Mutual regulation of the transcriptional activator NF-kappa B and its inhibitor, I kappa B-alpha

Genes associated with an effective host response by Chinook salmon to Renibacterium salmoninarum

An effective host response to Renibacterium salmoninarum, the etiologic agent of bacterial kidney disease, is poorly characterized. Using suppression subtractive hybridization, we exploited the difference in early host response in the pronephros of fish challenged by an attenuated strain (MT239) or a virulent strain (ATCC 33209) of R. salmoninarum. Among the 132 expressed sequence tag (EST) clones that were sequenced, 20 were selected for expression analysis at 24 and 72h after challenge. ESTs matching two interferon inducible genes (IFN-inducible GBP and VLIG1), the ligand GAS6, and the kinase VRK2 were upregulated in fish exposed to MT239, but downregulated or unchanged in fish exposed to 33209. A second group of ESTs matching genes involved in apoptosis (caspase 8) and immune function (IkappaBalpha, p47(phoX), EMR/CD97) were more slowly upregulated in fish exposed to 33209 compared to fish exposed to MT239. The ESTs displaying elevated expression in MT239-exposed fish may represent important cellular processes to bacterial challenge, and may be useful indicators of an effective host response to R. salmoninarum infection.

Microarray analysis of gene expression profiles in response to treatment with bee venom in lipopolysaccharide activated RAW 264.7 cells

AIM OF THE STUDY

The therapeutic application of bee venom (BV) has been used in traditional medicine to treat diseases such as arthritis, rheumatism and pain. Macrophages produce molecules that are known to play roles in inflammatory responses.

MATERIAL AND METHODS

We performed microarray analysis to evaluate the global gene expression profiles of RAW264.7 macrophage cells treated with BV. In addition, six genes were subjected to real-time PCR to confirm the results of the microarray. The cells were treated with lipopolysaccharide (LPS) or BV plus LPS for 30 min or 1h.

RESULTS

124 genes were found to be up-regulated and 158 were found to be down-regulated in cells that were treated with BV plus LPS for 30 min, whereas 211 genes were up-regulated and 129 were down-regulated in cells that were treated with BV plus LPS for 1h when compared with cells that were treated with LPS alone. Furthermore, the results of real-time PCR were similar to those of the microarray. BV inhibited the expression of specific inflammatory genes that were up-regulated by nuclear factor-kappa B in the presence of LPS, including mitogen-activated protein kinase kinase kinase 8 (MAP3K8), TNF, TNF-alpha-induced protein 3 (TNFAIP3), suppressor of cytokine signaling 3 (SOCS3), TNF receptor-associated factor 1 (TRAF1), JUN, and CREB binding protein (CBP).

CONCLUSIONS

These results demonstrate the potent activity of BV as a modulator of the LPS-mediated nuclear factor-kappaB (NF-kappaB)/MAPK pathway in activated macrophages. In addition, these results can be used to understand other effects of BV treatment.

Role of clathrin-mediated endocytosis of surfactant protein A by alveolar macrophages in intracellular signaling

We recently provided evidence that anti-inflammatory macrophage activation, i.e., the inhibition of constitutive and signal-induced NF-kappaB activity by the pulmonary collectin surfactant protein (SP)-A, critically involves a promoted stabilization of IkappaB-alpha, the predominant inhibitor of NF-kappaB, via posttranscriptional mechanisms comprising the activation of atypical (a)PKCzeta. SP-A uptake and degradation by alveolar macrophages (AMphi) occur in a receptor-mediated, clathrin-dependent manner. However, a mutual link between endocytosis of and signaling by SP-A remains elusive. The aim of this study was to investigate whether clathrin-mediated endocytosis (CME) of SP-A by AMphi is a prerequisite for its modulation of the IkappaB-alpha/NF-kappaB pathway. The inhibition of clathrin-coated pit (CCP) formation and clathrin-coated vesicle (CCV) formation/budding abrogates SP-A-mediated IkappaB-alpha stabilization and SP-A-mediated inhibition of LPS-induced NF-kappaB activation in freshly isolated rat AMphi, as determined by Western analysis, fluorescence-activated cell sorting, confocal microscopy, and EMSA. Actin depolymerization and inhibition of CCP formation further abolished SP-A-mediated inhibition of LPS-induced TNF-alpha release, as determined by ELISA. In addition, SP-A-induced atypical PKCzeta activation was abolished by pretreatment of AMphi with CCV inhibitors as determined by in vitro immunocomplex kinase assay. Although CME is classically considered as a means to terminate signaling, our results demonstrate that SP-A uptake via CME by AMphi has to precede the initiation of SP-A signaling.

