Janus kinase 2 is involved in lipopolysaccharide-induced activation of macrophages

Cyclovirobuxinum D suppresses lipopolysaccharide-induced inflammatory responses in murine macrophages in vitro by blocking JAK-STAT signaling pathway

AIM

Cyclovirobuxinum D (CVB-D), an alkaloid isolated from the Chinese medicinal plant Buxus microphylla, has been found to be effective to treat cardiac insufficiency, arrhythmias and coronary heart disease. In the present study, we investigated the effects of CVB-D on the inflammatory responses in lipopolysaccharide (LPS)-stimulated murine macrophages in vitro and the underlying mechanisms.

METHODS

Murine macrophage cell line RAW264.7 cells were incubated in the presence of LPS (0.1 μg/mL) for 24 h. The cell viability was measured using MTT assay. The release of NO and cytokines were detected using the Griess test and ELISA, respectively. The mRNA and protein levels were determined using RT-PCR and Western blot, respectively. Reporter gene assays were used to analyze the transcriptional activity of NF-κB.

RESULTS

Treatment of RAW264.7 cells with CVB-D (25-300 μmol/L) did not affect the cell viability. Pretreatment with CVB-D (50, 100 and 200 μmol/L) concentration-dependently decreased NO release and iNOS expression in LPS-treated RAW264.7 cells (its IC50 value in inhibition of NO production was 144 μmol/L). CVB-D also concentration-dependently inhibited the secretion and mRNA expression of IL-1β and IL-6 in LPS-treated RAW264.7 cells. Furthermore, CVB-D remarkably inhibited the phosphorylation of STAT1 and STAT3, as well as JAK2 in LPS-treated RAW264.7 cells, but did not affect the activation of NF-κB and MAPKs pathways. Pretreatment with the JAK2 specific inhibitor AG490 (30 μmol/L) produced similar effects on NO release and iNOS expression in LPS-treated RAW264.7 cells.

CONCLUSION

CVB-D exerts anti-inflammatory effects in LPS-stimulated murine macrophages in vitro at least in part by blocking the JAK-STAT signaling pathway. The anti-inflammatory actions of CVB-D may contribute to its cardioprotection.

Role of a Janus kinase 2-dependent signaling pathway in platelet activation

INTRODUCTION

Janus kinases (JAKs) are intracellular non-receptor tyrosine kinases that transduce cytokine-mediated signals through a pathway mediated by JAK and the signal transducer and activator of transcription (STAT) proteins. The JAK-STAT pathway is involved in immune response, inflammation, and tumorigenesis. Platelets are anuclear blood cells that play a central role in hemostasis.

METHODS

The aggregometry, immunoblotting, and platelet functional analysis used in this study.

RESULTS

We found that the JAK2 inhibitor AG490 (25 and 50μM) attenuated collagen-induced platelet aggregation and calcium mobilization in a concentration-dependent manner. In the presence of AG490, the phosphorylation of PLCγ2, protein kinase C (PKC), Akt or JNK in collagen-activated aggregation of human platelets was also inhibited. In addition, we found that various inhibitors, such as the PLCγ2 inhibitor U73122, the PKC inhibitor Ro318220, the phospoinositide 3-kinase inhibitor LY294002, the p38 mitogen-activated protein kinase inhibitor SB203580, the ERK inhibitor PD98059, and the JNK inhibitor SP600125, had no effects on collagen-induced JAK2 activity. However, U73122, Ro318220 and SP600125 significantly diminished collagen-induced STAT3 phosphorylation. These findings suggest that PLCγ2-PKC and JNK are involved in JAK2-STAT3 signaling in collagen-activated platelets.

CONCLUSION

Our results demonstrate that the JAK2-STAT3 pathway is involved in collagen-induced platelet activation through the activation of JAK2-JNK/PKC-STAT3 signaling. The inhibition of JAK2 may represent a potential therapeutic strategy for the preventing or treating thromboembolic disorders.

Skeletal muscle nitric oxide (NO) synthases and NO-signaling in "diabesity"--what about the relevance of exercise training interventions?

Type 2 diabetes mellitus associated with obesity, or "diabesity", coincides with an altered nitric oxide (NO) metabolism in skeletal muscle. Three isoforms of nitric oxide synthase (NOS) exist in human skeletal muscle tissue. Both neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) are constitutively expressed under physiological conditions, producing low levels of NO, while the inducible nitric oxide synthase (iNOS) is strongly up-regulated only under pathophysiological conditions, excessively increasing NO concentrations. Due to chronic inflammation, overweight/obese type 2 diabetic patients exhibit up-regulated protein contents of iNOS and concomitant elevated amounts of NO in skeletal muscle. Low muscular NO levels are important for attaining an adequate cellular redox state--thereby maintaining metabolic integrity--while high NO levels are believed to destroy cellular components and to disturb metabolic processes, e.g., through strongly augmented posttranslational protein S-nitrosylation. Physical training with submaximal intensity has been shown to attenuate inflammatory profiles and iNOS protein contents in the long term. The present review summarizes signaling pathways which induce iNOS up-regulation under pathophysiological conditions and describes molecular mechanisms by which high NO concentrations are likely to contribute to triggering skeletal muscle insulin resistance and to reducing mitochondrial capacity during the development and progression of type 2 diabetes. Based on this information, it discusses the beneficial effects of regular physical exercise on the altered NO metabolism in the skeletal muscle of overweight/obese type 2 diabetic subjects, thus unearthing new perspectives on training strategies for this particular patient group.

Is there a role for treating inflammation in moyamoya disease?: a review of histopathology, genetics, and signaling cascades

Moyamoya disease is a slowly progressing steno-occlusive condition affecting the cerebrovasculature. Affecting the terminal internal carotid arteries (ICA) and there branches, bilaterally, a resulting in a fine vascular network in the base of the brain to allow for compensation of the stenosed vessels. While there is obvious evidence of the involvement of inflammatory proteins in the condition, this has historically not been acknowledged as a causal factor. Here we describe the fundamental histopathology, genetics, and signaling cascades involved in moyamoya and debate whether these factors can be linked as causal factor for the condition or whether they are simply a secondary result of the ischemia described in the condition. A particular focus has been placed on the multitude of signaling cascades linked to the condition as these are viewed as having the greatest therapeutic potential. As such we hope to draw some novel insight into potential diagnostic and therapeutic inflammatory targets in the condition.

The role of JAK-3 in regulating TLR-mediated inflammatory cytokine production in innate immune cells

The role of JAK-3 in TLR-mediated innate immune responses is poorly understood, although the suppressive function of JAK3 inhibition in adaptive immune response has been well studied. In this study, we found that JAK3 inhibition enhanced TLR-mediated immune responses by differentially regulating pro- and anti- inflammatory cytokine production in innate immune cells. Specifically, JAK3 inhibition by pharmacological inhibitors or specific small interfering RNA or JAK3 gene knockout resulted in an increase in TLR-mediated production of proinflammatory cytokines while concurrently decreasing the production of IL-10. Inhibition of JAK3 suppressed phosphorylation of PI3K downstream effectors including Akt, mammalian target of rapamycin complex 1, glycogen synthase kinase 3β (GSK3β), and CREB. Constitutive activation of Akt or inhibition of GSK3β abrogated the capability of JAK3 inhibition to enhance proinflammatory cytokines and suppress IL-10 production. In contrast, inhibition of PI3K enhanced this regulatory ability of JAK3 in LPS-stimulated monocytes. At the transcriptional level, JAK3 knockout lead to the increased phosphorylation of STATs that could be attenuated by neutralization of de novo inflammatory cytokines. JAK3 inhibition exhibited a GSK3 activity-dependent ability to enhance phosphorylation levels and DNA binding of NF-κB p65. Moreover, JAK3 inhibition correlated with an increased CD4(+) T cell response. Additionally, higher neutrophil infiltration, IL-17 expression, and intestinal epithelium erosion were observed in JAK3 knockout mice. These findings demonstrate the negative regulatory function of JAK3 and elucidate the signaling pathway by which JAK3 differentially regulates TLR-mediated inflammatory cytokine production in innate immune cells.

