Synergy between interferon-gamma and tumor necrosis factor-alpha in transcriptional activation is mediated by cooperation between signal transducer and activator of transcription 1 and nuclear factor kappaB

IFN-gamma/STAT1 acts as a proinflammatory signal in T cell-mediated hepatitis via induction of multiple chemokines and adhesion molecules: a critical role of IRF-1

We have previously shown that IFN-gamma/STAT1 plays an essential role in concanavalin A (ConA)-induced T cell hepatitis via activation of apoptotic signaling pathways. Here we demonstrate that IFN-gamma/STAT1 also plays a crucial role in leukocyte infiltration into the liver in T cell hepatitis. After injection of ConA, leukocytes were significantly infiltrated into the liver, which was suppressed in IFN-gamma(-/-) and STAT1(-/-) mice. Disruption of the IFN regulatory factor-1 (IRF-1) gene, a downstream target of IFN-gamma/STAT1, abolished ConA-induced liver injury and suppressed leukocyte infiltration into the liver. Additionally, ConA injection induced expression of a wide variety of chemokines and adhesion molecules in the liver. Among them, expression of ICAM-1, VCAM-1, monokine induced by IFN-gamma (Mig), CC chemokine ligand-20, epithelial cell-derived neutrophil-activating peptide (ENA)-78, IFN-inducible T cell-alpha chemoattractant (I-TAC), and IFN-inducible protein-10 (IP-10) was markedly attenuated in IFN-gamma(-/-), STAT1(-/-), and IRF-1(-/-) mice. In primary mouse hepatocytes, Kupffer cells, and endothelial cells, in vitro treatment with IFN-gamma activated STAT1, STAT3, and IRF-1, and induced expression of VCAM-1, ICAM-1, Mig, ENA-78, I-TAC, and IP-10 mRNA. Induction of these chemokines and adhesion molecules was markedly diminished in STAT1(-/-) and IRF-1(-/-) hepatic cells compared with wild-type hepatic cells. These findings suggest that in addition to induction of apoptosis, previously well documented, IFN-gamma also stimulated hepatocytes, sinusoidal endothelial cells, and Kupffer cells partly via an STAT1/IRF-1-dependent mechanism to produce multiple chemokines and adhesive molecules responsible for promoting infiltration of leukocytes and, ultimately, resulting in hepatitis.

LPS-induced upregulation of SHIP is essential for endotoxin tolerance

An initial exposure to lipopolysaccharide (LPS) induces a transient state of hyporesponsiveness to a subsequent challenge with LPS. The mechanism underlying this phenomenon, termed endotoxin tolerance, remains poorly understood despite a recent resurgence of interest in this area. We demonstrate herein that SHIP(-/-) bone marrow-derived macrophages (BMmphis) and mast cells (BMMCs) do not display endotoxin tolerance. Moreover, an initial LPS treatment of wild-type BMmphis or BMMCs increases the level of SHIP, but not SHIP2 or PTEN, and this increase is critical for the hyporesponsiveness to subsequent LPS stimulation. Interestingly, this increase in SHIP protein is mediated by the LPS-induced production of autocrine-acting TGFbeta and neutralizing antibodies to TGFbeta block LPS-induced endotoxin tolerance. In vivo studies with SHIP(+/+) and SHIP(-/-) mice confirm these in vitro findings and show a correlation between the duration of endotoxin tolerance and elevated SHIP levels.

Rabies virus stimulates nitric oxide production and CXC chemokine ligand 10 expression in macrophages through activation of extracellular signal-regulated kinases 1 and 2

Macrophages represent an essential part of innate immunity, and the viral infection of macrophages results in the release of multiple proinflammatory mediators, such as nitric oxide (NO), cytokines, and chemokines. This study was undertaken to define the molecular mechanism of macrophage activation in response to rabies virus (RV) infection. In RAW264 murine macrophage cells, a well-characterized macrophage model, RV replication was strictly restricted, whereas cell proliferation was significantly enhanced upon RV inoculation. Transcriptional analyses for the expression of inducible forms of NO synthase (iNOS), cytokines, and chemokines revealed that RV virions potentiate the gene expression of iNOS and CXC chemokine ligand 10 (CXCL10), a major chemoattractant of T helper cell type 1. However, RV stimulation had little or no effect on the expression profiles of proinflammatory cytokines and other types of chemokines. In macrophages stimulated with UV-inactivated RV virions, as well as infectious viruses, the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, members of the mitogen-activated protein kinase family, was significantly induced. Specific inhibitors of MAPK/ERK kinase reduced the RV-induced production of NO and CXCL10. Furthermore, the RV-induced activation of the ERK1/2 pathway was severely impaired by the neutralization of the endosomal and lysosomal pH environment with lysosomotropic agents, indicating that endocytosis is a key step leading to the activation of ERK1/2 signaling. Taken together, these results suggest that the ERK1/2-mediated signaling pathway plays a cardinal role in the selective activation of macrophages in response to RV virions, thereby regulating cellular functions during virus infection.

Nuclear factor-kappaB motif and interferon-alpha-stimulated response element co-operate in the activation of guanylate-binding protein-1 expression by inflammatory cytokines in endothelial cells

The large GTPase GBP-1 (guanylate-binding protein-1) is a major IFN-gamma (interferon-gamma)-induced protein with potent anti-angiogenic activity in endothelial cells. An ISRE (IFN-alpha-stimulated response element) is necessary and sufficient for the induction of GBP-1 expression by IFN-gamma. Recently, we have shown that in vivo GBP-1 expression is strongly endothelial-cell-associated and is, in addition to IFN-gamma, also activated by interleukin-1beta and tumour necrosis factor-alpha, both in vitro and in vivo [Lubeseder-Martellato, Guenzi, Jörg, Töpolt, Naschberger, Kremmer, Zietz, Tschachler, Hutzler, Schwemmle et al. (2002) Am. J. Pathol. 161, 1749-1759; Guenzi, Töpolt, Cornali, Lubeseder-Martellato, Jörg, Matzen, Zietz, Kremmer, Nappi, Schwemmle et al. (2001) EMBO J. 20, 5568-5577]. In the present study, we identified a NF-kappaB (nuclear factor kappaB)-binding motif that, together with ISRE, is required for the induction of GBP-1 expression by interleukin-1beta and tumour necrosis factor-alpha. Deactivation of the NF-kappaB motif reduced the additive effects of combinations of these cytokines with IFN-gamma by more than 50%. Importantly, NF-kappaB p50 rather than p65 activated the GBP-1 promoter. The NF-kappaB motif and ISRE were detected in an almost identical spatial organization, as in the GBP-1 promoter, in the promoter regions of various inflammation-associated genes. Therefore both motifs may constitute a cooperative inflammatory cytokine response module that regulates GBP-1 expression. Our findings may open new perspectives for the use of NF-kappaB inhibitors to support angiogenesis in inflammatory diseases including ischaemia.

Influenza virus-induced sleep responses in mice with targeted disruptions in neuronal or inducible nitric oxide synthases

Influenza viral infection induces increases in non-rapid eye movement sleep and decreases in rapid eye movement sleep in normal mice. An array of cytokines is produced during the infection, and some of them, such as IL-1β and TNF-α, are well-defined somnogenic substances. It is suggested that nitric oxide (NO) may mediate the sleep-promoting effects of these cytokines. In this study, we use mice with targeted disruptions of either the neuronal NO synthase (nNOS) or the inducible NO synthase (iNOS) gene, commonly referred to as nNOS or iNOS knockouts (KOs), to investigate sleep changes after influenza viral challenge. We report that the magnitude of viral-induced non-rapid eye movement sleep responses in both nNOS KOs and iNOS KOs was less than that of their respective controls. In addition, the duration of rapid eye movement sleep in nNOS KO mice did not decrease compared with baseline values. All strains of mice had similar viral titers and cytokine gene expression profiles in the lungs. Virus was not isolated from the brains of any strain. However, gene expression in the brain stem differed between nNOS KOs and their controls: mRNA for the interferon-induced gene 2′,5′-oligoadenylate synthase 1a was elevated in nNOS KOs relative to their controls at 15 h, and IL-1β mRNA was elevated in nNOS KOs relative to their controls at 48 h. Our results suggest that NO synthesized by both nNOS and iNOS plays a role in virus-induced sleep changes and that nNOS may modulate cytokine expression in the brain.

Growth arrest of epithelial cells during measles virus infection is caused by upregulation of interferon regulatory factor 1

Natural infection with measles virus (MeV) is initiated when the virus reaches epithelial cells in the respiratory tract, oropharynx, or conjunctivae. Human epithelial cells infected with MeV frequently show growth suppression. In this study, we investigated the possible mechanisms for this suppression. The bronchiolar epithelial cell A549 showed growth arrest in G(0)/G(1) following MeV infection or treatment with gamma interferon (IFN-gamma). IFN regulatory factor-1 (IRF-1) was upregulated during MeV infection, although A549 did not produce IFN-gamma. Cells of the cervical squamous cell line SiHa persistently infected with various strains of MeV displayed slower growth than uninfected SiHa cells, although the growth rates varied depending on the MeV strain. Transfection of antisense-oriented IRF-1 cDNA released the MeV-infected SiHa cells from growth suppression. Although these infected cells did not produce IFN-gamma and suppressed IFN-alpha/beta-induced Jak1 phosphorylation, Jak1 was constitutively phosphorylated. The growth rates negatively correlated with levels of both IRF-1 expression and constitutively phosphorylated Jak1. These results indicate that MeV upregulates IRF-1 in a manner that is independent of IFN but dependent on the JAK/STAT pathway. This induction of IRF-1 appears to suppress cell growth, although the extent seems to vary among MeV strains.

