IFN-gamma activates cAMP/PKA/CREB signaling pathway in murine peritoneal macrophages

Zinc finger protein 189 promotes the differentiation of lamina propria T helper 17.1 cells in dextran sulfate sodium-induced colitis

The factors regulating the heterogeneity of interleukin-17A (IL-17A)-expressing CD4⁺ T cells in inflammatory bowel diseases remain unclear. In the current study, we characterised the expression and function of zinc finger protein 189 (ZFP189) in a murine colitis model. Mice were given dextran sulphate sodium to induce acute colitis. Flow cytometry was applied to recognise and enrich Th17 and Th17.1 cells based on the expression of IL-17A, interferon-γ (IFN-γ), C-X-C motif chemokine receptor 3 (CXCR3), and C-C motif chemokine receptor 4 (CCR4). The expression of ZFP189 in Th17 and Th17.1 cells was determined by Immunoblotting. Lentivirus-mediated ZFP189 knockdown was conducted to evaluate the effect of ZFP189 on the differentiation of Th17 and Th17.1 cells. The adoptive transfer was performed to analyse the pathogenicity of Th17.1 cells in vivo. We found that ZFP189 was mildly up-regulated in IL-17A-expressing CD4⁺ T cells in colonic lamina propria. Lamina propria Th17.1 cells expressed higher ZFP189 than Th17 cells. In vitro ZFP189 knockdown in CD4⁺ T cells did not impact Th17 cell differentiation but suppressed Th17.1 cell differentiation, as evidenced by lower T-box expressed in T cells (T-bet) and IFN-γ. When adoptively transferred into mice, ZFP189-deficient Th17.1 cells produced fewer IFN-γ, tumour necrosis factor-alpha (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than ZFP189-expressing Th17.1 cells. Moreover, ZFP189-deficient Th17.1 cells induced less severe colitis than ZFP189-expressing Th17.1 cells, as evidenced by less body weight loss, a lower disease activity index, and a lower colon histological score. In summary, ZFP189 acts as a positive regulator of the differentiation and pathogenicity of lamina propria Th17.1 cells in colitis.

High throughput screening identifies auranofin and pentamidine as potent compounds that lower IFN-γ-induced Nitric Oxide and inflammatory responses in mice: DSS-induced colitis and Salmonella Typhimurium-induced sepsis

Interferon-gamma (IFN-γ) is a type II interferon produced primarily by T cells and natural killer cells. IFN-γ induces the expression of inducible nitric oxide synthase (NOS2) to catalyze Nitric Oxide (NO) production in various immune and non-immune cells. Excessive IFN-γ-activated NO production is implicated in several inflammatory diseases, including peritonitis and inflammatory bowel diseases. In this study, we screened the LOPAC®1280 library in vitro on the H6 mouse hepatoma cell line to identify novel non-steroidal small molecule inhibitors of IFN-γ-induced NO production. Compounds with the highest inhibitory activity were validated, which led to identifying the lead compounds: pentamidine, azithromycin, rolipram, and auranofin. Auranofin was the most potent compound determined based on IC50 and goodness of fit analyses. Mechanistic investigations revealed that majority of the lead compounds suppress the IFN-γ-induced transcription of Nos2 without negatively affecting NO-independent processes, such as the IFN-γ-induced transcription of Irf1, Socs1 and MHC class 1 surface expression. However, all four compounds lower IFN-γ-induced reactive oxygen species amounts. In addition, auranofin significantly reduced IFN-γ-mediated NO and IL6 production in resident as well as thioglycolate-elicited peritoneal macrophages (PMs). Finally, in vivo testing of the lead compounds in the pre-clinical DSS-induced ulcerative colitis mice model revealed pentamidine and auranofin to be the most potent and protective lead compounds. Also, pentamidine and auranofin greatly increase the survival of mice in another inflammatory model: Salmonella Typhimurium-induced sepsis. Overall, this study identifies novel anti-inflammatory compounds targeting IFN-γ-induced NO-dependent processes to alleviate two distinct inflammatory models of disease.