Baicalein reduces lipopolysaccharide-induced inflammation via suppressing JAK/STATs activation and ROS production

OBJECTIVE

To investigate the precise molecular mechanisms by which baicalein exerts beneficial biochemical activities in RAW264.7 macrophages treated with LPS.

MATERIALS AND METHODS

RAW264.7 cells were cultured in the absence or presence of baicalein together with or without LPS. iNOS and COX-2 expression were measured by western blot and RT-PCR analyses. TNF-α, IL-1β, and IL-6 were determined by using double-antibody sandwich ELISA. Phosphorylations of JAK1 and JAK2, and of STAT1 and STAT3 were detected by western blotting. Nuclear translocation of STAT1 and STAT3 was visualized by confocal microscopy. ROS production was detected by ROS assay.

RESULTS

Baicalein significantly reduced the phosphorylation of STAT1 and STAT3 and the phosphorylation of JAK1 and JAK2, but without affecting MAPKs phosphorylation in LPS-stimulated RAW264.7 cells. Baicalein suppressed the nuclear translocation of STAT1 and STAT3 and inhibited production of iNOS upon LPS-stimulation, resulting in the inhibition of releases of NO and pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α, in a dose-dependent manner. In addition, we found that baicalein reduced the LPS-induced accumulation of ROS, confirming that baicalein serves as an antioxidant.

CONCLUSIONS

Our results suggested that suppressing JAK/STATs activation and interfering with ROS production might contribute to the anti-inflammatory action of baicalein in macrophages.

Toll-like receptor 4-linked Janus kinase 2 signaling contributes to internalization of Brucella abortus by macrophages

Brucella abortus is an intracellular pathogen that uses a crafty strategy to invade and proliferate within host cells, but the distinct signaling pathways associated with phagocytic mechanisms of B. abortus remain unclear. The present study was performed to test the hypothesis that Toll-like receptor 4 (TLR4)-linked signaling interacting with Janus kinase 2 (JAK2) plays an essential role in B. abortus phagocytosis by macrophages. The effects of TLR4-JAK2 signaling on B. abortus phagocytosis in murine macrophage RAW 264.7 cells were observed through an infection assay and confocal microscopy. We determined that the uptake of B. abortus was negatively affected by the dysfunction of TLR4 and JAK2. F-actin polymerization detected by flow cytometry and F-actin assay was amplified for B. abortus entry, whereas that event was attenuated by the disruption of TLR4 and JAK2. Importantly, JAK2 phosphorylation and actin skeleton reorganization were suppressed immediately after B. abortus infection in bone marrow-derived macrophages (BMDMs) from TLR4(-/-) mice, showing the cooperation of JAK2 with TLR4. Furthermore, small GTPase Cdc42 participated in the intermediate pathway of TLR4-JAK2 signaling on B. abortus phagocytosis. Consequently, TLR4-associated JAK2 activation in the early cellular signaling events plays a pivotal role in B. abortus-induced phagocytic processes in macrophages, implying the pathogenic significance of JAK2-mediated entry. Here, we elucidate that this specific phagocytic mechanism of B. abortus might provide achievable strategies for inhibiting B. abortus invasion.

Myeloid depletion of SOCS3 enhances LPS-induced acute lung injury through CCAAT/enhancer binding protein δ pathway

Although uncontrolled inflammatory response plays a central role in the pathogenesis of acute lung injury (ALI), the precise molecular mechanisms underlying the development of this disorder remain poorly understood. SOCS3 is an important negative regulator of IL-6-type cytokine signaling. SOCS3 is induced in lung during LPS-induced lung injury, suggesting that generation of SOCS3 may represent a regulatory product during ALI. In the current study, we created mice lacking SOCS3 expression in macrophages and neutrophils (LysM-cre SOCS3(fl/fl)). We evaluated the lung inflammatory response to LPS in both LysM-cre SOCS3(fl/fl) mice and the wild-type (WT) mice (SOCS3(fl/fl)). LysM-cre SOCS3(fl/fl) mice displayed significant increase of the lung permeability index (lung vascular leak of albumin), neutrophils, lung neutrophil accumulation (myeloperoxidase activity), and proinflammatory cytokines/chemokines in bronchial alveolar lavage fluids compared to WT mice. These phenotypes were consistent with morphological evaluation of lung, which showed enhanced inflammatory cell influx and intra-alveolar hemorrhage. We further identify the transcription factor, CCAAT/enhancer-binding protein (C/EBP) δ as a critical downstream target of SOCS3 in LPS-induced ALI. These results indicate that SOCS3 has a protective role in LPS-induced ALI by suppressing C/EBPδ activity in the lung. Elucidating the function of SOCS3 would represent prospective targets for a new generation of drugs needed to treat ALI.

A critical role for MAPK signalling pathways in the transcriptional regulation of toll like receptors

Toll-like Receptors (TLR) are phylogenetically conserved transmembrane proteins responsible for detection of pathogens and activation of immune responses in diverse animal species. The stimulation of TLR by pathogen-derived molecules leads to the production of pro-inflammatory mediators including cytokines and nitric oxide. Although TLR-induced events are critical for immune induction, uncontrolled inflammation can be life threatening and regulation is a critical feature of TLR biology. We used an avian macrophage cell line (HD11) to determine the relationship between TLR agonist-induced activation of inflammatory responses and the transcriptional regulation of TLR. Exposure of macrophages to specific TLR agonists induced upregulation of cytokine and nitric oxide pathways that were inhibited by blocking various components of the TLR signalling pathways. TLR activation also led to changes in the levels of mRNA encoding the TLR responsible for recognising the inducing agonist (cognate regulation) and cross-regulation of other TLR (non-cognate regulation). Interestingly, in most cases, regulation of TLR mRNA was independent of NFκB activity but dependent on one or more of the MAPK pathway components. Moreover, the relative importance of ERK, JNK and p38 was dependent upon both the stimulating agonist and the target TLR. These results provide a framework for understanding the complex pathways involved in transcriptional regulation of TLR, immune induction and inflammation. Manipulation of these pathways during vaccination or management of acute inflammatory disease may lead to improved clinical outcome or enhanced vaccine efficacy.

Advanced-glycation-end-product-induced formation of immunoproteasomes: involvement of RAGE and Jak2/STAT1

AGEs (advanced glycation-end products) accumulate during aging and several pathologies such as Alzheimer's disease and diabetes. These protein products are known to inhibit proteolytic pathways. Moreover, AGEs are known to be involved in the activation of immune responses. In the present study we demonstrate that AGEs induce the expression of immunoproteasomal subunits. To elucidate a molecular basis underlying the observed effects we were able to demonstrate an activation of the Jak2 (Janus kinase 2)/STAT1 (signal transducer and activator of transcription 1) pathway. Inhibition of Jak2 by AG-490 and STAT1 by specific siRNA (small interfering RNA) abolished AGE-induced expression of immunoproteasomal subunits. Furthermore, silencing of RAGE (receptor for AGEs) revealed that AGE-induced up-regulation of the immunoproteasome is mediated by a RAGE signalling process. Thus we have described for the first time that the signalling pathway of Jak2 and STAT1 activated by AGEs via RAGE is involved in the induction of the immunoproteasome.