Induction of RANTES by TWEAK/Fn14 Interaction in Human Keratinocytes

TNF-like weak inducer of apoptosis (TWEAK), a member of the tumor necrosis factor (TNF) family, is a multifunctional cytokine that regulate cellular proliferation, angiogenesis, inflammation, and apoptosis. In this study, we investigated the effect of TWEAK on human keratinocytes. Primary cultured normal human keratinocytes constitutively expressed a TWEAK receptor, fibroblast growth factor-inducible 14 (Fn14), and produced regulated on activation, normal T expressed and secreted (RANTES) upon TWEAK stimulation in a concentration-dependent manner. The TWEAK-induced RANTES production was abrogated by anti-Fn14 antibody, and synergistically augmented by simultaneous stimulation with transforming growth factor-beta. In addition, human keratinocytes differentiated in vitro with high Ca(2+)-containing medium showed enhanced production of RANTES upon TWEAK stimulation. Furthermore, TWEAK induced rapid phosphorylation of IkappaB-alpha in human keratinocytes. Collectively, TWEAK acts on human keratinocytes as an inducer of RANTES via Fn14. Because RANTES has been implicated in inflammation, TWEAK/Fn14 interaction in human keratinocytes may be involved in the pathophysiology of inflammatory skin disorders.

Expression of the CXCR3 ligand I-TAC by hepatocytes in chronic hepatitis C and its correlation with hepatic inflammation

The factors that regulate lymphocyte traffic in chronic hepatitis C (CHC) are not completely defined. Interferon (IFN)-inducible T cell alpha chemoattractant (I-TAC) is a relatively new member of the CXCR3 chemokine ligand family that selectively recruits activated T cells to sites of inflammation. To determine if I-TAC plays a role in CHC, we investigated I-TAC expression in hepatitis C virus (HCV)-infected liver biopsy material. I-TAC messenger RNA (mRNA) levels were significantly increased in HCV-infected liver compared with normal liver, which correlated with both portal and lobular inflammation. I-TAC expression was localized to hepatocytes throughout the liver lobule, with those in close proximity to active areas of inflammation expressing the highest concentration of I-TAC. In vitro, I-TAC mRNA and protein expression was inducible in Huh-7 cells following either IFN-alpha or -gamma stimulation and synergistically with tumor necrosis factor (TNF)-alpha. Furthermore, transfection of Huh-7 cells with either poly(I:C) or HCV RNA representing the HCV subgenomic replicon induced I-TAC mRNA expression. HCV replication was also found to modulate I-TAC expression, with stimulation of Huh-7 cells harboring either the HCV subgenomic or genomic replicon showing significantly increased synergistic effects compared with those previously seen in Huh-7 cells alone with IFN-gamma and TNF-alpha. In conclusion, these results suggest I-TAC, one of the most potent chemoattractants for activated T cells, is produced by hepatocytes in the HCV-infected liver and plays an important role in T cell recruitment and ultimately the pathogenesis of CHC.

A recombinant vaccinia virus encoding the interferon-inducible T-cell alpha chemoattractant is attenuated in vivo

Murine interferon-inducible T-cell alpha chemoattractant (I-TAC) is a potent non-ELR CXC chemokine that predominantly attracts activated T lymphocytes, binds to the receptor CXCR3 and is induced by interferon-gamma (IFN-gamma). We analysed I-TAC expression by reverse transcriptase-polymerase chain reaction during three different virus-infection models in mice, respiratory syncytial virus (RSV), influenza A and vaccinia virus western reserve (VV-WR). In the lungs from mice infected with RSV or influenza A viruses, peak expression of I-TAC coincided with peak viraemia. Surprisingly, there was no expression in the lungs of mice infected with vaccinia, unlike the elevated expression shown previously for other interferon-regulated chemokines, such as Crg2 and Mig. To further investigate the importance of this difference during vaccinia infection in mice, a recombinant virus encoding I-TAC (rVV I-TAC) was generated. Studies in C57BL/6 and Swiss nude mice showed that I-TAC expression caused increased mononuclear cell infiltration and significantly attenuated the VV. Infection of the footpads of naïve or already immune (with VV-WR) mice with either rVV I-TAC or VV-WR demonstrated that I-TAC expression reduced overall inflammation during infection and that this reduction was more pronounced in already immune mice. The data presented here show that I-TAC can have an important role during virus infections and that vaccinia has evolved ways to avoid inducing I-TAC expression.

Expression and regulation of novel human beta-defensins in gingival keratinocytes

This study evaluated the expression and regulation of beta-defensins DEFB-104 and the recently identified DEFB-105-14 in gingival keratinocytes. Keratinocytes from healthy subjects were exposed to cytokines, Escherichia coli lipopolysaccharide or Candida species. Total RNA was extracted and defensin expression analyzed by reverse transcription-polymerase chain reaction. Three patterns of expression were seen: no expression, constitutive expression and inducible expression. Constitutive mRNA expression was evident for DEFB-104, 107, 109, 111, and 112. DEFB-108 and 114 were induced by interleukin (IL)-1beta and Candida species. For DEFB-108 expression, synergism was observed when IL-1beta was combined with tumor necrosis factor-alpha or interferon-gamma. Downregulation of DEFB-109 occurred following treatment with Candida albicans. These findings suggest a role for multiple beta-defensins in response to oral infection. Further investigation is needed to better understand their function, both in terms of antimicrobial activities and contributions to innate and acquired immunity.

Donor-derived TNF-alpha regulates pulmonary chemokine expression and the development of idiopathic pneumonia syndrome after allogeneic bone marrow transplantation

Idiopathic pneumonia syndrome (IPS) is a significant cause of mortality after allogeneic bone marrow transplantation (allo-BMT), and tumor necrosis factor-alpha (TNF-alpha) is a significant effector molecule in this process. However, the relative contribution of donor-versus host-derived TNF-alpha to the development of IPS has not been elucidated. Using a lethally irradiated parent --> F1 mouse IPS model, we showed that 5 weeks after transplantation allo-BMT recipients developed significant lung injury compared with syngeneic controls, which was associated with increased bronchoalveolar lavage (BAL) fluid levels of TNF-alpha, elevated numbers of donor-derived TNF-alpha-secreting T cells, and increased pulmonary macrophage production of TNF-alpha to lipopolysaccharide (LPS) stimulation. Allo-BMT with TNF-alpha(-/-) donor cells resulted in significantly reduced IPS severity, whereas utilization of TNF-alpha-deficient mice as BMT recipients had no effect on IPS. We next determined that TNF-alpha secretion from both donor accessory cells (monocytes/macrophages) and T cells significantly contributed to the development of IPS. Importantly, the absence of donor T-cell-derived TNF-alpha resulted in a significant decrease in inflammatory chemokine production in the lung and near complete abrogation of IPS. Collectively, these data demonstrate that donor TNF-alpha is critical to the development of IPS and reveal a heretofore unknown mechanism for T-cell-derived TNF-alpha in the evolution of this process.

Discriminative motifs

This paper takes a new view of motif discovery, addressing a common problem in existing motif finders. A motif is treated as a feature of the input promoter regions that leads to a good classifier between these promoters and a set of background promoters. This perspective allows us to adapt existing methods of feature selection, a well-studied topic in machine learning, to motif discovery. We develop a general algorithmic framework that can be specialized to work with a wide variety of motif models, including consensus models with degenerate symbols or mismatches, and composite motifs. A key feature of our algorithm is that it measures overrepresentation while maintaining information about the distribution of motif instances in individual promoters. The assessment of a motif's discriminative power is normalized against chance behaviour by a probabilistic analysis. We apply our framework to two popular motif models and are able to detect several known binding sites in sets of co-regulated genes in yeast.

Synergistic induction of CXCL9 and CXCL11 by Toll-like receptor ligands and interferon-gamma in fibroblasts correlates with elevated levels of CXCR3 ligands in septic arthritis synovial fluids

The synovial cavity constitutes the ideal stage to study the interplay between microbial Toll-like receptor (TLR) ligands and cytokines. Infiltrated leukocytes and synovial fibroblasts produce cytokine- and chemokine-induced proteases for remodeling the extracellular matrix. The regulation of chemokine function for attraction and activation of leukocytes constitutes a key feature in host immunity and resolution of inflammation after infection. Enhanced levels of the CXC chemokine ligand (CXCL9)/monokine induced by interferon-gamma (IFN-gamma) and CXCL11/IFN-inducible T cell alpha chemoattractant, two chemoattractants for activated T cells and natural killer cells, and ligands for CXC chemokine receptor 3 (CXCR3) were detected in the synovial fluid of septic arthritis compared with osteo- and crystal arthritis patients. In vitro, IFN-gamma and TLR3 ligation by double-stranded RNA (dsRNA) induced the expression of CXCL9 and CXCL11 in leukocytes and skin-muscle fibroblasts, whereas ligation of TLR2, TLR4, TLR5, and TLR9 by peptidoglycan (PGN), lipopolysaccharide (LPS), flagellin, and unmethylated CpG oligonucleotides, respectively, did not. PGN and LPS, but not unmethylated CpG oligonucleotides, even inhibited IFN-gamma-induced CXCL9 and CXCL11 expression in leukocytes. In sharp contrast, in fibroblasts, the TLR ligands PGN, dsRNA, LPS, and flagellin synergized with IFN-gamma for the production of CXCL9 and CXCL11. Although TLR ligands stimulate leukocytes to produce CXCL8/interleukin-8 during the early innate defense, they contribute less to the production of CXCR3 ligands, whereas fibroblasts are important sources of CXCR3 ligands. These results illustrate the complex interaction between cytokines and TLR ligands in infection.