Withaferin A inhibits iNOS expression and nitric oxide production by Akt inactivation and down-regulating LPS-induced activity of NF-kappaB in RAW 264.7 cells

Induction of inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production is thought to have beneficial immunomodulatory effects in acute and chronic inflammatory disorders. In Raw 264.7 cells stimulated with lipopolysaccharide (LPS) to mimic inflammation, withaferin A inhibited LPS-induced expression of both iNOS protein and mRNA in a dose-dependent manner. To investigate the mechanism by which withaferin A inhibits iNOS gene expression, we examined activation of mitogen-activated protein kinases (MAPKs) and Akt in Raw 264.7 cells. We did not observe any significant changes in the phosphorylation of p38 MAPK in cells treated with LPS alone or LPS plus withaferin A. However, LPS-induced Akt phosphorylation was markedly inhibited by withaferin A, while the phosphorylation of p42/p44 extracellular signal-regulated kinases (ERKs) was slightly inhibited by withaferin A treatment. Withaferin A prevented IkappaB phosphorylation, blocking the subsequent nuclear translocation of nuclear factor-kappaB (NF-kappaB) and inhibiting its DNA binding activity. LPS-induced p65 phosphorylation, which is mediated by extracellular signal-regulated kinase (ERK) and Akt pathways, was attenuated by withaferin A treatment. Moreover, LPS-induced NO production and NF-kappaB activation were inhibited by SH-6, a specific inhibitor of Akt. Taken together, these results suggest that withaferin A inhibits inflammation through inhibition of NO production and iNOS expression, at least in part, by blocking Akt and subsequently down-regulating NF-kappaB activity.

The potential of proteasome inhibitors in cancer therapy

BACKGROUND

The ubiquitin-proteasome system has become a promising novel molecular target in cancer due to its critical role in cellular protein degradation, its interaction with cell cycle and apoptosis regulation and its unique mechanism of action.

OBJECTIVE

This review focuses both on preclinical results and on data from clinical trials with proteasome inhibitors in cancer.

METHODS

Results in hematological malignancies and solid tumors were included, and important data presented in abstract form were considered in this review.

RESULTS/CONCLUSION

Bortezomib as first-in-class proteasome inhibitor has proven to be highly effective in some hematological malignancies, overcomes conventional chemoresistance, directly induces cell cycle arrest and apoptosis, and also targets the tumor microenvironment. It has been granted approval by the FDA for relapsed multiple myeloma, and recently for relapsed mantle cell lymphoma. Combination chemotherapy regimens have been developed providing high remission rates and remission quality in frontline treatment or in the relapsed setting in multiple myeloma. The combination of proteasome inhibition with novel targeted therapies is an emerging field in oncology. Moreover, novel proteasome inhibitors, such as NPI-0052 and carfilzomib, have been developed. This review summarizes our knowledge of the ubiquitin-proteasome system and recent data from cancer clinical trials.

Roles of cytosolic phospholipase A2 and Src kinase in the early action of 2,3,7,8-tetrachlorodibenzo-p-dioxin through a nongenomic pathway in MCF10A cells

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, or dioxin) is known to induce rapid inflammatory cellular responses through the mechanism that has not yet been fully elucidated. In this report, we show that in MCF10A cells, an immortalized, normal mammary epithelial cell line, TCDD rapidly activates the enzymatic activity of cytosolic phospholipase A2 (cPLA2) as at-tested to by arachidonic acid release within 15 min, followed by activation of Src kinase and induction of several inflammation markers. Such an action of TCDD is clearly blocked by methylarachidonyl fluorophosphonate, a specific inhibitor of cPLA2, short interfering RNA against cPLA2, and several calcium signaling blockers, indicating that this action of TCDD is mediated by calcium-triggered activation of cPLA2. This action of TCDD is quite different from the classic action of TCDD to induce cytochrome P450 1A1 (CYP1A1) because blocking this newly identified pathway did not affect the induction of CYP1A1. Moreover, this newly identified pathway was found to depend only on aryl hydrocarbon receptor but not on aryl hydrocarbon receptor nuclear translocator. Together, these findings support the model that the early action of TCDD to induce rapid inflammatory responses is carried out through a characteristic "nongenomic" pathway, which is clearly different from the conventional model of action of TCDD through the "genomic" pathway.

