Extending the nuclear roles of IkappaB kinase subunits

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

The importance of natural chalcones in ischemic organ damage: Comprehensive and bioinformatic analysis review

Over the last few decades, extensive research has been conducted, yielding a detailed account of thousands of newly discovered compounds of natural origin and their biological activities, all of which have the potential to be used for a wide range of therapeutic purposes. There are multiple research papers denoting the central objective of chalcones, which have been shown to have therapeutic potential against various forms of ischemia. The various aspects of chalcones are discussed in this review regarding molecular mechanisms involved in the promising anti-ischemic potential of these chalcones. The main mechanisms involved in these protective effects are Nrf2/Akt activation and NF-κB/TLR4 suppression. Furthermore, in-silico studies were carried out to discover the probable binding of these chalcones to Keap-1 (an inhibitor of Nrf2), Akt, NF-κB, and TLR4 protein molecules. Besides, network pharmacology analysis was conducted to predict the interacting partners of these signals. The obtained results indicated that Nrf2, Akt, NF-κB, and TLR4 are involved in the beneficial anti-ischemic actions of chalcones. Conclusively, the present findings show that chalcones as anti-ischemic agents have a valid rationale. The discussed studies will provide a comprehensive viewpoint on chalcones and can help to optimize their effects in different ischemia. PRACTICAL APPLICATIONS: Ischemic organ damage is an unavoidable pathological condition with a high worldwide incidence. According to the current research progress, natural chalcones have been proved to treat and/or prevent various types of ischemic organ damage by alleviating oxidative stress, inflammation, and apoptosis by different molecular mechanisms. This article displays the comprehensive research progress and the molecular basis of ischemic organ damage pathophysiology and introduces natural chalcones' mechanism in the ischemic organ condition.

Colonic Epithelial PHLPP2 Deficiency Promotes Colonic Epithelial Pyroptosis by Activating the NF-κB Signaling Pathway

Background

Ulcerative colitis (UC) is a chronic inflammatory disease with increasing prevalence worldwide. Barrier defect in intestinal epithelial cells (IECs) is one of the main pathogeneses in UC. Pyroptosis is a programmed lytic cell death and is triggered by inflammatory caspases, while little is known about its role in UC.

Methods

Differentially expressed genes (DEGs) were identified by comparing UC patients with healthy controls from the GEO datasets. The candidate genes involved in pyroptosis were obtained, and the underlying molecular mechanism in the progression of UC was explored in vivo and in vitro.

Results

Pleckstrin homology domain leucine-rich repeat protein phosphatase 2 (PHLPP2), a protein phosphatase, was downregulated and involved in regulating inflammation-induced IEC pyroptosis by modulating the NF-κB signaling in UC through bioinformatics analysis. Moreover, we demonstrated that PHLPP2 was downregulated in UC patients and UC mice. Besides, we found that PHLPP2 depletion activated the NF-κB signaling and increased the expressions of caspase-1 P20, Gasdermin N, IL-18, and IL-1β contributing to IEC pyroptosis and inflammation in UC mice. Furthermore, we found that PHLPP2^−/− mice developed hypersensitivity to dextran sulfate sodium (DSS) treatment toward colitis showing activated NF-κB signaling and dramatically induced expressions of caspase-1 P20, Gasdermin N, IL-18, and IL-1β. Mechanically, this inflammation-induced downregulation of PHLPP2 was alleviated by an NF-κB signaling inhibitor in intestinal organoids of PHLPP2^−/− mice and fetal colonic cells.

Conclusions

PHLPP2 downexpression activated the NF-κB signaling and promoted the IEC pyroptosis, leading to UC progression. Therefore, PHLPP2 might be an attractive candidate therapeutic target for UC.

Metformin reverses the effects of high glucose on human dermal fibroblasts of aged skin via downregulating RELA/p65 expression

Metformin has been successfully used as an anti-aging agent but exact molecular mechanisms of metformin in anti-aging remain unknown. Hyperglycemia during skin aging not only causes oxidative damage to cellular macromolecules, like dermal collagen, but also modulates the activation of transcription factor nuclear factor kappa B (NF-kB). We aimed to investigate in vitro effects of high glucose (HG) and metformin treatment on proliferation and apoptosis of human primary dermal fibroblasts (HDFs), and the expression of COL1A1, COL3A1, and RELA/p65 genes. Effects of normal glucose (5.5 mM) and HG concentration (50 mM HG) on HDFs, with two doses of metformin (50 μM and 500 μM), were investigated by immunostaining. Apoptotic levels were analyzed by flow cytometry. Expression of COL1A1, COL3A1, and RELA/p65 genes was measured by quantitative real-time PCR. The proliferation of HDFs was decreased significantly (P < 0.01) and expression of COL1A1 was downregulated by HG without metformin, whereas proliferation was elevated and expression was upregulated with 500 μM metformin + HG compared to 5.5 mM glucose (P < 0.05). The expression of COL3A1 and RELA/p65 were upregulated (P < 0.01 for COL3A1), and percentage of late apoptotic cells increased significantly by HG without metformin (P < 0.001) while it decreased in two concentrations of metformin dramatically compared with 5.5 mM glucose (P < 0.01 for expressions and < 0.001 for apoptosis). Metformin not only significantly downregulated RELA/p65 expression, but also inhibited the apoptosis of HDFs from aged human skin at toxic glucose concentrations which could be inversely mediated via COL1A1 and COL3A1 expression.

Syringin exerts neuroprotective effects in a rat model of cerebral ischemia through the FOXO3a/NF-κB pathway

Inflammation plays an important role in the pathogenesis of cerebral ischemia. Syringin (SYR) is an active substance isolated from Acanthopanax senticosus plants, and possesses anti-inflammatory and neuroprotective properties. However, its effects on cerebral ischemic injury, as well as the underlying molecular events, are still unclear. The purpose of this study was to investigate the effect of SYR in a rat model of cerebral ischemia and address the related molecular mechanism. A middle cerebral artery occlusion/reperfusion model (MCAO) was used to simulate ischemic injury. SYR treatment clearly reduced the infarct volume, decreased cerebral water content, improved the neurological score, and attenuated neuronal death. Moreover, SYR decreased the expression of NF-κB, IL-1β, IL-6, TNF-α, and MPO, promoted FOXO3a phosphorylation and cytoplasmic retention, and inhibited the nuclear translocation of NF-κB. FOXO3a knockdown by RNA interference significantly prevented SYR-induced inhibition of NF-κB-mediated inflammation. Confocal microscopy revealed that SYR reduced NF-κB translocation to the nucleus, and FOXO3a silencing reversed this effect. Finally, immunofluorescence and CO-IP experiments showed that SYR promoted the interaction between FOXO3a and NF-κB. In conclusion, SYR exerted a protective effect against brain I/R injury by reducing the inflammation accompanying cerebral ischemia. This effect was mediated by the FOXO3a /NF-κB pathway.