Roxithromycin downmodulates Th2 chemokine production by keratinocytes and chemokine receptor expression on Th2 cells: its dual inhibitory effects on the ligands and the receptors

Roxithromycin (RXM), an anti-bacterial macrolide, has various immunomodulatory activities. To investigate the ability of RXM to downregulate skin-infiltration of T-lymphocytes, we examined the effects of RXM on keratinocyte production of chemokines and T cell expression of chemokine receptors. Normal human and HaCaT keratinocytes were cultured with RXM and stimulants. RXM at 1 or 10 microM significantly suppressed the production/expression of Th2 chemokines MDC and TARC in these keratinocytes, but the production of IP-10 was not affected. The effect of RXM on T-cell expression of the corresponding chemokine receptors was also tested in Th2-rich peripheral blood lymphocytes. The IL-2-enhanced expression level of Th2 chemokine receptor CCR4 was decreased by RXM at 10 microM, whereas the expression of CXCR3 was unchanged. Thus, RXM downmodulates both the production and receptor expression of Th2 but not Th1 chemokines involved in cutaneous immunity, suggesting its beneficial therapeutic effects on Th2-mediated or allergic skin disorders.

Posttranscriptional Inhibition of Gene Expression byMycobacterium tuberculosisOffsets Transcriptional Synergism with IFN-γ and Posttranscriptional Up-Regulation by IFN-γ

Host defense against Mycobacterium tuberculosis requires the cytokine IFN-gamma and IFN regulatory factor 1 (IRF-1), a transcription factor that is induced to high levels by IFN-gamma. Therefore, we chose to study regulation of IRF-1 expression as a model for effects of M. tuberculosis on response to IFN-gamma. We found that IRF-1 mRNA abundance increased far more than transcription rate in human monocytic THP-1 cells stimulated by IFN-gamma, but less than transcription rate in cells infected by M. tuberculosis. IFN-gamma stimulation of infected cells caused a synergistic increase in IRF-1 transcription, yet IRF-1 mRNA abundance was similar in uninfected and infected cells stimulated by IFN-gamma, as was the IRF-1 protein level. Comparable infection by Mycobacterium bovis bacillus Calmette-Guérin failed to induce IRF-1 expression and had no effect on the response to IFN-gamma. We also examined the kinetics of transcription, the mRNA t(1/2), and the distribution of IRF-1 transcripts among total nuclear RNA, poly(A) nuclear RNA, and poly(A) cytoplasmic RNA pools in cells that were infected by M. tuberculosis and/or stimulated by IFN-gamma. Our data suggest that infection by M. tuberculosis inhibits RNA export from the nucleus. Moreover, the results indicate that regulated entry of nascent transcripts into the pool of total nuclear RNA affects IRF-1 expression and that this process is stimulated by IFN-gamma and inhibited by M. tuberculosis. The ability of infection by M. tuberculosis to limit the increase in IRF-1 mRNA expression that typically follows transcriptional synergism may contribute to the pathogenicity of M. tuberculosis.

Activation of the STAT pathway in acute lung injury

Acute lung injury (ALI) is a devastating clinical problem with a mortality as high as 60%. It is now appreciated that ALI represents a cytokine excess state that involves the microvasculature of multiple organs. The signal transducers and activators of transcription (STAT) family of transcription factors activate critical mediators of cytokine responses, but there is limited knowledge about their role in mediating ALI. In the present study, we demonstrate that the STAT transcription factors are activated rapidly in the lungs after intraperitoneal and intranasal LPS administration in mice. We also demonstrated that LPS activates both the STAT kinases, Src and JAK, in the lung with kinetics that are consistent with STAT activation. LPS treatment resulted in STAT3 activation throughout the resident lung cells, as well as in the recruited inflammatory cells. Whereas direct LPS treatment did not lead to STAT activation in cultured epithelial or endothelial cells, IL-6 activated STAT3 in both of these cell types. Furthermore, IL-6 was induced by LPS in serum and in the lung with kinetics consistent with STAT3 activation, suggesting that IL-6 may be one mechanism of STAT activation by LPS. In addition, STAT activation required reactive oxygen species, as the overexpression of catalase in mice prevented LPS-mediated STAT activation in the lung. STATs may be a common pathway for mediating ALI, regardless of the inciting factor, as STAT activation also occurred in both a gastric acid aspiration and acute pancreatitis model of ALI. Finally, STATs are activated in the lung long before signs of ALI are present, suggesting that the STAT transcription factors may play a role in initiating the inflammatory response seen in the lung.

Arsenic enhances the activation of Stat1 by interferon gamma leading to synergistic expression of IRF-1

Arsenic trioxide (As2O3) can induce clinical remission in patients with acute promyelocytic leukemia (APL), including those who have relapsed after treatment with all-trans-retinoic acid (RA). In vitro studies with the APL-derived NB4 cell line showed that As2O3 exerts a dose-dependent dual effect, which induces apoptosis at 1 microM, whereas at a lower concentration of 0.1 microM, a partial differentiation of APL is observed. In non-APL cells, interferon (IFN) alpha and 1 microM As2O3 act synergistically to induce apoptosis. In this report, we show that in NB4 cells and in two RA-resistant NB4-derived cell lines, NB4-R1 and NB4-R2, IFNalpha or IFNgamma combined with 0.1 microM As2O3 lead to an increased maturation effect. Moreover, IFNgamma alone is able to differentiate RA-sensitive and -resistant cells with a higher maturation effect on NB4-R2 cells. In contrast, all these cells underwent apoptosis in the presence of the cytokine and a higher concentration of As2O3. IFNgamma boosted As2O3-induced apoptosis in APL cells as tested by TUNEL, Annexin V staining and activation of caspase 3. As2O3 differently altered IFN-induced gene products; it downregulated PML/RARalpha and PML, did not alter PKR and Stat1, and upregulated interferon regulatory family (IRF)-1. Synergism by IFNgamma and arsenic on IRF-1 expression is mediated by a composite element in the IRF-1 promoter that includes an IFNgamma-activation site (GAS) overlapped by a nonconsensus site for nuclear factor kappa B (NFkappaB). Arsenic has no effect on NFkappaB, whereas it enhances the activation of Stat1 by IFNgamma in NB4 cells leading to an increase in IRF-1 expression.

Effects of mycophenolic acid on IL-6 expression of human renal proximal and distal tubular cells in vitro

BACKGROUND

Interleukin-6 (IL-6) is a multifunctional cytokine which regulates immune responses and host defence mechanisms. IL-6 has been found to be increased in certain inflammatory conditions of the kidney, in which tubular epithelial cells play a pivotal role. Human renal tubular cells express IL-6. Until now no data about the effect of the immunosuppressant drug mycophenolic acid (MPA) on IL-6 expression were available.

METHODS

Proximal and distal tubular epithelial cells (PTC/DTC) have been isolated immunomagnetically. Confluent monolayers were stimulated with interleukin-1beta (IL-1beta; 25 U/ml), IL-1beta+ MPA (0.25-50 micro M) or MPA alone for 48 h. Release of IL-6 protein into the supernatant was evaluated with an enzyme immunoassay, IL-6 mRNA expression was evaluated using the Quantikine mRNA kit.

RESULTS

After IL-1beta stimulation, a highly significant 2.6- (PTC) and 3.8-fold (DTC) upregulation of IL-6 expression was detectable. IL-6 mRNA was upregulated by IL-1beta [1.57- (PTC) and 2.03-fold (DTC)]. MPA inhibited this cytokine-induced IL-6 expression in a dose-dependent manner. Incubation with the lowest MPA concentration had no effect on the stimulated upregulation, whereas all higher doses significantly decreased IL-6 expression. Dexamethasone significantly inhibited the cytokine-induced IL-6 protein release in PTC, but not in DTC.

CONCLUSIONS

In this study we demonstrated for the first time an inhibitory effect of MPA on the stimulated IL-6 expression of renal tubular epithelial cells. In contrast to older data, which showed a synergistic upregulation of the expression of a CC-chemokine by a combination of cytokines and MPA, in the present study we could demonstrate an immunosuppressive effect of MPA on the expression of an important cytokine.

Replicated studentized-deviate detection applied to the identification of differentially expressed genes in TNF-α-stimulated cells

Among the applications of DNA microarray expression data, identification of differentially expressed genes is widely used to search for genes involved in specific biological processes. Previous studies have shown that replication is necessary to reliably identify differentially expressed genes. In practice, however, further guidelines are required to provide references for experiment design, that is, to fulfill the needs for determining the replication number on a desired confidence level or the detection sensitivity of the microarrays. Here, we performed simulations to build a simple statistical table of general guidelines adapted specifically for identifying differentially expressed genes using replications of a microarray experiment, and we present an accompanying nonparametric method, replicated studentized-deviate detection (RSD). The analysis results of the TNF-alpha-stimulated cells showed that RSD is simple and robust, and that the resulting statistical table is plausible.