Mollugin inhibits the inflammatory response in lipopolysaccharide-stimulated RAW264.7 macrophages by blocking the Janus kinase-signal transducers and activators of transcription signaling pathway

Mollugin, a kind of naphthohydroquinone, is a major constituent isolated from Rubia cordifolia L. and demonstrated to possess anti-inflammatory activity in recent reports. However, the effects and mechanism of action of mollugin in inflammation have not been fully defined. The present study was therefore designed to investigate whether mollugin suppresses the inflammatory response in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Mollugin attenuated the LPS-induced expression of nitric oxide (NO), inducible nitric oxide synthase (iNOS), interleukin (IL)-1β and IL-6 but augmented the expression of tumor necrosis factor (TNF)-α. Mollugin did not inhibit the degradation of inhibitory kappa B (IκB)-α or the nuclear translocation of p65 nuclear factor-kappa B (NF-κB) but rather enhanced the phosphorylation of p65 subunits evoked by LPS. Mollugin did not inhibit the phosphorylation of extracellular-signal-related kinase (ERK) 1/2, p38, and c-Jun N-terminal kinase (JNK) 1/2 either. Mollugin significantly reduced the LPS-mediated phosphorylation of Janus kinase (JAK) 2, signal transducers and activators of transcription (STAT) 1 and STAT3. Molecular docking analysis showed that mollugin binds to JAK2 in a manner similar to that of AG490, a specific JAK2 inhibitor. We conclude that mollugin may be a JAK2 inhibitor and inhibits LPS-induced inflammatory responses by blocking the activation of the JAK-STAT pathway.

STAT1 mediates oroxylin a inhibition of iNOS and pro-inflammatory cytokines expression in microglial BV-2 cells

Microglia-mediated inflammation is implicated in pathogenesis of neurodegenerative diseases. Oroxylin A, a flavonoid isolated from Scutellariae baicalensis, has been shown to ameliorate microglia activation-mediated neurodegeneration in vivo. The molecular mechanism underlying the inhibitory effects of oroxylin A on microglia activation, however, remains unknown. In the present study, effects of oroxylin A co-treated with lipopolysaccharide (LPS, 100 ng/ml) on LPS-induced activation of cultured microglial BV-2 cells were examined. Nitric oxide (NO) production was determined by Greiss method. Expression of inducible nitric oxide synthase (iNOS), interleukin (IL)-1β and IL-6 was assessed using real-time RT-PCR or Western blot analysis. Furthermore, activation of the nuclear factor κB (NFκB) and the signal transducer and activator of transcription 1 (STAT1) was examined by Western blot analysis and transcription factor DNA-binding activity assay. Our results indicated that oroxylin A (10-100 µM) in a concentration-dependent manner inhibited LPS-induced NO production via blocking iNOS expression at both mRNA and protein levels without affecting the degradation rate of iNOS mRNA. Moreover, oroxylin A significantly attenuated LPS-induced late expression (20 hours after LPS challenge) of IL-1β and IL-6. Furthermore, oroxylin A significantly suppressed LPS-induced JAK2-mediated STAT1 phosphorylation without affecting LPS-induced NFκB-p65 nuclear translocation or NFκB-p65 DNA-binding activity. This is consistent with the finding that AG490, a specific JAK2 inhibitor, significantly inhibited LPS-induced STAT1 phosphorylation with almost completely diminished iNOS expression. These results suggest that oroxylin A, via suppressing STAT1 phosphorylation, inhibits LPS-induced expression of pro-inflammatory genes in BV-2 microglial cells.

Inducible microRNA-223 down-regulation promotes TLR-triggered IL-6 and IL-1β production in macrophages by targeting STAT3

MicroRNAs are small non-coding RNA molecules that regulate gene expression by either translational inhibition or mRNA degradation. MicroRNAs play pivotal roles in the regulation of both innate and adaptive immune responses, including TLR-triggered inflammatory response. Here we reported that the expression of microRNA-223 (miR-223) was significantly decreased in murine macrophages during activation by lipopolysaccharide (LPS) or poly (I∶C) stimulation. The inducible miR-223 down-regulation resulted in the activation of signal transducer and activator of transcription 3 (STAT3), which is directly targeted by miR-223, thus promoting the production of pro-inflammatory cytokines IL-6 and IL-1β, but not TNF-α. Interestingly, IL-6 was found to be a main factor in inducing the decrease in miR-223 expression after LPS stimulation, which formed a positive feedback loop to regulate IL-6 and IL-1β. Herein, our findings provide a new explanation characterizing the molecular mechanism responsible for the regulation of IL-6 production after TLR-triggered macrophage activation.

Acanthopanax senticosus has a heme oxygenase-1 signaling-dependent effect on Porphyromonas gingivalis lipopolysaccharide-stimulated macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Acanthopanax senticosus (Rupr. & Maxim.) Harms (AS) has been used as a traditional medicine for the treatment of hypertension, rheumatism, ischemic heart disease, diabetes, and hepatitis in East Asia. This herb has been reported to possess anti-cancer, anti-diabetes, and anti-inflammatory properties.

AIM OF THE STUDY

To examine the anti-inflammatory activity of AS extract (ASE) and its mechanism of action in Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS)-stimulated macrophages.

MATERIALS AND METHODS

P. gingivalis LPS was used to induce an inflammatory response in the murine macrophage cell line RAW 264.7. Pro-inflammatory cytokines were measured by using an enzyme-linked immunosorbent assay. We used western blot assays and real-time quantitative polymerase chain reaction to detect protein and mRNA expression, respectively. Luciferase assays were performed to determine the transactivity of transcription factors. Nuclear translocation of nuclear factor (NF)-κB was assessed by confocal microscopy.

RESULTS

ASE significantly induced the expression and activity of heme oxygenase-1 (HO-1), which is known to produce an anti-inflammatory effect, in RAW 264.7 cells, through NF-E2-related factor 2 (Nrf-2), Janus kinase, and extracellular signal-regulated kinase activation. ASE also effectively suppressed the production of pro-inflammatory cytokines, tumor necrosis factor α, interleukin (IL)-1β, and IL-6, and decreased the nuclear translocation and transactivity of activator protein-1 (AP-1) and NF-κB by inhibiting the phosphorylation of IκB-α in P. gingivalis LPS-stimulated macrophage cells. Furthermore, ASE inhibits signal transducer and activator of transcription (STAT)1 phosphorylation while it activates STAT3 phosphorylation in P. gingivalis LPS-stimulated RAW 264.7 cells.

CONCLUSIONS

Our study suggests that ASE produces anti-inflammatory effects on P. gingivalis LPS-stimulated macrophages through a reduction in AP-1 and NF-κB activity, modulation of STAT1 and STAT3 phosphorylation, and upregulation of HO-1 expression through the activation of mitogen-activated protein kinase and Nrf-2 signaling pathways. Therefore, ASE could be a candidate for the prevention and treatment of periodontal diseases that involve excessive inflammation.