Activation of FoxO1/SIRT1/RANKL/OPG pathway may underlie the therapeutic effects of resveratrol on aging-dependent male osteoporosis

Background

Age-dependent male osteoporosis remains a poorly studied medical problem despite its significance. It is estimated that at least 1 of 5 men will suffer from osteoporotic consequences. Given that multiple mechanisms are involved in the process of senescence, much attention has been given to compounds with polymodal actions. To challenge such a health problem, we tested here the therapeutic potential of resveratrol in male osteoporosis. We also studied the possible molecular mechanisms that may underlie resveratrol effects.

Methods

Thirty male Wistar albino rats were used in the present study. Rats were divided (10/group) into: control (3–4 months old weighing 150–200 g receiving vehicle), aged (18–20 months old, weighing 350–400 g and receiving vehicle), and resveratrol treated aged (18–20 months old, weighing 350–400 g and receiving resveratrol 20 mg/kg/day for 6 weeks) groups. Assessment of serum calcium, phosphate, bone specific alkaline phosphatase, inflammatory cytokines, oxidative stress markers, and rat femur gene expression of FoxO1, SIRT1, RANKL and OPG proteins was carried out. Histopathological assessment of different levels of rat femur was also performed.

Results

Age-dependent osteoporosis resulted in significant increase in serum levels of phosphate, bone specific alkaline phosphatase, hsCRP, IL-1β, IL-6, TNF-α, MDA, NO, and RANKL gene expression. However, there was significant decrease in serum level of GSH, and gene expression of FoxO1, SIRT1 and OPG. Osteoporotic changes were seen in femur epiphysis, metaphysis and diaphysis. Resveratrol restored significantly age-dependent osteoporotic changes.

Conclusion

We concluded that resveratrol can play an important role in the prevention of male osteoporosis. Resveratrol can counter the molecular changes in male osteoporosis via anti-inflammatory, anti-oxidant and gene modifying effects.

NF-κB as the mediator of metformin's effect on ageing and ageing-related diseases

Ageing can be defined as the progressive failure of repair and maintenance systems with a consequent accumulation of cellular damage in nucleic acids, proteins, and lipids. These various types of damage promote ageing by driving cellular senescence and apoptosis. The nuclear factor-kappa B (NF-kB) pathway is one of the key mediators of ageing and this pathway is activated by genotoxic, oxidative and inflammatory stress, and regulates expression of cytokines, growth factors, and genes that regulate apoptosis, cell-cycle progression, and inflammation. Therefore, NF-kB is increased in a variety of tissues with ageing, thus the inhibition of NF-kB leads to delayed onset of ageing-related symptoms and pathologies such as diabetes, atherosclerosis, and cancer. Metformin is often used as an anti-diabetic medication in type 2 diabetes throughout the world and appears to be a potential anti-ageing agent. Owing to its antioxidant, anticancer, cardio-protective and anti-inflammatory properties, metformin has become a potential candidate drug, improving in the context of ageing and ageing-related diseases. An inappropriate NF-kB activation is associated with diseases and pathologic conditions which can impair the activity of genes involved in cell senescence, apoptosis, immunity, and inflammation. Metformin, inhibiting the expression of NF-kB gene, eliminates the susceptibility to common diseases. This review underlines the pleiotropic effects of metformin in ageing and different ageing-related diseases and attributes its effects to the modulation of NF-kB.

Safflower Yellow B Protects Brain against Cerebral Ischemia Reperfusion Injury through AMPK/NF-kB Pathway

Inflammation had showed its important role in the pathogenesis of cerebral ischemia and secondary damage. Safflower yellow B (SYB) had neuroprotective effects against oxidative stress-induced brain injuries, but the mechanisms were still largely unknown to us. In this study, we tried to investigate the anti-inflammation effects of SYB and the possible roles of AMPK/NF-κB signaling pathway on these protective effects. In vivo, brain ischemia/reperfusion (I/R) was induced by transient middle cerebral artery occlusion for 2 h and reperfusion for 20 h. Neurofunctional evaluation, infarction area, and brain water contents were measured. Brain injury markers and inflammatory cytokines levels were measured by ELISA kits. In vitro, cell viability, apoptosis, and LDH leakage were measured after I/R in PC12 cells. The expression and phosphorylation levels of AMPK, NF-κB p65, and P-IκB-α in cytoplasm and nuclear were measured by Western blotting. SiRNA experiment was performed to certify the role of AMPK. The results showed SYB reduced infarct size, improved neurological outcomes, and inhibited brain injury after I/R. In vitro test, SYB treatment alleviated PC12 cells injury and apoptosis and inhibited the inflammatory cytokines (IL-1, IL-6, TNF-α, and COX-2) in a dose-dependent manner. SYB treatment induced AMPK phosphorylation and inhibited NF-κB p65 nuclear translocation both in brain and in PC12 cells. Further studies also showed that the inhibition of NF-κB activity of SYB was through AMPK. In conclusion, SYB protected brain I/R injury through reducing expression of inflammatory cytokines and this effect might be partly due to the inhibition of NF-κB mediated by AMPK.

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IgE-mediated mast cell activation through attenuation of NFκB and AP-1 transcription

Mast cell activation via the high-affinity IgE receptor (FcεRI) elicits production of inflammatory mediators central to allergic disease. As a synthetic antioxidant and a potent ribonucleotide reductase (RNR) inhibitor, Didox (3,4-dihyroxybenzohydroxamic acid) has been tested in clinical trials for cancer and is an attractive therapeutic for inflammatory disease. We found that Didox treatment of mouse bone marrow-derived mast cells (BMMC) reduced IgE-stimulated degranulation and cytokine production, including IL-6, IL-13, TNF and MIP-1a (CCL3). These effects were consistent using BMMC of different genetic backgrounds and peritoneal mast cells. While the RNR inhibitor hydroxyurea had little or no effect on IgE-mediated function, high concentrations of the antioxidant N-acetylcysteine mimicked Didox-mediated suppression. Furthermore, Didox increased expression of the antioxidant genes superoxide dismutase and catalase, and suppressed DCFH-DA fluorescence, indicating reduced reactive oxygen species production. Didox effects were not due to changes in FcεRI expression or cell viability, suggesting it inhibits signaling required for inflammatory cytokine production. In support of this, we found that Didox reduced FcεRI-mediated AP-1 and NFκB transcriptional activity. Finally, Didox suppressed mast cell-dependent, IgE-mediated passive systemic anaphylaxis in vivo. These data demonstrate the potential use for Didox asa means of antagonizing mast cell responses in allergic disease.

