transporter activities in intestinal epithelial cells. Serum interferon-gamma was elevated 5-fold in NHE3-deficient mice; however, there was no evidence of inflammation, and unlike conditions such as inflammatory bowel disease, levels of other cytokines were unchanged. In addition, quantitative PCR analysis showed that up-regulation of interferon-gamma mRNA was localized to the small intestine and did not occur in the colon, spleen, or kidney. These in vivo data suggest that elevated interferon-gamma, produced by gut-associated lymphoid tissue in the small intestine, is part of a homeostatic mechanism that is activated in response to the intestinal absorptive defect in order to regulate the fluidity of the intestinal tract.

The CXC chemokine murine monokine induced by IFN-gamma (CXC chemokine ligand 9) is made by APCs, targets lymphocytes including activated B cells, and supports antibody responses to a bacterial pathogen in vivo

Monokine induced by IFN-gamma (Mig; CXC chemokine ligand 9) is an IFN-gamma-inducible CXC chemokine that signals through the receptor CXCR3 and is known to function as a chemotactic factor for human T cells, particularly following T cell activation. The mig gene can be induced in multiple cell types and organs, and Mig has been shown to contribute to T cell infiltration into immune/inflammatory reactions in peripheral tissues in mice. We have investigated the expression and activities of Mig and CXCR3 in mouse cells and the role of Mig in models of host defense in mice. Murine (Mu)Mig functioned as a chemotactic factor for resting memory and activated T cells, both CD4(+) and CD8(+), and responsiveness to MuMig correlated with surface expression of MuCXCR3. Using mig(-/-) mice, we found that MuMig was not necessary for survival after infections with a number of intracellular pathogens. Surprisingly, however, we found that mig(-/-) mice showed reductions of 50-75% in Abs produced against the intracellular bacterium Francisella tularensis live vaccine strain. Furthermore, we found that MuMig induced both calcium signals and chemotaxis in activated B cells, and that B cell activation induced expression of MuCXCR3. In addition, IFN-gamma induced the expression of mumig in APCs, including CD8 alpha(+) and CD8 alpha(-) dendritic cells. Together, our data suggest that Mig and CXCR3 may be important not only to recruit T cells to peripheral inflammatory sites, but also in some cases to maximize interactions among activated T cells, B cells, and dendritic cells within lymphoid organs to provide optimal humoral responses to pathogens.

The roles of ATF3 in liver dysfunction and the regulation of phosphoenolpyruvate carboxykinase gene expression

Activating transcription factor 3 (ATF3), a member of the ATF/cAMP-responsive element-binding protein family of transcription factors, is a transcriptional repressor, and the expression of its corresponding gene, ATF3, is induced by many stress signals. In this report, we demonstrate that transgenic mice expressing ATF3 in the liver had symptoms of liver dysfunction such as high levels of serum bilirubin, alkaline phosphatase, alanine transaminase, aspartate transaminase, and bile acids. In addition, these mice had physiological responses consistent with hypoglycemia including a low insulin:glucagon ratio in the serum and reduced adipose tissue mass. Electrophoretic mobility shift assays indicated that ATF3 bound to the ATF/cAMP-responsvie element site derived from the promoter of the gene encoding the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK). Furthermore, transient transfection assays indicated that ATF3 repressed the activity of the PEPCK promoter. Taken together, our results are consistent with the model that the expression of ATF3 in the liver results in defects in glucose homeostasis by repressing gluconeogenesis. Because ATF3 is a stress-inducible gene, these mice may provide a model to investigate the molecular mechanisms of some stress-associated liver diseases.

Expression of the chemokine MIG is a sensitive and predictive marker for antigen-specific, genetically restricted IFN-gamma production and IFN-gamma-secreting cells

The evaluation of antigen-specific immune responses is critical for understanding the mechanisms of immune protection and for establishing the efficacy of candidate vaccines. Here, we describe a novel assay for IFN-gamma activity which is based on the flow cytometric detection of the chemokine, monokine induced by gamma interferon (MIG) as a sensitive and predictive measure of IFN-gamma-mediated effector function, and a surrogate marker for IFN-gamma-producing cells. Upregulation of MIG expression was demonstrated following in vitro activation of peripheral blood mononuclear cells (PBMCs) with defined CD8+ T-cell epitopes derived from influenza virus, cytomegalovirus (CMV), or Epstein-Barr virus (EBV) and was antigen-specific, genetically restricted and dependent on both CD8+ T cells and IFN-gamma. Furthermore, antigen-specific MIG expression was also demonstrated with Plasmodium falciparum circumsporozoite protein (CSP) peptides, using PBMCs from volunteers immunized with irradiated P. falciparum sporozoites. In multiple parallel experiments, the MIG assay was compared to conventional IFN-gamma ELISPOT, IFN-gamma ELISA, MIG ELISA and intracellular cytokine staining assays. The level of MIG expression was shown to be directly associated with the number of IFN-gamma spot-forming cells (SFCs) detected by ELISPOT (r2=0.94). Moreover, in all instances where cultures were considered positive by ELISPOT, a higher stimulation index was noted with the MIG assay as compared with the ELISPOT assay (on average at least threefold higher) and, in some cases, responses as detected by the MIG assay were significant, but the corresponding response as measured by ELISPOT was not significant. Finally, the flow-based MIG assay offers a number of practical and technical advantages over the ELISPOT assay. Our data validate this novel method for the detection of low as well as high levels of antigen-specific and genetically restricted IFN-gamma activity.

