NF-IL6 and NF-κB in Cytokine Gene Regulation

C/EBPzeta (CHOP/Gadd153) is a negative regulator of LPS-induced IL-6 expression in B cells

C/EBPzeta was originally identified as a gene induced upon DNA damage and growth arrest. It has been shown to be involved in the cellular response to endoplasmic reticulum stress. Because of sequence divergence from other C/EBP family members in its DNA-binding domain and its consequent inability to bind the C/EBP consensus-binding motif, C/EBPzeta can act as a dominant negative inhibitor of other C/EBPs. C/EBP transactivators are essential to the expression of many proinflammatory cytokines and acute phase proteins, but a role for C/EBPzeta in regulating their expression has not been described. We found that expression of C/EBPzeta is induced in response to LPS treatment of B cells at both the mRNA and protein levels. Correlating with the highest levels of C/EBPzeta expression at 48 h after LPS treatment, there is an increased association of C/EBPzeta with C/EBPbeta, and both the abundance of C/EBP DNA-binding species and IL-6 expression are downregulated. Furthermore, ectopic expression of C/EBPzeta inhibited C/EBPbeta-dependent IL-6 expression from both the endogenous IL-6 gene and an IL-6 promoter-reporter. These results suggest that C/EBPzeta functions as negative regulator of IL-6 expression in B cells and that it contributes to the transitory expression of IL-6 that is observed after LPS treatment.

MeCP2/H3meK9 are involved in IL-6 gene silencing in pancreatic adenocarcinoma cell lines

The aim of the present study was to analyse the molecular mechanisms involved in the Interleukin-6 (IL-6) silencing in pancreatic adenocarcinoma cell lines. Our results demonstrate that TNF-alpha, a major IL-6 inducer, is able to induce IL-6 only in three out of six cell lines examined. 5-aza-2'-deoxycytidine (DAC), but not trichostatin A (TSA), activates the expression of IL-6 in all cell lines, indicating that DNA methylation, but not histone deacetylation, plays an essential role in IL-6 silencing. Indeed, the IL-6 upstream region shows a methylation status that correlates with IL-6 expression and binds MeCP2 and H3meK9 only in the non-expressing cell lines. Our results suggest that critical methylations located from positions -666 to -426 relative to the transcription start site of IL-6 may act as binding sites for MeCP2.

H89, an inhibitor of PKA and MSK, inhibits cyclic-AMP response element binding protein-mediated MAPK phosphatase-1 induction by lipopolysaccharide

OBJECTIVE

Lipopolysaccharide (LPS) stimulates the production of inflammatory cytokines and the amplification of immune responses via MAPK pathways. MAPK phosphatases (MKPs) feedback-regulate the activities of MAPKs to prevent excessive immunological functions. H89 has been used as an inhibitor of the protein kinase A (PKA) and mitogen- and stress-activated protein kinase (MSK) pathways. In view of the potential roles of PKA and MSK for MKP-1 induction and the ability of H89 to inhibit these kinases, this study examined the effect of H89 on MKP-1 induction by LPS and the role of cyclic-AMP response element binding protein (CREB) in the MKP-1 induction.

RESULTS

H89 treatment inhibited increases in MKP-1 protein and mRNA levels, and gene transcription by LPS in Raw264.7 cells. Immunoblot, gel-shift, and chromatin-immunoprecipitation assays showed the activation of CREB by LPS, and the ability of H89 to inhibit it, suggesting that H89's inhibition of CREB may affect MKP-1 induction. In addition, H89 prevented the ability of LPS to induce other MKP genes (Dusp-2, 4, 8, and 16). Experiments using MAPK inhibitors showed that MAPKs are involved in CREB phosphorylation and MKP-1 induction, suggesting that CREB-mediated MKP-1 induction serves in part as a feedback-inhibitory loop of MAPKs.

CONCLUSION

Our results demonstrate that H89 inhibits the activation of CREB and the CREB-mediated MKP-1 induction by LPS, which may result from its inhibition of PKA and MSK.

CCAAT/enhancer binding protein beta mediates expression of matrix metalloproteinase 13 in human articular chondrocytes in inflammatory arthritis

OBJECTIVE

To determine the function of CCAAT/enhancer binding protein beta (C/EBPbeta) in the expression of matrix metalloproteinase 13 (MMP-13) in chondrocytes in inflammatory arthritis.

METHODS

Cartilage obtained from patients with rheumatoid arthritis and osteoarthritis was immunostained for expression of C/EBPbeta or MMP-13. Interleukin-1beta- or tumor necrosis factor alpha (TNFalpha)-stimulated chondrocytes were subjected to Western blotting and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). MMP-13 promoter assays were conducted, and the C/EBPbeta response element was characterized by deletion and mutation analysis. C-28/I2 cells were treated with TNFalpha and subjected to chromatin immunoprecipitation (ChIP) assays. Finally, C/EBPbeta-liver-enriched activator protein (LAP) was overexpressed in C-28/I2 cells or cartilage tissues, and MMP-13 expression was analyzed.

RESULTS

C/EBPbeta and MMP-13 expression was colocalized in chondrocytes in arthritic cartilage. MMP-13 promoter activity was stimulated by C/EBPbeta overexpression in a dose-dependent manner. Luciferase assays revealed that a -981-bp promoter had the greatest activity, while deletion to -936 bp strongly diminished promoter activity. Luciferase activity was repressed to basal levels by mutations in potential C/EBP binding sites. The stimulatory effects of C/EBPbeta overexpression were diminished by mutation. ChIP assays revealed that TNFalpha treatment enhanced the binding of C/EBPbeta to the MMP-13 promoter. When C/EBPbeta-LAP was overexpressed in C-28/I2 cells, endogenous MMP-13 expression was stimulated up to 32-fold as detected by real-time RT-PCR. Furthermore, following adenoviral overexpression of C/EBPbeta-LAP in organ culture of articular cartilage, stimulation of MMP-13 was also detected by immunohistochemistry.

CONCLUSION

C/EBPbeta directly binds to the MMP-13 promoter region and stimulates the expression of MMP-13 in chondrocytes in inflammatory arthritis.

NF-IL6 (C/EBPbeta) induces HIV-1 replication by inhibiting cytidine deaminase APOBEC3G

T cell activation is crucial for the productive HIV-1 infection of primary T cells; however, little is known about the host molecules involved in this process. We show that the host transcription factor NF-IL6 (also called C/EBPbeta) renders primary CD4(+) T cells highly permissive for HIV-1 replication. NF-IL6 facilitates reverse transcription of the virus by binding to and inhibiting the antiviral cytidine deaminase APOBEC3G. A mutation in NF-IL6 at Ser-288 weakened its binding to APOBEC3G and strongly inhibited HIV-1 replication. NF-IL6 also induced the replication of a Vif-deficient strain of HIV-1 in nonpermissive HUT78 cells. These data indicate that NF-IL6 is a natural inhibitor of APOBEC3G that facilitates HIV-1 replication. Host factors, such as NF-IL6, that are involved in early HIV-1 replication are potential targets for anti-HIV-1 therapy. Our findings shed light on the activation of HIV-1 replication by T cell host molecules and reveal a unique regulation of DNA deamination by APOBEC3G and NF-IL6.

Mincle is an ITAM-coupled activating receptor that senses damaged cells

Macrophage-inducible C-type lectin (Mincle) is expressed mainly in macrophages and is induced after exposure to various stimuli and stresses. Here we show that Mincle selectively associated with the Fc receptor common gamma-chain and activated macrophages to produce inflammatory cytokines and chemokines. Mincle-expressing cells were activated in the presence of dead cells, and we identified SAP130, a component of small nuclear ribonucloprotein, as a Mincle ligand that is released from dead cells. To investigate whether Mincle is required for normal responses to cell death in vivo, we induced thymocyte death by irradiating mice and found that transient infiltration of neutrophils into the thymus could be blocked by injection of Mincle-specific antibody. Our results suggest that Mincle is a receptor that senses nonhomeostatic cell death and thereby induces the production of inflammatory cytokines to drive the infiltration of neutrophils into damaged tissue.