The microbiota-gut-brain interaction in regulating host metabolic adaptation to cold in male Brandt's voles (Lasiopodomys brandtii)

Gut microbiota play a critical role in orchestrating metabolic homeostasis of the host. However, the crosstalk between host and microbial symbionts in small mammals are rarely illustrated. We used male Brandt's voles (Lasiopodomys brandtii) to test the hypothesis that gut microbiota and host neurotransmitters, such as norepinephrine (NE), interact to regulate energetics and thermogenesis during cold acclimation. We found that increases in food intake and thermogenesis were associated with increased monoamine neurotransmitters, ghrelin, short-chain fatty acids, and altered cecal microbiota during cold acclimation. Further, our pair-fed study showed that cold temperature can alter the cecal microbiota independently of overfeeding. Using cecal microbiota transplant along with β3-adrenoceptor antagonism and PKA inhibition, we confirmed that transplant of cold-acclimated microbiota increased thermogenesis through activation of cAMP-PKA-pCREB signaling. In addition, NE manipulation induced a long-term alteration in gut microbiota structure. These data demonstrate that gut microbiota-NE crosstalk via cAMP signaling regulates energetics and thermogenesis during cold acclimation in male Brandt's voles.

Interferon-Gamma-Mediated Osteoimmunology

Osteoimmunology is the interdiscipline that focuses on the relationship between the skeletal and immune systems. They are interconnected by shared signal pathways and cytokines. Interferon-gamma (IFN-γ) plays important roles in immune responses and bone metabolism. IFN-γ enhances macrophage activation and antigen presentation. It regulates antiviral and antibacterial immunity as well as signal transduction. IFN-γ can promote osteoblast differentiation and inhibit bone marrow adipocyte formation. IFN-γ plays dual role in osteoclasts depending on its stage. Furthermore, IFN-γ is an important pathogenetic factor in some immune-mediated bone diseases including rheumatoid arthritis, postmenopausal osteoporosis, and acquired immunodeficiency syndrome. This review will discuss the contradictory findings of IFN-γ in osteoimmunology and its clinical application potential.

Neuropeptide FF increases M2 activation and self-renewal of adipose tissue macrophages

The quantity and activation state of adipose tissue macrophages (ATMs) impact the development of obesity-induced metabolic diseases. Appetite-controlling hormones play key roles in obesity; however, our understanding of their effects on ATMs is limited. Here, we have shown that human and mouse ATMs express NPFFR2, a receptor for the appetite-reducing neuropeptide FF (NPFF), and that NPFFR2 expression is upregulated by IL-4, an M2-polarizing cytokine. Plasma levels of NPFF decreased in obese patients and high-fat diet-fed mice and increased following caloric restriction. NPFF promoted M2 activation and increased the proliferation of murine and human ATMs. Both M2 activation and increased ATM proliferation were abolished in NPFFR2-deficient ATMs. Mechanistically, the effects of NPFF involved the suppression of E3 ubiquitin ligase RNF128 expression, resulting in enhanced stability of phosphorylated STAT6 and increased transcription of the M2 macrophage-associated genes IL-4 receptor α (Il4ra), arginase 1 (Arg1), IL-10 (Il10), and alkylglycerol monooxygenase (Agmo). NPFF induced ATM proliferation concomitantly with the increase in N-Myc downstream-regulated gene 2 (Ndrg2) expression and suppressed the transcription of Ifi200 cell-cycle inhibitor family members and MAF bZIP transcription factor B (Mafb), a negative regulator of macrophage proliferation. NPFF thus plays an important role in supporting healthy adipose tissue via the maintenance of metabolically beneficial ATMs.

Individual and interactive sex-specific effects of acute restraint and systemic IFN-γ treatment on neurochemistry