Transgenic mice with cardiac-specific expression of activating transcription factor 3, a stress-inducible gene, have conduction abnormalities and contractile dysfunction

Activating transcription factor 3 (ATF3) is a member of the CREB/ATF family of transcription factors. Previously, we demonstrated that the expression of the ATF3 gene is induced by many stress signals. In this report, we demonstrate that expression of ATF3 is induced by cardiac ischemia coupled with reperfusion (ischemia-reperfusion) in both cultured cells and an animal model. Transgenic mice expressing ATF3 under the control of the alpha-myosin heavy chain promoter have atrial enlargement, and atrial and ventricular hypertrophy. Microscopic examination showed myocyte degeneration and fibrosis. Functionally, the transgenic heart has reduced contractility and aberrant conduction. Interestingly, expression of sorcin, a gene whose product inhibits the release of calcium from sarcoplasmic reticulum, is increased in these transgenic hearts. Taken together, our results indicate that expression of ATF3, a stress-inducible gene, in the heart leads to altered gene expression and impaired cardiac function.

The roles of ATF3 in glucose homeostasis. A transgenic mouse model with liver dysfunction and defects in endocrine pancreas

Activating transcription factor 3 (ATF3) is a member of the ATF/cAMP-response element-binding protein family of transcription factors. It is a transcriptional repressor, and the expression of its corresponding gene is induced by stress signals in a variety of tissues, including the liver. In this report, we demonstrate that ATF3 is induced in the pancreas by partial pancreatectomy, streptozotocin treatment, and ischemia coupled with reperfusion. Furthermore, ATF3 is induced in cultured islet cells by oxidative stress. Interestingly, transgenic mice expressing ATF3 in the liver and pancreas under the control of the transthyretin promoter have defects in glucose homeostasis and perinatal lethality. We present evidence that expression of ATF3 in the liver represses the expression of genes encoding gluconeogenic enzymes. Furthermore, expression of ATF3 in the pancreas leads to abnormal endocrine pancreas and reduced numbers of hormone-producing cells. Analyses of embryos indicated that the ATF3 transgene is expressed in the ductal epithelium in the developing pancreas, and the transgenic pancreas has fewer mitotic cells than the non-transgenic counterpart, providing a potential explanation for the reduction of endocrine cells. Because ATF3 is a stress-inducible gene, these mice may represent a model to investigate the molecular mechanisms for some stress-associated diseases.

The T cell chemoattractant IFN-inducible protein 10 is essential in host defense against viral-induced neurologic disease

The contribution of the T cell chemoattractant chemokine IFN-inducible protein 10 (IP-10) in host defense following viral infection of the CNS was examined. IP-10 is expressed by astrocytes during acute encephalomyelitis in mouse hepatitis virus-infected mice, and the majority of T lymphocytes infiltrating into the CNS expressed the IP-10 receptor CXCR3. Treatment of mice with anti-IP-10 antisera led to increased mortality and delayed viral clearance from the CNS as compared with control mice. Further, administration of anti-IP-10 led to a >70% reduction (p </= 0.001) in CD4+ and CD8+ T lymphocyte infiltration into the CNS, which correlated with decreased (p </= 0.01) levels of IFN-gamma. These data indicate that IP-10 functions as a sentinel molecule in host defense and is essential in the development of a protective Th1 response against viral infection of the CNS.

The murine chemokine CXCL11 (IFN-inducible T cell alpha chemoattractant) is an IFN-gamma- and lipopolysaccharide-inducible glucocorticoid-attenuated response gene expressed in lung and other tissues during endotoxemia