Constitutive nuclear factor kappaB activity is required to elicit interferon-gamma-induced expression of chemokine CXC ligand 9 (CXCL9) and CXCL10 in human tumour cell lines

CXC ligand 10 (CXCL10) and CXCL9 are chemoattractants for activated T cells and possess angiostatic activity. Both CXCL9 and CXCL10 have been considered as important components for the anti-tumour activities of interferon-gamma (IFNgamma) and interleukin-12 in animal models. In this article we show that the CXCL9 and CXCL10 genes in some types of human tumour cell lines are not inducible by IFNgamma and we describe experiments designed to explore the molecular mechanisms involved in this impaired induction. The human oral squamous carcinoma line Ca9-22 and the glioma line A172 failed to express CXCL9 and CXCL10 mRNAs in response to IFNgamma, whereas other carcinoma lines including HSC-2 did express these mRNAs. Production of these chemokine proteins was also impaired in Ca9-22 cells. The impaired expression was not due to any deficiency in the IFNgamma/signal transducer and activator of transcription 1 (STAT1)-dependent signalling pathway. Instead, analysis of nuclear factor kappaB (NF-kappaB) activity revealed that the constitutive low level of NF-kappaB activity, which is seen in cells that express these chemokines, was absent in Ca9-22 and A172 cells. Activation of NF-kappaB in Ca9-22 cells restored the expression of IFNgamma-stimulated CXCL9 and CXCL10 mRNAs. In contrast, inhibition of the constitutive NF-kappaB in HSC-2 cells by adenovirus-mediated gene transfer of a dominant-negative IkappaBalpha suppressed the IFNgamma-induced expression of the CXCL9 and CXCL10 mRNAs. These results indicate that constitutive NF-kappaB activity, which is often associated with tumour development, is required for the induced expression of CXCL9 and CXCL10 genes in human tumour cell lines in response to IFNgamma.

Mechanisms of inflammation-mediated airway smooth muscle plasticity and airways remodeling in asthma

Recent evidence points to progressive structural change in the airway wall, driven by chronic local inflammation, as a fundamental component for development of irreversible airway hyperresponsiveness. Acute and chronic inflammation is orchestrated by cytokines from recruited inflammatory cells, airway myofibroblasts and myocytes. Airway myocytes exhibit functional plasticity in their capacity for contraction, proliferation, and synthesis of matrix protein and cytokines. This confers a principal role in driving different components of the airway remodeling process, and mediating constrictor hyperresponsiveness. Functional plasticity of airway smooth muscle (ASM) is regulated by an array of environmental cues, including cytokines, which mediate their effects through receptors and a number of intracellular signaling pathways. Despite numerous studies of the cellular effects of cytokines on cultured airway myocytes, few have identified how intracellular signaling pathways modulate or induce these cellular responses. This review summarizes current understanding of these concepts and presents a model for the effects of inflammatory mediators on functional plasticity of ASM in asthma.

Dexamethasone enhances osteoclast formation synergistically with transforming growth factor-beta by stimulating the priming of osteoclast progenitors for differentiation into osteoclasts

Long-term administration of glucocorticoids (GCs) causes osteoporosis with a rapid and severe bone loss and with a slow and prolonged bone disruption. Although the involvement of GCs in osteoblastic proliferation and differentiation has been studied extensively, their direct action on osteoclasts is still controversial and not conclusive. In this study, we investigated the direct participation of GCs in osteoclastogenesis. Dexamethasone (Dex) at <10(-8) M stimulated, but at >10(-7) M depressed, receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast formation synergistically with transforming growth factor-beta. The stimulatory action of Dex was restricted to the early phase of osteoclast differentiation and enhanced the priming of osteoclast progenitors (bone marrow-derived monocytes/macrophages) toward differentiation into cells of the osteoclast lineage. The osteoclast differentiation depending on RANKL requires the activation of NF-kappaB and AP-1, and the DNA binding of these transcription factors to their respective consensus cis-elements was enhanced by Dex, consistent with the stimulation of osteoclastogenesis. However, Dex did not affect the RANKL-induced signaling pathways such as the activation of IkappaB kinase followed by NF-kappaB nuclear translocation or the activation of JNK. On the other hand, Dex significantly decreased the endogenous production of interferon-beta, and this cytokine depressed the RANKL-elicited DNA binding of NF-kappaB and AP-1, as well as osteoclast formation. Thus, the down-regulation of inhibitory cytokines such as interferon-beta by Dex may allow the osteoclast progenitors to be freed from the suppression of osteoclastogenesis, resulting in an increased number of osteoclasts, as is observed in the early phase of GC-induced osteoporosis.

Role for nuclear factor-kappaB and signal transducer and activator of transcription 1/interferon regulatory factor-1 in cytokine-induced endothelin-1 release in human vascular smooth muscle cells

Endothelin-1 (ET-1) is a potent vasoconstrictor and growth-promoting mediator that is involved in the maintenance of vascular tone within the healthy circulation. However, a pathogenic role has been implicated by its overproduction in a number of cardiovascular diseases, which include pulmonary hypertension, congestive heart failure, atherosclerosis, and coronary vasospasm. ET-1 mRNA expression and peptide production in human vascular smooth muscle cells (HVSMCs) are markedly increased by exposure to tumor necrosis factor-alpha and interferon-gamma. The intracellular signaling mechanism involved in this pathway is not known. Because the transcription factors nuclear factor-kappaB (NF-kappaB), signal transducer and activator of transcription 1 (STAT1), and interferon regulatory factor-1 (IRF-1) often mediate the effects of cytokines in target cells the aim of this study was to determine whether the production of ET-1 after exposure of HVSMCs to cytokines depends upon synergism between NF-kappaB and STAT1/IRF-1. Immunoblotting showed that cytokine-stimulation of ET-1 release in VSMCs involves nuclear translocation of NF-kappaB and STAT1. Cytokines also induced an increase in IRF-1 protein expression. Antisense oligonucleotides to NF-kappaB, STAT1, and IRF-1 significantly inhibited cytokine induced ET-1 release. In conclusion, NF-kappaB, STAT1, and IRF-1 activation are involved in the stimulation by cytokines of ET-1 release from HVSMCs. However, nuclear run-on assays would provide definitive proof that ET-1 is regulated transcriptionally by cytokines. Because up-regulated production of ET-1 within VSMCs may underlie the causative role of ET-1 in a number of disease states, this finding indicates that NF-kappaB, STAT1, and IRF-1 within HVSMCs could be central to a number of vascular pathologies and that inhibition of this pathway could be of therapeutic benefit.

Mullerian inhibiting substance promotes interferon gamma-induced gene expression and apoptosis in breast cancer cells

This report demonstrates that in addition to interferons and cytokines, members of the TGF beta superfamily such as Mullerian inhibiting substance (MIS) and activin A also regulate IRF-1 expression. MIS induced IRF-1 expression in the mammary glands of mice in vivo and in breast cancer cells in vitro and stimulation of IRF-1 by MIS was dependent on activation of the NF kappa B pathway. In the rat mammary gland, IRF-1 expression gradually decreased during pregnancy and lactation but increased at involution. In breast cancer, the IRF-1 protein was absent in 13% of tumors tested compared with matched normal glands. Consistent with its growth suppressive activity, expression of IRF-1 in breast cancer cells induced apoptosis. Treatment of breast cancer cells with MIS and interferon gamma (IFN-gamma) co-stimulated IRF-1 and CEACAM1 expression and synergistic induction of CEACAM1 by a combination of MIS and IFN-gamma was impaired by antisense IRF-1 expression. Furthermore, a combination of IFN-gamma and MIS inhibited the growth of breast cancer cells to a greater extent than either one alone. Both reagents alone significantly decreased the fraction of cells in the S-phase of the cell cycle, an effect not enhanced when they were used in combination. However, MIS promoted IFN-gamma-induced apoptosis demonstrating a functional interaction between these two classes of signaling molecules in regulation of breast cancer cell growth.

Interferon-gamma: an overview of signals, mechanisms and functions

Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.

Lactobacilli and streptococci induce inflammatory chemokine production in human macrophages that stimulates Th1 cell chemotaxis

Macrophages have a central role in innate-immune responses to bacteria. In the present work, we show that infection of human macrophages with Gram-positive pathogenic Streptococcus pyogenes or nonpathogenic Lactobacillus rhamnosus GG enhances mRNA expression of inflammatory chemokine ligands CCL2/monocyte chemoattractant protein-1 (MCP-1), CCL3/macrophage-inflammatory protein-1alpha (MIP-1alpha), CCL5/regulated on activation, normal T expressed and secreted, CCL7/MCP-3, CCL19/MIP-3beta, and CCL20/MIP-3alpha and CXC chemokine ligands CXCL8/interleukin (IL)-8, CXCL9/monokine induced by interferon-gamma (IFN-gamma), and CXCL10/IFN-inducible protein 10. Bacteria-induced CCL2, CCL7, CXCL9, and CXCL10 mRNA expression was partially dependent on ongoing protein synthesis. The expression of these chemokines and of CCL19 was dependent on bacteria-induced IFN-alpha/beta production. CCL19 and CCL20 mRNA expression was up-regulated by IL-1beta or tumor necrosis factor alpha (TNF-alpha), and in addition, IFN-alpha together with TNF-alpha further enhanced CCL19 gene expression. Synergy between IFN-alpha and TNF-alpha was also seen for CXCL9 and CXCL10 mRNA expression. Bacteria-stimulated macrophage supernatants induced the migration of T helper cell type 1 (Th1) cells, suggesting that in human macrophages, these bacteria can stimulate efficient inflammatory chemokine gene expression including those that recruit Th1 cells to the site of inflammation. Furthermore, L. rhamnosus-induced Th1 chemokine production could in part explain the proposed antiallergenic properties of this bacterium.