Compelling evidence supports the involvement of the pro-inflammatory cytokines, IL-6, IFN-α and TNF-α in depression and related stress-associated pathologies. A role has also been suggested for the Th1-type cytokine, IFN-γ, with most mechanistic accounts focusing on the cytokine's capacity to induce indoleamine 2,3-dioxygenase (IDO), leading to diminished tryptophan and the generation of kynurenine metabolites. Beyond these IDO-dependent routes, there is surprisingly little evidence directly linking IFN-γ to alterations of brain regional monoamine activity and HPA axis functioning. Our specific aims in the present study were twofold: 1) assess the behavioural, plasma corticosterone and brain regional monoamine effects of acute systemic IFN-γ, with or without short duration restraint stress (15 min), and 2) determine the sex-specific nature of these effects. As predicted, IFN-γ stimulated monoaminergic activity within a number of stressor-sensitive limbic brain regions, most notably the paraventricular nucleus of the hypothalamus, central amygdala and prefrontal cortex. While several of these effects were sex-specific, there was little in the way of synergism between the cytokine and stressor treatments. Nonetheless, IFN-γ did synergistically interact with acute restraint stress to increase plasma corticosterone concentrations, and this effect was most pronounced in the male mice. These data are among the first to show that systemically administered IFN-γ can alone or in conjunction with psychologically relevant stressor, modify brain regional monoamine activity and the plasma corticosterone response.

Interferon γ-Induced Nuclear Interleukin-33 Potentiates the Release of Esophageal Epithelial Derived Cytokines

Background

Esophageal epithelial cells are an initiating cell type in esophageal inflammation, playing an essential role in the pathogenesis of gastroesophageal reflux disease (GERD). A new tissue-derived cytokine, interleukin-33 (IL-33), has been shown to be upregulated in esophageal epithelial cell nuclei in GERD, taking part in mucosal inflammation. Here, inflammatory cytokines secreted by esophageal epithelial cells, and their regulation by IL-33, were investigated.

Methods

In an in vitro stratified squamous epithelial model, IL-33 expression was examined using quantitative RT-PCR, western blot, ELISA, and immunofluorescence. Epithelial cell secreted inflammatory cytokines were examined using multiplex flow immunoassay. IL-33 was knocked down with small interfering RNA (siRNA) in normal human esophageal epithelial cells (HEECs). Pharmacological inhibitors and signal transducers and activators of transcription 1 (STAT1) siRNA were used to explore the signaling pathways.

Results

Interferon (IFN)γ treatment upregulated nuclear IL-33 in HEECs. Furthermore, HEECs can produce various inflammatory cytokines, such as IL-6, IL-8, monocyte chemoattractant protein 1 (MCP-1), regulated on activation normal T-cell expressed and presumably secreted (RANTES), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in response to IFNγ. Nuclear, but not exogenous IL-33, amplified IFN induction of these cytokines. P38 mitogen-activated protein kinase (MAPK) and janus protein tyrosine kinases (JAK)/STAT1 were the common signaling pathways of IFNγ-mediated induction of IL-33 and other cytokines.

Conclusions

Esophageal epithelial cells can actively participate in GERD pathogenesis through the production of various cytokines, and epithelial-derived IL-33 might play a central role in the production of these cytokines.

Flow-induced protein kinase A-CREB pathway acts via BMP signaling to promote HSC emergence

Kim et al. identify a novel shear stress–induced pathway involving protein kinase A, CREB, and bone morphogenetic protein that regulates hematopoietic stem cell generation in the embryonic aorta.

Fluid shear stress promotes the emergence of hematopoietic stem cells (HSCs) in the aorta–gonad–mesonephros (AGM) of the developing mouse embryo. We determined that the AGM is enriched for expression of targets of protein kinase A (PKA)–cAMP response element-binding protein (CREB), a pathway activated by fluid shear stress. By analyzing CREB genomic occupancy from chromatin-immunoprecipitation sequencing (ChIP-seq) data, we identified the bone morphogenetic protein (BMP) pathway as a potential regulator of CREB. By chemical modulation of the PKA–CREB and BMP pathways in isolated AGM VE-cadherin⁺ cells from mid-gestation embryos, we demonstrate that PKA–CREB regulates hematopoietic engraftment and clonogenicity of hematopoietic progenitors, and is dependent on secreted BMP ligands through the type I BMP receptor. Finally, we observed blunting of this signaling axis using Ncx1-null embryos, which lack a heartbeat and intravascular flow. Collectively, we have identified a novel PKA–CREB–BMP signaling pathway downstream of shear stress that regulates HSC emergence in the AGM via the endothelial-to-hematopoietic transition.