Pre-folding IkappaBalpha alters control of NF-kappaB signaling

Transcription complex components frequently show coupled folding and binding but the functional significance of this mode of molecular recognition is unclear. IkappaBalpha binds to and inhibits the transcriptional activity of NF-kappaB via its ankyrin repeat (AR) domain. The beta-hairpins in ARs 5-6 in IkappaBalpha are weakly-folded in the free protein, and their folding is coupled to NF-kappaB binding. Here, we show that introduction of two stabilizing mutations in IkappaBalpha AR 6 causes ARs 5-6 to fold cooperatively to a conformation similar to that in NF-kappaB-bound IkappaBalpha. Free IkappaBalpha is degraded by a proteasome-dependent but ubiquitin-independent mechanism, and this process is slower for the pre-folded mutants both in vitro and in cells. Interestingly, the pre-folded mutants bind NF-kappaB more weakly, as shown by both surface plasmon resonance and isothermal titration calorimetry in vitro and immunoprecipitation experiments from cells. One consequence of the weaker binding is that resting cells containing these mutants show incomplete inhibition of NF-kappaB activation; they have significant amounts of nuclear NF-kappaB. Additionally, the weaker binding combined with the slower rate of degradation of the free protein results in reduced levels of nuclear NF-kappaB upon stimulation. These data demonstrate clearly that the coupled folding and binding of IkappaBalpha is critical for its precise control of NF-kappaB transcriptional activity.

Effect of weight loss on proinflammatory state of mononuclear cells in obese women

In order to investigate whether weight loss can lead to improvement of the mononuclear cell (MNC) proinflammatory state, 21 nondiabetic obese women with mean age 34+/-2 years (mean+/-s.e.m.) and BMI 32.5+/-1.2 kg/m2 were enrolled in a 12-week caloric restriction and light exercise-based weight loss program. Ten lean women served as controls. Reverse transcription-PCR of proinflammatory cytokines and adipocytokines as well as homeostasis model assessment of insulin resistance (HOMA-IR) were determined before and after weight reduction. Nuclear factor kappaB (NF-kappaB) binding to DNA and inhibitors of NF-kappaB (IkappaB-alpha and IkappaB-beta) obtained from peripheral MNCs were measured. Overall, subjects lost a mean of 4.0+/-0.4 kg (5.0+/-0.3% of their initial body weight) (P<0.01). In addition to significant reductions in BMI, fasting glucose and insulin concentrations, mean serum high-sensitivity C-reactive protein (hs-CRP), migration inhibitor factor (MIF), leptin and visfatin levels decreased by 49.0, 66.6, 17.2, and 50.2%, respectively (all P<0.05), while adiponectin concentrations rose by 33.9% (P<0.05). The DNA binding of the transcriptionally active NF-kappaB from (p65/p50) decreased by 38.1% (P<0.05). Elevated levels of mRNA of NF-kappaB related proinflammatory genes, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), MIF, and matrix metalloproteinase-9 (MMP-9), decreased significantly after weight loss. Although mRNA expression of Rel-A, p105, IkappaB-alpha, IkappaB-beta decreased significantly, their protein levels did not change after weight loss. As a group, NF-kappaB binding activity correlated with HOMA-IR (r=0.332, P=0.049) and marginally with values of BMI (r=0.308, P=0.059). In conclusion, weight loss by 5% of initial weight in nondiabetic obese women led to significant improvement in activated intranuclear NF-kappaB binding as well as several transcriptions of proinflammatory genes regulated by NF-kappaB.

Induction of the IL-9 gene by HTLV-I Tax stimulates the spontaneous proliferation of primary adult T-cell leukemia cells by a paracrine mechanism

The etiologic agent of adult T-cell leukemia (ATL) is human T cell lymphotropic virus type I (HTLV-I). The HTLV-I protein Tax alters gene expression, including those of cytokines and their receptors, which plays an important role in early stages of ATL. Here we demonstrate that expression of interleukin-9 (IL-9) is activated by Tax via an NF-kappaB motif in its proximal promoter, whereas IL-9 receptor-alpha (IL-9Ralpha) expression is not induced by Tax. However, supporting a role for IL-9/IL-9Ralpha in ATL, a neutralizing monoclonal antibody directed toward IL-9Ralpha inhibited ex vivo spontaneous proliferation of primary ATL cells from several patients. Fluorescence-activated cell sorter analysis of freshly isolated peripheral blood mononuclear cells from these patients revealed high level expression of IL-9Ralpha on their CD14-expressing monocytes. Furthermore, purified T cells or monocytes alone from these patients did not proliferate ex vivo, whereas mixtures of these cell types manifested significant proliferation through a contact-dependent manner. Taken together, our data suggest that primary ATL cells, via IL-9, support the action of IL-9Ralpha/CD14-expressing monocytes, which subsequently support the ex vivo spontaneous proliferation of malignant T cells. In summary, these data support a role for IL-9 and its receptor in ATL by a paracrine mechanism.