Interplay between IFN-gamma and IL-6 signaling governs neutrophil trafficking and apoptosis during acute inflammation

Regulated recruitment and clearance of neutrophils (PMN) is the hallmark of competent host defense and resolution of inflammation. We now report that IFN-gamma controls PMN infiltration and modulates IL-6 signaling through its soluble receptor (sIL-6R) to promote their apoptosis and clearance. Induction of peritoneal inflammation in IFN-gamma-deficient (IFN-gamma-/-) mice emphasized that the initial rate of PMN recruitment was impaired. This defect in PMN recruitment was also associated with the suppressed intraperitoneal expression of IL-1beta and IL-6. Reconstitution of IFN-gamma signaling restored the rate of PMN infiltration and IL-6 levels and was accompanied by normalization of PMN-activating CXC chemokine expression. To test whether local IL-6 signaling modulated PMN recruitment, inflammation was induced in IFN-gamma-/- and IL-6-/- mice and cytokine signaling adapted by intraperitoneal sIL-6R-IL-6 fusion protein (HYPER-IL-6) or IFN-gamma. Although HYPER-IL-6 attenuated PMN influx in IFN-gamma-/- mice, IFN-gamma had no effect on PMN infiltration in IL-6-/- mice. Examination of the leukocyte infiltrate from IFN-gamma-/-, IL-6-/-, and wild-type mice showed that apoptosis was aberrant in the absence of IFN-gamma and IL-6 as a result of impaired sIL-6R signaling. These data emphasize a pivotal role for IFN-gamma in regulating innate immunity through control of both the recruitment and clearance phases of PMN trafficking.

A giant GTPase, very large inducible GTPase-1, is inducible by IFNs

The complex, partially overlapping, cellular responses to IFN type I (IFN-alpha and -beta) and IFN type II (IFN-gamma) involve several hundred genes that can be largely classified in terms of specific cellular programs functional in innate and adaptive immunity. Among these programs are previously unconsidered mechanisms of cell-autonomous resistance against various pathogens mediated by dedicated, largely novel families of GTPases. We report here the identification and characterization of a new GTPase family that contributes to the cellular response to both type I and type II IFNs. We name this family the very large inducible GTPases (VLIGs). The prototype VLIG, VLIG-1, is a strongly IFN-inducible, soluble, cytosolic and nuclear protein of 280 kDa. The open reading frame of VLIG-1 is encoded on a single very large exon, and outside the canonical GTP-binding motifs, sequence and structural prediction suggest a unique family without significant relationship to other known protein families. Within the GTPase superfamily the VLIG family is more closely related to IFN-inducible GTPases mediating cell-autonomous resistance than to other GTPase families. In addition, we provide evidence that VLIG-1 is polymorphic in mice of different genetic backgrounds and is a member of a small gene family on mouse chromosome 7 with a conserved homologue located on human chromosome 11.

Inhibition of IFN-gamma-mediated inducible nitric oxide synthase induction by the peroxisome proliferator-activated receptor gamma agonist, 15-deoxy-delta 12,14-prostaglandin J2, involves inhibition of the upstream Janus kinase/STAT1 signaling pathway

Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands have been reported to exert anti-inflammatory activities in macrophages by competition for transcriptional coactivators with some transcriptional factors, including NF-kappaB. In the present study the influence of PPARgamma activators on IFN-gamma-elicited macrophage stimulation and signaling cascades was investigated. The results show that IFN-gamma-induced inducible NO synthase (iNOS) gene transcription, iNOS protein induction, and NO production are more sensitive to inhibition by 15-deoxy-Delta(12,14)-prostaglandin J(2) (15dPGJ(2)) than by the other two PPARgamma agonists, GW1929 and ciglitazone. Delayed addition of 15dPGJ(2) for 2 h resulted in reduced inhibition, suggesting action by 15dPGJ(2) on the upstream signaling cascades. Immunoblotting, DNA binding, and reporter gene assays consistently revealed the inhibitory ability of 15dPGJ(2), but not GW1929 or ciglitazone, on IFN-gamma-elicited signaling cascades, including tyrosine phosphorylation of Janus tyrosine protein kinase 2 and STAT1, DNA binding, and IFN regulatory factor-1 trans-activation of STAT1. These effects of 15dPGJ(2) were not abrogated by the PPARgamma antagonist, bisphenol A diglycidyl ether, indicating the PPARgamma-independent actions. 15dPGJ(2) also attenuated IL-6-induced tyrosine phosphorylation of STAT1 and STAT3 in Hep3B hepatoma cells. Consistent with the inhibitory effect of reactive oxygen species on STAT1 signaling, STAT1 inhibition by 15dPGJ(2) was abrogated by N-acetylcysteine, glutathione, superoxide dismutase, and catalase. Furthermore, 15dPGJ(2)-induced inhibition of STAT1 phosphorylation and NO production still occurred in the presence of peroxovanadate, ruling out the action mechanism of 15dPGJ(2) on tyrosine phosphatase. Taken together, for the first time in this study we demonstrate that 15dPGJ(2) can inhibit cytokine-stimulated Janus kinase 2-STAT signaling through a PPARgamma-independent, reactive oxygen species-dependent mechanism. These data provide a novel molecular mechanism of iNOS inhibition by 15dPGJ(2) and confirm its physiological role in anti-inflammation.

Glucocorticoids: new mechanisms and future agents

Glucocorticoids are widely used to treat inflammatory and immune diseases. The most common use of glucocorticoids today is in the treatment of asthma. Inhaled glucocorticoids are first-line treatment in adults and children with persistent asthma, the most common chronic airway inflammatory disease. Our knowledge of how glucocorticoids suppress inflammation is based on recent developments in understanding the fundamental mechanisms of gene transcription, namely recruitment of histone-modifying co-factors. The determination of the crystal structure of the ligand-binding domain of the human glucocorticoid receptor (GR) has advanced our understanding of how ligands interact with GR and provide a glimpse of a future of rational drug design based on "space-filling" structures with dissociated properties. This might have important clinical implications, leading to a better understanding of the inflammatory mechanisms of many diseases and might signal the development of new anti-inflammatory treatments in the future.

IRAK-dependent phosphorylation of Stat1 on serine 727 in response to interleukin-1 and effects on gene expression

Interleukin-1 (IL-1) induces the phosphorylation of Stat1 on serine 727 but not on tyrosine 701. Analyses of mutant I1A cells, which lack the IL-1 receptor-associated kinase (IRAK), and of I1A cells reconstituted with deletion mutants of IRAK show that the IL-1-mediated phosphorylation of Stat1 on serine requires the IRAK protein but not its kinase activity and does not involve phosphatidylinositol-3'-kinase (PI3K) or the mitogen-activated protein (MAP) kinases p38 or ERK. IRAK and Stat1 interact in vivo, and this interaction is increased in response to IL-1, suggesting that IRAK may serve to recruit the as yet unknown IL-1-induced Stat1 serine kinase. Chemical inhibitors or dominant-negative forms of signaling components required to activate NF-kappa B, ATF, or AP-1 in response to IL-1 do not affect the phosphorylation of Stat1 on serine. IL-1 and tumor necrosis factor (TNF) enhance the serine phosphorylation of Stat1 that occurs in response to interferon-gamma (IFN-gamma) and potentiate IFN-gamma-mediated, Stat1-driven gene expression, thus contributing to the synergistic activities of these proinflammatory cytokines.

Overexpressed nuclear factor-kappaB can participate in endogenous C-reactive protein induction, and enhances the effects of C/EBPbeta and signal transducer and activator of transcription-3

C-reactive protein (CRP), the prototypical human acute phase protein, is produced primarily by hepatocytes. Its expression is modestly induced by interleukin (IL)-6 in Hep3B cells while IL-1, which alone has no effect, synergistically enhances the effects of IL-6. In previous studies of the proximal CRP promoter, we found that signal transducer and activator of transcription-3 (STAT3) and C/EBPbeta -mediated IL-6-induced transcription and that Rel p50 acted synergistically with C/EBPbeta, in the absence of p65, to enhance CRP transcription. Neither a requirement nor a binding site for the classic nuclear factor (NF)-kappaB heterodimer p50/p65 were found. The current studies were undertaken to determine whether similar novel transcription factor interactions might regulate the endogenous CRP gene. Transiently overexpressed p50 or p65 induced CRP mRNA accumulation in Hep3B cells. The heterodimer p50/p65 was markedly more effective than p50 or p65 homodimers. Co-overexpression of p50 or p65 with C/EBPbeta or STAT3 synergistically enhanced CRP expression. Maximal expression was observed with overexpression of all four transcription factors; comparable effects were observed with IL-1beta treatment of cells overexpressing STAT3 + C/EBPbeta. Data from the Human Genome Project revealed 13 potential kappaB sites in the first 4000 bases of the CRP promoter, only one of which, centred at -2652, bound nuclear p50/p65 heterodimer activated by IL-1beta. Our findings indicate that classical NF-kappaB activation can participate in endogenous CRP induction, and that activated NF-kappaB may synergistically enhance the effects of C/EBPbeta and STAT3. They raise the possibility, not as yet established, that NF-kappaB activation may be responsible for the synergistic effect of IL-1beta on IL-6-induced CRP expression.