Challenging a Misnomer? The Role of Inflammatory Pathways in Inflammatory Breast Cancer

Inflammatory breast cancer is a rare, yet highly aggressive form of breast cancer, which accounts for less than 5% of all locally advanced presentations. The clinical presentation of inflammatory breast cancer often differs significantly from that of noninflammatory breast cancer; however, immunohistochemistry reveals few, if any, distinguishing features. The more aggressive triple-negative and HER2-positive breast cancer subtypes are overrepresented in inflammatory breast cancer compared with noninflammatory breast cancer, with a poorer prognosis in response to conventional therapies. Despite its name, there remains some controversy regarding the role of inflammation in inflammatory breast cancer. This review summarises the current molecular evidence suggesting that inflammatory signaling pathways are upregulated in this disease, including NF-κB activation and excessive IL-6 production among others, which may provide an avenue for novel therapeutics. The role of the tumor microenvironment, through tumor-associated macrophages, infiltrating lymphocytes, and cancer stem cells is also discussed, suggesting that these tumor extrinsic factors may help account for the differences in behavior between inflammatory breast cancer and noninflammatory breast cancer. While there are various novel treatment strategies already underway in clinical trials, the need for further development of preclinical models of this rare but aggressive disease is paramount.

Molecular pathways driving disease-specific alterations of intestinal epithelial cells

Due to the fact that chronic inflammation as well as tumorigenesis in the gut is crucially impacted by the fate of intestinal epithelial cells, our article provides a comprehensive overview of the composition, function, regulation and homeostasis of the gut epithelium. In particular, we focus on those aspects which were found to be altered in the context of inflammatory bowel diseases or colorectal cancer and also discuss potential molecular targets for a disease-specific therapeutic intervention.

Resveratrol as anti-aging therapy for age-related bone loss

INTRODUCTION

Previous studies have indicated that resveratrol, a natural phytoestrogen, can act as an anti-aging therapy to resist age-related changes of several body tissues. However, the anti-aging effects of resveratrol on bone have been poorly investigated in this natural aging population. Accordingly, this study was design to evaluate the effects of resveratrol on bone mass and biomechanical properties in old rat femora.

METHODS

Twenty 22-month-old male Wistar rats were divided into two randomly assigned groups (n=10). The first group was treated for 10 weeks with resveratrol (10 mg/kg per day) and the second group was left untreated (control). Rat femora were collected. Bone mass and bone microestructure were investigated by microcomputed tomography and histomorphometry. Biomechanical properties were determined by a three-point bending test. Plasma levels of CTX (carboxy-terminal telopeptide of type I collagen) and osteocalcin were also determined. Statistical analyses were performed by a Student two-tailed unpaired t-test. In all experiments, a value of p<0.05 was considered significant.

RESULTS

Microcomputed tomography analyses demonstrated that resveratrol-treated rats had significant higher bone volume, bone trabecular number, and cortical thickness and lower spacing between trabeculae in comparison to the control group. Histomorphometric analyses confirmed the increase of bone volume in resveratrol-treated rats compared to controls. Resveratrol-treated rats had significant higher bone flexural modulus, stiffness, and ultimate load compared to control group. Treatment was not associated with changes in plasma CTX or osteocalcin.

CONCLUSION

These findings demonstrate that resveratrol increases bone microstructure and bone mechanical properties in old male rats, suggesting that resveratrol might be used as anti-aging therapy to resist age-induced bone loss.

Clathrin complexes with the inhibitor kappa B kinase signalosome: imaging the interactome

Many receptors involved with innate immunity activate the inhibitor kappa B kinase signalosome (IKK). The active complex appears to be assembled from the two kinase units, IKKα and IKKβ with the regulatory protein NEMO. Because we previously found that RNA silencing of clathrin heavy chains (CHC), in transformed human lung pneumocytes (A549), decreased TNFα‐induced signaling and phosphorylation of inhibitor kappa B (IκB), we hypothesized that CHC forms cytoplasmic complexes with members of the IKK signalosome. Widely available antibodies were used to immunoprecipitate IKKα and NEMO interactomes. Analysis of the affinity interactomes by mass spectrometry detected clathrin with both baits with high confidence. Using the same antibodies for indirect digital immunofluorescence microscopy and FRET, the CHC–IKK complexes were visualized together with NEMO or HSP90. The natural variability of protein amounts in unsynchronized A549 cells was used to obtain statistical correlation for several complexes, at natural levels and without invasive labeling. Analyses of voxel numbers indicated that: (i) CHC–IKK complexes are not part of the IKK signalosome itself but, likely, precursors of IKK–NEMO complexes. (ii) CHC–IKKβ complexes may arise from IKKβ–HSP90 complexes.

Clathrin forms complexes with IKKa, IKKb, and NEMO, but apparently not the canonical signalosome. These complexes are identified, for the first time, by affinity proteomics and triple FRET without altering molecular structure.

The role of inflammation in inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer. Despite extensive study, whether inflammation contributes to the tumorigenicity or aggressiveness of IBC remains largely unknown. In this chapter, we will review the potential role played by inflammation in IBC based on the results of in vitro, in vivo, and patient studies. Current evidence suggests that several major inflammatory signaling pathways are constitutively active in IBC and breast cancer. Among them, the NF-κB, COX-2, and JAK/STAT signaling systems seem to play a major role in the tumorigenesis of IBC. Inflammatory molecules such as interleukin-6, tumor necrosis factor alpha (TNF-α), and gamma interferon have been shown to contribute to malignant transformation in preclinical studies of IBC, while transforming growth factor-β, interleukins 8 and 1β, as well as TNF-α appear to play a role in proliferation, survival, epithelial-mesenchymal transition, invasion, and metastasis. In this chapter, we also describe work thus far involving inhibitors of inflammation in the development of prevention and treatment strategies for IBC.

Sam68 modulates the promoter specificity of NF-κB and mediates expression of CD25 in activated T cells

CD25, the alpha chain of the interleukin-2 receptor, is expressed in activated T cells and has a significant role in autoimmune disease and tumorigenesis; however, the mechanisms regulating transcription of CD25 remain elusive. Here we identify the Src-associated substrate during mitosis of 68 kDa (Sam68) as a novel non-Rel component in the nuclear factor-kappaB (NF-κB) complex that confers CD25 transcription. Our results demonstrate that Sam68 has an essential role in the induction and maintenance of CD25 in T cells. T-cell receptor engagement triggers translocation of the inhibitor of NF-κB kinase alpha (IKKα) from the cytoplasm to the nucleus, where it phosphorylates Sam68, causing complex formation with NF-κB in the nucleus. These findings reveal the important roles of KH domain-containing components and their spatial interactions with IKKs in determining the binding targets of NF-κB complexes, thus shedding novel insights into the regulatory specificity of NF-κB.