Lycopene inhibits TNF-alpha-induced endothelial ICAM-1 expression and monocyte-endothelial adhesion

Inflammatory mediators such as TNF-alpha and interleukin (IL)-1beta, and IL-8, which can enhance binding of low-density lipoprotein (LDL) to endothelium and upregulate expression of leukocyte adhesion molecules on endothelium during atherogenesis. Lycopene, a natural carotenoid from tomato and other sources, has been shown to prevent cardiovascular diseases in epidemiological studies. However, its anti-inflammatory action mechanism remains unclear. In the present study, we studied the effect of lycopene on TNF-alpha-induced signaling in human umbilical endothelial cells (HUVECs). We found that TNF-alpha-induced intercellular adhesion molecule-1 (ICAM-1) expression in HUVECs was inhibited by lycopene, whereas cyclooxygenase-2 (COX-2) and platelet-endothelial cell adhesion molecule (PECAM-1) expression were not affected. A further analysis indicated that lycopene attenuated TNF-alpha-induced IkappaB phosphorylation, NF-kappaB expression, and NF-kappaB p65 translocation from cytosol to nucleus. In line with this, TNF-alpha-induced NF-kappaB-DNA but not AP1-DNA complexes formation was inhibited by lycopene, as determined by the electrophoretic mobility shift assay (EMSA). On the other hand, lycopene did not affect TNF-alpha-induced p38 and extracellular matrix-regulated kinase1/2 (ERK1/2) phosphorylation and interferon-gamma (IFN-gamma)-induced signaling, suggesting that lycopene primarily affects TNF-alpha-induced NF-kappaB signaling pathway. In a functional study, lycopene dose-dependently attenuated monocyte adhesion to endothelial monolayer but not that adhesion to extracellular matrix. Taken together, we provided here the first evidence showing that lycopene is able to inhibit TNF-alpha-induced NF-kappaB activation, ICAM-1 expression, and monocyte-endothelial interaction, suggesting an anti-inflammatory role of lycopene and possibly explaining in part why lycopene can prevent cardiovascular diseases.

LPS reduces HIV-1 replication in primary human macrophages partly through an endogenous production of type I interferons

It has been proposed that the systemic immune activation state seen in HIV-1-infected patients is caused by circulating microbial products such as lipopolysaccharide (LPS). Given that macrophages play a key role in HIV-1 pathogenesis, we investigated the LPS-mediated effect on HIV-1 replication in cells of the myeloid lineage. We demonstrate that LPS promotes virus gene expression in a monocytic cell line while it diminishes virus production in primary human monocyte-derived macrophages (MDM). The incapacity of LPS to drive HIV-1 production in MDM was not due to its inability to activate the ubiquitous transcription factor NF-kappaB even in virus-infected cells. Neutralization of type I interferons (IFN) with B18R, a soluble vaccinia virus-coded type I IFN receptor, significantly but not totally diminished the antiviral activity of LPS. Therefore, inhibition of HIV-1 replication in MDM treated with microbial-derived LPS resulted from the induction of type I interferons and a yet to be defined soluble factor.

Molecular modeling of the oxidized form of nuclear factor-κB suggests a mechanism for redox regulation of DNA binding and transcriptional activation

NF-kappa B is an important transcriptional regulator of numerous cellular genes, as well as viruses such as HIV-1. Oxidative stimuli in the cytosol are associated with nuclear translocation of NF-kappa B, whereas in the nucleus, reductive activation by thioredoxin is required for NF-kappa B to bind to DNA and activate target genes. Experimental structures of the reduced form of NF-kappa B bound to its DNA targets are available, from which we have modeled the oxidized form of NF-kappa B homodimer by removal of bound DNA, and modification via a hinge movement of a linker between the dimerization and DNA-binding domains of each subunit. These torsional motions enabled the formation of an inter-subunit disulfide bond between the Cys62 residues of each monomer; the resulting structure was refined using molecular dynamics simulation. The final model of oxidized, disulfide-bridged NF-kappaB is more compact than the open, reduced form. This may facilitate its nuclear translocation through small pores in the nuclear envelope, in response to oxidative stimuli in the cytosol. Furthermore, the inter-subunit disulfide blocks DNA from entering the active site of the oxidized dimer, explaining why subsequent reduction to the thiol form in the nucleus is essential for DNA binding and transcriptional activation to occur.