β-Glucan from Lentinus edodes inhibits nitric oxide and tumor necrosis factor-α production and phosphorylation of mitogen-activated protein kinases in lipopolysaccharide-stimulated murine RAW 264.7 macrophages

Lentinan (LNT), a β-glucan from the fruiting bodies of Lentinus edodes, is well known to have immunomodulatory activity. NO and TNF-α are associated with many inflammatory diseases. In this study, we investigated the effects of LNT extracted by sonication (LNT-S) on the NO and TNF-α production in LPS-stimulated murine RAW 264.7 macrophages. The results suggested that treatment with LNT-S not only resulted in the striking inhibition of TNF-α and NO production in LPS-activated macrophage RAW 264.7 cells, but also the protein expression of inducible NOS (iNOS) and the gene expression of iNOS mRNA and TNF-α mRNA. It is surprising that LNT-S enhanced LPS-induced NF-κB p65 nuclear translocation and NF-κB luciferase activity, but severely inhibited the phosphorylation of JNK1/2 and ERK1/2. The neutralizing antibodies of anti-Dectin-1 and anti-TLR2 hardly affected the inhibition of NO production. All of these results suggested that the suppression of LPS-induced NO and TNF-α production was at least partially attributable to the inhibition of JNK1/2 and ERK1/2 activation. This work discovered a promising molecule to control the diseases associated with overproduction of NO and TNF-α.

The JAK2-Akt-glycogen synthase kinase-3β signaling pathway is involved in toll-like receptor 2-induced monocyte chemoattractant protein-1 regulation

Monocyte chemoattractant protein-1 (MCP-1) is an essential cytokine for the migration of monocytes into vessels, and is also involved in the pathogenesis of atherosclerosis. In this study, we investigated the importance of janus kinase 2 (JAK2) and the function of the Akt and glycogen synthase kinase-3β (GSK3β) pathway in toll-like receptor (TLR2)-mediated MCP-1 expression. The TLR2 agonist, Pam₃CSK₄, induced MCP-1 expression in the Raw264.7 cell line. The induction of MCP-1 was seen in the bone marrow-derived macrophages of wild-type mice but not in TLR2 knockout mice. The TLR2-mediated MCP-1 induction was myeloid differentiation primary response gene 88 (MyD88)-independent. By contrast, the inactivation of JAK2 attenuated TLR2-mediated MCP-1 expression. The JAK inhibitor suppressed the phosphorylation of GSK3β as well as Akt by Pam₃CSK₄ stimulation. While the inactivation of Akt by LY294002 suppressed TLR2-mediated MCP-1 induction, the inactivation of GSK3β by LiCl potentiated TLR2-mediated MCP-1 induction. Furthermore, Akt inhibitor suppressed TLR2-mediated phosphorylation of GSK3β. Taken together, these results suggest that a MyD88-independent pathway exists in TLR2 signaling; the JAK2-Akt-GSK3β pathway is a novel MyD88-independent pathway for MCP-1 induction.

Arctigenin inhibits lipopolysaccharide-induced iNOS expression in RAW264.7 cells through suppressing JAK-STAT signal pathway

Arctigenin has been demonstrated to have an anti-inflammatory function, but the precise mechanisms of its action remain to be fully defined. In the present study, we determined the effects of arctigenin on lipopolysaccharide (LPS)-induced production of proinflammatory mediators and the underlying mechanisms involved in RAW264.7 cells. Our results indicated that arctigenin exerted its anti-inflammatory effect by inhibiting ROS-dependent STAT signaling through its antioxidant activity. Arctigenin also significantly reduced the phosphorylation of STAT1 and STAT 3 as well as JAK2 in LPS-stimulated RAW264.7 cells. The inhibitions of STAT1 and STAT 3 by arctigenin prevented their translocation to the nucleus and consequently inhibited expression of iNOS, thereby suppressing the expression of inflammation-associated genes, such as IL-1β, IL-6 and MCP-1, whose promoters contain STAT-binding elements. However, COX-2 expression was slightly inhibited at higher drug concentrations (50 μM). Our data demonstrate that arctigenin inhibits iNOS expression via suppressing JAK-STAT signaling pathway in macrophages.

Calcium/calmodulin-dependent protein kinase (CaMK) Ialpha mediates the macrophage inflammatory response to sepsis

Dysregulated Ca(2+) handling is prevalent during sepsis and postulated to perpetuate the aberrant inflammation underlying subsequent organ dysfunction and death. The signal transduction cascades mediating these processes are unknown. Here, we identify that CaMKIα mediates the Mϕ response to LPS in vitro and the inflammation and organ dysfunction of sepsis in vivo. We show that LPS induced active pThr(177)-CaMKIα in RAW 264.7 cells and murine peritoneal Mϕ, which if inhibited biochemically with STO609 (CaMKK inhibitor) or by RNAi, reduces LPS-induced production of IL-10. Transfection of constitutively active CaMKIα (CaMKI293), but not a kinase-deficient mutant (CaMKI293(K49A)), induces IL-10 release. This production of IL-10 is mediated by CaMKIα-dependent regulation of p38 MAPK activation. CaMKIα activity also mediates the cellular release of HMGB1 by colocalizing with and regulating the packaging of HMGB1 into secretory lysosomes. During endotoxemia, mice receiving in vivo CaMKIα(RNAi) display reduced systemic concentrations of IL-10 and HMGB1 in comparison with mice receiving NT(RNAi). These data support the biological relevance of CaMKIα-dependent IL-10 production and HMGB1 secretion. In a CLP model of sepsis, CaMKIα(RNAi) mice display reduced systemic concentrations of IL-10, IL-6, TNF-α, and HMGB1 in comparison with NT(RNAi) mice, which correlate with reductions in the development of renal dysfunction. These data support that CaMKIα signaling is integral to the Mϕ responding to LPS and may also be operant in vivo in regulating the inflammation and organ dysfunction consequent to sepsis.

Influence of iNOS and COX on peroxiredoxin gene expression in primary macrophages

Peroxiredoxins (Prxs) are a family of multifunctional antioxidant thiol-dependent peroxidases. This study aimed to examine the regulatory mechanisms of Prx gene expression in murine bone marrow-derived macrophages (BMMs) using standardized serum-free conditions. Stimulation with LPS and IFNγ increased mRNA levels of Prx 1, 2, 4, 5, and 6 in BMMs of both C57BL/6 and BALB/c mice, with Prx 1, 2, 4, and 6 more strongly induced in C57BL/6 BMMs. Further investigations on signaling pathways in C57BL/6 BMMs demonstrated that up-regulation of Prx 5 and 6 by LPS and IFNγ was associated with the activation of multiple protein kinases, most notably JAK2, PI3K, and p38 MAPK. Our experiments also revealed a contribution of inducible NO synthase-derived nitric oxide to the increase in Prx 1, 2, 4, and 6 mRNA expression, whereas NADPH oxidase-derived superoxide was not involved. Furthermore, we could show that LPS- and IFNγ-induced gene expression of Prx 6 was also regulated in an NO-independent manner by cyclooxygenases and prostaglandin E(2). Taken together our results indicate a possible role for Prxs in defense mechanisms of activated macrophages against oxidative stress during inflammation or infection.