Epithelial-derived nuclear IL-33 aggravates inflammation in the pathogenesis of reflux esophagitis

BACKGROUND

IL-33 is a new tissue-derived cytokine constitutively expressed in epithelial cells and plays a role in sensing damage caused by inflammatory diseases. The function of IL-33 in the esophageal mucosa has not been previously described. Accordingly, we examined the expression of IL-33 and its role in the pathogenesis of reflux esophagitis (RE).

METHODS

IL-33 in the esophageal mucosa of RE patients and in an in vitro stratified normal esophageal squamous epithelial model was examined at the messenger RNA and protein levels. The correlation of the level of IL-33 and IL-8 or IL-6 was examined. Cell layers were stimulated with bile acids and cytokines. IL-33 was knocked down by small interfering RNA (siRNA). Pharmacological inhibitors and signal transducer and activator of transcription 1 (STAT1) siRNA were used.

RESULTS

IL-33 was significantly upregulated in RE patients, and was located in the nuclei of basal and suprabasal layers. Upregulated IL-33 messenger RNA expression was correlated with IL-8 and IL-6 expression. In vitro, IL-33 was upregulated in the nuclei of basal and suprabasal layers by interferon-γ (IFNγ), and the upregulation was aggravated by the combination of deoxycholic acid (DCA) and IFNγ. IL-33 knockdown dampened IFNγ- and DCA-induced IL-8 and IL-6 production. IFNγ-induced IL-33 was inhibited by a Janus kinase inhibitor, a p38 mitogen-activated protein kinase inhibitor, and STAT1 siRNA.

CONCLUSIONS

Nuclear IL-33 is upregulated in erosive mucosa of RE patients and is correlated with IL-8 and IL-6 levels. The normal esophageal epithelial model enables us to show for the first time that epithelial-cell-derived nuclear but not exogenous IL-33 is located upstream of the production of inflammatory cytokines and can aggravate the inflammation.

Hepatitis C virus suppresses C9 complement synthesis and impairs membrane attack complex function

Hepatitis C virus (HCV) proteins inhibit complement component expression, which may attenuate immunity against infection. In this study, we examined whether HCV regulates the membrane attack complex (MAC) via complement component C9. MAC is composed of C5b to C9 (C5b-9) and mediates cell lysis of invaded pathogens. Liver biopsy specimens from chronically HCV-infected patients exhibited a lower level of C9 mRNA expression than liver biopsy specimens from unrelated disease or healthy control human liver RNA. Hepatocytes infected with cell culture-grown HCV or expressing HCV core protein also displayed significant repression of C9 mRNA and protein levels. Promoter analysis suggested that the T cell factor-4 (TCF-4E) transcription factor is responsible for HCV core-mediated C9 promoter regulation. Sera from chronically HCV-infected patients displayed a lower level of C5b-9 and a reduced antimicrobial effect on model organisms compared to unrelated patient sera or sera from healthy volunteers. Together, these results for C9 regulation by HCV core protein coupled with functional impairment of the membrane attack complex underscore HCV-mediated attenuation of immune mechanisms.

Immune sculpting of norepinephrine on MHC-I, B7-1, IDO and B7-H1 expression and regulation of proliferation and invasion in pancreatic carcinoma cells

BACKGROUND

The sympathetic neurotransmitter Norepinephrine (NE) contributes to tumorigenesis and cancer progression. This study aims to investigate the role of NE in modulating the immune phenotype and allowing pancreatic carcinoma (PC) cells to escape the immune response.

METHODS

Varied concentrations of NE and interferon-gamma (IFN-γ) were administrated to MIA PaCa-2 and BxPC-3 cell lines for 48 hours. Proliferation and invasion were then investigated using an MTT assay and a membrane invasion culture system respectively. MHC-I, B7-1, IDO and B7-H1 expression were measured using real-time quantitative RT-PCR, western blotting and immunocytochemistry. The synergistic and time-dependent effects of NE/IFN-γ were also investigated. Adrenergic antagonists were used to identify the relevant target receptor of NE.