Regulation of liver regeneration and hepatocarcinogenesis by suppressor of cytokine signaling 3

Suppressor of cytokine signaling 3 (SOCS3) down-regulates several signaling pathways in multiple cell types, and previous data suggest that SOCS3 may shut off cytokine activation at the early stages of liver regeneration (Campbell, J.S., L. Prichard, F. Schaper, J. Schmitz, A. Stephenson-Famy, M.E. Rosenfeld, G.M. Argast, P.C. Heinrich, and N. Fausto. 2001.J. Clin. Invest. 107:1285–1292). We developed Socs3 hepatocyte-specific knockout (Socs3 h-KO) mice to directly study the role of SOCS3 during liver regeneration after a two-thirds partial hepatectomy (PH). Socs3 h-KO mice demonstrate marked enhancement of DNA replication and liver weight restoration after PH in comparison with littermate controls. Without SOCS3, signal transducer and activator of transcription 3 (STAT3) phosphorylation is prolonged, and activation of the mitogenic extracellular signal-regulated kinase 1/2 (ERK1/2) is enhanced after PH. In vitro, we show that SOCS3 deficiency enhances hepatocyte proliferation in association with enhanced STAT3 and ERK activation after epidermal growth factor or interleukin 6 stimulation. Microarray analyses show that SOCS3 modulates a distinct set of genes, which fall into diverse physiological categories, after PH. Using a model of chemical-induced carcinogenesis, we found that Socs3 h-KO mice develop hepatocellular carcinoma at an accelerated rate. By acting on cytokines and multiple proliferative pathways, SOCS3 modulates both physiological and neoplastic proliferative processes in the liver and may act as a tumor suppressor.

Inhibition of LPS-induced NO and PGE2 production by asiatic acid via NF-kappa B inactivation in RAW 264.7 macrophages: possible involvement of the IKK and MAPK pathways

In the present study, we investigated the effect of asiatic acid (the aglycon of asiaticoside) and asiaticoside isolated from the leaves of Centella asiatica (Umbelliferae) on LPS-induced NO and PGE(2) production in RAW 264.7 macrophage cells. Asiatic acid more potently inhibited LPS-induced NO and PGE(2) production than asiaticoside. Consistent with these observations, the protein and mRNA expression levels of inducible iNOS and COX-2 enzymes were inhibited by asiatic acid in a concentration-dependent manner. In addition, asiatic acid dose-dependently reduced the production of IL-6, IL-1 beta and TNF-alpha in LPS-stimulated RAW 264.7 macrophage cells. Furthermore, asiatic acid inhibited the NF-kappaB activation induced by LPS, and this was associated with the abrogation of I kappa B-alpha degradation and with subsequent decreases in nuclear p65 and p50 protein levels. Moreover, the phosphorylations of IKK, p38, ERK1/2, and JNK in LPS-stimulated RAW 264.7 cells were suppressed by asiatic acid in a dose-dependent manner. These results suggest that the anti-inflammatory properties of asiatic acid might be the results from the inhibition of iNOS, COX-2, IL-6, IL-1 beta, and TNF-alpha expressions through the down-regulation of NF-kappaB activation via suppression of IKK and MAP kinase (p38, ERK1/2, and JNK) phosphorylation in RAW 264.7 cells.

Surfactant protein A activation of atypical protein kinase C zeta in IkappaB-alpha-dependent anti-inflammatory immune regulation

The pulmonary collectin surfactant protein (SP)-A has a pivotal role in anti-inflammatory modulation of lung immunity. The mechanisms underlying SP-A-mediated inhibition of LPS-induced NF-kappaB activation in vivo and in vitro are only partially understood. We previously demonstrated that SP-A stabilizes IkappaB-alpha, the primary regulator of NF-kappaB, in alveolar macrophages (AM) both constitutively and in the presence of LPS. In this study, we show that in AM and PBMC from IkappaB-alpha knockout/IkappaB-beta knockin mice, SP-A fails to inhibit LPS-induced TNF-alpha production and p65 nuclear translocation, confirming a critical role for IkappaB-alpha in SP-A-mediated LPS inhibition. We identify atypical (a) protein kinase C (PKC) zeta as a pivotal upstream regulator of SP-A-mediated IkappaB-alpha/NF-kappaB pathway modulation deduced from blocking experiments and confirmed by using AM from PKCzeta-/- mice. SP-A transiently triggers aPKCThr(410/403) phosphorylation, aPKC kinase activity, and translocation in primary rat AM. Coimmunoprecipitation experiments reveal that SP-A induces aPKC/p65 binding under constitutive conditions. Together the data indicate that anti-inflammatory macrophage activation via IkappaB-alpha by SP-A critically depends on PKCzeta activity, and thus attribute a novel, stimulus-specific signaling function to PKCzeta in SP-A-modulated pulmonary immune response.