The identification of C/EBPbeta as a transcription factor necessary for the induction of MAPK phosphatase-1 by toll-like receptor-4 ligand

Toll-like receptor activates mitogen-activated protein kinases (MAPKs), which contributes to inflammatory responses. The activities of MAPKs are counter-balanced by MAPK phosphatases (MKPs). Because the transcriptional regulatory mechanism of mkp-1 has not been completely established, this study investigated the effect of toll-like receptor-4 ligand (TLR4L, lipopolysaccharide) on CCAAT/enhancer binding protein-beta (C/EBP beta)-dependent induction of MKP-1 in Raw264.7 cells. TLR4L treatment induced MKP-1 through gene transcription. Other TLRLs also transactivated mkp-1. Gel-shift, immunoblot and chromatin immunoprecipitation assays identified the activation of C/EBPbeta by TLR4L. Consistently, C/EBP beta transfection promoted mkp-1 transactivation, which was reversed by its dominant-negative mutant (AC/EBP). Experiments using chemical inhibitors or dominant-negative mutants of MAPKs indicated that both C/EBP beta activation and MKP-1 induction depend on the activation of MAPKs. TLR4L activation of C/EBP beta also contributed to the induction of dusp-2,dusp-4,dusp-8 and dusp-16. These results identify C/EBP beta as a transcription factor necessary for the induction of MKP-1 by TLRL.

Effect of mitogen-activated protein kinases on chemokine synthesis induced by substance P in mouse pancreatic acinar cells

Substance P, acting via its neurokinin 1 receptor (NK1 R), plays an important role in mediating a variety of inflammatory processes. Its interaction with chemokines is known to play a crucial role in the pathogenesis of acute pancreatitis. In pancreatic acinar cells, substance P stimulates the release of NFκB-driven chemokines. However, the signal transduction pathways by which substance P-NK1 R interaction induces chemokine production are still unclear. To that end, we went on to examine the participation of mitogen-activated protein kinases (MAPKs) in substance P-induced synthesis of pro-inflammatory chemokines, monocyte chemoanractant protein-1 (MCP-I), macrophage inflammatory protein-lα (MIP-lα) and macrophage inflammatory protein-2 (MIP-2), in pancreatic acini. In this study, we observed a time-dependent activation of ERK1/2, c-Jun N-terminal kinase (JNK), NFκB and activator protein-1 (AP-1) when pancreatic acini were stimulated with substance P. Moreover, substance P-induced ERK 1/2, JNK, NFκB and AP-1 activation as well as chemokine synthesis were blocked by pre-treatment with either extracellular signal-regulated protein kinase kinase 1 (MEK1) inhibitor or JNK inhibitor. In addition, substance P-induced activation of ERK 112, JNK, NFκB and AP-1-driven chemokine production were attenuated by CP96345, a selective NK1 R antagonist, in pancreatic acinar cells. Taken together, these results suggest that substance P-NK1 R induced chemokine production depends on the activation of MAPKs-mediated NFκB and AP-1 signalling pathways in mouse pancreatic acini.

Identification of a novel regulatory region in the interleukin-6 gene promoter

Interleukin-6 (IL6) is an important pleiotropic cytokine that is regulated at the transcriptional level. To date, most work on its regulation has focused on a 1.2kb region 5' from the start of transcription, similar to published reports on other cytokine genes. This report demonstrates for the first time that a cytokine gene can be regulated by cis-acting regions much further upstream than previously examined. Comparative genomic analysis showed that a 120 kb region contains blocks of sequence conservation between human and rodent genomes, and that a 15 kb region proximal to the start of transcription contains 10 highly homologous sequence blocks of between 100 and 250 bp. By means of a reporter gene assay, a novel transcriptionally active region located between -5307 and -5202 bp upstream from the start of transcription was identified. Electrophoretic mobility shift assays showed nuclear protein(s) binding to this region, thus raising the possibility that the regulatory activity shown by the reporter gene constructs may be mediated by these proteins. These results suggest that the regulation of IL6 expression involves a much larger upstream region than previously examined and the control of IL6 transcription is likely to be regulated by a complex mechanism of modular cis-regulatory elements.

The Med1 subunit of transcriptional mediator plays a central role in regulating CCAAT/enhancer-binding protein-beta-driven transcription in response to interferon-gamma

Transcription factor CCAAT/enhancer-binding protein (C/EBP)-beta is crucial for regulating transcription of genes involved in a number of diverse cellular processes, including those involved in some cytokine-induced responses. However, the mechanisms that contribute to its diverse transcriptional activity are not yet fully understood. To gain an understanding into its mechanisms of action, we took a proteomic approach and identified cellular proteins that associate with C/EBP-beta in an interferon (IFN)-gamma-dependent manner. Transcriptional mediator (Mediator) is a multisubunit protein complex that regulates signal-induced cellular gene transcription from enhancer-bound transcription factor(s). Here, we report that the Med1 subunit of the Mediator as a C/EBP-beta-interacting protein. Using gene knock-out cells and mutational and RNA interference approaches, we show that Med1 is critical for IFN-induced expression of certain genes. Med1 associates with C/EBP-beta through a domain located between amino acids 125 and 155 of its N terminus. We also show that the MAPK, ERK1/2, and an ERK phosphorylation site within regulatory domain 2, more specifically the Thr(189) residue, of C/EBP-beta are essential for it to bind to Med1. Last, an ERK-regulated site in Med1 protein is also essential for up-regulating IFN-induced transcription although not critical for binding to C/EBP-beta.

Activation of oxidative stress-responsive signaling pathways in early splenotoxic response of aniline

Aniline exposure causes toxicity to the spleen, which leads to a variety of sarcomas, and fibrosis appears to be an important preneoplastic lesion. However, early molecular mechanisms in aniline-induced toxicity to the spleen are not known. Previously, we have shown that aniline exposure results in iron overload and induction of oxidative stress in the spleen, which can cause transcriptional upregulation of fibrogenic/inflammatory cytokines via activation of oxidative stress (OS)-responsive signaling pathways. To test this mechanism, male SD rats were treated with aniline (1mmol/kg/day via gavage) for 7 days, an experimental condition that precedes the appearance of fibrosis. Significant increases in both NF-kappaB and AP-1 binding activity was observed in the nuclear extracts of splenocytes from aniline-treated rats as determined by ELISAs, and supported by Western blot data showing increases in p-IkappaBalpha, p-p65 and p-c-Jun. To understand the upstream signaling events which could account for the activation of NF-kappaB and AP-1, phosphorylation patterns of IkappaB kinases (IKKalpha and IKKbeta) and mitogen-activated protein kinases (MAPKs) were pursued. Our data showed remarkable increases in both p-IKKalpha and p-IKKbeta in the splenocytes from aniline-treated rats, suggesting their role in the phosphorylation of both IkappaBalpha and p65 subunits. Furthermore, aniline exposure led to activation of all three classes of MAPKs, as evident from increased phosphorylation of extracellular-signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK1/2) and p38 MAPKs, which could potentially contribute to the observed activation of both AP-1 and NF-kappaB. Activation of upstream signaling molecules was also associated with simultaneous increases in gene transcription of cytokines IL-1, IL-6 and TNF-alpha. The observed sequence of events following aniline exposure could initiate a fibrogenic and/or tumorigenic response in the spleen.

Critical role for transcription factor C/EBP-beta in regulating the expression of death-associated protein kinase 1

Transcription factor C/EBP-beta regulates a number of physiological responses. During an investigation of the growth-suppressive effects of interferons (IFNs), we noticed that cebpb(-/-) cells fail to undergo apoptosis upon gamma IFN (IFN-gamma) treatment, compared to wild-type controls. To examine the basis for this response, we have performed gene expression profiling of isogenic wild-type and cebpb(-/-) bone marrow macrophages and identified a number of IFN-gamma-regulated genes that are dependent on C/EBP-beta for their expression. These genes are distinct from those regulated by the JAK-STAT pathways. Genes identified in this screen appear to participate in various cellular pathways. Thus, we identify a new pathway through which the IFNs exert their effects on cellular genes through C/EBP-beta. One of these genes is death-associated protein kinase 1 (dapk1). DAPK1 is critical for regulating the cell cycle, apoptosis, and metastasis. Using site-directed mutagenesis, RNA interference, and chromatin immunoprecipitation assays, we show that C/EBP-beta binds to the promoter of dapk1 and is required for the regulation of dapk1. Both mouse dapk1 and human dapk1 exhibited similar dependences on C/EBP-beta for their expression. The expression of the other members of the DAPK family occurred independently of C/EBP-beta. Members of the C/EBP family of transcription factors other than C/EBP-beta did not significantly affect dapk1 expression. We identified two elements in this promoter that respond to C/EBP-beta. One of these is a consensus C/EBP-beta-binding site that constitutively binds to C/EBP-beta. The other element exhibits homology to the cyclic AMP response element/activating transcription factor binding sites. C/EBP-beta binds to this site in an IFN-gamma-dependent manner. Inhibition of ERK1/2 or mutation of an ERK1/2 site in the C/EBP-beta protein suppressed the IFN-gamma-induced response of this promoter. Together, our data show a critical role for C/EBP-beta in a novel IFN-induced cell growth-suppressive pathway via DAPK1.