Proteasome inhibition by bortezomib increases IL-8 expression in androgen-independent prostate cancer cells: the role of IKKα

Expression of the proinflammatory and proangiogenic chemokine IL-8, which is regulated at the transcriptional level by NF-κB, is constitutively increased in androgen-independent metastatic prostate cancer and correlates with poor prognosis. Inhibition of NF-κB-dependent transcription was used as an anticancer strategy for the development of the first clinically approved 26S proteasome inhibitor, bortezomib (BZ). Even though BZ has shown remarkable antitumor activity in hematological malignancies, it has been less effective in prostate cancer and other solid tumors; however, the mechanisms have not been fully understood. In this article, we report that proteasome inhibition by BZ unexpectedly increases IL-8 expression in androgen-independent prostate cancer PC3 and DU145 cells, whereas expression of other NF-κB-regulated genes is inhibited or unchanged. The BZ-increased IL-8 expression is associated with increased in vitro p65 NF-κB DNA binding activity and p65 recruitment to the endogenous IL-8 promoter. In addition, proteasome inhibition induces a nuclear accumulation of IκB kinase (IKK)α, and inhibition of IKKα enzymatic activity significantly attenuates the BZ-induced p65 recruitment to IL-8 promoter and IL-8 expression, demonstrating that the induced IL-8 expression is mediated, at least partly, by IKKα. Together, these data provide the first evidence, to our knowledge, for the gene-specific increase of IL-8 expression by proteasome inhibition in prostate cancer cells and suggest that targeting both IKKα and the proteasome may increase BZ effectiveness in treatment of androgen-independent prostate cancer.

Bruton's tyrosine kinase phosphorylates Toll-like receptor 3 to initiate antiviral response

Toll-like receptor 3 (TLR3) mediates antiviral response by recognizing double-stranded RNA. Its cytoplasmic domain is tyrosine phosphorylated upon ligand binding and initiates downstream signaling via the adapter TIR-containing adaptor inducing interferon-β (TRIF). However, the kinase responsible for TLR3 phosphorylation remains unknown. We show here that Bruton's tyrosine kinase (BTK)-deficient macrophages failed to secrete inflammatory cytokines and IFN-β upon TLR3 stimulation and were impaired in clearing intracellular dengue virus infection. Mutant mice were also less susceptible to d-galactosamine/p(I:C)-induced sepsis. In the absence of BTK, TLR3-induced phosphoinositide 3-kinase (PI3K), AKT and MAPK signaling and activation of NFκB, IRF3, and AP-1 transcription factors were all defective. We demonstrate that BTK directly phosphorylates TLR3 and in particular the critical Tyr759 residue. BTK point mutations that abrogate or led to constitutive kinase activity have opposite effects on TLR3 phosphorylation. Loss of BTK also compromises the formation of the downstream TRIF/receptor-interacting protein 1 (RIP1)/TBK1 complex. Thus, BTK plays a critical role in initiating TLR3 signaling.

Minireview: Inflammation: an instigator of more aggressive estrogen receptor (ER) positive breast cancers

Approximately 75% of breast tumors express the estrogen receptor (ER), and women with these tumors will receive endocrine therapy. Unfortunately, up to 50% of these patients will fail ER-targeted therapies due to either de novo or acquired resistance. ER-positive tumors can be classified based on gene expression profiles into Luminal A- and Luminal B-intrinsic subtypes, with distinctly different responses to endocrine therapy and overall patient outcome. However, the underlying biology causing this tumor heterogeneity has yet to become clear. This review will explore the role of inflammation as a risk factor in breast cancer as well as a player in the development of more aggressive, therapy-resistant ER-positive breast cancers. First, breast cancer risk factors, such as obesity and mammary gland involution after pregnancy, which can foster an inflammatory microenvironment within the breast, will be described. Second, inflammatory components of the tumor microenvironment, including tumor-associated macrophages and proinflammatory cytokines, which can act on nearby breast cancer cells and modulate tumor phenotype, will be explored. Finally, activation of the nuclear factor κB (NF-κB) pathway and its cross talk with ER in the regulation of key genes in the promotion of more aggressive breast cancers will be reviewed. From these multiple lines of evidence, we propose that inflammation may promote more aggressive ER-positive tumors and that combination therapy targeting both inflammation and estrogen production or actions could benefit a significant portion of women whose ER-positive breast tumors fail to respond to endocrine therapy.

Chondroitin sulfate reduces cell death of rat hippocampal slices subjected to oxygen and glucose deprivation by inhibiting p38, NFκB and iNOS

The glycosaminoglycan chondroitin sulfate (CS) is a major constituent of the extracellular matrix of the central nervous system where it can constitute part of the perineuronal nets. Constituents of the perineuronal nets are gaining interest because they have modulatory actions on their neighbouring neurons. In this study we have investigated if CS could afford protection in an acute in vitro ischemia/reoxygenation model by using isolated hippocampal slices subjected to 60min oxygen and glucose deprivation (OGD) followed by 120min reoxygenation (OGD/Reox). In this toxicity model, CS afforded protection of rat hippocampal slices measured as a reduction of lactate dehydrogenase (LDH) release; maximum protection (70% reduction of LDH) was obtained at the concentration of 3mM. To evaluate the intracellular signaling pathways implicated in the protective effect of CS, we first analysed the participation of the mitogen-activated protein kinases (MAPKs) p38 and ERK1/2 by western blot. OGD/Reox induced the phosphorylation of p38 and dephosphorylation of ERK1/2; however, CS only inhibited p38 but had no effect on ERK1/2. Furthermore, OGD/Reox-induced translocation of p65 to the nucleus was prevented in CS treated hippocampal slices. Finally, CS inhibited iNOS induction caused by OGD/Reox and thereby nitric oxide (NO) production measured as a reduction in DAF-2 DA fluorescence. In conclusion, the protective effect of CS in hippocampal slices subjected to OGD/Reox can be related to a modulatory action of the local immune response by a mechanism that implies inhibition of p38, NFκB, iNOS and the production of NO.

NF-κB addiction and its role in cancer: 'one size does not fit all'

Activation of nuclear factor (NF)-κB, one of the most investigated transcription factors, has been found to control multiple cellular processes in cancer including inflammation, transformation, proliferation, angiogenesis, invasion, metastasis, chemoresistance and radioresistance. NF-κB is constitutively active in most tumor cells, and its suppression inhibits the growth of tumor cells, leading to the concept of 'NF-κB addiction' in cancer cells. Why NF-κB is constitutively and persistently active in cancer cells is not fully understood, but multiple mechanisms have been delineated including agents that activate NF-κB (such as viruses, viral proteins, bacteria and cytokines), signaling intermediates (such as mutant receptors, overexpression of kinases, mutant oncoproteins, degradation of IκBα, histone deacetylase, overexpression of transglutaminase and iNOS) and cross talk between NF-κB and other transcription factors (such as STAT3, HIF-1α, AP1, SP, p53, PPARγ, β-catenin, AR, GR and ER). As NF-κB is 'pre-active' in cancer cells through unrelated mechanisms, classic inhibitors of NF-κB (for example, bortezomib) are unlikely to mediate their anticancer effects through suppression of NF-κB. This review discusses multiple mechanisms of NF-κB activation and their regulation by multitargeted agents in contrast to monotargeted agents, thus 'one size does not fit all' cancers.