Association of human leukocyte antigen ancestral haplotype 8.1 with adverse outcome of non-Hodgkin's lymphoma

Previous reports have implicated the tumor necrosis factor (TNF-308) locus to non-Hodgkin's lymphoma (NHL) outcome. The purpose of the study was to examine other chromosome components of the HLA 8.1 ancestral haplotype (AH) and their relation to the clinical course of NHL. HLA class I, II, TNF-308, and lymphotoxin alpha (LTA+252) alleles were analyzed in 154 newly diagnosed NHL patients. Three locus haplotypes were inferred from the unphased genotypes by a Bayesian implementation of the expectation maximization (EM) algorithm using the PHASE 2.1 program. TNF-308A was the only allele associated with fever, poor performance status, elevated beta2-microglobulin, TNF and its p75 receptor plasma levels. Although TNF-308A was in strong linkage disequilibrium with the remaining alleles of 8.1 AH, only HLA-A*01 and HLA-B*08 showed association with prognostic variables. A part of 8.1 AH (A*01-B*08-TNF-308A) was predictive for shorter freedom from progression and overall survival (RR=2.47, P=0.041; RR=3.15; P=0.0049), an association that was stronger than TNF-308A alone and independent from International Prognostic Index (RR=1.55, P<0.001; RR=2.36; P<0.0001). A*01-B*08-TNF-308A fragment of 8.1 AH remained an independent predictive factor in a multivariate model. We conclude that 8.1 AH is an important contributor to NHL outcome. In contrast to A*01-B*08-TNF(-308A, the remaining alleles (Cw*07, DRB1*03, LTA+252G) associated with the 8.1 AH seem to be its passive components.

TCR/CD28-stimulated actin dynamics are required for NFAT1-mediated transcription of c-rel leading to CD28 response element activation

TCR/CD28 engagement triggers the initiation of a variety of signal transduction pathways that lead to changes in gene transcription. Although reorganization of the actin cytoskeleton is required for T cell activation, the molecular pathways controlled by the actin cytoskeleton are ill defined. To this end, we analyzed TCR/CD28-stimulated signaling pathways in cytochalasin D-treated T cells to determine the cytoskeletal requirements for T cell activation. Cytochalasin D treatment impaired T cell activation by causing a reduction in TCR/CD28-mediated calcium flux, and blocked activation of two regulatory elements within the IL-2 promoter, NFAT/AP-1 and CD28RE/AP. Treatment had no effect on signaling leading to the activation of either AP-1 or NF-kappaB. Significantly, we found that NFAT1 is required for optimal c-rel up-regulation in response to TCR/CD28 stimulation. In fact, NFAT1 could be detected bound at the c-rel promoter in response to TCR/CD28 stimulation, and targeting of NFAT1 using RNA interference in human CD4(+) T cells abrogated c-rel transcription. Overall, these findings establish that disrupting actin cytoskeletal dynamics impairs TCR/CD28-mediated calcium flux required for NFAT1-mediated c-rel transcription and, thus, activation of the CD28RE/AP.

Varicella-zoster virus modulates NF-kappaB recruitment on selected cellular promoters

Intercellular adhesion molecule 1 (ICAM-1) expression is down-regulated in the center of cutaneous varicella lesions despite the expression of proinflammatory cytokines such as gamma interferon and tumor necrosis factor alpha (TNF-alpha). To study the molecular basis of this down-regulation, the ICAM-1 induction of TNF-alpha was analyzed in varicella-zoster virus (VZV)-infected melanoma cells (MeWo), leading to the following observations: (i) VZV inhibits the stimulation of icam-1 mRNA synthesis; (ii) despite VZV-induced nuclear translocation of p65, p52, and c-Rel, p50 does not translocate in response to TNF-alpha; (iii) the nuclear p65 present in VZV-infected cells is no longer associated with p50 and is unable to bind the proximal NF-kappaB site of the icam-1 promoter, despite an increased acetylation and accessibility of the promoter in response to TNF-alpha; and (iv) VZV induces the nuclear accumulation of the NF-kappaB inhibitor p100. VZV also inhibits icam-1 stimulation of TNF-alpha by strongly reducing NF-kappaB nuclear translocation in MRC5 fibroblasts. Taken together, these data show that VZV interferes with several aspects of the immune response by inhibiting NF-kappaB binding and the expression of target genes. Targeting NF-kappaB activation, which plays a central role in innate and adaptive immune responses, leads to obvious advantages for the virus, particularly in melanocytes, which are a site of viral replication in the skin.