Inflammation and lung cancer: roles of reactive oxygen/nitrogen species

The lung is a highly specialized organ that facilitates uptake of oxygen and release of carbon dioxide. Due to its unique structure providing enormous surface area to outside ambient air, it is vulnerable to numerous pathogens, pollutants, oxidants, gases, and toxicants that are inhaled continuously from air, which makes the lung susceptible to varying degrees of oxidative injury. To combat these unrelenting physical, chemical, and biological insults, the respiratory epithelium is covered with a thin layer of lining fluid containing several antioxidants and surfactants. Inhaled toxic agents stimulate the generation of reactive oxygen/nitrogen species (ROS/RNS), which in turn provoke inflammatory responses resulting in the release of proinflammatory cytokines and chemokines. These subsequently stimulate the influx of polymorphonuclear leukocytes (PMNs) and monocytes into the lung so as to combat the invading pathogens or toxic agents. In addition to the beneficial effects, persistent inhalation of the invading pathogens or toxic agents may result in overwhelming production of ROS/RNS, producing chronic inflammation and lung injury. During inflammation, enhanced ROS/RNS production may induce recurring DNA damage, inhibition of apoptosis, and activation of proto-oncogenes by initiating signal transduction pathways. Therefore, it is conceivable that chronic inflammation-induced production of ROS/RNS in the lung may predispose individuals to lung cancer. This review describes the complex relationship between lung inflammation and carcinogenesis, and highlights the role of ROS/RNS in cancer development.

Effect of thiol-containing molecule cysteamine on the induction of inducible nitric oxide synthase in hepatocytes

BACKGROUND

Cysteamine, which is a known antioxidant and anti-inflammatory agent, is believed to be a key regulator of essential metabolic pathways in organisms. Cysteamine has beneficial effects in liver damaged by a variety of insults. During liver injury, inducible nitric oxide synthase (iNOS) is induced by lipopolysaccharide or proinflammatory cytokines, leading to excessive nitric oxide (NO) production. Accumulated evidence indicates that NO is an important factor associated with hepatic dysfunction. We examined whether cysteamine influences the induction of iNOS in hepatocytes.

METHODS

Primary cultured rat hepatocytes were treated with interleukin (IL)-1beta in the presence and absence of cysteamine. NO production, iNOS induction, and iNOS signal were analyzed.

RESULTS

IL-1beta stimulated the inhibitory protein kappaB (IkappaB)/nuclear factor kappaB (NFkappaB) pathway, resulting in the activation of NFkappaB (nuclear translocation and DNA binding), which was followed by the induction of iNOS and NO production. The addition of IL-1beta and cysteamine (1-4 mmol/L) markedly inhibited NO production, with a maximal effect at 4 mmol/L (80%-90% inhibition). Cysteamine also decreased the levels of iNOS protein and mRNA. Transfection experiments revealed that cysteamine decreased the transactivation activity of the iNOS promoter. An electrophoretic mobility shift assay demonstrated that cysteamine inhibited the activation of NFkappaB. Furthermore, cysteamine decreased the mRNA levels of the NFkappaB subunit p65 but increased those of the inhibitory protein IkappaB.

CONCLUSIONS

These findings suggest that cysteamine inhibits iNOS induction at the step of NFkappaB activation. Further study is necessary to define the molecular basis of this effect of cysteamine on the regulation of NFkappaB and its pharmacologic implications.

Effect of active hexose correlated compound on the production of nitric oxide in hepatocytes

BACKGROUND

Active hexose correlated compound (AHCC) is a "complex compound" containing polysaccharides. AHCC has been reported to improve the prognosis of postoperative hepatocellular carcinoma patients. However, the molecular mechanism of this improvement is not fully understood. In the diseased liver, nitric oxide (NO) generated by inducible nitric oxide synthase (iNOS) is considered to be a causal factor for various hepatopathies. In this study, the possibility of AHCC regulation of NO production by iNOS was pursued as a potential liver-protecting mechanism.

METHODS

Primary cultured rat hepatocytes were treated with interleukin-1beta (IL-1beta) in the presence or absence of AHCC. NO production, iNOS induction, and iNOS signal were analyzed.

RESULTS

IL-1beta stimulated iNOS induction through the activation of nuclear factor kappaB (NFkappaB), leading to NO production. The addition of AHCC inhibited NO production, showing >80% inhibition at 8 mg/mL. AHCC also decreased the levels of iNOS protein and mRNA. However, AHCC influenced neither the degradation of inhibitory protein kappaB (IkappaB) nor the activation of NFkappaB stimulated by IL-1beta. Transfection experiments with an iNOS promoter-luciferase construct (iNOS-Luc) revealed that AHCC had no effect on the transactivation activity of the iNOS promoter. By contrast, AHCC inhibited the activity of iNOS-Luc containing a 3'untranslated region (UTR) with adenosine and uridine (AU)-rich elements, which shows the stabilizing activity of iNOS mRNA.

CONCLUSIONS

Results indicated that AHCC inhibits the induction of iNOS at the level of transcription, causing a decrease in NO production in hepatocytes. AHCC seems to decrease the levels of iNOS mRNA by reducing mRNA stabilization rather than inhibiting its synthesis.

The C/EBPβ Isoform 34-kDa LAP Is Responsible for NF-IL-6-Mediated Gene Induction in Activated Macrophages, but Is Not Essential for Intracellular Bacteria Killing

The C/ebpb gene is translated into three different protein isoforms, two transcriptional activating proteins (38-kDa Full and 34-kDa liver-enriched transcriptional activation protein (LAP)) and one transcriptional inhibitory protein, by alternative use of different AUG initiation codons within the same open reading frame. The isoform 34-kDa LAP is thought to be the most transcriptionally active form of C/EBPbeta in macrophages. To assess the function of the 34-kDa LAP in vivo, we generated knock-in mice, in which methionine 20 of C/EBPbeta, the start site for the 34-kDa LAP is replaced with an alanine. The expression of the 34-kDa LAP was abolished in C/ebpb(M20A/M20A) mice. The induction of C/EBPbeta target genes, such as inflammatory cytokines, chemokines, prostanoid synthetase, and antimicrobial peptides, was abolished in C/ebpb(M20A/M20A) macrophages, and C/ebpb(M20A/M20A) mice were susceptible to Listeria monocytogenes infection. Furthermore, the heat-killed Propionibacterium acnes-induced Th1 response, granuloma formation, and LPS shock were severely impaired. Nevertheless, impairment of intracellular bacteria killing, which is the most prominent phenotype in C/EBPbeta-deficient mice, was not observed in C/ebpb(M20A/M20A) mice. Collectively, we demonstrated that 34-kDa LAP is responsible for NF-IL6-mediated gene induction, but not essential for intracellular bacteria killing in activated macrophages.

Potentiation of NF-kappaB-dependent transcription and inflammatory mediator release by histamine in human airway epithelial cells

BACKGROUND AND PURPOSE

In asthma, histamine contributes to bronchoconstriction, vasodilatation and oedema, and is associated with the late phase response. The current study investigates possible inflammatory effects of histamine acting on nuclear factor kappaB (NF-kappaB)-dependent transcription and cytokine release.

EXPERIMENTAL APPROACH

Using BEAS-2B bronchial epithelial cells, NF-kappaB-dependent transcription and both release and mRNA expression of IL-6 and IL-8 were examined by reporter assay, ELISA and quantitative RT-PCR. Histamine receptors were detected using qualitative RT-PCR and function examined using selective agonists and antagonists.

KEY RESULTS

Addition of histamine to TNFalpha-stimulated BEAS-2B cells maximally potentiated NF-kappaB-dependent transcription 1.8 fold, whereas IL-6 and IL-8 protein release were enhanced 7.3- and 2.7-fold respectively. These responses were, in part, NF-kappaB-dependent and were associated with 2.6- and 1.7-fold enhancements of IL-6 and IL-8 mRNA expression. The H(1) receptor antagonist, mepyramine, caused a rightward shift in the concentration-response curves of TNFalpha-induced NF-kappaB-dependent transcription (pA(2)=9.91) and release of IL-6 (pA(2)=8.78) and IL-8 (pA(2)=8.99). Antagonists of histamine H(2), H(3) and H(4) receptors were without effect. Similarly, H(3) and H(4) receptor agonists did not affect TNFalpha-induced NF-kappaB-dependent transcription, or IL-6 and IL-8 release at concentrations below 10 microM. The anti-inflammatory glucocorticoid, dexamethasone, inhibited the histamine enhanced NF-kappaB-dependent transcription and IL-6 and IL-8 release.

CONCLUSIONS AND IMPLICATIONS

Potentiation of NF-kappaB-dependent transcription and inflammatory cytokine release by histamine predominantly involves receptors of the H(1) receptor subtype. These data support an anti-inflammatory role for H(1) receptor antagonists by preventing the transcription and release of pro-inflammatory cytokines.