RNA-binding protein HuR regulates RGS4 mRNA stability in rabbit colonic smooth muscle cells

Regulator of G protein signaling 4 (RGS4) regulates the strength and duration of G protein signaling and plays an important role in smooth muscle contraction, cardiac development, and psychiatric disorders. Little is known about the posttranscriptional regulation of RGS4 expression. We cloned the full-length cDNA of rabbit RGS4, which contains a long 3'-untranslated region (UTR) with several AU-rich elements (AREs). We determined whether RGS4 mRNA stability is mediated by the RNA-binding protein human antigen R (HuR) and contributes to IL-1β-induced upregulation of RGS4 expression. We show that IL-1β treatment in colonic smooth muscle cells doubled the half-life of RGS4 mRNA. Addition of RGS4 3'-UTR to the downstream of Renilla luciferase reporter induced dramatic reduction in the enzyme activity and mRNA expression of luciferase, which was attenuated by the site-directed mutation of the two 3'-most ARE sites. IL-1β increased luciferase mRNA stability in a UTR-dependent manner. Knockdown of HuR significantly aggravated UTR-mediated instability of luciferase and inhibited IL-1β-induced upregulation of RGS4 mRNA. In addition, IL-1β increased cytosolic translocation and RGS4 mRNA binding of HuR. These findings suggest that 3'-most ARE sites within RGS4 3'-UTR are essential for the instability of RGS4 mRNA and IL-1β promotes the stability of RGS4 mRNA through HuR.

The IKK complex, a central regulator of NF-kappaB activation

The IKK kinase complex is the core element of the NF-kappaB cascade. It is essentially made of two kinases (IKKalpha and IKKbeta) and a regulatory subunit, NEMO/IKKgamma. Additional components may exist, transiently or permanently, but their characterization is still unsure. In addition, it has been shown that two separate NF-kappaB pathways exist, depending on the activating signal and the cell type, the canonical (depending on IKKbeta and NEMO) and the noncanonical pathway (depending solely on IKKalpha). The main question, which is still only partially answered, is to understand how an NF-kappaB activating signal leads to the activation of the kinase subunits, allowing them to phosphorylate their targets and eventually induce nuclear translocation of the NF-kappaB dimers. I will review here the genetic, biochemical, and structural data accumulated during the last 10 yr regarding the function of the three IKK subunits.

Specification of the NF-kappaB transcriptional response by p65 phosphorylation and TNF-induced nuclear translocation of IKK epsilon

Here we investigated the regulation of NF-κB activity by post-translational modifications upon reconstitution of NF-κB p65-deficient cells with the wild-type protein or phosphorylation-defect mutants. Analysis of NF-κB target gene expression showed that p65 phosphorylations alone or in combination function to direct transcription in a highly target gene-specific fashion, a finding discussed here as the NF-κB barcode hypothesis. High-resolution microscopy and surface rendering revealed serine 536 phosphorylated p65 predominantly in the cytosol, while serine 468 phosphorylated p65 mainly localized in nuclear speckles. TNF stimulation resulted in the translocation of the cytosolic p65 kinase IKKε to the nucleus and also to promyelocytic leukemia (PML) nuclear bodies. This inducible IKKε translocation was dependent on p65 phosphorylation and was prevented by the oncogenic PML-RARα fusion protein. Chromatin immunoprecipitation experiments revealed the inducible association of IKKε to the control regions of several NF-κB target genes. In the nucleus, the kinase contributes to the expression of a subset of NF-κB-regulated genes, thus revealing a novel role of IKKε for the control of nuclear NF-κB activity.

NFkappaB promotes inflammation, coagulation, and fibrosis in the aging glomerulus

The peak prevalence of ESRD from glomerulosclerosis occurs at 70 to 79 years. To understand why old glomeruli are prone to failure, we analyzed the Fischer 344 rat model of aging under ad libitum-fed (rapid aging) and calorie-restricted (slowed aging) conditions. All glomerular cells contained genes whose expression changed "linearly" during adult life from 2 to 24 months: mesangial cells (e.g., MMP9), endothelial cells (e.g., ICAM and VCAM), parietal epithelial cells (e.g., ceruloplasmin), and podocytes (e.g., nephrin and prepronociceptin). Patterns of aging glomerular gene expression closely resembled atherosclerosis, including activation of endothelial cells, epithelial cells, and macrophages, as well as proinflammatory pathways related to cell adhesion, chemotaxis, blood coagulation, oxidoreductases, matrix metalloproteinases, and TGF-beta activation. We used a nonbiased data-mining approach to identify NFkappaB as the likely transcriptional regulator of these events. We confirmed NFkappaB activation by two independent methods: translocation of NFkappaB p50 to glomerular nuclei and ChIP assays demonstrating NFkappaB p50 binding to the kappaB motif of target genes in old versus young glomeruli. These data suggest that old glomeruli exhibit NFkappaB-associated up-regulation of a proinflammatory, procoagulable, and profibrotic phenotype compared with young glomeruli; these distinctions could explain their enhanced susceptibility to failure. Furthermore, these results provide a potential mechanistic explanation for the close relationship between ESRD and atherosclerotic organ failure as two parallel arms of age-associated NFkappaB-driven processes.

A peptidyl-glucosamine derivative affects IKKalpha kinase activity in human chondrocytes

Introduction

Nuclear factor-κB (NF-κB) transcription factor regulates several cell signaling pathways, such as differentiation and inflammation, which are both altered in osteoarthritis. Inhibitor κB kinase (IKK)α and IKKβ are kinases involved in the activation of the NF-κB transcription factor. The aim of the present study was to determine the effects of glucosamine (GlcN), which is administered in the treatment of osteoarthritis, and of its 2-(N-Acetyl)-L-phenylalanylamido-2-deoxy-β-D-glucose (NAPA) derivative on IKK kinases and, consequently, on NF-κB activation in human chondrocytes.

Methods

The human chondrosarcoma cell line HTB-94 and human primary chondrocytes were stimulated with tumor necrosis factor (TNF)α after pre-treatment with GlcN or NAPA. Gene mRNA expression level was evaluated by real-time PCR. Inhibitor κB protein (IκB)α phosphorylation and p65 nuclear re-localization were analyzed by Western blotting; IKKα nuclear re-localization was also investigated by immunocytochemistry and Western blotting. IKK kinase activity was studied by in vitro kinase assay.

Results

After TNFα stimulation, the mRNA expression level of some of the genes under NF-κB control, such as interleukin (IL)-6 and IL-8, increased, while treatment with GlcN and NAPA reverted the effect. We investigated the possibility that GlcN and NAPA inhibit IKK kinase activity and found that NAPA inhibits the IKKα kinase activity, whereas GlcN does not. Interestingly, both GlcN and NAPA inhibit IKKα nuclear re-localization.

Conclusions

Our results demonstrate that glucosamine and its peptidyl derivative can interfere with NF-κB signaling pathway by inhibiting IKKα activity in human chondrocytes. However, the mechanism of action of the two molecules is not completely overlapping. While NAPA can both specifically inhibit the IKKα kinase activity and IKKα nuclear re-localization, GlcN only acts on IKKα nuclear re-localization.