MicroRNA-101 targets MAPK phosphatase-1 to regulate the activation of MAPKs in macrophages

MAPK phosphatase-1 (MKP-1) is an archetypical member of the dual-specificity phosphatase family that deactivates MAPKs. Induction of MKP-1 has been implicated in attenuating the LPS- or peptidoglycan-induced biosynthesis of proinflammatory cytokines, but the role of noncoding RNA in the expression of the MKP-1 is still poorly understood. In this study, we show that MKP-1 is a direct target of microRNA-101 (miR-101). Transfection of miR-101 attenuates induction of MKP-1 by LPS as well as prolonged activation of p38 and JNK/stress-activated protein kinase, whereas inhibition of miR-101 enhances the expression of MKP-1 and shortens p38 and JNK activation. We also found that expression of miR-101 is induced by multiple TLR ligands, including LPS, peptidoglycan, or polyinosinic-polycytidylic acid, and that inhibition of PI3K/Akt by LY294002 or Akt RNA interference blocks the induction of miR-101 by LPS in RAW264.7 macrophage cells. Moreover, treatment of cells with dexamethasone, a widely used anti-inflammatory agent, markedly inhibits miR-101 expression and enhances the expression of MKP-1 in LPS-stimulated macrophages. Together, these results indicate that miR-101 regulates the innate immune responses of macrophages to LPS through targeting MKP-1.

SOCS1, a Negative Regulator of Cytokine Signals and TLR Responses, in Human Liver Diseases

Toll-like receptor (TLR) signaling pathways are strictly coordinated by several mechanisms to regulate adequate innate immune responses. Recent lines of evidence indicate that the suppressor of cytokine signaling (SOCS) family proteins, originally identified as negative-feedback regulators in cytokine signaling, are involved in the regulation of TLR-mediated immune responses. SOCS1, a member of SOCS family, is strongly induced upon TLR stimulation. Cells lacking SOCS1 are hyperresponsive to TLR stimulation. Thus, SOCS1 is an important regulator for both cytokine and TLR-induced responses. As an immune organ, the liver contains various types of immune cells such as T cells, NK cells, NKT cells, and Kupffer cells and is continuously challenged with gut-derived bacterial and dietary antigens. SOCS1 may be implicated in pathophysiology of the liver. The studies using SOCS1-deficient mice revealed that endogenous SOCS1 is critical for the prevention of liver diseases such as hepatitis, cirrhosis, and cancers. Recent studies on humans suggest that SOCS1 is involved in the development of various liver disorders in humans. Thus, SOCS1 and other SOCS proteins are potential targets for the therapy of human liver diseases.

Human lung mast cells mediate pneumococcal cell death in response to activation by pneumolysin

Mast cells are emerging as contributors to innate immunity. Mouse mast cells have a pivotal role in protection against bacterial infection, and human cord blood-derived mast cells reduce bacterial viability in culture. The objectives of this study were to determine whether human lung mast cells (HLMCs) might be protective against pneumococcal lung infection through direct antimicrobial activity. Tissue-derived HLMCs and the human mast cell lines HMC-1 and LAD2 were cocultured with wild-type and mutant pneumococci, and viability and functional assays were performed. Mast cells were also stimulated with purified pneumolysin. HLMCs killed wild-type serotype-2 (D39) pneumococci in coculture but had no effect on an isogenic pneumolysin-deficient (PLN-A) pneumococcus. D39 wild-type, but not PLN-A pneumococci, induced the release of leukotriene C4 from human mast cells in a dose-dependent manner, which was not accompanied by histamine release. Stimulation of mast cells with sublytic concentrations of purified pneumolysin replicated this effect. Furthermore, pneumolysin induced the release of the cathelicidin LL-37 from HLMCs, purified LL-37 reduced pneumococcal viability, and neutralizing Ab to LL-37 attenuated mast cell-dependent pneumococcal killing. In addition, at high concentrations, all pneumococcal strains tested reduced HLMC viability through a combination of pneumolysin and H2O2-dependent mechanisms. HLMCs exhibit direct antimicrobial activity to pneumococci through their activation by pneumolysin. This antimicrobial activity is mediated, in part, by the release of LL-37 from HLMCs. This suggests that mast cells provide an early warning system and potentially limit pneumococcal dissemination early in the course of invasive pulmonary pneumococcal disease.

Identification of JAK-STAT pathways as important for the anti-inflammatory activity of a Hypericum perforatum fraction and bioactive constituents in RAW 264.7 mouse macrophages

Hypericum perforatum extracts have been used to treat diseases, including mild-to-moderate depression and inflammatory conditions. It is particularly important to identify which constituents present in the H. perforatum extracts are responsible for its anti-inflammatory activity since consumers are taking H. perforatum preparations to treat inflammation. We used a combination of four putative bioactive constituents, called the 4-component-system that interacted synergistically to explain the light-activated anti-inflammatory activity of an H. perforatum fraction in RAW 264.7 mouse macrophages. We also combined the constituents at concentrations detected in the fraction to identify key molecular targets. LPS was used to model an inflammatory response, and the 4-component-system and H. perforatum fraction were used as treatments that inhibited LPS-induced prostaglandin E(2) (PGE(2)) production in RAW 264.7 mouse macrophages in the studies of gene expression profiles. We used Affymetrix genechips, statistical analysis, and quantitative real-time PCR to identify key gene targets of the 4-component-system and the sub-fraction from an H. perforatum ethanol extract. The H. perforatum sub-fraction, with or without LPS stimulation, affected far more genes than the 4-component-system with and without LPS. Genes involved in Janus kinase, as well as a signal transducer and activator of transcription (JAK-STAT) and eicosanoid pathways were identified that could account for the reduction in PGE(2) observed with both treatments in LPS-stimulated macrophages. Ten genes may be particularly important targets for activity of the 4-component-system and the fraction with LPS stimulation and these genes were involved in inflammatory signaling pathways, namely the JAK-STAT and eicosanoid pathways.

Induction of peroxiredoxin I gene expression by LPS involves the Src/PI3K/JNK signalling pathway

Peroxiredoxin I (Prx I) belongs to a family of proteins with thiol-dependent peroxidase activity and is involved in the cellular protection against oxidative stress, the modulation of intracellular signalling cascades as well as the regulation of cell proliferation and apoptosis. In RAW 264.7 mouse macrophage cells Prx I was up-regulated on the mRNA and protein level by lipopolysaccharide (LPS). Treatment of cells with LPS increased the phosphorylation of c-Jun-NH(2) terminal kinase (JNK) and protein kinase B (PKB). Both SP600125, an inhibitor of JNK, and LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), dose-dependently decreased LPS-induced Prx I mRNA expression. Furthermore, up-regulation of Prx I mRNA by LPS was diminished by the Src tyrosine kinase inhibitor PP2 and the iNOS inhibitor L-NMMA. LPS-dependent induction of Prx I is likely mediated by an activator protein-1 site within the Prx I promoter region binding JunB and c-Fos. In contrast, NFkappaB was not involved in the activation of Prx I transcription. Our results suggest that the up-regulation of Prx I gene expression by LPS is part of the cellular response to stress and may protect against oxidative stress-related injury in RAW 264.7 cells.