Rebamipide, anti-gastric ulcer drug, up-regulates the induction of iNOS in proinflammatory cytokine-stimulated hepatocytes

Nitric oxide (NO) generated from inducible NO synthase (iNOS) during hepatic injury has been reported to contribute to cytoprotection or cellular damage. Rebamipide, anti-gastric ulcer drug, has protective effects in a variety of tissue and organ injury. However, it remains unknown whether rebamipide is involved in the regulation of iNOS gene expression under pathological conditions. We examined whether rebamipide influences the induction of iNOS in hepatocytes exposed to pro-inflammatory cytokine. Primary cultured rat hepatocytes were treated with interleukin (IL)-1beta in the presence or absence of rebamipide. Pretreatment of cells with rebamipide resulted in up-regulation of iNOS induction by IL-1beta, followed by increased NO production. Rebamipide enhanced the degradation of IkappaBalpha and the activation of NF-kappaB. Further, rebamipide super-induced the up-regulation of type I IL-1 receptor (IL-1RI), which is essential for iNOS induction in addition to the IkappaB/NF-kappaB pathway. Transfection experiments revealed that rebamipide increased the transactivation of iNOS promoter and the stability of iNOS mRNA. In the latter, rebamipide increased the antisense-transcript corresponding to the 3'-UTR of iNOS mRNA, which stabilizes iNOS mRNA by interacting with the 3'-UTR and RNA-binding proteins. These findings demonstrate that rebamipide up-regulates iNOS by iNOS promoter activation through NF-kappaB, and by its mRNA stabilization presumably through the super-induction of IL-1RI and antisense-transcript. Rebamipide may contribute to a novel potentiated treatment in liver injuries.

CCAAT enhancer-binding protein beta regulates constitutive gene expression during late stages of monocyte to macrophage differentiation

Human monocyte to macrophage differentiation is accompanied by pronounced phenotypical changes and generally proceeds in the absence of proliferation. The molecular events governing this process are poorly understood. Here, we studied the regulation of the macrophage-specific chitotriosidase (CHIT1) gene promoter to gain insights into the mechanisms of transcriptional control during the differentiation of human blood monocytes into macrophages. We used transient transfections to define a cell type-specific minimal promoter that was mainly dependent on a proximal C/EBP motif that bound multiple C/EBP factors in gel shift assays. In depth analysis of occupied promoter elements using in vivo footprinting and chromatin immunoprecipitation analyses demonstrated the differentiation-associated recruitment of C/EBPbeta and PU.1 at the proximal promoter in parallel with CHIT1 mRNA induction. Notably, the induction of C/EBPbeta promoter binding strongly correlated with increased nuclear levels of Thr-235-phosphorylated C/EBPbeta protein during the differentiation process, whereas C/EBPbeta mRNA and total protein expression remained relatively stable. Our data suggest an important constitutive gene regulatory function for C/EBPbeta in differentiated macrophages but not in human blood monocytes.

Nucleocapsid protein of SARS-CoV activates interleukin-6 expression through cellular transcription factor NF-kappaB

High levels of interleukin-6 (IL-6) in the acute stage associated with lung lesions were found in SARS patients. To evaluate the mechanisms behind this event, we investigated the roles of SARS-CoV proteins in the regulation of IL-6. Results showed that the viral nucleocapsid (N) protein activated IL-6 expression in a concentration-dependent manner. Promoter analyses suggested that NF-κB binding element was required for IL-6 expression regulated by N protein. Further studies demonstrated that N protein bound directly to NF-κB element on the promoter. We also showed that N protein activated IL-6 expression through NF-κB by facilitating the translocation of NF-κB from cytosol to nucleus. Mutational analyses revealed that two regions of N protein were essential for its function in the activation of IL-6. These results provided new insights into understanding the mechanism involved in the function of SARS-CoV N protein and pathogenesis of the virus.

TRAF activation of C/EBPbeta (NF-IL6) via p38 MAPK induces HIV-1 gene expression in monocytes/macrophages

C/EBPbeta plays a pivotal role in activation of human immunodeficiency virus type 1 (HIV-1) in monocytes/macrophages. However, mechanisms for functional regulation of C/EBPbeta remain uncharacterized. Previous studies indicated that NF-kappaB activation by tumor necrosis factor (TNF) receptor family, which activates TNF receptor associated factor (TRAF), induces HIV-1 expression. We found that TRAF signals activate HIV-1 LTR with mutations of NF-kappaB sites in promonocytic cell line U937, suggesting existence of an alternative HIV-1 activating pathway. In this study, we have characterized the signal transduction pathway of TRAF other than that leading to NF-kappaB, using U937 cell line, and its subline, U1, which is chronically infected by HIV-1. We show that signals downstream of TRAF2 and TRAF5 activate p38 MAPK, which directly phosphorylates C/EBPbeta, and that activation of p38 MAPK potently activates C/EBPbeta-mediated induction of HIV-1 gene expression. We also show TRAF2 and TRAF5 are expressed in monocytes/macrophages of spleen samples from HIV-1 infected patients. Identification of TRAF-p38 MAPK-CEBPbeta pathway provides a new target for controlling reactivation of latent HIV-1 in monocytes/macrophages.

Nuclear factor activation by FcgammaR in human peripheral blood neutrophils detected by a novel flow cytometry-based method

In mammals, neutrophils are the most abundant circulating leukocytes. Neutrophils are short-lived cells presenting at least two important transcriptionally regulated cellular responses, initiated by cell activation: the production of pro-inflammatory cytokines and the inhibition of apoptosis. The study of transcriptionally regulated processes in these cells cannot be approached through conventional reporter gene strategies, as there are currently not available methods for neutrophil transfection. Here we describe a novel flow cytometry-based method that allowed quantification of nuclear factor NF-kappaB activation in neutrophils, in response to FcgammaIIA and FcgammaRIIIB stimulation. The sensitivity of this method allowed the detection of small changes in NF-kappaB activation, due to pharmacological inhibition of receptor-initiated signaling pathways. NF-kappaB activation was also detected by this method in various leukocyte cell lines. In addition, quantification of Fcgamma receptor-initiated nuclear activation of ERK and Elk-1 was successfully achieved through this method. The broad applicability and versatility of this flow cytometry-based method position it as a fast and reliable alternative to traditional methods for analyzing activation of transcription factors in a variety of cell types.

Regulation of interleukin-8 expression in melanoma-stimulated neutrophil inflammatory response

Inflammation facilitates tumor progression including metastasis. Interleukin-8 (IL-8) is a chemokine that regulates polymorphonuclear neutrophil (PMN) mobilization and activity and we hypothesize that this cytokine influences tumor behavior. We have demonstrated that IL-8 is crucial for PMN-mediated melanoma extravasation under flow conditions. In addition, IL-8 is up-regulated in PMNs upon co-culturing with melanoma cells. Melanoma cells induce IkappaB-alpha degradation in PMNs indicating that NF-kappaB signaling is active in PMNs. Furthermore, the production of IL-8 in PMNs is NF-kappaB dependent. We have further identified that interleukin-6 (IL-6) and interleukin-1beta (IL-1beta) from PMN-melanoma co-cultures synergistically contribute to IkappaB-alpha degradation and IL-8 synthesis in PMNs. Taken together, these findings show that melanoma cells induce PMNs to secrete IL-8 through activation of NF-kappaB and suggest a model in which this interaction promotes a microenvironment that is favorable for metastasis.

C/EBPβ Blocks p65 Phosphorylation and Thereby NF-κB-Mediated Transcription in TNF-Tolerant Cells

TNF is a major mediator of inflammation, immunity, and apoptosis. Pre-exposure to TNF reduces sensitivity to restimulation, a phenomenon known as tolerance, considered as protective in sepsis, but also as a paradigm for immunoparalysis. Earlier experiments in TNF-tolerant cells display inhibition of NF-kappaB-dependent IL-8 gene expression at the transcriptional level with potential involvement of C/EBPbeta. In this study, we have shown that a kappaB motive was sufficient to mediate transcriptional inhibition under TNF tolerance conditions in monocytic cells. Furthermore, in tolerant cells, TNF-induced NF-kappaB p65 phosphorylation was markedly decreased, which was accompanied by the formation of C/EBPbeta-p65 complexes. Remarkably, in C/EBPbeta(-/-) cells incubated under the conditions of TNF tolerance, neither impairment of transcription nor inhibition of p65 phosphorylation was observed. Finally, we showed that C/EBPbeta overexpression reduced p65-mediated transactivation and that association of C/EBPbeta with p65 specifically prevented p65 phosphorylation. Our data demonstrate that C/EBPbeta is an essential signaling component for inhibition of NF-kappaB-mediated transcription in TNF-tolerant cells and suggest that this is caused by blockade of p65 phosphorylation. These results define a new molecular mechanism responsible for TNF tolerance in monocytic cells that may contribute to the unresponsiveness seen in patients with sepsis.