A new murine chemokine was identified in a search for glucocorticoid-attenuated response genes induced in the lung during endotoxemia. The first 73 residues of the predicted mature peptide are 71% identical and 93% similar to human CXCL11/IFN-inducible T cell alpha chemoattractant (I-TAC) (alias beta-R1, H174, IFN-inducible protein 9 (IP-9), and SCYB9B). The murine chemokine has six additional residues at the carboxyl terminus not present in human I-TAC. Identification of this cDNA as murine CXCL11/I-TAC is supported by phylogenetic analysis and by radiation hybrid mapping of murine I-TAC (gene symbol Scyb11) to mouse chromosome 5 close to the genes for monokine induced by IFN-gamma (MIG) and IP10. Murine I-TAC mRNA is induced in RAW 264.7 macrophages by IFN-gamma or LPS and is weakly induced by IFN-alphabeta. IFN-gamma induction of murine I-TAC is markedly enhanced by costimulation with LPS or IL-1beta in RAW cells and by TNF-alpha in both RAW cells and Swiss 3T3 fibroblasts. Murine I-TAC is induced in multiple tissues during endoxemia, with strongest expression in lung, heart, small intestine, and kidney, a pattern of tissue expression different from those of MIG and IP10. Peak expression of I-TAC message is delayed compared with IP10, both in lung after i.v. LPS and in RAW 264.7 cells treated with LPS or with IFN-gamma. Pretreatment with dexamethasone strongly attenuates both IFN-gamma-induced I-TAC expression in RAW cells and endotoxemia-induced I-TAC expression in lung and small intestine. The structural and regulatory similarities of murine and human I-TAC suggest that mouse models will be useful for investigating the role of this chemokine in human biology and disease.

Transcriptional autorepression of the stress-inducible gene ATF3

Previously, we demonstrated that ATF3 (activating transcription factor-3) is a stress-inducible gene, and the protein it encodes is a transcriptional repressor. In this report, we present evidence suggesting that ATF3 represses the transcription of its own gene. Interestingly, efficient repression requires a consensus ATF/cAMP-responsive element site in the promoter and a previously unidentified ATF3-binding site immediately downstream from the TATA box. Although this new site resembles the known ATF/cAMP-responsive element sequences at the flanking sequence, it differs from them at the center key residues. These observations indicate that ATF3 can tolerate variations in the center of the binding sites if the flanking sequences are favorable. The repression of the ATF3 promoter by its own gene product provides a mechanistic explanation, at least in part, for the transient expression pattern of the ATF3 gene upon stress induction.

Cloning of DLM-1, a novel gene that is up-regulated in activated macrophages, using RNA differential display

Tumors interact with their environment, reprogramming host cells to induce responses such as angiogenesis, inflammation, immunity and immune suppression. To understand these processes, it is important to identify and isolate new genes whose expression is induced in host tissues in response to tumors. Ascites tumors offer an attractive model for isolating such genes, because responding host peritoneal lining tissues can be cleanly separated from tumor cells growing in suspension within the peritoneal cavity. We here report the cloning by differential display of a novel gene, DLM-1, that is highly up-regulated in the peritoneal lining tissue of mice bearing MOT ascites tumors. Mouse peritoneal macrophages, stimulated by IFN-gamma or LPS, also expressed significant amounts of DLM-1. Up-regulation of DLM-1 became evident by 4h after stimulation with IFN-gamma and was not blocked by cycloheximide, suggesting the presence of IFN responding elements in its transcription regulation region. DLM-1 RNA was detected at significant levels in normal mouse lung, intestinal epithelium, liver and thymus by Northern blot analysis. In situ hybridization of MOT and HT-29 mouse subcutaneous transplanted solid tumors revealed strong DLM-1 expression in the host reactive stromal cells, but not the tumor cells. Sequence analysis of the full-length cDNA clone revealed that it encodes a protein of approx. M(r) 44330 with multiple potential protein kinase C and casein kinase II phosphorylation sites. Our data suggest that DLM-1 plays a role in such important processes as host response in neoplasia.

Use of Immunodeficient Mice for the Evaluation of CXC Chemokines in the Regulation of Tumor-associated Angiogenesis

Angiogenesis, defined as the growth of new capillaries from pre-existing vessels, is a pervasive biological phenomenon that is at the core of many physiologic and pathologic processes such as tumor growth. The use of human tumor xenografts in immunodeficient mice has provided significant insight into the biology of angiogenesis as it relates to tumor growth and metastasis. Work reviewed in this article supports the notion that net tumor-derived angiogenesis during tumorigenesis of human tumors is determined, in part, by an imbalance in favor of the overexpression of angiogenic (compared with angiostatic) juxtaposed cysteine residue (CXC) chemokines. This paradigm predicts an environment that favors angiogenesis (tumorigenesis) and supports the potential for spontaneous metastases. The article describes the use of immunodeficient mice as an animal model system for characterizing the qualitative and quantitative presence of these angiogenic and angiostatic CXC chemokines during tumorigenesis, as well as determining their net contribution to human tumorigenesis and metastasis in vivo. Various cancer cell lines have been used and xenografted into immunodeficient mice to create human tumor/mouse chimeras, indicating that an imbalance in the biology of angiogenic versus angiostatic CXC chemokines supports a significant portion of human tumor-derived angiogensis that leads to augmented tumorigenesis and spontaneous metastases. It has also been possible to identify potentially therapeutic novel strategies to manipulate the imbalance of angiogenic (compared with angiostatic) CXC chemokines, which may be directly translational to human disease.