Role of phosphatidylinositol-3 kinase in transcriptional regulation of TLR-induced IL-12 and IL-10 by Fc gamma receptor ligation in murine macrophages

Ligation of FcgammaR concurrent with LPS stimulation of murine macrophages results in decreased IL-12 and increased IL-10 production. Because PI3K deficiency has been associated with increased IL-12, we hypothesized that PI3K was central to the anti-inflammatory effect of FcgammaR ligation on TLR-induced IL-12. FcgammaR ligation of macrophages increased pAKT, a correlate of PI3K activity, above levels induced by TLR4 or TLR2 agonists. This increase was blocked by PI3K inhibitors, wortmannin or LY294002, as was the effect of FcgammaR ligation on TLR-induced IL-12 and IL-10. LPS-induced binding of NF-kappaB to the IL-12 p40 promoter NF-kappaB-binding site was not affected by FcgammaR ligation at 1 h; however, by 4 h, NF-kappaB binding was markedly inhibited, confirmed in situ by chromatin immunoprecipitation analysis. This effect was wortmannin sensitive. Although TLR-induced IkappaBalpha degradation was not affected by FcgammaR ligation, IkappaBalpha accumulated in the nuclei of cells treated with LPS and FcgammaR ligation for 4 h, and was blocked by PI3K inhibitors. LPS-induced IFN regulatory factor-8/IFN consensus sequence-binding protein mRNA, and an IFN regulatory factor-8-dependent gene, Nos2, were inhibited by concurrent FcgammaR ligation, and this was also reversed by wortmannin. Thus, FcgammaR ligation modulates LPS-induced IL-12 via multiple PI3K-sensitive pathways that affect production, accumulation, and binding of key DNA-binding proteins required for IL-12 induction.

Estrogen receptor alpha mediates breast cancer cell resistance to paclitaxel through inhibition of apoptotic cell death

Estrogen receptors (ER) are expressed in approximately 65% of human breast cancer. Cumulative data from clinical trials and retrospective analyses suggest that some chemotherapeutic agents may be less effective in patients with ER-positive (ER+) tumors than those with ER-negative (ER-) tumors. Paclitaxel is an active agent used in breast cancer chemotherapy. To investigate the possible influence of ER on the therapeutic efficacy of paclitaxel and its underlying mechanism, we established several isogenic ER+ cell lines by stable transfection of ERalpha expression vectors into ER- breast cancer BCap37 cells. We showed that 17-beta estradiol significantly reduces the overall cytotoxicity of paclitaxel in BCap37-expressing ERalpha but has no influence on the ER- parental cells. Further analyses indicate that expression of ERalpha in BCap37 cells mainly interferes with paclitaxel-induced apoptotic cell death, without affecting paclitaxel-induced microtubule bundling and mitotic arrest. Moreover, we found that the addition of ICI 182,780 (Fulvestrant), a selective ER down-regulator, could completely reverse the resistance of ER+ BCap37 cells to paclitaxel. These findings showed that ERalpha-mediated breast tumor cell resistance to paclitaxel was through selective inhibition of paclitaxel-induced tumor cell apoptosis. Additionally, the combination of ICI 182,780 also sensitizes MCF-7 and T47D cell lines to the treatment of paclitaxel, which further confirmed the correlation between ERalpha and drug resistance in ER+ tumor cells. The results obtained from this study provide useful information for understanding ER-mediated resistance to paclitaxel and possibly other antineoplastic agents.

Combining radioimmunotherapy with antihypoxia therapy 2-deoxy-D-glucose results in reduction of therapeutic efficacy

PURPOSE

The efficacy of solid tumor radioimmunotherapy is reduced by heterogeneous tumor distribution of the radionuclide, with dose mainly deposited in the normoxic region and by the relative radioresistance of hypoxic tumor cells. In an attempt to overcome these challenges, radioimmunotherapy was combined with 2-deoxy-d-glucose (2DG), a hypoxia-selective cytotoxic inhibitor of glucose metabolism.