Screening for Toxoplasma gondii-regulated transcriptional responses in lipopolysaccharide-activated macrophages

Toxoplasma gondii-infected macrophages are blocked in production of the proinflammatory cytokines interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-alpha) upon activation with lipopolysaccharide (LPS). Here, we used pathway-focused cDNA arrays to identify additional T. gondii-regulated transcriptional responses. Parasite infection decreased 57 (inclusive of IL-12 and TNF-alpha) and increased expression of 7 of 77 LPS-activated cytokine and cytokine-related genes. Interestingly, we found that the LPS-induced transcriptional response of the anti-inflammatory cytokine IL-10 was synergistically increased by T. gondii, results that we validated by conventional reverse transcription-PCR and enzyme-linked immunosorbent assay. Importantly, although the parasite exerted disparate effects in LPS-signaling leading to TNF-alpha versus IL-10 production, both responses required functional Toll-like receptor 4. We suggest that these effects represent parasite defense mechanisms to avoid or delay induction of antimicrobial activity and/or T-cell-mediated immunity during Toxoplasma infection.

CCAAT/enhancer binding proteins and interferon signaling pathways

Interferons (IFNs) regulate a number of host responses, including innate and adaptive immunity against viruses, microbes, and neoplastic cells. These responses are dependent on the expression of IFN-stimulated genes (ISGs). Given the diversities in these responses and their kinetics, it is conceivable that a number of different factors are required for controlling them. Here, we describe one such pathway wherein transcription factor CAAAT/enhancer binding protein-beta (C/EBP-beta) is controlled via IFN-gamma-induced MAPK signaling pathways. At least two IFN-gamma-induced MAPK signals converge on to C/EBP-beta for inducing transcription. One of these, driven by extracellular signal-regulated kinases (ERKs), phosphorylates the C/EBP-beta protein in its regulatory domain. The second, driven by the mixed-lineage kinases (MLKs), induces a dephosphorylation leading to the recruitment of transcriptional coactivators.

Superoxide dismutase expression attenuates cigarette smoke- or elastase-generated emphysema in mice

RATIONALE

Oxidants are believed to play a major role in the development of emphysema.

OBJECTIVES

This study aimed to determine if the expression of human copper-zinc superoxide dismutase (CuZnSOD) within the lungs of mice protects against the development of emphysema.

METHODS

Transgenic CuZnSOD and littermate mice were exposed to cigarette smoke (6 h/d, 5 d/wk, for 1 yr) and compared with nonexposed mice. A second group was treated with intratracheal elastase to induce emphysema.

MEASUREMENTS

Lung inflammation was measured by cell counts and myeloperoxidase levels. Oxidative damage was assessed by immunofluorescence for 3-nitrotyrosine and 8-hydroxydeoxyguanosine and lipid peroxidation levels. The development of emphysema was determined by measuring the mean linear intercept (Lm).

MAIN RESULTS

Smoke exposure caused a fourfold increase in neutrophilic inflammation and doubled lung myeloperoxidase activity. This inflammatory response did not occur in the smoke-exposed CuZnSOD mice. Similarly, CuZnSOD expression prevented the 58% increase in lung lipid peroxidation products that occurred after smoke exposure. Most important, CuZnSOD prevented the onset of emphysema in both the smoke-induced model (Lm, 68 exposed control vs. 58 exposed transgenic; p < 0.04) and elastase-generated model (Lm, 80 exposed control vs. 63 exposed transgenic; p < 0.03). These results demonstrate for the first time that antioxidants can prevent smoke-induced inflammation and can counteract the proteolytic cascade that leads to emphysema formation in two separate animal models of the disease.

CONCLUSIONS

These findings indicate that strategies aimed at enhancing or supplementing lung antioxidants could be effective for the prevention and treatment of this disease.

IFN-gamma-stimulated transcriptional activation by IFN-gamma-activated transcriptional element-binding factor 1 occurs via an inducible interaction with CAAAT/enhancer-binding protein-beta

IFN-gamma-activated transcriptional element (GATE)-binding factor 1 (GBF1) was identified as a transactivator that induces gene expression through GATE, a novel IFN-inducible element. Although it can induce gene expression, it is an extremely weak DNA-binding protein on its own. GATE also binds another transcription factor, C/EBP-beta. Therefore, we explored whether GBF1 physically interacts with C/EBP-beta to induce IFN-gamma-regulated transcription. In response to IFN-gamma, C/EBP-beta undergoes phosphorylation at a critical ERK1/2 phosphorylation motif. Mutational inactivation of this motif and/or interference with the ERK1/2 activation prevented the IFN-gamma-induced interactions between GBF1 and C/EBP-beta. A 37-aa long peptide derived from the GBF1 protein can associate with C/EBP-beta in an IFN-inducible manner. These results identify a converging point for two transactivators that exert their effects through a single response element. Together, our studies identify a novel regulatory mechanism that controls IFN-induced transcription.

Inhibition of inflammatory cytokine secretion from mouse microglia cells by DHMEQ, an NF-κB inhibitor

Activation of microglia has been implicated in various neurodegenerative disorders, and thus the inhibition of microglial activity may suppress these disorders. Earlier we designed and synthesized an NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ) that showed anti-inflammatory and anti-tumor activities in vivo. In the present research, we studied whether DHMEQ would inhibit the activation of mouse microglial cells. DHMEQ inhibited lipopolysaccharide (LPS)-induced activation of NF-kappaB in an electrophoresis mobility shift assay. It also inhibited LPS-induced secretions of TNF-alpha and IL-6 from mouse microglial cell line 6-1 cells.

A role for mixed lineage kinases in regulating transcription factor CCAAT/enhancer-binding protein-{beta}-dependent gene expression in response to interferon-{gamma}

Transcription factor CCAAT/enhancer-binding protein-beta (C/EBP-beta) regulates a variety of cellular functions in response to exogenous stimuli. We have reported earlier that C/EBP-beta induces gene transcription through a novel interferon (IFN)-response element called gamma-IFN-activated transcriptional element. We show here that IFN-gamma-induced, C/EBP-beta/gamma-IFN-activated transcriptional element-dependent gene expression is regulated by mixed lineage kinases (MLKs), members of the mitogen-activated protein kinase kinase kinase family. MLK3 appears to activate C/EBP-beta in response to IFN-gamma by a mechanism involving decreased phosphorylation of a specific phosphoacceptor residue, Ser(64), within the transactivation domain. Decreased phosphorylation of Ser(64) was independent of IFN-gamma-stimulated ERK1/2 activation and did not require the ERK phosphorylation site Thr(189) located in regulatory domain 2 of C/EBP-beta. Together these studies provide the first evidence that MLK3 is involved in IFN-gamma signaling and identify a novel mechanism of transcriptional activation by IFN-gamma.

Inhibition of p90 Ribosomal S6 Kinase-mediated CCAAT/Enhancer-binding Protein β Activation and Cyclooxygenase-2 Expression by Salicylate

We have previously shown that salicylate at a pharmacological concentration suppresses CCAAT/enhancer-binding protein beta (C/EBPbeta) binding, thereby reducing cyclooxygenase-2 (COX-2) and inducible nitric-oxide synthase expression (Saunders, M. A., Sansores-Garcia, L., Gilroy, D. W., and Wu, K. K. (2001) J. Biol. Chem. 276, 18897-18904; Cieslik, K., Zhu, Y., and Wu, K. K. (2002) J. Biol. Chem. 277, 49304-49310). We postulated that salicylate targets a kinase that phosphorylates and activates C/EBPbeta. Here we report the identification of p90 ribosomal S6 kinase (RSK) as a target of salicylate. Salicylate inhibited RSK in vivo and blocked the activity of RSK2 purified from cells stimulated by phorbol 12-myristate 13-acetate (PMA). Mutation of the RSK-phosphorylation site (T266A) of C/EBPbeta abrogated PMA-stimulated C/EBPbeta binding activity. RSK activation was required for PMA-induced COX-2 transcriptional activation. Salicylate also inhibited Ras and extracellular signal-regulated kinase (ERK) activation induced by PMA. We conclude that salicylate inhibits C/EBPbeta-mediated COX-2 transcriptional activation by blocking RSK activity and Ras signaling pathway.