Role of interferon regulatory factor 1 in monocyte/macrophage differentiation

Interferon regulatory factor-1 (IRF-1) has been recognized as an important tumor suppressor and growth regulatory transcription factor, which is also involved in cell differentiation. In this study we investigated the role of IRF-1 in phorbol 12-myristate 13-acetate (PMA)-induced monocyte/macrophage differentiation of human monoblastic U937 cells. For this purpose U937 cells were stably transfected with a vector overexpressing IRF-1 antisense mRNA (U937 IRF-1A cells) and with the SV-40 empty vector (U937-SV40 e.v. cells). We report here that U937 and U937-SV40 e.v. cells differentiated into macrophage-like cells upon PMA stimulation and showed IRF-1 up-regulation. On the contrary, U937 IRF-1A cells stimulated with PMA kept an undifferentiated phenotype and proliferated actively. A direct correlation between induction of IRF-1 and up-regulation of IRF-1 gene targets such as ornithine decarboxylase (ODC) and WAF-1/CIP-1 was also observed in U937 cells. On the other hand U937 IRF-1A cells down-regulated ODC and did not express WAF-1. Results show that IRF-1 plays a pivotal role in PMA-induced monocyte/macrophage differentiation.

ATF3 and stress responses

The purpose of this review is to discuss ATF3, a member of the ATF/CREB family of transcription factors, and its roles in stress responses. In the introduction, we briefly describe the ATF/CREB family, which contains more than 10 proteins with the basic region-leucine zipper (bZip) DNA binding domain. We summarize their DNA binding and heterodimer formation with other bZip proteins, and discuss the nomenclature of these proteins. Over the years, identical or homologous cDNA clones have been isolated by different laboratories and given different names. We group these proteins into subgroups according to their amino acid similarity; we also list the alternative names for each member, and clarify some potential confusion in the nomenclature of this family of proteins. We then focus on ATF3 and its potential roles in stress responses. We review the evidence that the mRNA level of ATF3 greatly increases when the cells are exposed to stress signals. In animal experiments, the signals include ischemia, ischemia coupled with reperfusion, wounding, axotomy, toxicity, and seizure; in cultured cells, the signals include serum factors, cytokines, genotoxic agents, cell death-inducing agents, and the adenoviral protein E1A. Despite the overwhelming evidence for its induction by stress signals, not much else is known about ATF3. Preliminary results suggest that the JNK/SAPK pathway is involved in the induction of ATF3 by stress signals; in addition, IL-6 and p53 have been demonstrated to be required for the induction of ATF3 under certain conditions. The consequences of inducing ATF3 during stress responses are not clear. Transient transfection and in vitro transcription assays indicate that ATF3 represses transcription as a homodimer; however, ATF3 can activate transcription when coexpressed with its heterodimeric partners or other proteins. Therefore, it is possible that, when induced during stress responses, ATF3 activates some target genes but represses others, depending on the promoter context and cellular context. Even less is understood about the physiological significance of inducing ATF3. We will discuss our preliminary results and some reports by other investigators in this regard.

IP-10 gene transcription by virus in astrocytes requires cooperation of ISRE with adjacent kappaB site but not IRF-1 or viral transcription

Transcription of the IP-10 gene requires interferon (IFN)-stimulated response element (ISRE) and kappaB sites to be induced by lipopolysaccharide (LPS), IFN-gamma, virus, and poly(I:C). A requirement for Stat1 binding to ISRE for IFN-gamma and IFN regulatory factor-1 (IRF-1) binding to ISRE for LPS, poly(I:C), and virus has been reported. We investigated whether viral transcription is required for IP-10 induction and how ISRE interacts with IRF-1 and with two kappaB sites. IP-10 mRNA was induced by Newcastle disease virus and Sendai virus in rat astrocytes and the human astrocytoma U251 cell line. IP-10 was also induced by UV-irradiated virus, which is unable to carry out viral transcription. The minimal IP-10 virus response element (VRE) consists of an ISRE and adjacent kappaB site between -236 and -153, to which p50/p65 NF-kappaB proteins and IRF-like proteins bind. Virus induced NF-kappaB binding to an isolated kappaB sequence adjacent to ISRE. However, no protein binding to isolated ISRE was induced by virus. Virus also induced IP-10 in cells expressing a defective IRF-1 gene. Therefore, effective ISRE activity of IP-10 VRE may require an IRF-like protein binding, which is enhanced by an NF-kappaB heterodimer binding to an adjacent KB site. IRF-1 is not required for virus-induced IP-10 gene expression.