RESULTS

The results showed that NE had dose-dependent and time-dependent effects on cell biological processes as well as on the expression of MHC-I, B7-1, IDO and B7-H1. These effects occurred mainly via the β(2)-adrenergic receptor. Long-term NE treatment was able to antagonize some of the effects of IFN-γ (after 2 weeks of treatment), but NE and IFN-γ had significant synergistic stimulatory effects on IDO and B7-H1 expression. The residual effects on biological activities lasted for 2 weeks, while the immunophenotypic changes decreased at early time points after treatment.

CONCLUSIONS

NE plays important roles in modulating PC cell biological activities and affecting MHC-I, B7-1, IDO and B7-H1 expression in vitro, mainly via the β2-adrenergic receptor (β2-AR) in a time- and dose-dependent fashion. Only at extended treatment durations could NE affect PC cell progression and immune evasion.

Oxidative stress induced interleukin-32 mRNA expression in human bronchial epithelial cells

Background

Chronic obstructive pulmonary disease (COPD) is characterized by airflow obstruction and persistent inflammation in the airways and lung parenchyma. Oxidative stress contributes to the pathogenesis of COPD. Interleukin (IL)-32 expression has been reported to increase in the lung tissue of patients with COPD. Here, we show that IFNγ upregulated IL-32 expression and that oxidative stress augmented IFNγ-induced-IL-32 expression in airway epithelial cells. We further investigated transcriptional regulation responsible for IFNγ induced IL-32 expression in human airway epithelial cells.

Methods

Human bronchial epithelial (HBE) cells were stimulated with H₂O₂ and IFNγ, and IL-32 expression was evaluated. The cell viability was confirmed by MTT assay. The intracellular signaling pathways regulating IL-32 expression were investigated by examining the regulatory effects of MAPK inhibitors and JAK inhibitor after treatment with H₂O₂ and IFNγ, and by using a ChIP assay to identify transcription factors (i.e. c-Jun, CREB) binding to the IL-32 promoter. Promoter activity assays were conducted after mutations were introduced into binding sites of c-Jun and CREB in the IL-32 promoter. IL-32 expression was also examined in HBE cells in which the expression of either c-Jun or CREB was knocked out by siRNA of indicated transcription factors.

Results

There were no significant differences of cell viability among groups. After stimulation with H₂O₂ or IFNγ for 48 hours, IL-32 expression in HBE cells was increased by IFNγ and synergistically upregulated by the addition of H₂O₂. The H₂O₂ augmented IFNγ induced IL-32 mRNA expression was suppressed by a JNK inhibitor, but not by MEK inhibitor, p38 inhibitor, and JAK inhibitor I. Significant binding of c-Jun and CREB to the IL-32 promoter was observed in the IFNγ + H₂O₂ stimulated HBE cells. Introducing mutations into the c-Jun/CREB binding sites in the IL-32 promoter prominently suppressed its transcriptional activity. Further, knocking down CREB expression by siRNA resulted in significant suppression of IL-32 induction by IFNγ and H₂O₂ in HBE cells.

Conclusion

IL-32 expression in airway epithelium may be augmented by inflammation and oxidative stress, which may occur in COPD acute exacerbation. c-Jun and CREB are key transcriptional factors in IFNγ and H₂O₂ induced IL-32 expression.

Aldose reductase inhibition prevents lipopolysaccharide-induced glucose uptake and glucose transporter 3 expression in RAW264.7 macrophages

Macrophages which play a central role in the injury, infection and sepsis, use glucose as their primary source of metabolic energy. Increased glucose uptake in inflammatory cells is well known to be one of the responsible processes that cause inflammatory response and cytotoxicity. We have shown recently that the inhibition of aldose reductase (AR) prevents bacterial endotoxin, lipopolysaccharide (LPS)-induced cytotoxicity and inflammatory response in macrophages. However, it is not known how AR inhibition prevents LPS-induced inflammation. Here in, we examined the effect of AR inhibition on LPS-induced glucose uptake and the expression of glucose transporter 3 (GLUT-3) in RAW264.7 murine macrophages. Stimulation of macrophages with LPS-increased glucose uptake as measured by using C(14) labeled methyl-d-glucose and inhibition of AR prevented it. Similarly, ablation of AR by using AR-siRNA also prevented the LPS-induced glucose uptake in macrophages. Further, AR inhibition also prevented the LPS-induced up-regulation of GLUT-3 expression, cyclic adenosine monophosphate (cAMP) accumulation and protein kinase A (PKA) activation in RAW264.7 cells. Moreover, LPS-induced down-regulation of cAMP response element modulator (CREM), phosphorylation of cAMP response element-binding protein (CREB) and DNA-binding of CREB were also prevented by AR inhibition. Further, inhibition of AR or PKA also prevented the LPS-induced levels of GLUT-3 protein as well as mRNA in macrophages. These results indicate that AR mediates LPS-induced glucose uptake and expression of glucose transporter-3 via cAMP/PKA/CREB pathway and thus represents a novel mechanism by which AR regulates LPS-induced inflammation.