Epicatechin induces NF-κB, activator protein-1 (AP-1) and nuclear transcription factor erythroid 2p45-related factor-2 (Nrf2) via phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) and extracellular regulated kinase (ERK) signalling in HepG2 cells

The dietary flavonoid epicatechin has been reported to exhibit a wide range of biological activities. The objective of the present study was to investigate the time-dependent regulation by epicatechin on the activity of the main transcription factors (NF-κB, activator protein-1 (AP-1) and nuclear transcription factor erythroid 2p45-related factor (Nrf2)) related to antioxidant defence and survival and proliferation pathways in HepG2 cells. Treatment of cells with 10 μm-epicatechin induced the NF-κB pathway in a time-dependent manner characterised by increased levels of IκB kinase (IKK) and phosphorylated inhibitor of κB subunit-α (p-IκBα) and proteolytic degradation of IκB, which was consistent with an up-regulation of the NF-κB-binding activity. Time-dependent activation of the AP-1 pathway, in concert with enhanced c-Jun nuclear levels and induction of Nrf2 translocation and phosphorylation were also demonstrated. Additionally, epicatechin-induced NF-κB and Nrf2 were connected to reactive oxygen species intracellular levels and to the activation of cell survival and proliferation pathways, being phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) and extracellular regulated kinase (ERK) associated to Nrf2 modulation and ERK to NF-κB induction. These data suggest that the epicatechin-induced survival effect occurs by the induction of redox-sensitive transcription factors through a tight regulation of survival and proliferation pathways.

Redox regulation of nuclear post-translational modifications during NF-kappaB activation

The transcription factor NF-kappaB controls the expression of hundreds of genes involved in the regulation of the immune/inflammatory response, development, and apoptosis. In resting cells, NF-kappaB proteins are sequestered in the cytoplasm through their tight association with IkappaB proteins. NF-kappaB activation relies on the signal-induced IkappaB phosphorylation and degradation, thereby allowing the nuclear translocation of NF-kappaB proteins. In the nucleus, several post-translational modifications of NF-kappaB and chromatin remodeling of target genes are mandatory for NF-kappaB DNA binding and full transcription. Since 1991, reactive oxygen species (ROS) have been implicated in NF-kappaB activation. ROS enhance the cytoplasmic signaling pathways leading to NF-kappaB nuclear translocation, but reduction/oxidation (redox) also controls several key steps in the nuclear phase of the NF-kappaB program, including chromatin remodeling, recruitment of co-activators, and DNA binding. Here we describe the redox regulation of NF-kappaB activity in the nucleus.

Prophylaxis with carnosol attenuates liver injury induced by intestinal ischemia/reperfusion

AIM: To investigate the possible protective effects of carnosol on liver injury induced by intestinal ischemia reperfusion (I/R).

METHODS: Rats were divided randomly into three experimental groups: sham, intestinal I/R and carnosol treatment (n = 18 each). The intestinal I/R model was established by clamping the superior mesenteric artery for 1 h. In the carnosol treatment group, surgery was performed as in the intestinal I/R group, with intraperitoneal administration of 3 mg/kg carnosol 1 h before the operation. At 2, 4 and 6 h after reperfusion, rats were killed and blood, intestine and liver tissue samples were obtained. Intestine and liver histology was investigated. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and interleukin (IL)-6 were measured. Liver tissue superoxide dismutase (SOD) and myeloperoxidase (MPO) activity were assayed. The liver intercellular adhesion molecule-1 (ICAM-1) and nuclear factor κB (NF-κB) were determined by immunohistochemical analysis and western blot analysis.

RESULTS: Intestinal I/R induced intestine and liver injury, characterized by histological changes, as well as a significant increase in serum AST and ALT levels. The activity of SOD in the liver tissue decreased after I/R, which was enhanced by carnosol pretreatment. In addition, compared with the control group, carnosol markedly reduced liver tissue MPO activity and serum IL-6 level, which was in parallel with the decreased level of liver ICAM-1 and NF-κB expression.

CONCLUSION: Our results indicate that carnosol pretreatment attenuates liver injury induced by intestinal I/R, attributable to the antioxidant effect and inhibition of the NF-κB pathway.

Cell Defence and Survival

Central to immune defence mechanisms is the role of transcription factor nuclear factor kappa B (NF-kB). This is a complex biochemical topic with ever more controls revealed. NF-kB determines the production of proinflammatory cytokines and chemokines. Pharmacologists step in with possible means of control. Other systems involved in defence include the cyclooxygenase 2 (Cox-2) enzyme and perioxisome proliferator-activated receptors. Insulin receptor activation needs to be seen in context. The mTOR system directs uptake of nutrients by cells. mTOR is suppressed by rapamycin, whose usage is now quite considerable in the control of transplant rejection.

Tumor necrosis factor receptor 1 induces interleukin-6 upregulation through NF-kappaB in a rat neuropathic pain model

Peripheral nerve injury resulting in neuropathic pain induces the upregulation of interleukin (IL)-6 and tumor necrosis factor-alpha, which binds to tumor necrosis factor receptor 1 (TNFR1) and induces NF-kappaB and p38 MAPK activation in the spinal cord and dorsal root ganglia (DRG). We here investigated whether TNFR1 regulates IL-6 expression through NF-kappaB or p38 MAPK activations in the spinal cord and DRG in rats with chronic constriction injury (CCI) of the sciatic nerve. Intrathecal treatment with a TNFR1 antisense oligonucleotide (ASO) significantly inhibited CCI-elevated IKKs phosphorylation, IkB-alpha degradation, the nuclear translocation, phosphorylation, and DNA-binding activity of NF-kappaB, p38 MAPK activation, and IL-6 mRNA and protein expression in the spinal cord and DRG. Interestingly, CCI remarkably elevated IKKalpha and p65 phosphorylations in the spinal cord rather than in the DRG. In addition, NF-kappaB decoy, but not p38 MAPK inhibitor, SB203580 reduced CCI-elevated IL-6 expression in the spinal cord and DRG. Therefore, these data suggest that TNFR1 induces IL-6 upregulation and neuropathic pain through NF-kappaB, but not p38 MAPK activation in the spinal cord and DRG and that the NF-kappaB/IL-6 pathways in the DRG may be less dependent on TNFR1 than the spinal cord pathway.

The IkappaB kinases IKKalpha and IKKbeta are necessary and sufficient for skeletal muscle atrophy

Nuclear factor-kappaB (NF-kappaB) signaling is necessary for many types of muscle atrophy, yet only some of the required components have been identified. Gene transfer of a dominant negative (d.n.) IKKbeta into rat soleus muscles showed complete inhibition of 7-day disuse-induced activation of a kappaB reporter gene, while overexpression of wild-type (w.t.) IKKbeta did not. Overexpression of a d.n. IKKbeta-EGFP fusion protein showed that atrophy was inhibited by 50%, indicating that IKKbeta is required for the atrophy process. Overexpression of constitutively active (c.a.) IKKbeta-EGFP showed a marked increase in NF-kappaB activity and a decrease in fiber size of weight-bearing soleus muscles, while muscles overexpressing w.t. IKKbeta-HA had no effect. The same results were found for IKKalpha; overexpression of a d.n. form of the protein decreased unloading-induced NF-kappaB activation and inhibited atrophy by 50%, while overexpression of the w.t. protein had no effect. Overexpression of a c.a. IKKalpha-EGFP fusion protein showed that IKKalpha was sufficient to activate NF-kappaB activity and induce fiber atrophy in muscle. Overexpression of d.n. IKKbeta plus d.n. IKKalpha showed an additive effect on the inhibition of disuse atrophy (70%), suggesting that both kinases of the IKK complex are required for muscle atrophy. These data show that both IKKalpha and IKKbeta are necessary and sufficient for physiological muscle atrophy.