Cytokine gene expression and activation of NF-kappa B in aniline-induced splenic toxicity

Exposure to aniline results in selective toxicity to the spleen, leading to a variety of sarcomas on chronic exposure in rats, and fibrosis appears to be an important initiating preneoplastic lesion of the spleen. However, the molecular mechanism(s) by which aniline leads to fibrogenic response is not well understood. Previously, we have shown that aniline exposure leads to iron overload and induction of oxidative stress in the spleen. We hypothesized that aniline-induced oxidative stress in the spleen causes transcriptional up-regulation of fibrogenic cytokines via activation of redox-sensitive transcription factor, nuclear factor-kappa B (NF-kappa B). To test this hypothesis, male SD rats were treated with 0.5 mmol/kg/day aniline hydrochloride via drinking water for 30 days. Cytokine mRNAs were measured by real-time quantitative PCR, while cytokine release was determined in the supernatants of the cultured splenocytes using specific ELISAs. IL-1alpha, IL-6, and TNF-alpha mRNA levels showed 6.9-, 2.9-, and 2.6-fold increases, respectively, in the spleens of aniline-treated rats in comparison to the controls. The increases in mRNA levels were associated with enhanced secretion of these cytokines in the splenocyte culture supernatants. NF-kappa B p65 level in the nuclear extracts of cultured splenocytes of aniline-treated rats showed a 2-fold increase in comparison to the controls as quantitated by NF-kappa B p65-specific ELISA. The binding activity of NF-kappa B, determined by electrophoretic mobility shift assay (EMSA), also showed an increase in NF-kappa B binding in the nuclear extracts of the splenocytes from aniline-treated rats. The specificity of NF-kappa B binding was further confirmed by supershift assays. The results indicate that aniline exposure causes enhanced expression of IL-1alpha, IL-6, and TNF-alpha, both at mRNA and protein levels, suggesting their role in splenic fibrosis. Also, the increased NF-kappa B binding activity suggests that up-regulation of these cytokines in the spleen is a redox-dependent mechanism.

C/EBPβ and Its Binding Element Are Required for NFκB-induced COX2 Expression Following Hypertonic Stress

NFkappaB plays a critical role mediating COX2 expression in renal medullary interstitial cells (RMICs). The trans-activating ability of NFkappaB can be modified by another nuclear factor C/EBPbeta that can physically bind to NFkappaB and regulate its activity. Because the COX2 promoter also contains a C/EBPbeta site adjacent to the NFkappaB site, the present study examined whether these two transcription factors cooperate to induce COX2 expression following hypertonic stress. Hypertonicity markedly induced COX2 expression in cultured medullary interstitial cells by immunoblot analysis. The tonicity-induced COX2 expression was suppressed by mutant IkappaB (IkappaBm) that blocks NFkappaB activation, demonstrating that tonicity-induced COX2 expression depends on NFkappaB activation. However, mutation of the NFkappaB site in the COX2 promoter failed to abolish tonicity-induced COX2 reporter activity. IkappaB kinase-1 (IKK1) significantly induced COX2-luciferase activity by 2.3-fold (n = 10, p < 0.01); mutation of the NFkappaB site also failed to abolish IKK1-stimulated COX2 reporter activity (86 +/- 3.1% of wild type, p > 0.05, n = 4). Interestingly, mutation of the C/EBPbeta site of the COX2 gene significantly reduced both IKK1 and hypertonicity-induced COX2 reporter activity (p < 0.01). To further examine the potential role of C/EBPbeta in tonicity-induced COX2 expression, a dominant negative C/EBPbeta-p20 was transduced into RMICs. C/EBPbeta-p20 markedly suppressed hypertonic (550 mOsm) induction of COX2 (immunoblot) to a similar extent as IkappaBm. No additional suppression was observed when both NFkappaB and C/EBPbeta were simultaneously blocked by IkappaBm and C/EBPbeta-p20. Interestingly, IKK-induced COX2 expression was not only blocked by IkappaBm, but also completely abolished by C/EBPbeta-p20. Further studies demonstrated physical association of C/EBPbeta to NFkappaB p65 by coimmunoprecipitation. Importantly, this interaction between C/EBPbeta and NFkappaB was greatly enhanced following hypertonic stress. These studies indicate C/EBPbeta is required for the transcriptional activation of COX2 by NFkappaB, suggesting a dominant role for the C/EBPbeta pathway in regulating induction of RMIC COX2 by hypertonicity.

Transcriptional Control of COX-2 via C/EBPbeta

Cyclooxygenase-2 (COX-2) is a highly inducible enzyme exerting diverse actions on cell functions, including proliferation, migration, and DNA damage. Enhanced COX-2 expression may be protective, but excessive expression may be harmful, causing inflammation, atheromatous plaque instability, and intimal hyperplasia. COX-2 transcriptional activation by proinflammatory mediators has been extensively characterized. In this review, the role of C/EBP in regulating COX-2 transcription is highlighted. Recent advances in control of COX-2 transcription by aspirin and salicylate and by a cell cycle-dependent endogenous mechanism are described. The recent progress sheds light on the pathophysiological mechanisms of COX-2 and new transcription-based strategy for controlling COX-2 overexpression and COX-2-mediated cardiovascular diseases.

Increased in vivo transcription of an IL-8 haplotype associated with respiratory syncytial virus disease-susceptibility

Interleukin-8 (IL-8) has been implicated in the pathogenesis of RSV-induced bronchiolitis. Previously, we have described an association between bronchiolitis disease severity and a specific IL-8 haplotype comprising six single-nucleotide polymorphisms (SNPs) (-251A/+396G/+781T/+1238delA/+1633T/+2767T, haplotype 2). Here we investigated the functional basis for this association by measuring haplotype-specific transcription in vivo in human primary cells. We found a significant increase in transcript level derived from the IL-8 haplotype 2 relative to the mirror haplotype 1 (-251T/+396T/+781C/+1238insA/+1633C/+2767A) in respiratory epithelial cells but not in lymphocytes. A promoter polymorphism, -251A, present on the high producer haplotype, had no significant affect on the allele-specific level of transcription when analyzed in reporter gene experiments in human respiratory epithelial A549 cells. We proceeded to systematically screen for allele-specific protein-DNA binding in this functional haplotype, which revealed significant differential binding at the +781T/C polymorphism. C/EBP beta was identified as being part of a transcription factor binding complex that preferentially bound in the presence of the +781 T allele. These results suggest that the mechanism for disease susceptibility to RSV-induced bronchiolitis may occur through a haplotype-specific increase in IL-8 transcription, which may be mediated by functional polymorphisms within that haplotype.

Glutathione, stress responses, and redox signaling in lung inflammation

Changes in the ratio of intracellular reduced and disulfide forms of glutathione (GSH/GSSG) can affect signaling pathways that participate in various physiological responses from cell proliferation to gene expression and apoptosis. It is also now known that many proteins have a highly conserved cysteine (sulfhydryl) sequence in their active/regulatory sites, which are primary targets of oxidative modifications and thus important components of redox signaling. However, the mechanism by which oxidants and GSH/protein-cysteine-thiols actually participate in redox signaling still remains to be elucidated. Initial studies involving the role of cysteine in various proteins have revealed that cysteine-SH may mediate redox signaling via reversible or irreversible oxidative modification to Cys-sulfenate or Cys-sulfinate and Cys-sulfonate species, respectively. Oxidative stress possibly via the modification of cysteine residues activates multiple stress kinase pathways and transcription factors nuclear factor-kappaB and activator protein-1, which differentially regulate the genes for proinflammatory cytokines as well as the protective antioxidant genes. Understanding the redox signaling mechanisms for differential gene regulation may allow for the development of novel pharmacological approaches that preferentially up-regulate key antioxidants genes, which, in turn, reduce or resolve inflammation and injury. This forum article features the current knowledge on the role of GSH in redox signaling, particularly the regulation of transcription factors and downstream signaling in lung inflammation.

Syk tyrosine kinase participates in beta1-integrin signaling and inflammatory responses in airway epithelial cells

The protein tyrosine kinase Syk is critically involved in immunoreceptor signaling in hematopoietic cells. Recent studies demonstrate Syk expression in nonhematopoietic cells, including fibroblasts, endothelial cells, hepatocytes, and breast epithelium. However, the role of Syk in these cells is uncertain. We hypothesized that Syk is expressed in respiratory epithelial cells (EC) and that it functions as a signaling molecule involved in inflammatory responses in the epithelium. With the use of immunohistochemistry, Western blot, PCR, and laser scanning confocal microscopy, Syk was detected in human, rat, and mouse bronchial epithelium in situ and in cultured human bronchial EC in primary cells and the cell lines HS-24 and BEAS-2B. Syk-dependent signaling pathways in EC were initiated by engagement of beta1-integrin receptors. Stimulation of beta1-integrin receptors by fibronectin or antibody cross-linking caused redistribution of Syk from a cytoplasmic to plasma membrane localization. In stimulated cells, Syk and beta1-integrin colocalized. In addition, following beta1-integrin receptor engagement, tyrosine phosphorylation of Syk was observed. Expression of the intercellular adhesion molecule-1 (ICAM-1) and production of IL-6, both important molecules in lung inflammation, was downregulated in EC treated with Syk small interfering RNA or Syk inhibitor piceatannol. We propose that Syk is involved in signaling pathways induced by integrin engagement in airway EC. Syk-mediated signaling regulates IL-6 and ICAM-1 expression and may be important in the pathophysiology of lung inflammation.