Glycogen synthase kinase-3 promotes the synergistic action of interferon-gamma on lipopolysaccharide-induced IL-6 production in RAW264.7 cells

Macrophages are the major effector cells of the innate immune system. Their function requires the integration of signals from pathogens, such as those induced by lipopolysaccharide (LPS), and from the host, such as those induced by interferon-gamma (IFN-gamma). The priming by IFN-gamma of Toll-like receptor-induced macrophage activation has long been recognized, but the mechanisms underlying this priming action remain unclear. We report in this study that the priming of macrophage-derived RAW264.7 cells by IFN-gamma is highly dependent on glycogen synthase kinase-3 (GSK3). Cooperative interactions of GSK3 and signal transducer and activator of transcription-3 (STAT3) were revealed by the findings that GSK3 inhibitors, or knockdown of the GSK3 beta isoform, strongly reduced the activation of STAT3, but not STAT1, induced by IFN-gamma without affecting upstream signaling events, and GSK3 was associated with STAT3. Direct inhibition of STAT3 activation abolished the synergistic action of IL-6 production by IFN-gamma administered with LPS. Similarly, inhibition of GSK3 abolished the synergistic stimulation of IFN-gamma on IL-6 production, and GSK3 was recruited to the IFN-gamma receptor by co-treatment with IFN-gamma and LPS. These results demonstrate the dependency of macrophage priming by IFN-gamma on STAT3 and GSK3, providing novel targets for intervention.

Selective regulation of interleukin-10 production via Janus kinase pathway in murine conventional dendritic cells

In this study, we examined the role of JAKs in regulation of inflammatory versus anti-inflammatory cytokine balance in murine conventional dendritic cells (DCs). Highly purified lipopolysaccharide (upLPS) combined with imiquimod (IQ) synergistically induced IL-10 production by DCs, while each ligand alone showed a slight effect on the IL-10 production. Marked phosphorylation of JAK2, STAT1 and STAT3 was detected in DCs following upLPS plus IQ stimulation. Blocking the JAK pathway by JAK inhibitor I (JAKi) resulted in significant inhibition of IL-10 production by the DCs. However, JAKi showed negligible effect on the DC production of IL-12, IL-6 and TNF-alpha. JAKi completely blocked the TLR-mediated STATs activation, and attenuated the activation of Akt, a downstream effector of PI3K, in DCs stimulated by upLPS plus IQ. LY294002, a specific inhibitor of PI3K, markedly inhibited the DC production of IL-10. Thus, JAK-PI3K axis appeared to be responsible for the IL-10 production by DCs.

Molecular biology of inflammation and sepsis: a primer

BACKGROUND

Remarkable progress has been made during the last decade in defining the molecular mechanisms that underlie septic shock. This rapidly expanding field is leading to new therapeutic opportunities in the management of severe sepsis.

AIM

To provide the clinician with a timely summary of the molecular biology of sepsis and to better understand recent advances in sepsis research.

DATA SELECTION

Medline search of relevant publications in basic mechanisms of sepsis/severe sepsis/septic shock, and selected literature review of other manuscripts about the signalosome, inflammasome, apoptosis, or mechanisms of shock. DATA SYNTHESIS AND FINDINGS: The identification of the toll-like receptors and the associated concept of innate immunity based upon pathogen- or damage-associated molecular pattern molecules allowed significant advances in our understanding of the pathophysiology of sepsis. The essential elements of the inflammasome and signal transduction networks responsible for activation of the host response have now been characterized. Apoptosis, mitochondrial dysfunction, sepsis-related immunosuppression, late mediators of systemic inflammation, control mechanisms for coagulation, and reprogramming of immune response genes all have critical roles in the development of sepsis.

CONCLUSIONS

Many of these basic discoveries have direct implications for the clinical management of sepsis. The translation of these "bench-to-bedside" findings into new therapeutic strategies is already underway. This brief review provides the clinician with a primer into the basic mechanisms responsible for the molecular biology of sepsis, severe sepsis, and septic shock.

CNTF protects oligodendrocytes from ammonia toxicity: intracellular signaling pathways involved

In pediatric patients, hyperammonemia can provoke irreversible damages to developing CNS like cortical atrophy, ventricular enlargement, demyelination or gray and white matter hypodensities which are concordant with alterations of neurons and oligodendrocytes. Cerebral injury triggers endogenous protective mechanisms that can prevent or limit brain damage. Understanding these mechanisms may lead to new therapeutic strategies. We investigated whether ciliary neurotrophic factor (CNTF), a cytokine-like protein expressed by astrocytes and described as an injury-associated survival factor, was up-regulated by ammonia in developing reaggregated 3D brain cell cultures. We showed that CNTF is up-regulated by ammonia exposure, through mediation of p38 MAPK activation in astrocytes. We also observed that SAPK/JNK and Erk1/2 activations in oligodendrocytes and neurons, respectively, also play indirect roles in CNTF synthesis by astrocytes. Co-treatment with exogenous CNTF demonstrated strong protective effects on oligodendrocytes, but not on neurons, against ammonia toxicity. These protective effects involved JAK/STAT, SAPK/JNK and c-jun proteins.

Modulation of LPS stimulated NF-kappaB mediated Nitric Oxide production by PKCepsilon and JAK2 in RAW macrophages

BACKGROUND

Nuclear factor kappa B (NF-kappaB) has been shown to play an important role in regulating the expression of many genes involved in cell survival, immunity and in the inflammatory processes. NF-kappaB activation upregulates inducible nitric oxide synthase leading to enhanced nitric oxide production during an inflammatory response. NF-kappaB activation is regulated by distinct kinase pathways independent of inhibitor of kappaB kinase (IKK). Here, we examine the role of protein kinase C isoforms and janus activated kinase 2 (JAK2) activation in NF-kappaB activation and LPS-stimulated NO production.

METHODS

Murine RAW 264.7 macrophages were treated with lipopolysaccharide (LPS), Phorbol 12-myristate 13-acetate (PMA) and a combination of LPS and PMA in the presence or absence of various inhibitors of PKC isoforms and JAK2. Nuclear translocation of the NF-kappaB p65 subunit, was assessed by Western blot analysis whilst NO levels were assessed by Greiss assay.

RESULTS

LPS-stimulated NO production was attenuated by PMA whilst PMA alone did not affect NO release. These effects were associated with changes in p65 nuclear translocation. The PKCalpha, beta, gamma, delta and zeta inhibitor Gö 6983 (Go) had no effect on LPS-induced NO release. In contrast, Bisindolymalemide I (Bis), a PKC alpha, betaI, betaII, gamma, delta and epsilon isoform inhibitors completely inhibited LPS-stimulated NO production without affecting p65 nuclear translocation. Furthermore, a partial inhibitory effect on LPS-induced NO release was seen with the JAK2 inhibitor AG-490 and the p38 MAPK inhibitor SB 203850.

CONCLUSION

The results further define the role of NF-kappaB in LPS stimulated NO production in RAW macrophages. The data support a function for PKCepsilon, JAK2 and p38 MAPK in NF-kappaB activation following p65 nuclear import.

Biphasic regulation of levofloxacin on lipopolysaccharide-induced IL-1β production

Fluoroquinolones have been known to exert modulatory activity on immune responses to microbial infection. However, the mechanism of this immunomodulation has not been well elucidated. In this study, we investigated the effect of levofloxacin on lipopolysaccharide (LPS)-induced production of interleukin-1beta (IL-1beta) in RAW264.7 cells. We showed that LPS-stimulated release of pre-synthesized IL-1beta was promoted by levofloxacin, in part via the p38 mitogen-activated protein kinase (MAPK) pathway. On the other hand, newly synthesized IL-1beta production was inhibited by levofloxacin. This immunoregulatory function of levofloxacin in the later phase as well as promotion of pre-synthesized IL-1beta release by levofloxacin in the early phase might be advantageous in the host defense to microbial pathogens.