A novel lipopolysaccharide inducible C-C chemokine receptor related gene in murine macrophages

To identify genes induced in activated macrophages, we screened a cDNA library prepared from the lipopolysaccharide (LPS)-treated cell line, RAW264, using the suppression subtractive hybridization technique. One of the clones isolated was dramatically induced by LPS in macrophages. The predicted protein sequence of this gene contains the domain unique to seven transmembrane receptors, and shows similarity with mouse C-C chemokine receptor 5 (CCR5). Therefore, we designated it LPS inducible C-C chemokine receptor related gene (L-CCR). Northern blot analysis revealed that L-CCR was specifically expressed in differentiated macrophages after LPS stimulation. These results show that L-CCR is a novel C-C chemokine receptor related gene induced by LPS in macrophages and may play an important role in inflammatory responses.

Identification and categorization of inducible mast cell genes in a subtraction library

Mast cells play an important role in allergic inflammation by releasing inducible proinflammatory cytokines. While many inducible genes have been identified, we hypothesized that a significant number remain to be identified. We thus constructed an activation-specific mast cell subtraction library to establish a profile of induced genes in mast cells following allergic stimulation. To date, we have sequenced 150 cDNA clones. Among them, we have isolated 22 known genes whose expression has not been reported in mast cells, and an additional 26 cDNA clones which do not have significant homology to known genes in the Genbank database. We next selected 10 cDNA clones with strong signals by differential plaque hybridization. Of these cDNA clones, five genes were induced in mast cells upon Fc epsilon RI-mediated stimulation. They are cofilin, annexinVI, interferon (IFN)-beta, serglycin, and a novel inducible mast cell (IMC) gene, IMC-415. Characterization and relevant studies of this novel gene and other inducible known genes in mast cells will provide insight into the functions of mast cells in mammalian biology.

Chemokines, lymphocytes, and HIV

Chemokines are members of a family of more than 30 human cytokines whose best-described activities are as chemotactic factors for leukocytes and that are presumed to be important in leukocyte recruitment and trafficking. While many chemokines can act on lymphocytes, the roles of chemokines and their receptors in lymphocyte biology are poorly understood. The recent discoveries that chemokines can suppress infection by HIV-1 and that chemokine receptors serve, along with CD4, as obligate co-receptors for HIV-1 entry have lent urgency to studies on the relationships between chemokines and lymphocytes. My laboratory has characterized Mig and Crg-2/IP-10, chemokines that are induced by IFN-gamma and that specifically target lymphocytes, particularly activated T cells. We have demonstrated that the genes for these chemokines are widely expressed during experimental infections in mice with protozoan and viral pathogens, but that the patterns of mig and crg-2 expression differed, suggesting non-redundant roles in vivo. Our related studies to identify new chemokine receptors from activated lymphocytes resulted in the cloning of STRL22 and STRL33. We and others have shown that STRL22 is a receptor for the CC chemokine MIP-3 alpha, and STRL22 has been renamed CCR6. Although STRL33 remains an orphan receptor, we have shown that it can function as a co-receptor for HIV-1 envelope glycoproteins, and that it is active with a broader range of HIV-1 envelope glycoproteins than the major co-receptors described to date. The ability of STRL33 to function with a wide variety of envelope glycoproteins may become particularly important if therapies are instituted to block other specific co-receptors. We presume that investigations into the roles of chemokines and their receptors in lymphocyte biology will provide information important for understanding the pathogenesis of AIDS and for manipulating immune and inflammatory responses for clinical benefit.

Regulation of macrophage cytokine production by prostaglandin E2. Distinct roles of cyclooxygenase-1 and -2

Prostaglandin E2 (PGE2) modulates a variety of physiological processes including the production of inflammatory cytokines. There are two cyclooxygenase (Cox) enzymes, Cox-1 and Cox-2, that are responsible for initiating PGE2 synthesis. These isozymes catalyze identical biosynthetic reactions but are regulated by different mechanisms in the cell. This report examines differences in the roles of Cox-1 and Cox-2 in regulating cytokine synthesis in macrophages. We employed agents that selectively modulate the activity of each isozyme and measured their effects on synthesis of interleukin (IL)-6, IL-1, and tumor necrosis factor-alpha by peritoneal macrophages. Among these three cytokines, only IL-6 synthesis was stimulated by production of endogenous PGE2. This effect was specifically linked to activation of Cox-2 and not Cox-1. The specificity derives, partly, from the timing of the production of PGE2 following stimulation of each isozyme and from induction of ancillary signals that control the response to PGE2. The experimental findings demonstrate that the effects of Cox-1 and Cox-2 activity on macrophage IL-6 synthesis are segregated. This provides a mechanism for IL-6 to be induced selectively during inflammation.