A nuclear role for Kaposi's sarcoma-associated herpesvirus-encoded K13 protein in gene regulation

Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded viral FLICE inhibitory protein K13 interacts with a cytosolic IkappaB kinase (IKK) complex to activate nuclear factor-kappaB (NF-kappaB). We recently reported that K13 antagonizes KSHV lytic regulator RTA (replication and transcription activator) and blocks lytic replication, but spares RTA-induced viral interleukin-6 (vIL6). Here we report that K13 is also present in the nuclear compartment, a property not shared by its structural homologs. K13 interacts with and activates the nuclear IKK complex, and binds to the IkappaBalpha promoter. K13 mutants that are retained in the cytosol lack NF-kappaB activity. However, neither the IKKs nor NF-kappaB activation is required for nuclear localization of K13. Instead, this ability is dependent on a nuclear localization signal located in its N-terminal 40 amino acids. Finally, K13, along with p65/RelA, binds to the promoters of a number of KSHV lytic genes, including RTA, ORF57 and vGPCR, but not to the promoter of the vIL6 gene. Thus, K13 has an unexpected nuclear role in viral and cellular gene regulation and its differential binding to the promoters of lytic genes may not only contribute to the inhibition of KSHV lytic replication, but may also account for the escape of vIL6 from K13-induced transcriptional suppression.

Activation of innate immunity system during aging: NF-kB signaling is the molecular culprit of inflamm-aging

Innate and adaptive immunity are the major defence mechanisms of higher organisms against inherent and environmental threats. Innate immunity is present already in unicellular organisms but evolution has added novel adaptive immune mechanisms to the defence armament. Interestingly, during aging, adaptive immunity significantly declines, a phenomenon called immunosenescence, whereas innate immunity seems to be activated which induces a characteristic pro-inflammatory profile. This process is called inflamm-aging. The recognition and signaling mechanisms involved in innate immunity have been conserved during evolution. The master regulator of the innate immunity is the NF-kB system, an ancient signaling pathway found in both insects and vertebrates. The NF-kB system is in the nodal point linking together the pathogenic assault signals and cellular danger signals and then organizing the cellular resistance. Recent studies have revealed that SIRT1 (Sir2 homolog) and FoxO (DAF-16), the key regulators of aging in budding yeast and Caenorhabditis elegans models, regulate the efficiency of NF-kB signaling and the level of inflammatory responses. We will review the role of innate immunity signaling in the aging process and examine the function of NF-kB system in the organization of defence mechanisms and in addition, its interactions with the protein products of several gerontogenes. Our conclusion is that NF-kB signaling seems to be the culprit of inflamm-aging, since this signaling system integrates the intracellular regulation of immune responses in both aging and age-related diseases.

Bruton's tyrosine kinase separately regulates NFkappaB p65RelA activation and cytokine interleukin (IL)-10/IL-12 production in TLR9-stimulated B Cells

B lymphocytes express both B cell receptor and Toll-like receptors (TLR). We show here that Bruton's tyrosine kinase (Btk), a critical component in B cell receptor signaling, is also involved in TLR9 signaling in B cells. Stimulation of B cells with TLR9 ligand CpG oligodeoxynucleotide (ODN) leads to transient phosphorylation of Btk, and in the absence of Btk, TLR9-induced proliferation of B cells is impaired. Interestingly, Btk(-/-) B cells secrete significantly more interleukin (IL)-12 but much less IL-10 compared with wild type B cells upon TLR9 stimulation. Immunization of Btk(-/-) mice with CpG ODN also leads to elevated levels of IL-12 in vivo and consequently, a greater -fold increment in the production of Th1 type IgG2b and IgG3 antibodies in these mice compared with wild type controls. The addition of exogenous recombinant IL-10 could suppress IL-12 production by TLR9-activated Btk(-/-) B cells, suggesting that in B cells, Btk negatively regulates IL-12 through the induction of autocrine IL-10 production. TLR9 signaling also leads to the activation of NFkappaB, including the p65RelA subunit in wild type B cells. The lack of Btk signaling affects the activation of NFkappaB and impairs the translocation of the p65RelA subunit to the nucleus of B cells upon TLR9 stimulation. However, p65RelA(-/-) B cells could respond similarly to wild type B cells in terms of IL-10 and IL-12 secretion when stimulated with CpG ODN, suggesting that the defect in NFkappaB p65RelA activation is additional to the impairment in cytokine production in TLR9-activated Btk(-/-) B cells. Thus, Btk plays an important role in TLR9 signaling and acts separately to regulate NFkappaB RelA activation as well as IL-10 and IL-12 production in B cells.

Innate immunity meets with cellular stress at the IKK complex: regulation of the IKK complex by HSP70 and HSP90

Several research models have shown that if cellular stress induces the heat shock response then this will suppress the NF-kappaB-mediated inflammatory response. The NF-kappaB signaling pathway mediates both stress signals and innate immunity signals. Heat shock proteins HSP70 and HSP90 regulate several signaling cascades to maintain cellular homeostasis. Recent studies have revealed that HSP70 and HSP90 proteins regulate the function of the IKK complex which is the major activator of the NF-kappaB complex. The heat shock response can cause the dissociation of the IKK complex, composed of protein kinase subunits IKKalpha and IKKbeta and the regulatory unit NEMO, and inhibit the activation of NF-kappaB signaling. Suppression of immune signaling during cellular stress may be a useful feedback response for helping cells to survive tissue injury. Furthermore, IKKalpha and IKKbeta kinases are important activators of tumorigenesis and hence the inhibition of long-term activation of the IKK complex by HSP70 and HSP90 proteins may prevent cancer development during chronic inflammation.