Proinflammatory cytokines induce NF-kappaB-dependent/NO-independent chemokine gene expression in MIN6 beta cells

BACKGROUND

Interactions between chemokines IP-10, MCP-1, and RANTES and their receptors may mediate graft rejection following islet transplantation. The mechanisms regulating chemokine gene expression in pancreatic islet cells have not been well characterized. We examined the cytokine-induced gene expression profiles for several chemokines in a transformed pancreatic beta-cell line (MIN6) cotreated with an inhibitor of nitric oxide synthase and in a mutated clone of MIN6 made to overexpress a dominant negative inhibitor of NF-kappaB (IkappaBalphaM).

METHODS

MIN6 and MIN6-IkappaBalphaM (Bm) cells were cultured in mixtures of IL-1beta and TNF-alpha or IL-1beta, TNF-alpha, and IFN-gamma plus/minus the iNOS inhibitor L-NMMA. RT-PCR and RNase Protection Assay were used to measure mRNA expression for the following chemokines: IP-10, MIP-1alpha, MIP-1beta, MCP-1, and RANTES. Enzyme linked immunosorbant assay was used to measure IP-10 and MCP-1 protein release.

RESULTS

Cytokine-treated MIN6 and Bm demonstrated increased expression of genes for IP-10 and MCP-1. Expression in MIN6 was first detected at 2 h of incubation and peaked at 6 h. MIN6 demonstrated a more marked increase in chemokine gene expression for both IP-10 and MCP-1 and a more marked increase in IP-10 protein release than did Bm. There was no detectable gene expression for MIP-1alpha, MIP-1beta, or RANTES from MIN6 or Bm. L-NMMA completely blocked NO production from MIN6 and Bm but had no effect on chemokine gene expression in either MIN6 or Bm.

CONCLUSIONS

These results suggest that beta cells produce a complement of rejection-relevant chemokines in response to a proinflammatory stimulus and that pathways governing cytokine-induced chemokine gene expression in MIN6 are dependent on NF-kappaB but independent of NO.

17beta-estradiol inhibits the production of interferon-induced protein of 10 kDa by human keratinocytes

The natural course of psoriasis is often modulated during pregnancy, indicating the regulatory effect of estrogen or progesterone on psoriasis. Interferon-induced protein of 10 kDa chemoattracts T helper 1 cells, and interferon-induced protein of 10 kDa production by keratinocytes is enhanced in psoriatic skin lesions. We examined in vitro effects of sex hormones on the interferon-induced protein of 10 kDa production by human keratinocytes. 17beta-estradiol inhibited interferon-gamma-induced interferon-induced protein of 10 kDa secretion, mRNA expression, and promoter activity. Interferon-stimulated response element on the promoter was responsible for the inhibition by 17beta-estradiol. Interferon-gamma-induced protein of 10 kDa production was also inhibited by anti-estrogens, ICI 182 780 and tamoxifen, and membrane-impermeable bovine serum albumin-conjugated 17beta-estradiol, suggesting the effects via membrane estrogen receptor, whereas 17alpha-estradiol, progesterone, and dihydrotestosterone had no effects. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to interferon-stimulated response element. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced tyrosine phosphorylation of signal transducer and activator of transcription 1alpha, and Janus tyrosine kinase 1 and 2. 17beta-estradiol-mediated suppression on the interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis was counteracted by adenylate cyclase inhibitor SQ22536. 17beta-estradiol, bovine serum albumin-conjugated 17beta-estradiol, ICI 182 780, and tamoxifen increased intracellular 3',5'-adenosine cyclic monophosphate level by activating adenylate cyclase in keratinocytes. Fluorescein isothiocyanate-labeled bovine serum albumin-conjugated 17beta-estradiol bound to the surface of keratinocytes, and mRNA for estrogen receptor beta but not for estrogen receptor alpha was detected in keratinocytes. These results suggest that 17beta-estradiol may interact with the membrane receptor on keratinocytes and generate 3',5'-adenosine cyclic monophosphate by activating adenylate cyclase, which may lead to the inhibition of interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis.

Synergistic stimulation of MUC1 expression in normal breast epithelia and breast cancer cells by interferon-gamma and tumor necrosis factor-alpha

The MUC1 gene encodes a transmembrane mucin glycoprotein that is overexpressed in human breast cancers. Persistent stimulation by proinflammatory cytokines may contribute to increased MUC1 transcription by tumor cells. We demonstrate that MUC1 expression in T47D breast cancer cells and normal human mammary epithelial cells (HMEC) is enhanced by tumor necrosis factor-alpha (TNF-alpha) in the presence of interferon-gamma (IFN-gamma). MUC1 responsiveness to these cytokines was modest in T47D cells and robustly induced in HMEC. Transient transfection of T47D cells with mutant MUC1 promoter constructs revealed that a kappaB site at -589/-580 and the STAT-binding element at -503/-495 and were required for cooperative stimulation by TNFalpha and IFN-gamma. Binding of NFkappaB p65 to the MUC1 kappaB site was induced by TNF-alpha treatment, as demonstrated by electrophoretic mobility shift assay. Specific mutation of the kappaB site prevented binding of NFkappaB p65 and blocked TNF-alpha stimulation of MUC1 promoter activity. Collectively, these studies demonstrate synergistic stimulation of MUC1 expression by TNF-alpha and IFN-gamma that is mediated by independent actions of NFkappaB p65 and STAT1alpha upon kappaB and STAT sites, respectively, in the MUC1 promoter. Strong induction of MUC1 expression by these proinflammatory cytokines is clearly evident in normal mammary epithelium. In contrast, breast tumor cells appear to override normal regulatory responses via as yet undefined cis-elements.

IFN-alpha beta released by Mycobacterium tuberculosis-infected human dendritic cells induces the expression of CXCL10: selective recruitment of NK and activated T cells

We recently reported that dendritic cells (DC) infected with Mycobacterium tuberculosis (Mtb) produce Th1/IFN-gamma-inducing cytokines, IFN-alpha beta and IL-12. In the present article, we show that maturing Mtb-infected DC express high levels of CCR7 and they become responsive to its ligand CCL21. Conversely, CCR5 expression was rapidly lost from the cell surface following Mtb infection. High levels of CCL3 and CCL4 were produced within 8 h after infection, which is likely to account for the observed CCR5 down-modulation on Mtb-infected DC. In addition, Mtb infection stimulated the secretion of CXCL9 and CXCL10. Interestingly, the synthesis of CXCL10 was mainly dependent on the Mtb-induced production of IFN-alpha beta. Indeed, IFN-alpha beta neutralization down-regulated CXCL10 expression, whereas the expression of CXCL9 appeared to be unaffected. The chemotactic activity of the Mtb-infected DC supernatants was evaluated by migration assays using activated NK, CD4(+), and CD8(+) cells that expressed both CCR5 and CXCR3. Mtb-induced expression of CCL3, CCL4, CXCL9, and CXCL10 was involved in the stimulation of NK and T cell migration. In accordance with the data on the IFN-alpha beta-induced expression of CXCL10, neutralization of IFN-alpha beta significantly reduced the chemotactic activity of the supernatant from Mtb-infected DC. This indicates that IFN-alpha beta may modulate the immune response through the expression of CXCL10, which along with CXCL9, CCL3, and CCL4 participates in the recruitment and selective homing of activated/effector cells, which are known to accumulate at the site of Mtb infection and take part in the formation of the granulomas.

The transcriptional coactivator CREB-binding protein cooperates with STAT1 and NF-kappa B for synergistic transcriptional activation of the CXC ligand 9/monokine induced by interferon-gamma gene

Signal transducers and activators of transcription 1 (STAT1) and NF-kappaB cooperatively regulate the expression of many inflammatory genes. In the present study, we demonstrate that the transcriptional coactivator CREB-binding protein (CBP) mediated the STAT1/NF-kappaB synergy for transcription of the gene for CXC ligand 9 (CXCL9), an interferon-gamma (IFN-gamma)-inducible chemokine. Reporter gene analysis showed that expression of CBP potentiated IFN-gamma and tumor necrosis factor (TNFalpha)-induced promoter activity and that the CBP-mediated synergy depended upon STAT1- and NF-kappaB-binding sites in the promoter. Experiments with CBP mutants indicated that the N-terminal and C-terminal regions were necessary for the transcriptional synergy, although the histone acetyltransferase activity of CBP was dispensable. A co-immunoprecipitation assay demonstrated that STAT1 and NF-kappaB RelA (p65) simultaneously associated with CBP in vivo. Furthermore, chromatin immunoprecipitation revealed that, although costimulation with IFN-gamma and TNFalpha did not cooperatively enhance the levels of acetylated histones, it did result in increased recruitment of STAT1, CBP, and RNA polymerase II at the promoter region of the CXCL 9 gene. Together, these results demonstrate that the STAT1/NF-kappaB-dependent transcriptional synergy could result from the enhanced recruitment of RNA polymerase II complex to the promoter via simultaneous interaction of CBP with STAT1 and NF-kappaB.