Induction of IP-10 chemokine promoter by measles virus: comparison with interferon-gamma shows the use of the same response element but with differential DNA-protein binding profiles

Measles virus (MV) and interferon (IFN)-gamma induced IP-10 chemokine mRNA in U373 glioblastoma cells. The minimal response element for both MV and IFN-gamma was localized between nucleotide -231 and -153 of muIP-10 promoter, which contains an IFN-stimulated response element (ISRE) and the distal NF-kappa Bd site. Mutation of individual elements showed that ISRE and NF-kappa Bd were required to function together. DNA-protein binding profiles with the minimal response element showed that IFN-gamma induced a complex consisting of STAT1 while MV induced a complex consisting of p50 and p65 in the absence of new protein synthesis. IFN-gamma and MV also induced IRF-1 DNA binding activity which persisted for longer time periods with IFN-gamma stimulation. Despite the functional requirement of both ISRE and NF-kappa Bd elements, different combinations of DNA binding factors are used in the induction of IP-10 by MV or IFN-gamma.

Identification of a lipopolysaccharide inducible transcription factor in murine macrophages

To study macrophage genes activated by lipopolysaccharide (LPS) we have constructed a cDNA library using the mouse macrophage cell line, RAW 264.7. By differential screening, a gene, designated LRG-21, was identified that showed nucleic acid sequence homology to rat liver regenerating factor-1 (LRF-1) and human activating transcription factor-3 (ATF3). Both LRG-21 and LRF-1 are transcribed within an hour following stimulation and in the absence of protein synthesis. The predicted protein sequence of LRG-21 consists of 181 amino acids with a molecular weight of 20.7 kDa. All three sequences contain basic and leucine zipper regions characteristic of the c-Fos and c-Jun family of transcription factors, but the remainder of the sequences are unrelated to this family. Recombinant LRG-21 has been shown to bind to a phorbol ester promoter element. Additional experiments have shown that LRG-21 is also induced by interferon-gamma (IFN-gamma) and by interleukin-4 (IL-4) in both RAW264.7 cells and murine peritoneal macrophages. Based on these observations, it is likely that LRG-21 plays an important role in macrophage activation.

Glucocorticoid-attenuated response genes encode intercellular mediators, including a new C-X-C chemokine

A major part of the anti-inflammatory effect of glucocorticoids is attributable to their attenuation of the induction of genes whose products mediate intercellular interactions, e.g. cytokines and the inducible forms of prostaglandin synthase and nitric oxide synthase. We hypothesized that (i) there exists a class of immediate-early/primary response genes whose induction by inflammatory agents, mitogens, and other stimuli is attenuated by glucocorticoids, and (ii) the products of these glucocorticoid-attenuated response genes (GARGs) function predominantly in paracrine cell processes. We constructed a lambda cDNA library from transforming growth factor beta 1-pretreated murine Swiss 3T3 cells stimulated with lipopolysaccharide (LPS) or serum in the presence of cycloheximide, screened 15,000 plaques by differential hybridization, and cloned 12 LPS-induced, dexamethasone-attenuated cDNAs. Seven were previously known. Six of these encode intercellular mediators (thrombospondin-1, MCSF, JE/MCP-1, MARC/fic/MCP-3, crg2/IP-10, and cyr61); one encodes a protein of unknown function (IRG2). Thus, a large majority of these GARG cDNAs encode intercellular mediators, as hypothesized. Of the five GARG cDNAs not previously known, one encodes a novel member of the CXC chemokine family, designated LIX (LPS-induced CXC chemokine). The predicted LIX protein has a 40-amino acid signal sequence and a 92-amino acid mature peptide with a distinctive COOH-terminal region. Surprisingly, segments of the 3'-untranslated regions of LIX and two other CXC chemokines have substantially greater nucleotide sequence homology than do their coding regions. These segments may perform an unknown regulatory function. The LIX message is strongly induced by LPS in fibroblasts, but not in macrophages, suggesting that LIX may participate in the recruitment of inflammatory cells by injured or infected tissue.

Differential expression of novel genes by bone marrow-derived macrophage populations

In the present study, we have constructed a subtraction cDNA library to identify novel genes induced by IFN-gamma in GM-CSF-derived bone marrow macrophage (m phi). M theta were treated with 50 U/ml IFN-gamma for 40, 70 and 140 min to induce expression of early genes regulated by IFN-gamma, and the M phi were pooled. Poly(A)+RNA was prepared from both unactivated and IFN-gamma-stimulated m theta, and cDNA libraries were constructed in lambda ZAP. Genes expressed in common by both m theta populations were removed by subtraction using biotin-avidin precipitation of hybrid complexes. Further selection was performed by differential screening using cDNA prepared from mRNA of unactivated m phi as a probe, followed by colony hybridization to remove sister clones. Of 17 clones from which sequence information was obtained, two appeared to be identical with the murine genes, C10 (clone GM2B1) and Mac-2 (clone GM2C4) and an additional two clones had high similarity to human cDNAs encoding proteins of unknown function. cDNAs containing sequences which did not match published sequences were used to probe Northern blots prepared from both unstimulated and IFN-gamma-activated GM-CSF- and CSF-1-derived m phi. Five clones (GM1A2, GM1B4, GM1F2, GM2A12 and GM2B8) showed enhanced transcript levels following IFN-gamma treatment of GM-CSF-derived m phi, but demonstrated high constitutive transcript levels in CSF-l-derived m phi. In addition, C10 transcripts were constitutively expressed by GM-CSF-derived m phi, but not by CSF-1-derived m phi, even after activation by IFN-gamma. These data suggest that much of the functional heterogeneity of GM-CSF- and CSF-1-derived m phi resides in the differential expression of early genes specifically induced by IFN-gamma.