Pirfenidone inhibits the induction of iNOS stimulated by interleukin-1beta at a step of NF-kappaB DNA binding in hepatocytes

BACKGROUND/AIMS

Pirfenidone has antiinflammatory effects in animals with endotoxemia. We reported that pirfenidone inhibits the enhancement of inflammatory cytokines and inducible nitric oxide synthase (iNOS) in liver of endotoxin-treated rats, leading to the prevention of hepatic injury. However, the mechanisms involved in suppression of these gene inductions are obscure. Studies were performed to investigate whether pirfenidone directly influences iNOS induction in hepatocytes.

METHODS

Cultured hepatocytes were treated with interleukin-1beta (IL-1beta) in the presence and absence of pirfenidone, and iNOS induction and its signal including NF-kappaB were analyzed.

RESULTS

Pirfenidone inhibited the induction of iNOS mRNA and protein, resulting in the decrease of nitric oxide production. Gel shift assay demonstrated that pirfenidone inhibited the activation of NF-kappaB. Consistent with this observation, transfection experiments revealed that pirfenidone decreased transcriptional activation of iNOS gene promoter. In contrast, pirfenidone had no effect on the degradation of IkappaB, and could not prevent nuclear translocation of p50/p65. Finally, pirfenidone inhibited the activation of Akt and up-regulation of IL-1 receptor stimulated by IL-1beta.

CONCLUSIONS

Results indicate that pirfenidone inhibits the induction of iNOS gene expression at a step of NF-kappaB DNA binding, but not its nuclear translocation, partly through the inhibition of IL-1 receptor induction in hepatocytes.

Nuclear factor kappa B activation in human cord blood mononuclear cells

The immunologic signals participating in immune responses early in life have not been completely elucidated. Regarding the characterization of neonatal cells, little is known concerning the activity of transcription factor nuclear factor kappa B (NF-kappaB), which regulates inflammatory genes and cytokine production. The aim of this study was to characterize NF-kappaB activation in cord blood mononuclear cells (CBMC). We analyzed the potential association of NF-kappaB activity with lymphocyte proliferation and influences on cytokine secretion in the early immune system. To determine the contribution of a disease whereby inheritance may impact neonatal immunity, we assessed the influence of maternal allergic disease on NF-kappaB regulation and cytokine secretion. CBMC from healthy newborns were isolated and stimulated with mitogen (n = 28). Nuclear extracts were analyzed by electrophoretic mobility shift assay, cytokine secretion by ELISA. FISH analysis excluded relevant maternal contamination of CBMC. All samples showed a positive lymphoproliferative response, and NF-kappaB activity was both increased and decreased after mitogen stimulation. Increased NF-kappaB activation was significantly associated with decreased TNF-alpha secretion (median 6.1 versus 50.3 pg/mL) in unstimulated CBMC. Mitogen stimulation resulted in increased NF-kappaB activity with a trend to increased IL-13 production. Maternal allergic disease was associated with higher TNF-alpha (median 982 versus 173 pg/mL) and IL-13 secretion (median 1328 versus 1120 pg/mL) after mitogen stimulation. Together, NF-kappaB activity is differentially activated in cord blood and associated with a distinct cytokine pattern. Whether differential NF-kappaB activity in cord blood is related to the subsequent development of immune diseases requires further investigation.

Up-regulation of IL-1 receptor through PI3K/Akt is essential for the induction of iNOS gene expression in hepatocytes

BACKGROUND/AIMS

Nuclear translocation and DNA binding of NF-kappaB is essential, as interleukin-1beta (IL-1beta) stimulates the induction of inducible nitric oxide synthase (iNOS) gene expression in hepatocytes. However, recent evidence indicates that the activation of NF-kappaB is not sufficient to induce the NF-kappaB-dependent transcription, and the existence of a second signaling is postulated.

METHODS

Primary cultured hepatocytes were treated with IL-1beta, and the expression of iNOS and type 1 IL-1 receptor (IL-1R1) was analyzed in the presence of antisense of IL-1R1, phosphatidylinositol 3-kinase (PI3K) inhibitor, proteasome inhibitor and hypoxia. Moreover, the activities of Akt and NF-kappaB were recorded and the cotransfection was carried out.

RESULTS

Antisense experiment revealed that IL-1R1 was required for iNOS transcription. IL-1beta markedly stimulated the induction of IL-1R1, which preceded the induction of iNOS. The IL-1R1 induction was found to be PI3K/Akt-dependent but NF-kappaB-independent. The up-regulation of IL-1R1 was associated with the second activation of Akt, which accelerated the phosphorylation of NF-kappaB p65 subunit. Cotransfection experiments revealed that Akt increased the transcriptional activity of iNOS gene promoter.

CONCLUSIONS

These results indicate that the up-regulation of IL-1R1 in concert with the activation of NF-kappaB is required for the transcriptional activation of iNOS gene.

Cloning of bovine MAIL and its mRNA expression in white blood cells of Holstein cows

Molecule possessing ankyrin-repeats induced by lipopolysaccharide (MAIL) is known as an IkappaB protein induced after administration of bacterial lipopolysaccharide (LPS) to mice. In the present study, we cloned bovine MAIL cDNA and examined its mRNA expression in white blood cells isolated from Holstein cows. Bovine MAIL had more than 80% amino acid identities with murine and human MAILs, highly conserved ankyrin-repeat motifs and PEST-like sequences. Bovine MAIL mRNA was undetectable in isolated peripheral white blood cells, but rapidly induced (<1h) after stimulation by LPS and lipid A in vitro in a dose-dependent manner. The lipid A-induced MAIL mRNA expression was found in polymorphonuclear cells, monocytes/macrophages and total lymphocytes, but not in T-lymphocytes. MAIL mRNA was also induced in vivo in peripheral blood leukocytes of cows after intramammary injection of Escherichia coli derived from coliform mastitis. Thus, bovine MAIL, as rodent MAILs, is induced by inflammatory stimuli in specific immune cells in vitro and in vivo, suggesting a role in inflammatory responses to bacterial infection in cattle.

Alternate interferon signaling pathways

More than a half a century ago, interferons (IFN) were identified as antiviral cytokines. Since that discovery, IFN have been in the forefront of basic and clinical cytokine research. The pleiotropic nature of these cytokines continues to engage a large number of investigators to define their actions further. IFN paved the way for discovery of Janus tyrosine kinase (JAK)-signal transducing activators of transcription (STAT) pathways. A number of important tumor suppressive pathways are controlled by IFN. Several infectious pathogens counteract IFN-induced signaling pathways. Recent studies indicate that IFN activate several new protein kinases, including the MAP kinase family, and downstream transcription factors. This review not only details the established IFN signaling paradigms but also provides insights into emerging alternate signaling pathways and mechanisms of pathogen-induced signaling interference.

Thymulin evokes IL-6-C/EBPbeta regenerative repair and TNF-alpha silencing during endotoxin exposure in fetal lung explants

Chorioamnionitis is associated with increased risks of perinatal respiratory failure; however, components of the inflammatory acute-phase response are known to actively promote lung maturation. To manipulate this relationship, we examined the effect of the thymic immunomodulator thymulin on fetal lung mesenchyme-epithelial differentiation during exposure to Escherichia coli lipopolysaccharide (LPS). Gestation day 14 fetal rat lung explants were cultured for 96 h at fetal (23 mmHg) or ambient (142 mmHg) Po(2). Airway surface complexity (ASC, perimeter/ radical area(2)) was greater at fetal vs. ambient Po(2); however, exposure to 0.1-50 microg/ml LPS significantly raised ASC at 2 microg/ml in ambient Po(2) explants. LPS (50 microg/ml) depressed ASC in both conditions to untreated ambient Po(2) control values without changes in necrosis or apoptosis. To manipulate LPS-evoked TNF-alpha and IL-6 release, we exposed explants and A549 cells to combinations of 50 microg/ml LPS, 10 microM ZnCl(2), and 0.1-1,000 ng/ml thymulin at either Po(2). Thymulin+Zn(2+) suppressed and potentiated LPS-evoked TNF-alpha and IL-6 release, yielding an IC(50(TNF-alpha)) of 0.5 +/- 0.01 ng/ml and EC(50(IL-6)) of 1.4 +/- 0.3 ng/ml in A549 cells. This was accompanied by activation of the p38 MAPKMAPKAP-K2 pathway with sustained expression of TNF-alpha and IL-6 transcripts at ambient Po(2). LPS+thymulin+Zn(2+)-treated explants showed proliferation of CCAAT-enhancer binding protein-beta (C/EBPbeta) and fibroblast growth factor-9 immunoreactive mesenchyme, which was abolished by IL-6 antisense oligonucleotides. The posttranscriptional suppression of immunogenic TNF-alpha synthesis coupled with raised IL-6 and C/EBPbeta-dependent mesenchyme proliferation suggests a role for bioactive thymulin in regulating regenerative repair in the fetal lung.