Substance P enhances the production of interferon-induced protein of 10 kDa by human keratinocytes in synergy with interferon-gamma

A neuropeptide substance P is related to skin inflammation. Interferon-induced protein of 10 kDa (IP-10) chemoattracts T helper 1 cells, and interferon-induced protein of 10 kDa production by keratinocytes is enhanced in inflammatory skin diseases such as psoriasis. We examined the in vitro effects of substance P on interferon-induced protein of 10 kDa production by human keratinocytes. Though substance P alone did not induce interferon-induced protein of 10 kDa production, it enhanced interferon-induced protein of 10 kDa secretion, mRNA expression, and promoter activity induced by suboptimal concentrations of interferon-gamma. Interferon-stimulated response element and two nuclear factor-kappaB sites on interferon-induced protein of 10 kDa promoter were responsible for the enhancement by substance P. Substance P alone enhanced transcriptional activity and transcription factor binding through the two nuclear factor-kappaB sites, whereas it did not alter interferon-gamma-induced transcriptional activity and transcription factor binding through interferon-stimulated response element. The effects of substance P on interferon-induced protein of 10 kDa production and nuclear factor-kappaB activation were inhibited by neurokinin-1 receptor antagonist, phospholipase C inhibitor, intracellular Ca2+ chelator, and anti-oxidant. These results suggest that substance P may induce nuclear factor-kappaB activation and interferon-induced protein of 10 kDa production in synergy with interferon-gamma via neurokinin-1 receptor on keratinocytes. These effects of substance P may be mediated via phospholipase C activation, intra-cellular Ca2+ signal, and reactive oxygen intermediates.

Histamine inhibits the production of interferon-induced protein of 10 kDa in human squamous cell carcinoma and melanoma

Interferon-induced protein of (IP-10) inhibits tumor progression. Tumor cells can produce interferon-induced protein of IP-10 in response to interferon-g. Histamine in the vicinity of tumor cells may sustain the tumor progression. We examined the in vitro effects of histamine on interferon-induced protein of IP-10 production in human squamous cell carcinoma and melanoma. Histamine suppressed interferon-g-mediated interferon-induced protein of IP-10 secretion and mRNA expression in SV40-transformed keratinocytes, SCC15, SCC4, and melanoma WM115, WM266-4, and C32. Histamine suppressed interferon-g-induced interferon-mediated protein of IP-10 promoter activation in these cells, and the interferon-stimulated response element on the promoter was responsible for the suppression. Histamine suppressed interferon-g-mediated transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element. Histamine suppressed interferon-g-induced tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine-mediated suppression on the interferon-g-induced interferon-mediated protein of IP-10 synthesis was counteracted by the H2 receptor antagonist cimetidine, adenylate cyclase inhibitor SQ22536, and protein kinase A inhibitor H-89, but were not affected by H1 receptor antagonist mepyramine. Cimetidine, SQ22536, and H-89 also counteracted histamine-mediated suppression on the interferon-g-induced transcription through the interferon-stimulated response element, signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element, and tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine increased intracellular 3',5'-adenosine cyclic monophosphate level and protein kinase A activity in squamous cell carcinoma and melanoma, and the effects of histamine were blocked by cimetidine. These results suggest that histamine may interact with H2 receptor on squamous cell carcinoma and melanoma and generate 3',5'-adenosine cyclic monophosphate, which may activate protein kinase A. The cyclic 3',5'-adenosine monophosphate/protein kinase A signaling pathway induced by histamine may inhibit interferon-g-induced signal transducer and activator of transcription 1alpha activation and suppress interferon-induced protein of IP-10 synthesis.

Cyclooxygenase-2 inhibitor enhances whereas prostaglandin E2 inhibits the production of interferon-induced protein of 10 kDa in epidermoid carcinoma A431

Interferon-induced protein of 10 kDa (IP-10) induces antitumor immunity. Cyclooxygenase-2 and its metabolite prostaglandin E2 (PGE2) are overexpressed in tumor cells, which may suppress antitumor immunity. We examined the in vitro effects of cyclooxygenase-2 inhibitor NS398 on IP-10 production in human epidermoid carcinoma A431. NS398 enhanced interferon-gamma-induced IP-10 secretion, mRNA expression, and promoter activation in A431, and exogenous PGE2 antagonized the enhancement. Interferon-stimulated response element (ISRE) on IP-10 promoter was responsible for the transcriptional regulation by NS398 and PGE2. NS398 enhanced interferon-gamma-induced transcription through ISRE and binding of signal transducer and activator of transcription 1alpha (STAT1alpha to ISRE in A431, and PGE2 antagonized the enhancement. NS398 enhanced interferon-gamma-induced tyrosine phosphorylation of STAT1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2, and PGE2 antagonized the enhancement. PGE2-mediated suppression of IP-10 synthesis was counteracted by adenylate cyclase inhibitor SQ22536 and protein kinase A inhibitor H-89, and PGE2 receptor EP4 antagonist AH23848B. AH23848B, SQ22536, and H-89 counteracted the PGE2-mediated suppression of ISRE-dependent transcription, STAT1alpha binding to ISRE, and tyrosine phosphorylation of STAT1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. PGE2 increased intracellular cAMP level and protein kinase A activity in A431 pretreated with NS398, and AH23848B blocked the effects of PGE2. These results suggest that A431-derived PGE2 may generate cAMP signal via EP4 in A431, which may activate protein kinase A, and may resultantly inhibit interferon-gamma-induced STAT1alpha activation and IP-10 synthesis. The results also suggest that NS398 may restore IP-10 synthesis by preventing PGE2 production in A431 and thus may be therapeutically useful for skin cancer.

Signal transducers and activators of transcription 3 (STAT3) inhibits transcription of the inducible nitric oxide synthase gene by interacting with nuclear factor kappaB

Prolific generation of NO by inducible nitric oxide synthase (iNOS) can cause unintended injury to host cells during glomerulonephritis and other inflammatory diseases. While much is known about the mechanisms of iNOS induction, few transcriptional repressors have been found. We explored the role of signal transducers and activators of transcription 3 (STAT3) proteins in interleukin (IL)-1beta- and lipopolysaccharide (LPS)+interferon (IFN)-gamma-mediated iNOS induction in murine mesangial cells. Both stimuli induced rapid phosphorylation of STAT3 and sequence-specific STAT3 DNA-binding activity. Supershift assays with a STAT3 element probe demonstrated that nuclear factor kappaB (NF-kappaB) p65 and p50 complexed with STAT3 in the DNA-protein complex. The direct interaction of STAT3 and NF-kappaB p65 was verified in vivo by co-immunoprecipitation and in vitro by pull-down assays with glutathione S-transferase-NF-kappaB p65 fusion protein and in vitro -translated STAT3alpha. Overexpression of STAT3 dramatically inhibited IL-1beta- or LPS+IFN-gamma-mediated induction of iNOS promoter-luciferase constructs that contained the wild-type iNOS promoter or ones harbouring mutated STAT-binding elements. In tests of indirect inhibitory effects of STAT3, overexpression of STAT3 dramatically inhibited the activity of an NF-kappaB-dependent promoter devoid of STAT-binding elements without affecting NF-kappaB DNA-binding activity. Thus STAT3, via direct interactions with NF-kappaB p65, serves as a dominant-negative inhibitor of NF-kappaB activity to suppress indirectly cytokine induction of the iNOS promoter in mesangial cells. These results provide a new model for the termination of NO production by activated iNOS following exposure to pro-inflammatory stimuli.

Regulation of the expression of mouse TAP-associated glycoprotein (tapasin) by cytokines

The expression of antigen presenting MHC class I molecules can be enhanced through cytokines, e.g. upon infection with bacteria or viruses, either directly by enhancing class I gene transcription or by increasing the amounts of accessory proteins of the loading complex. Tapasin plays a significant role in the peptide loading of class I molecules. Here, we describe recognition motifs of cytokine inducible transcription factors in the promoter region of the mouse tapasin gene, most of them clustered within the 140 base pairs upstream of the start codon. Tapasin mRNA was strongly induced in vivo after infection with the facultatively intracellular bacterium Listeria monocytogenes in an IFN-gamma-dependent fashion. Accordingly, both tapasin mRNA and protein were strongly induced in a time and dose dependent manner in embryonic fibroblasts treated with the cytokines IFN-gamma and IFN-beta, and weakly induced after treatment with TNF-alpha. Co-stimulation of tapasin by TNF-alpha and IFN-gamma resulted in a weak synergistic effect. Using fibroblasts either lacking IRF-1 or inhibited in protein synthesis we show that secondary transcription factors are necessary for a maximal stimulation of tapasin expression upon IFN-gamma stimulation. The sequential induction of TAP1, LMP2, and tapasin before the stimulated expression of class I heavy chain is discussed.