Protein tyrosine phosphorylation as a mechanism which regulates cytokine activation of early response genes

Two well-defined rapid responses which occur as a consequence of growth factors binding to their cell surface receptors involve tyrosine phosphorylation of cellular proteins and the induction of the transcription of cellular genes. Recent advances have been made in purification and cloning of Src homology 2 and 3 (SH2/SH3) domain-containing transcription factors which are required for the activation of early response genes by interferons. These transcription factors are covalently modified by tyrosine phosphorylation such that they interact with enhancers needed for interferon-stimulated gene expression. The Jak family of tyrosine kinases are also an integral component in these signalling cascades. The information gained concerning interferon signalling has now been extended to include a broad network of cytokine-regulated signalling systems which use tyrosine phosphorylation of a family of structurally related proteins to activate transcription of early response genes.

Anatomic patterns of Fos immunostaining in rat brain following systemic endotoxin administration

To identify brain neurons that participate in the acute phase response, rat brains were examined immunocytochemically for Fos protein following the intravenous administration of bacterial endotoxin (lipopolysaccharide, LPS). Two to three hours after the injection of LPS, 150 micrograms/kg body weight, to adult male Long-Evans rats, a consistent anatomic pattern of Fos immunostained cell nuclei is seen. In the brain stem, prominant Fos immunostaining is induced in tyrosine hydroxylase immunoreactive neurons of the caudal ventral-lateral medulla (the A1 cell group), in both tyrosine hydroxylase positive and negative neurons of nu. tractus solitarius, in the parabrachial nu., and in a few neurons of the locus ceruleus. In the hypothalamus, endotoxin induces Fos expression in magnocellular neurons of the paraventricular and supraoptic nuclei and internuclear cell groups. A higher percentage of oxytocin-immunoreactive cells is double labeled for Fos nuclear immunostaining than vasopressin-immunoreactive cells. A minority of somatostatin immunoreactive periventricular hypothalamic neurons are Fos positive. Other hypothalamic nuclei that contain endotoxin-induced Fos nuclear immunostaining include the parvocellular neurons of the paraventricular nu., the dorsomedial and arcuate nuclei, the lateral hypothalamus, the dorsal hypothalamic area (zona incerta), and the median nucleus of the preoptic area. LPS induces numerous Fos-positive neurons in regions known to respond to a variety of stressful stimuli; these regions include the preoptic area, bed nucleus of the stria terminalis, lateral septum, and the central and medial nuclei of the amygdala. Moreover, Fos nuclear immunostaining is seen in neurons of circumventricular organs: the organum vasculosum of the lamina terminalis, the subfornical organ, and the area postrema. The maximum intensity of Fos nuclear immunostaining occurs 2-3 h after endotoxin administration and declines thereafter. It is attenuated by pretreatment with indomethacin, 25 mg/kg body weight Sc, or dexamethasone, 1 mg/kg IP. These observations are consistent with the participation of a variety of brain neuronal systems in the acute phase response and elucidate the functional neuroanatomy of that response at the cellular level.

Regulation of macrophage gene expression by T-cell-derived lymphokines

Cytokines secreted from antigen-specific T lymphocytes provide important positive and negative control of inflammation through their effects on non-antigen-specific inflammatory leukocytes. These effects often involve modulation of gene expression. Lymphokine-inducible macrophage gene expression is largely controlled at the level of transcription. Multiple cis-acting sequence motifs cooperate with one another to produce patterns of expression that are relatively unique to individual genes. Members of trans-acting transcription factor families, which recognize related regulatory sequence elements, participate frequently in complex protein-protein interactions that generate remarkable complexity in terms of the number of potential combinations and the consequential functional differences exhibited by each combination. Thus, the remarkable plasticity of immune-mediated inflammation derives from combinations of finite numbers of options at several points in the cellular and molecular sequence.

Possible role of the transcription factor interferon regulatory factor 1 (IRF-1) in the regulation of ornithine decarboxylase (ODC) gene expression during IFN gamma macrophage activation

In this report we discuss the role of interferon regulatory factor 1 (IRF-1) in the regulation of ornithine decarboxylase (ODC) transcription during IFN gamma human macrophage activation. We show that a binding sequence for the transcription factor IRF-1 is contained in the first intron of the human ODC gene (from nt +2711 to nt +2722) and we demonstrate that the level of expression of IRF-1 increases in human macrophages and in the human promonocytic cell line, U937, previously differentiated in monocytes/macrophages by phorbol myristate acetate (PMA), after 2 h of IFN gamma stimulation. We also show that the hamster tk-ts13 cell line, stably transfected with the IRF-1 cDNA, over-expresses ODC. In addition, a specific complex was detected, by gel-shift assay after incubating a 20 bp double-stranded oligomer containing the binding sequence for IRF-1 with nuclear proteins extracted from human macrophages and from (PMA-differentiated) U937 cells stimulated with IFN gamma for 2 h.