Increased phosphorylation of cyclic AMP response element-binding protein in the spinal cord of Lewis rats with experimental autoimmune encephalomyelitis

To investigate whether the phosphorylation of cyclic AMP response element-binding protein (CREB) is implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), the change in the level of CREB phosphorylation was analyzed in the spinal cord of Lewis rats with EAE. Western blot analysis showed that the phosphorylation of CREB in the spinal cord of rats increased significantly at the peak stage of EAE compared with the controls (p<0.05) and declined significantly in the recovery stage (p<0.05). Immunohistochemistry showed that the phosphorylated form of CREB (p-CREB) was constitutively immunostained in few astrocytes and dorsal horn neurons in the spinal cord of normal rats. In the EAE-affected spinal cord, p-CREB was mainly found in ED1-positive macrophages at the peak stage of EAE, and the number of p-CREB-immunopositive astrocytes was markedly increased in the spinal cord with EAE compared with the controls. Moreover, p-CREB immunoreactivity of sensory neurons, which are closely associated with neuropathic pain, was significantly increased in the dorsal horns at the peak stage of EAE. Based on these results, we suggest that the increased phosphorylation of CREB in EAE lesions was mainly attributable to the infiltration of inflammatory cells and astrogliosis, possibly activating gene transcription, and that its increase in the sensory neurons in the dorsal horns is involved in the generation of neuropathic pain in the rat EAE model.

Variable p-CREB expression depicts different asthma phenotypes

BACKGROUND

Chromatin modification may play a role in inflammatory gene regulation in asthma. Cyclic adenosine mono-phosphate response element-binding protein (CREB), with the specific co-activator, the CREB-binding protein (CBP), contributes to the acetylation of chromatin and to the transcription of pro-inflammatory genes.

OBJECTIVES

To evaluate the expression of CBP and of phospho-CREB (p-CREB) in bronchial biopsies and in peripheral blood mononuclear cells (PBMC) of controls (C), untreated (UA), inhaled steroid treated (ICS) and steroid-dependent asthmatic (SDA) patients.

METHODS

We used immunohistochemistry in bronchial biopsies and western blot analysis and immunocytochemistry in PBMC.

RESULTS

Cyclic adenosine mono-phosphate response element-binding protein expression, in the epithelium was similar in all groups, while p-CREB expression was increased in UA and in SDA in comparison with ICS and C subjects (C vs UA P = 0.002, C vs SDA P = 0.007), (ICS vs SDA P = 0.005), (ICS vs UA P = 0.001). Interestingly, also in the submucosa, p-CREB was increased in UA and SDA in comparison with ICS and C subjects (C vs UA P = 0.0004) (C vs SDA P < 0.0001) (ICS vs UA P = 0.002) (ICS vs SDA P < 0.0001) and positively correlated with leukocyte infiltration within the bronchi (CD45RB+ cells). Similar results were obtained with PBMC isolated from the same patient groups. Incubation of PBMC in vitro, with fluticasone propionate, decreased the p-CREB expression induced by cytokine activation (interferon-gamma, tumor necrosis factor-alpha).

CONCLUSIONS

This study demonstrates that the expression of p-CREB is related, in asthma, to the persistent inflammation according to the disease severity. p-CREB expression can be modulated by glucocorticoids in responsive patients.