Monocyte p110alpha phosphatidylinositol 3-kinase regulates phagocytosis, the phagocyte oxidase, and cytokine production

Mononuclear phagocytes are critical modulators and effectors of innate and adaptive immune responses, and PI-3Ks have been shown to be multifunctional monocyte regulators. The PI-3K family includes eight catalytic isoforms, and only limited information is available about how these contribute to fine specificity in monocyte cell regulation. We examined the regulation of phagocytosis, the phagocyte oxidative burst, and LPS-induced cytokine production by human monocytic cells deficient in p110alpha PI-3K. We observed that p110alpha PI-3K was required for phagocytosis of IgG-opsonized and nonopsonized zymosan in differentiated THP-1 cells, and the latter was inhibitable by mannose. In contrast, p110alpha PI-3K was not required for ingestion serum-opsonized zymosan. Taken together, these results suggest that FcgammaR- and mannose receptor-mediated phagocytosis are p110alpha-dependent, whereas CR3-mediated phagocytosis involves a distinct isoform. It is notable that the phagocyte oxidative burst induced in response to PMA or opsonized zymosan was also found to be dependent on p110alpha in THP-1 cells. Furthermore, p110alpha was observed to exert selective and bidirectional effects on the secretion of pivotal cytokines. Incubation of p110alpha-deficient THP-1 cells with LPS showed that p110alpha was required for IL-12p40 and IL-6 production, whereas it negatively regulated the production of TNF-alpha and IL-10. Cells deficient in p110alpha also exhibited enhanced p38 MAPK, JNK, and NF-kappaB phosphorylation. Thus, p110alpha PI-3K appears to uniquely regulate important monocyte functions, where other PI-3K isoforms are uninvolved or unable to fully compensate.

Critical role for casein kinase 2 and phosphoinositide-3-kinase in the interferon-gamma-induced expression of monocyte chemoattractant protein-1 and other key genes implicated in atherosclerosis

OBJECTIVE

The interferon-gamma (IFN-gamma)-mediated regulation of macrophage gene expression is of crucial importance in the pathogenesis of atherosclerosis. The mechanisms underlying the actions of IFN-gamma signaling in macrophages were investigated using monocyte chemoattractant protein (MCP)-1 as a model gene.

METHODS AND RESULTS

The IFN-gamma-induced expression of MCP-1 in macrophages was attenuated by inhibitors of phosphoinositide-3-kinase (PI3K), casein kinase 2 (CK2), and Janus kinase (JAK)-2. AKT was the downstream target for PI3K action. Electrophoretic mobility shift assays and chromatin immunoprecipitation showed that signal transducer and activator of transcription (STAT)-1 interacted with IFN-gamma responsive elements in the MCP-1 gene promoter. The IFN-gamma-induced activity of the MCP-1 gene promoter and an artificial promoter containing STAT1 responsive elements was inhibited by expression of dominant negative forms of JAK-1 and -2, STAT1, CK2, and AKT. The action of CK2 and AKT on STAT1 activation was mediated, at least in part, through the regulation of serine 727 phosphorylation. Analysis of a number of other genes regulated by this cytokine and implicated in atherosclerosis revealed a gene-specific action for PI3K/AKT in IFN-gamma signaling.

CONCLUSIONS

These studies provide novel insights into the role of PI3K/AKT and CK2 in IFN-gamma signaling relevant to changes in macrophage gene expression during atherosclerosis.

Macrophage glucocorticoid receptors regulate Toll-like receptor 4-mediated inflammatory responses by selective inhibition of p38 MAP kinase

To explore the role of glucocorticoids in regulation of kinase pathways during innate immune responses, we generated mice with conditional deletion of glucocorticoid receptor (GR) in macrophages (MGRKO). Activation of toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) caused greater mortality and cytokine production in MGRKO mice than in controls. Ex vivo, treatment with dexamethasone (Dex) markedly inhibited LPS-mediated induction of inflammatory genes in control but not GR-deficient macrophages. We show that Dex inhibits p38 MAPK, but not PI3K/Akt, ERK, or JNK, in control macrophages. Associated with p38 inhibition, Dex induced MAP kinase phosphatase-1 (MKP-1) in control, but not MGRKO, macrophages. Consistent with the ex vivo studies, treatment with a p38 MAPK-specific inhibitor resulted in rescue of MGRKO mice from LPS-induced lethality. Taken together, we identify p38 MAPK and its downstream targets as essential for GR-mediated immunosuppression in macrophages.

Bacterial flagellin inhibits T cell receptor-mediated activation of T cells by inducing suppressor of cytokine signalling-1 (SOCS-1)

Flagellin, the structural component of bacterial flagella, is secreted by pathogenic and commensal bacteria, and is recognized by Toll-like receptor (TLR) 5. Flagellin is a common bacterial antigen present on most motile bacteria and is speculated to contribute to the activation of CD4+ T cells in the intestine. However, molecular mechanisms by which flagellin regulate T cell activation remains to be determined. Using Jurkat T cells or human primary T cell, we showed that flagellin stimulation induced tyrosine phosphorylation of TLR5 and activation of both mitogen-activated protein kinases and nuclear factor kappaB. In addition, stimulation by flagellin did not induce nuclear factor of activated T cells (NFAT) activation, while stimulation via the T cell receptor (TCR) leads to activation of NFAT. However, TCR-mediated NFAT activation and tyrosine phosphorylation of zeta-associated protein 70 (Zap-70) were inhibited in cells pre-stimulated by flagellin. Furthermore, flagellin stimulation induced suppressor of cytokine signalling-1 (SOCS-1), which formed a complex with Zap-70 after stimulation via TCR, and inhibition of SOCS-1 expression by SOCS-1-specific small interfering RNA reinstated TCR-mediated activation of NFAT in cells pre-stimulated with flagellin. These results collectively indicate that bacterial flagellin inhibits TCR-mediated activation of T cells by inducing SOCS-1.

An essential role for Akt1 in dendritic cell function and tumor immunotherapy

Current dendritic cell (DC) vaccine preparations involving ex vivo differentiation and maturation produce short-lived, transiently active DCs that may curtail T-cell responses in vivo. We demonstrate that Akt1, downregulation of which decreases DC lifespan, is critical for proinflammatory signal-mediated DC survival and maturation. Lipopolysaccharide or CD40 signaling stabilizes Akt1, promoting both activation and Bcl-2-dependent survival of DCs. Expression of a potent allele encoding a lipid raft-targeted Akt1, M(F)-DeltaAkt, is sufficient for maturation and survival of murine bone marrow-derived DCs in vivo. M(F)-DeltaAkt-transduced DCs enhanced T-cell proliferation, activation and long-term memory responses, enabling eradication of large pre-established lymphomas and aggressive B16 melanomas. Human myeloid DCs expressing constitutively active M(F)-DeltahAkt also survived significantly longer and promoted antigen-specific T-cell responses. Thus, Akt1 is a critical regulator of DC lifespan, and its manipulation in DCs can improve the clinical efficacy of DC-based tumor vaccines.