Enhancement of inducible-type NO synthase gene transcription by protein synthesis inhibitors. Activation of an intracellular signal transduction pathway by low concentrations of cycloheximide

Treatment of mouse macrophage-like RAW 264.7 cells with certain protein synthesis inhibitors is followed by accumulation of the mRNA for the inducible isoform of nitric oxide synthase (i-NOS). The activity of these compounds on the i-NOS gene in RAW 264.7 cells was analyzed here in detail. Results show that both cycloheximide and anisomycin can efficiently induce i-NOS mRNA, even when used at concentrations so low (0.25 microgram/ml) to have only negligible effects on protein synthesis; puromycin, on the other hand, shows only a limited effect on i-NOS mRNA expression, detectable only when cells are treated with higher concentrations of inhibitor (25 micrograms/ml). In RAW 264.7 cells, low concentrations of cycloheximide trigger an immediate-early gene response, as indicated by induction of c-fos and JE mRNAs, and can efficiently activate transcription of transiently transfected recombinant reporter genes including either the i-NOS or the c-fos gene promoters.

Inhibition of IFN-gamma induction of class II MHC genes by cAMP and prostaglandins

Triggering of the cyclic AMP (cAMP) signal transduction pathway inhibits the the interferon gamma (IFN-gamma)-mediated induction of class II major histocompatibility (MHC) genes. We have investigated the mechanism of the inhibition of IFN-gamma induction of the murine A alpha class II MHC gene by cAMP and E series prostaglandins (PGEs). 151 base pairs of the A alpha promoter were sufficient to confer positive regulation by IFN-gamma and negative regulation by cAMP which accurately mirrored the regulation of the endogenous A alpha gene. cAMP also inhibited the IFN-gamma activation of the Fc gamma receptor I (Fc gamma RI) gene promoter, an "early" promoter which is activated immediately after treatment of cells with IFN-gamma. PGEs, which cause an elevation in intracellular cAMP, inhibited the induction of the A alpha promoter, and inhibition was greater in the presence of tumor necrosis factor alpha (TNF alpha). A mutational analysis of the A alpha promoter showed that all four conserved class II promoter elements, the S, X1, X2, and Y boxes, play a role in mediating A alpha promoter activation by IFN-gamma. Mutations in these elements did not diminish the cAMP inhibition of promoter activation by IFN-gamma. Thus, conserved class II promoter sequences which mediate most known examples of positive and negative regulation, including cAMP inhibition of constitutive class II expression, do not mediate cAMP inhibition of IFN-gamma activation of the A alpha promoter. We suggest that this inhibition may be mediated by a novel class II promoter element or by disruption of an early step in the IFN-gamma signal transduction pathway.

"Macrophage" nitric oxide synthase is a glucocorticoid-inhibitable primary response gene in 3T3 cells

Both nitric oxide and prostaglandins are potent paracrine mediators of intercellular communication. An endotoxin-lipopolysaccharide (LPS) inducible form of nitric oxide synthase (mac-NOS) has recently been cloned from murine macrophages. An inducible prostaglandin synthase (TIS10/PGS-2), cloned from 3T3 cells, is also induced in LPS-activated macrophage. Because of the wide range of ligands that induce primary response genes in 3T3 cells, the ease of studying chimeric promoter constructs in 3T3 cells, and the importance of both nitric oxide and prostaglandins as paracrine mediators, we examined expression of mac-NOS in 3T3 cells. Tetradecanoyl phorbol-13-acetate (TPA), forskolin, platelet-derived growth factor, fibroblast growth factor, and serum all induce mac-NOS expression in Swiss 3T3 cells. Thus the mac-NOS gene can respond to a far wider range of inducers than previously suspected. mac-NOS is a primary response gene; cycloheximide does not block induction. TPA-induced mac-NOS and TIS10/PGS-2 mRNA accumulation patterns are similar. LPS is a potent inducer of mac-NOS in Swiss 3T3 cells but cannot induce TIS10/PGS-2. In contrast, v-src expression induces TIS10/PGS-2 message, but not iNOS message in a BALB/c 3T3 cell line containing a temperature-sensitive v-src gene. Dexamethasone (DEX) prevents induction of TIS10/PGS-2, but not most other primary response genes. DEX also blocks mac-NOS induction in Swiss 3T3 cells. The inducible TIS10/PGS-2 and mac-NOS genes, responsible for the production of two distinct paracrine agents, appear to share many regulatory features in 3T3 cells.