Adenylate cyclase/cAMP pathway downmodulation counteracts apoptosis induced by IFN-alpha in human epidermoid cancer cells

We have reported previously that interferon-alpha (IFN-alpha) induces apoptosis that is counteracted by an epidermal growth factor (EGF) --> Ras --> extracellular signal-regulated kinase (ERK)-dependent survival response in human epidermoid cancer KB cells. We have studied the effects of the cytokine on the cAMP-dependent pathway in these cells. A decrease in the intracellular cAMP levels was recorded in KB cells treated with IFN-alpha, whereas forskolin induced an increase in the production of cAMP that was reduced in the presence of IFN-alpha, suggesting a reduction in the activity of adenylate cyclase (AC) induced by IFN-alpha. These effects were paralleled by significant change in the expression of some AC catalytic subunit(s) and by reduction in the activity of protein kinase A (PKA). 8-Br-cAMP completely antagonized the reduction of PKA activity induced by IFN-alpha, whereas PKA inhibitor KT5720 enhanced the reduction of the enzyme activity induced by IFN-alpha. We have found that IFN-alpha induced a decrease in cAMP response element binding protein (CREB) phosphorylation without changes in its total expression. The concomitant treatment with IFN-alpha and 8-Br-cAMP potentiated and KT5720 counteracted apoptosis induced by IFN-alpha alone. In conclusion, these data suggest that the decrease in AC/cAMP pathway activity is a survival response to the apoptosis induced by IFN-alpha. Therefore, this pathway could represent a target to enhance the antitumor activity of IFN-alpha.

Heat-shock response down-regulates interleukin-18 expression in murine peritoneal macrophages

BACKGROUND INFORMATION

The heat-shock response is a self-defence mechanism that protects cells and organisms from a wide range of harmful stresses. Recent studies revealed that it involved the regulation of cytokine expression. Interleukin-18 (IL-18) is an important cytokine in mediating immune response.

RESULTS

We studied interferon-gamma (IFN-gamma)-induced IL-18 expression in heat-shock-treated murine peritoneal macrophages. Our results showed that the heat-shock response significantly inhibited the expression of IFN-gamma-induced pro-inflammatory cytokine IL-18. Interferon consensus sequence binding protein (ICSBP) is a transcription factor that binds to the promoter of IL-18 and regulates the transcription of IL-18. Further research on the down-regulation mechanism showed that the DNA-binding activity of ICSBP was greatly reduced by the heat shock response.

CONCLUSIONS

These results suggest that the inhibitory effect of heat-shock response on IL-18 production in IFN-gamma-stimulated macrophages is related to the suppression of the binding activity of ICSBP.

CD46-utilizing adenoviruses inhibit C/EBPbeta-dependent expression of proinflammatory cytokines

The majority of adenovirus serotypes utilize the coxsackievirus-adenovirus receptor (CAR) for virus-host cell attachment, but subgroup B and subgroup D (adenovirus type 37 [Ad37]) viruses recognize CD46. CD46 is a ubiquitously expressed receptor that serves as a cofactor for the inactivation of the complement components C3b and C4b, and it also serves as a receptor for diverse microbial pathogens. A reported consequence of CD46 engagement is a reduced capability of human immune cells to express interleukin-12 (IL-12), a cytokine involved in both the innate and adaptive immune responses. Studies were thus undertaken to determine whether CD46-utilizing Ads alter the expression of proinflammatory cytokines. Subgroup B (Ad16 and -35) and Ad37, but not Ad2 or -5, significantly reduced IL-12 production by human peripheral blood mononuclear cells stimulated with gamma interferon (IFN-gamma) and lipopolysaccharide. IL-12 mRNA (p35 and p40 subunits) levels as well as other cytokine mRNA levels (IL-1alpha and -beta, IL-1Ra, and IL-6) were decreased upon interaction with CD46-utilizing Ads. Analysis of transcription factor activity required for cytokine expression indicated that CD46-utilizing Ads preferentially inhibited IFN-gamma-induced C/EBPbeta protein expression, consequently reducing its ability to form DNA complexes. Interference with IFN-gamma signaling events by CD46-utilizing Ads, but not CAR-utilizing Ads, reveals a potentially critical difference in the host immune response against distinct Ad vectors, a situation that has implications for gene delivery and vaccine development.