Extracellular heat shock protein 70 mediates heat stress-induced epidermal growth factor receptor transactivation in A431 carcinoma cells

The initial steps of heat stress in A431 cells were previously characterized by ligand-independent EGFR transactivation via an unknown mechanism and concomitant secretion of Hsp70. In this work we demonstrate that the depletion of Hsp70 from the conditioned medium of heated cells abolishes EGFR transactivation indicating that secreted Hsp70 is essential for EGFR transactivation during heat shock. This notion is supported by the findings that purified Hsp70 can induce EGFR transactivation and the activation of EGFR-dependent signaling pathways. Both heat stress and pure Hsp70 stimulate activation of TLR2/4 and their association with EGFR. These results suggest that the secreted Hsp70 mediates the cross-communication of TLR and EGFR signaling systems in A431 cells.

Regulation of Lipopolysaccharide-Induced Inducible Nitric-Oxide Synthase Expression through the Nuclear Factor-κB Pathway and Interferon-β/Tyrosine Kinase 2/Janus Tyrosine Kinase 2-Signal Transducer and Activator of Transcription-1 Signaling Cascades by 2-Naphthylethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (THI 53), a New Synthetic Isoquinoline Alkaloid

The effects of 2-naphthylethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (THI 53), on nitric oxide (NO) production and inducible nitric-oxide synthase (iNOS) protein induction by lipopolysaccharide (LPS) were investigated in RAW 264.7 cells and mice. In cells, THI 53 concentration dependently reduced NO production and iNOS protein induction by LPS. In addition, THI 53 inhibited NO production and iNOS protein induction in LPS-treated mice. LPS-mediated iNOS protein induction was inhibited significantly by the specific tyrosine kinase inhibitor alpha-cyano-(3-hydroxy-4-nitro)cinnamonitrile (AG126) as well as by THI 53. In addition, a c-Jun NH(2)-terminal kinase (JNK) inhibitor anthra[1,9-cd]pyrazole-6 (2H)-one) (SP600125) but not an extracellular regulated kinase inhibitor [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one (PD98029)] or a p38 inhibitor [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB230580)] reduced the iNOS protein level induced by LPS. Moreover, a Janus kinase 2 (JAK2) inhibitor alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide (AG490) dose-dependently prevented LPS-mediated iNOS protein induction. LPS activated phosphorylations of tyrosine kinases, especially tyrosine kinase 2 (Tyk2) and signal transducer and activator of transcription-1 (STAT-1); these were reduced by THI 53. LPS also phosphorylated the JNK pathway; however, this phosphorylation was unaffected by THI 53. Interestingly, a JNK inhibitor (SP600125) and another tyrosine kinase inhibitor (genistein) significantly inhibited STAT-1 phosphorylation, suggesting that the LPS-activated JNK pathway and a tyrosine kinase pathway (especially Tyk2) may link to the STAT-1 pathway, which is involved in iNOS induction. However, THI 53 regulates LPS-mediated iNOS protein induction by affecting the Tyk2/JAK2-STAT-1 pathway, not the JNK pathway. The inhibition by THI 53 of LPS-induced NO production was recovered by a tyrosine phosphatase inhibitor (Na(3)VO(4)), which supports the possibility that THI 53 inhibits the LPS-induced inflammatory response through regulation of tyrosine kinase pathways. THI 53 also inhibited LPS-mediated interferon (IFN)-beta production and nuclear factor-kappaB (NF-kappaB) activation. Thus, THI 53 may regulate LPS-mediated inflammatory response through both the NF-kappaB and IFN-beta/Tyk2/JAK2-STAT-1 pathways.

New players in TLR-mediated innate immunity: PI3K and small Rho GTPases

Toll-like receptors (TLRs) play a crucial role in the innate immune system as a first line of defense against pathogens. TLR activation in phagocytes produces pro-inflammatory cytokines and chemokines that contribute directly to elimination of infectious agents and activation of adaptive immune responses. However, a sustained inflammatory response can result in tissue damage and generalized sepsis. This review summarizes the complex and sometimes conflicting links of TLR signaling with two important regulators of immune cells functions: phosphoinositide 3-kinases (PI3Ks) and small GTPases of the Rho family. A unified model of hierarchical organization of these signaling participants is still premature, given that the tools for delineating how control of TLRmediated pathways is achieved are just emerging. Critical progress in our understanding of spatial-temporal propagation of TLR signaling will certainly be provided in the near future by pharmacological targeting of PI3Ks using recently characterized, second-generation PI3K inhibitors in combination with gene-targeting strategies for PI3K subunits and Rho GTPases targeted to the murine myeloid compartment.

Glycine-extended gastrin inhibits apoptosis in colon cancer cells via separate activation of Akt and JNK pathways

Glycine-extended gastrin (G-Gly) is produced by colon cancers and has growth promoting and anti-apoptotic effects in the colonic epithelium. We have examined the anti-apoptotic effects of G-Gly and the signal transduction pathways involved. G-Gly stimulated HT-29 cell proliferation in a concentration dependent manner and inhibited serum-starvation and celecoxib-induced apoptosis. Inhibition of signalling via c-Jun NH2-terminal kinase (JNK) with SP600125 or PI3-kinase/Akt with LY294002 abolished the effects of G-Gly. G-Gly significantly increased phosphorylation of both JNK and Akt. The JAK2 inhibitor AG490 abolished the anti-apoptotic effect of G-Gly and inhibited phosphorylation of Akt but not of JNK. G-Gly stimulated tyrosine phosphorylation of JAK2. G-Gly-increased activation of AP-1 was JNK-dependant and activation of STAT3 was JAK2-dependant. We conclude that G-Gly promotes growth and inhibits apoptosis in colon cancer cells. These effects are mediated via the JAK2, PI3-kinase/Akt and JNK pathways. Activation of JAK2 is upstream of Akt but not of JNK.

Divergent Mechanisms Utilized by SOCS3 to Mediate Interleukin-10 Inhibition of Tumor Necrosis Factor α and Nitric Oxide Production by Macrophages

The cytokine interleukin-10 (IL-10) potently inhibits macrophage function through activation of the transcription factor STAT3. The expression of SOCS3 (suppressor of cytokine signaling-3) has been shown to be induced by IL-10 in a STAT3-dependent manner. However, the relevance of SOCS3 expression to the anti-inflammatory effect of IL-10 on macrophages has been controversial. Through kinetic analysis of the requirement for SOCS3 in IL-10 inhibition of lipopolysaccharide (LPS)-stimulated tumor necrosis factor-alpha (TNFalpha) transcription and translation, SOCS3 was found to be necessary for TNFalpha expression during the early phase, but not the late phase of IL-10 action. SOCS3 was essential for IL-10 inhibition of LPS-stimulated production of iNOS (inducible nitric-oxide synthase) protein and nitric oxide (NO). To determine the domains of SOCS3 protein important in mediating these effects, SOCS3-/- macrophages were reconstituted with SOCS3 mutated for the SH2, KIR, SOCS box domains, and tyrosines 204 (Tyr204) and 221 (Tyr221). The SH2 domain, SOCS box, and both Tyr204 and Tyr221 were required for IL-10 inhibition of TNFalpha mRNA and protein expression, but interestingly the KIR domain was necessary only for IL-10 inhibition of TNFalpha protein expression. In contrast, Tyr204 and Tyr221 were the only structural features of SOCS3 that were necessary in mediating IL-10 inhibition of iNOS protein expression and NO production. These data define SOCS3 as an important mediator of IL-10 inhibition of macrophage activation and that SOCS3 interferes with distinct LPS-stimulated signal transduction events through differing mechanisms.