Constitutive NF-kappaB DNA-binding activity in AML is frequently mediated by a Ras/PI3-K/PKB-dependent pathway

In the present study, we aimed to elucidate the mechanism responsible for constitutive NF-kappaB DNA-binding activity in AML cells. Intervening in aberrant signaling pathway provides a rational approach for in vivo targeting of AML cells. Constitutive NF-kappaB DNA-binding activity was observed in 16 of 22 (73%) investigated AML cases and was, in general, associated with resistance to spontaneous apoptosis. Indeed, inhibition of NF-kappaB activity by the NF-kappaB inhibitor SN-50 peptide resulted in enhanced chemotherapy-induced apoptosis. In the majority of cases, constitutive NF-kappaB activity was mediated by a Ras/PI3 kinase (PI3-K)/protein kinase B (PKB)-mediated pathway. The PI3-K inhibitor Ly294002 and the Ras inhibitor L-744832 both inhibited PKB phosphorylation and NF-kappaB DNA-binding activity. The constitutive activation of Ras GTP-ase was caused by mutations in the gene encoding for N-Ras in 29% of the cases. The constitutive NF-kappaB activity could so far not be ascribed to the autocrine production of growth factors or to mutations in the Flt3 receptor, since anti-GM-CSF, -IL-1, -IL6, -TNFalpha or the tyrosine kinase inhibitor AG1296 did not affect the NF-kappaB DNA-binding activity. The present study demonstrates that Ras activation is an important pathway for triggering the NF-kappaB pathway in AML cells.

Microarray analysis supports a role for ccaat/enhancer-binding protein-beta in brain injury

CCAAT/enhancer-binding protein-beta (C/EBPbeta) is a transcription factor that plays an important role in regulating cell growth and differentiation. This protein plays a central role in lymphocyte and adipocyte differentiation and hepatic regeneration and in the control of inflammation and immunity in the liver and in cells of the myelomonocytic lineage. Our previous studies suggested that this protein could also have important functions in the brain. Therefore, we were interested in the identification of downstream targets of this transcription factor in cells of neural origin. We performed cDNA microarray analysis and found that a total of 48 genes were up-regulated in C/EBPbeta-overexpressing neuronal cells. Of the genes that displayed significant changes in expression, several were involved in inflammatory processes and brain injury. Northern blot analysis confirmed the up-regulation of ornithine decarboxylase, 24p3/LCN2, GRO1/KC, spermidine/spermine N(1)-acetyltransferase, xanthine dehydrogenase, histidine decarboxylase, decorin, and TM4SF1/L6. Using promoter-luciferase reporter transfection assays, we showed the ornithine decarboxylase and 24p3 genes to be biological downstream targets of C/EBPbeta in neuroblastoma cells. Moreover, the levels of C/EBPbeta protein were significantly induced after neuronal injury, which was accompanied by increased levels of cyclooxygenase-2 enzyme. This strongly supports the concept that C/EBPbeta may play an important role in brain injury.

Effects of interleukin-10 on titanium particle-induced macrophage transcription factor activation and cytokine expressionin vitro

This study tests the hypothesis that transcription factor activation by exposure of macrophages to titanium particles can be modulated by the addition of the antiinflammatory cytokine, interleukin 10 (IL-10). The experiments were carried out with primary human monocyte/macrophages that were treated in the presence or absence of IL-10 with and without exposure to titanium particles. The time course for experiments varied from 1 h-5 h for analysis of nuclear protein and up to 48 h for analysis of cytokine release. Transcription factor translocation to the nucleus was analyzed using electrophoretic gel shift assays and cytokine release was quantified by enzyme-linked immunosorbent assay. Addition of titanium particles increased release of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1 beta (IL-1 beta). In addition, titantium particle induced translocation of the transcription factors, NF-kappa B and NF-IL6, in the nucleus within 1 h. Treatment of macrophages with IL-10 prior to exposure to titanium particles decreased translocation of NF-IL6 but did not significantly alter nuclear levels of NF-kappa B. In addition, pretreatment of the cells with IL-10 decreased particle-induced cytokine release. These data show that antiinflammatory cytokines may provide a mechanism by which particle-induced inflammatory response may be modulated in vivo.

Transcriptional regulation of limulus factor C: repression of an NFkappaB motif modulates its responsiveness to bacterial lipopolysaccharide

Serine proteases play fundamental roles in invertebrate development, hemostasis, and innate immunity. This is exemplified by the limulus Factor C, which is a serine protease that binds a pathogen-associated molecule, lipopolysaccharide (LPS) to trigger a blood coagulation cascade. As a central molecule in the limulus innate immunity and hemostasis, Factor C gene expression has been detected in two major immune defense tissues, the amebocytes and hepatopancreas. Infection of the limulus with live Gram-negative bacteria induces a 2-3-fold increase in mRNA transcripts in both tissues. However, in vitro studies in Drosophila cell lines using Factor C promoter-reporter chimera DNA constructs, and site-directed mutagenesis of the promoter demonstrated that a proximal kappaB binding site, aided by an adjacent dorsal-like binding motif responds dramatically to LPS and dorsal transcription factor overexpression. Electrophoretic mobility shift assay further confirmed a strong interaction of the limulus kappaB motif with Rel proteins. However, deletion constructs of the Factor C promoter harboring different numbers of dorsal-like binding sites upstream of the kappaB motif as well as the electrophoretic mobility shift assay of these motifs with Rel proteins strongly suggest that the up-regulation of Factor C gene expression is attenuated during microbial challenge. The repression of the dramatic activation of this pathogen-responsive gene by LPS is probably effected via competition between the dorsal-like motifs over the proximal LPS-responsive kappaB unit, or through inhibition from the upstream repressive element(s), which accounts for the gene expression pattern observed in vivo. Our findings demonstrate that blood coagulation and innate immune response are integrated at the transcriptional level in this ancient organism, and that this LPS-responsive serine protease is controlled by an evolutionarily conserved NFkappaB pathway.

High glucose enhances interleukin-6-induced vascular endothelial growth factor 165 expression via activation of gp130-mediated p44/42 MAPK-CCAAT/enhancer binding protein signaling in gingival fibroblasts

Diabetic patients are susceptible to severe inflammatory periodontitis manifesting as swollen gingiva with bleeding, but the underlying mechanism is not well understood. Our purpose was to determine the effect of a high glucose (HG) condition on the interleukin-6/soluble interleukin-6 receptor (IL-6/sIL-6R)-induced activation of signaling and vascular endothelial growth factor (VEGF) expression in human gingival fibroblasts (HGFs). In this study, HGFs were cultured for at least two passages under a normal glucose (NG; 5.5 mM) condition or high glucose (25 mM) condition. Importantly, the HG condition significantly induced expression of gp130 mRNA in HGFs compared with levels in control cells. Consistent with the expression of its mRNA, the HG condition also increased the expression of gp130 protein, and phosphorylation of the tyrosine residue by gp130 was enhanced significantly by IL-6/sIL-6R stimulation. Furthermore, the HG condition enhanced the IL-6/sIL-6R-induced phosphorylation of p44/42 MAPK and led to subsequent activation of CCAAT/enhancer binding protein in nuclei. In contrast, there was no significant difference in phosphorylation of JNK between the HG and NG condition. Interestingly, HGFs increased IL-6/sIL-6R-induced VEGF165 mRNA expression and VEGF165 secretion under the HG condition compared with levels under the NG condition. In contrast, the induction of VEGF165 secretion was partially inhibited by PD98059 (selective p44/42 MAPK inhibitor) under the HG condition. In addition, the VEGF165 secretion was completely inhibited by the combination of PD98059 and SP600125 (JNK inhibitor). Our findings suggest that the HG condition indirectly increases VEGF expression via activation of gp130-mediated p44/42 MAPK-CCAAT/enhancer binding protein signaling in HGFs. Thus, elevated VEGF secretion in HGFs under the HG condition may play a role in the development of the severe periodontitis observed in diabetic patients.