Complement factor B gene regulation: synergistic effects of TNF-alpha and IFN-gamma in macrophages

Complement factor B (Bf) plays an important role in activating the alternative complement pathway. The inflammatory cytokines, in particular TNF-alpha and IFN-gamma, are critical in the regulation of Bf gene expression in macrophages. In this study, we investigated the mechanisms of Bf gene regulation by TNF-alpha and IFN-gamma in murine macrophages. Northern analysis revealed that Bf mRNA expression was synergistically up-regulated by TNF-alpha and IFN-gamma in MH-S cells. Truncations of the 5' Bf promoter identified a region between -556 and -282 bp that mediated TNF-alpha responsiveness as well as the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. Site-directed mutagenesis of a NF-kappaB-binding element in this region (-433 to -423 bp) abrogated TNF-alpha responsiveness and decreased the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. EMSAs revealed nuclear protein binding to this NF-kappaB cis-binding element on TNF-alpha stimulation. Supershift analysis revealed that both p50 and p65 proteins contribute to induction of Bf by TNF-alpha. An I-kappaB dominant negative mutant blocked Bf induction by TNF-alpha and reduced the synergistic induction by TNF-alpha and IFN-gamma. In addition, the proteasome inhibitor MG132, which blocks NF-kappaB induction, blocked TNF-alpha-induced Bf promoter activity and the synergistic induction of Bf promoter activity by TNF-alpha and IFN-gamma. LPS was found to induce Bf promoter activity through the same NF-kappaB cis-binding site. These findings suggest that a NF-kappaB cis-binding site between -433 and -423 bp is required for TNF-alpha responsiveness and for TNF-alpha- and IFN-gamma-stimulated synergistic responsiveness of the Bf gene.

Suppression of growth by all-trans retinoic acid requires prolonged induction of interferon regulatory factor 1 in cervical squamous carcinoma (SiHa) cells

All-trans retinoic acid (ATRA) suppresses growth of cervical dysplasias in vivo, although the sensitivity to retinoids is frequently lost during cervical carcinogenesis. It has been suggested that prolonged treatment or use of higher doses of retinoids might offer favorable response rates. We found SiHa cervical squamous carcinoma cells that were virtually resistant to ATRA-induced growth-inhibitory effects at physiological doses (10(-7 to) 10(-6) M) to be more responsive at pharmacological doses (10(-5 to) 10(-4) M). The growth inhibition by high-dose (10(-4) M) ATRA was associated with a sustained activation of interferon regulatory factor 1 (IRF-1), while a low dose (10(-6) M) of ATRA activated IRF-1 only transiently. Antisense IRF-1 inhibited the high-dose (10(-4) M), ATRA-mediated growth arrest; forced expression of IRF-1 caused a significant reduction in cell growth. High-dose (10(-4) M) ATRA increased binding of NF-kappaB and STAT1 proteins to sequences that originated from the IRF-1 promoter region, while low-dose (10(-6) M) ATRA induced only NF-kappaB binding. A delayed tyrosine phosphorylation of the signal transducer and activator of transcription-1 (STAT1) was observed after high-dose (10(-4) M) but not low-dose (10(-6) M) ATRA treatment. In agreement with this, induction of IRF-1 mRNA by ATRA was only modest and transient in a STAT1 knockout cell line, suggesting the importance of STAT1 in sustained IRF-1 expression. Our data showed that ATRA is capable of inducing dose-dependent cellular changes, which might be appropriate to overcome resistance to retinoids that frequently develops during cervical carcinogenesis.

STAT3 contributes to the mitogenic response of hepatocytes during liver regeneration

STAT3 is rapidly induced during liver regeneration in an interleukin 6 (IL-6)-dependent fashion, and IL-6 is required for normal liver regeneration. We wanted to know whether STAT3 was also required for liver regeneration but disruption of the STAT3 gene during embryonic stages causes lethality. Therefore, an albumin promoter-driven Cre-loxP recombination system was used to create a STAT3 deletion in the adult mouse liver to study the role of STAT3 in liver regeneration. After partial hepatectomy, there was virtually no STAT3 RNA or protein induction in Alb(+) STAT3(fl/fl) livers. STAT3 DNA binding activity was also absent in Alb(+) STAT3(fl/fl) livers. Unlike in control livers, STAT1 was activated in STAT3 conditional-mutant livers posthepatectomy. Hepatocyte DNA synthesis at 40 h posthepatectomy in Alb(+) STAT3(fl/fl) livers was reduced to approximately one-third of the control. Alb(+) STAT3(fl/fl) livers had abnormalities in immediate-early gene activation that largely correlated with but were not identical to those seen in IL-6-/- livers. G(1) phase cyclins including cyclins D1 and E had lower expression levels in Alb(+) STAT3(fl/fl) livers, indicating an abnormal G(1) to S phase transition. Therefore, STAT3 accounts for part of the DNA synthetic response of the hepatocytes during liver regeneration, which cannot be compensated for by induction of STAT1. Normal activation of the MAPK pathway in Alb(+) STAT3(fl/fl) livers reinforces the fact that at least part of the effect of IL-6 on hepatocyte proliferation is not mediated by STAT3. This study provides the first in vivo evidence that STAT3 promotes cell cycle progression and cell proliferation under physiological growth conditions.

Interferon-gamma, a strong suppressor of cell proliferation, induces upregulation of keratin K6, one of the inflammatory- and proliferation-associated keratins

Keratin K6 is known as an inflammatory and hyperproliferative keratin, and is induced by an inflammatory and hyperproliferative agent. In this study, we demonstrated that interferon-gamma, an antiproliferative agent, also induces keratin K6. We used normal human ex vivo skin, normal human cultured keratinocytes, HaCaT keratinocytes, and DJM cells to examine the induction of K6 by interferon-gamma, by immunohistochemical staining, Western blot analysis, promoter chloramphenicol acetyl transferase assay, and reverse transcriptase polymerase chain reaction of mRNA. We succeeded in demonstrating the induction of keratin K6 by interferon-gamma in ex vivo human skin and HaCaT keratinocytes at the protein and message level, and in cultured normal human keratinocytes at the promoter level. The inhibition of the signal transducing activator of transcription 1 pathway by a dominant-negative transfer gene caused the inhibition of K6 induction by interferon-gamma, and the blocking of nuclear factor kappaB using antisense oligonucleotides also inhibited the K6 induction. We also blocked the released interleukin-1alpha from keratinocytes after stimulation with interferon-gamma by neutralizing antibodies, which showed a decrease in the K6 induction. Our results suggest that a small amount of interleukin-1alpha, which cannot induce K6 by itself, is secreted upon stimulation by interferon-gamma, and that the induction of K6 occurs through the synergistic effect of the interferon-gamma/signal transducing activator of transcription 1 and interleukin-1alpha/nuclear factor kappaB pathways. This is the first report to describe K6 induction in epidermal keratinocytes by interferon-gamma and indicate a probable signal transduction pathway, and demonstrates that K6 is a possible partner of K17 in the inflammatory process.

Selective expression of type I IFN genes in human dendritic cells infected with Mycobacterium tuberculosis

Type I IFN regulates different aspects of the immune response, inducing a cell-mediated immunity. We have recently shown that the infection of dendritic cells (DC) with Mycobacterium tuberculosis (Mtb) induces IFN-alpha. In this work we have monitored a rapid induction of IFN-beta followed by the delayed production of the IFN-alpha1 and/or -alpha13 subtypes. The Mtb infection rapidly activates the NF-kappaB complex and stimulates the phosphorylation of IFN regulatory factor (IRF)-3, events known to induce IFN-beta expression in viral infection. In turn, the autocrine production of IFN-beta induces the IFN-stimulated genes that contain binding sites for activated STATs in their promoters. Among the IFN-stimulated genes induced in DC through STAT activation are IRF-1 and IRF-7. The expression of IRF-1 appears to be dependent on the sequential activation of NF-kappaB and STAT-1. Once expressed, IRF-1 may further stimulate the transcription of IFN-beta. Induction of IRF-7 is also regulated at the transcriptional level through the binding of phosphorylated STAT-1 and STAT-2, forming the IFN-stimulated gene factor-3 complex. In turn, the IRF-1 and IRF-7 expression appears to be required for the delayed induction of the IFN-alpha1/13 genes. Although correlative, our results strongly support the existence of a cascade of molecular events in Mtb-infected DC. Upon infection, constitutively expressed NF-kappaB and IRF-3 are activated and likely contribute to the rapid IFN-beta expression. In turn, IFN-beta-induced IRF-1 and IRF-7 may cooperate toward induction of IFN-alpha1/13 if infection persists and these factors are activated.

Synergistic action of prolactin (PRL) and androgen on PRL-inducible protein gene expression in human breast cancer cells: a unique model for functional cooperation between signal transducer and activator of transcription-5 and androgen receptor

The signal transducer and activator of transcription 5 (Stat5) has been shown to cooperate with some nuclear receptors. However, an interaction has never been demonstrated with the androgen receptor (AR). Given that the PRL-inducible protein/gross cystic disease fluid-15 (PIP/GCDFP-15) is both a PRL-controlled and an androgen-controlled protein, we used its promoter region to investigate the potential interaction between Stat5 and androgen receptor. Dihydrotestosterone or PRL alone slightly modulated or did not modulate the luciferase activity of all reporter gene constructs. In contrast, a maximal increase was observed using the -1477+42 reporter gene construct after exposure to both dihydrotestosterone and PRL. The requirement of half-site androgen-responsive elements and two consensus Stat5-binding elements, Stat5#1 and Stat5#2, was determined by site-directed mutagenesis. Activated Stat5B binds with a higher affinity to Stat5#2 than to Stat5#1. Stat5ADelta749 and Stat5BDelta754 mutants demonstrated that the Stat5 trans-activation domain is involved in the hormonal cooperation. The cooperation depends on the PRL-induced phosphorylation on Tyr(694) in Stat5A and Tyr(699) in Stat5B, as demonstrated using the Stat5AY694F and Stat5BY699F proteins. The use of AR Q798E, C619Y, and C784Y mutants showed that trans-activation, DNA-binding, and ligand-binding domains of AR are essential. Our study thus suggests a functional cooperation between AR and Stat5.