Tumor necrosis factor-alpha (TNF-alpha) regulates Toll-like receptor 2 (TLR2) expression in microglia

Microglia represent one effector arm of CNS innate immunity as evident by their role in pathogen recognition. We previously reported that exposure of microglia to Staphylococcus aureus (S. aureus), a prevalent CNS pathogen, led to elevated Toll-like receptor 2 (TLR2) expression, a pattern recognition receptor capable of recognizing conserved structural motifs associated with gram-positive bacteria such as S. aureus. In this study, we demonstrate that the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) enhances TLR2 expression in microglia, whereas interleukin-1beta has no significant effect. To determine the downstream signaling events responsible for elevated microglial TLR2 expression in response to TNF-alpha, a series of signal transduction inhibitors were employed. Treatment with caffeic acid phenethyl ester, an inhibitor of redox-mediated nuclear factor-kappa B activation, significantly attenuated TNF-alpha-induced TLR2 expression. Similar results were observed with the IKK-2 and IkappaB-alpha inhibitors SC-514 and BAY 11-7082, respectively. In contrast, no significant alterations in TLR2 expression were observed with protein kinase C or p38 mitogen-activated protein kinase inhibitors. A definitive role for TNF-alpha was demonstrated by the inability of S. aureus to augment TLR2 expression in microglia isolated from TNF-alpha knockout mice. In addition, TLR2 expression was significantly attenuated in brain abscesses of TNF-alpha knockout mice. Collectively, these results indicate that in response to S. aureus, TNF-alpha acts in an autocrine/paracrine manner to enhance TLR2 expression in microglia and that this effect is mediated, in part, by activation of the nuclear factor-kappa B pathway.

Promoter-dependent Effect of IKKα on NF-κB/p65 DNA Binding

IKKalpha regulates many chromatin events in the nuclear phase of the NF-kappaB program, including phosphorylation of histone H3 and removal of co-repressors from NF-kappaB-dependent promoters. However, all of the nuclear functions of IKKalpha are not understood. In this study, using mouse embryonic fibroblasts IKKalpha knock-out and reexpressing IKKalpha after retroviral transduction, we demonstrate that IKKalpha contributes to NF-kappaB/p65 DNA binding activity on an exogenous kappaB element and on some, but not all, endogenous NF-kappaB-target promoters. Indeed, p65 chromatin immunoprecipitation assays revealed that IKKalpha is crucial for p65 binding on kappaB sites of icam-1 and mcp-1 promoters but not on ikappabalpha promoter. The mutation of IKKalpha putative nuclear localization sequence, which prevents its nuclear translocation, or of crucial serines in the IKKalpha activation loop completely inhibits p65 binding on icam-1 and mcp-1 promoters and rather enhances p65 binding on the ikappabalpha promoter. Further molecular studies demonstrated that the removal of chromatin-bound HDAC3, a histone deacetylase inhibiting p65 DNA binding, is differentially regulated by IKKalpha in a promoter-specific manner. Indeed, whereas the absence of IKKalpha induces HDAC3 recruitment and repression on the icam-1 promoter, it has an opposite effect on the ikappabalpha promoter, where a better p65 binding occurs. We conclude that nuclear IKKalpha is required for p65 DNA binding in a gene-specific manner.

Post-translational modifications regulate distinct functions of CARMA1 and BCL10

Activation of the transcription factor nuclear factor (NF)-kappaB is essential for the normal functioning of the immune system. Deregulated NF-kappaB signalling in lymphocytes can lead to immunodeficiency, but also to autoimmunity or lymphomas. Many of the signalling components controlling NF-kappaB activation in lymphocytes are now known, but it is less clear how distinct molecular components of this pathway are regulated. Here, we summarize recent findings on post-translational modifications of intracellular components of this pathway. Phosphorylation of the CARMA1 and BCL10 proteins and ubiquitylation of BCL10 affect the formation and stability of the CARMA1-BCL10-MALT1 (CBM) complex, and also control negative feedback regulation of the NF-kappaB signalling pathway. Moreover, the study of BCL10 phosphorylation isoforms has revealed a new mechanism controlling BCL10 nuclear translocation and an unexpected role for BCL10 in the regulation of the actin cytoskeleton.

Histone Deacetylase Inhibitor Trichostatin A Sustains Sodium Pervanadate-induced NF-κB Activation by Delaying IκBα mRNA Resynthesis

NF-kappaB is a crucial transcription factor tightly regulated by protein interactions and post-translational modifications, like phosphorylation and acetylation. A previous study has shown that trichostatin A (TSA), a histone deacetylase inhibitor, potentiates tumor necrosis factor (TNF) alpha-elicited NF-kappaB activation and delays IkappaBalpha cytoplasmic reappearance. Here, we demonstrated that TSA also prolongs NF-kappaB activation when induced by the insulino-mimetic pervanadate (PV), a tyrosine phosphatase inhibitor that initiates an atypical NF-kappaB signaling. This extension is similarly correlated with delayed IkappaBalpha cytoplasmic reappearance. However, whereas TSA causes a prolonged IKK activity when added to TNFalpha, it does not when added to PV. Instead, quantitative reverse transcriptase-PCR revealed a decrease of ikappabalpha mRNA level after TSA addition to PV stimulation. This synthesis deficit of the inhibitor could explain the sustained NF-kappaB residence in the nucleus. In vivo analysis by chromatin immunoprecipitation assays uncovered that, for PV induction but not for TNFalpha, the presence of TSA provokes several impairments on the ikappabalpha promoter: (i) diminution of RNA Pol II recruitment; (ii) reduced acetylation and phosphorylation of histone H3-Lys(14) and -Ser(10), respectively; (iii) decreased presence of phosphorylated p65-Ser(536); and (iv) reduction of IKKalpha binding. The recruitment of these proteins on the icam-1 promoter, another NF-kappaB-regulated gene, is not equally affected, suggesting a promoter specificity of PV with TSA stimulation. Taken together, these data suggest that TSA acts differently depending on the NF-kappaB pathway and the targeted promoter in question. This indicates that one overall histone deacetylase role is to inhibit NF-kappaB activation by molecular mechanisms specific of the stimulus and the promoter.

Inhibition of NEMO, the regulatory subunit of the IKK complex, induces apoptosis in high-risk myelodysplastic syndrome and acute myeloid leukemia

In high-risk myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), blasts constitutively activate the antiapoptotic transcription factor nuclear factor-kappaB (NF-kappaB). Here, we show that this NF-kappaB activation relies on the constitutive activation of the IkappaB kinase (IKK) complex, which is formed by the IKKalpha, IKKbeta and IKKgamma/NF-kappaB essential modulator (NEMO) subunits. A cell-permeable peptide that mimics the leucine zipper subdomain of IKKgamma, thus preventing its oligomerization, inhibited the constitutive NF-kappaB activation and induced apoptotic cell death in a panel of human MDS and AML cell lines (P39, MOLM13, THP1 and MV4-11). Small interfering RNA-mediated knockdown of the p65 NF-kappaB subunit or the three IKK subunits including IKKgamma/NEMO also induced apoptotic cell death in P39 cells. Cell death induced by the IKKgamma/NEMO-antagonistic peptide involved the caspase-independent loss of the mitochondrial transmembrane potential as well as signs of outer mitochondrial membrane permeabilization with the consequent release of cytochrome c, apoptosis-inducing factor and endonuclease G. Primary bone marrow CD34(+) cells from high-risk MDS and AML patients also succumbed to the IKKgamma/NEMO-antagonistic peptide, but not to a mutated control peptide. Altogether, these data indicate that malignant cells in high-risk MDS and AML cells critically depend on IKKgamma/NEMO to survive. Moreover, our data delineate a novel procedure for their therapeutic removal, through inhibition of IKKgamma/NEMO oligomerization.