EXPERIMENTAL DESIGN

In vitro toxicity of 2DG in LS174T cultures was tested using a colony-forming assay. The effect of combining 2DG with radioimmunotherapy in vivo was tested by administering radiolabeled anti-carcinoembryonic antigen antibody ([(131)I]A5B7 IgG1 whole monoclonal) to nude mice bearing s.c. LS174T tumors, followed by 10 daily injections of 2DG (2.0 g/kg). Tumors were measured to assess therapeutic efficacy.

RESULTS

Data from in vitro studies confirmed 2DG cytotoxicity in this cell line. Greater toxicity was observed under standard laboratory conditions and in hypoxic cultures than at intermediate, physiologically relevant levels of glucose and oxygen. Alone, 2DG had no effect on in vivo tumor growth (P = 0.377 compared with saline-treated controls). Combination of radioimmunotherapy with 2DG reduced the therapeutic effect of radioimmunotherapy (e.g., 150 microCi (131)I alone mean survival time, 48.33 +/- 16.83 days; combined with 2DG, 30.67 +/- 5.62 days, P = 0.038).

CONCLUSIONS

The combination investigated had a detrimental effect on survival. It is suggested that a cellular metabolic response to more aggressive therapy, previously reported in vitro, caused this. The results of this study have implications for the clinical application of combined cancer therapies with an antimetabolic modality component.

Persistent activation of NF-kappaB related to IkappaB's degradation profiles during early chemical hepatocarcinogenesis

BACKGROUND

To define the NF-kappaB activation in early stages of hepatocarcinogenesis and its IkappaB's degradation profiles in comparison to sole liver regeneration.

METHODS

Western-blot and EMSA analyses were performed for the NF-kappaB activation. The transcriptional activity of NF-kappaB was determined by RT-PCR of the IkappaB-alpha mRNA. The IkappaB's degradation proteins were determined by Western-blot assay.

RESULTS

We demonstrated the persistent activation of NF-kappaB during early stages of hepatocarcinogenesis, which reached maximal level 30 min after partial hepatectomy. The DNA binding and transcriptional activity of NF-kappaB, were sustained during early steps of hepatocarcinogenesis in comparison to only partial hepatectomy, which displayed a transitory NF-kappaB activation. In early stages of hepatocarcinogenesis, the IkappaB-alpha degradation turned out to be acute and transitory, but the low levels of IkappaB-beta persisted even 15 days after partial hepatectomy. Interestingly, IkappaB-beta degradation is not induced after sole partial hepatectomy.

CONCLUSION

We propose that during liver regeneration, the transitory stimulation of the transcription factor response, assures blockade of NF-kappaB until recovery of the total mass of the liver and the persistent NF-kappaB activation in early hepatocarcinogenesis may be due to IkappaB-beta and IkappaB-alpha degradation, mainly IkappaB-beta degradation, which contributes to gene transcription related to proliferation required for neoplastic progression.

Nuclear accumulation and activation of nuclear factor kappaB after split-dose irradiation in LS174T cells

Although radiation-induced gene expression has been extensively studied, most of the studies to date have focused on that after single-dose irradiation. As split-dose irradiation, rather than single-dose irradiation, is usual in clinical situations, we investigated the effects of split-dose irradiation on nuclear factor kappaB (NF-kappaB) in the human rectum carcinoma cell line, LS174T. After either single- or split-dose irradiation with a different interval, nuclear localization of NF-kappaB was examined by Western blot and immunofluorescence and its DNA-binding activity was measured by ELISA-based assay. Irradiation-induced NF-kappaB nuclear accumulation and DNA binding activity increased in a dose-dependent manner. The peak of NF-kappaB nuclear accumulation and DNA binding activity was seen 2 to 6 hours after a single dose of 4 Gy irradiation and returned to control levels after 12 hours. In split-dose irradiation, NF-kappaB activity was similar after the first and second doses of 4 Gy irradiation separated by 12 hours. In addition, NF-kappaB activity was decreased by lengthening the interval between irradiation. The cell survival, which was assessed by colony formation assay, showed inverse correlation to this: the surviving fraction was higher after split-dose irradiation than after single-dose irradiation of the same total dose and it increased as the interval between irradiation was lengthened. Thus the present results showed a correlation between NF-kappaB activation and the repair of sublethal damage in split-dose irradiation.

Dehydroepiandrosterone inhibits the TNF-alpha-induced inflammatory response in human umbilical vein endothelial cells

Dehydroepiandrosterone (DHEA) has a protective role against atherosclerosis. We determined the effect of pharmacological doses of DHEA upon the adhesion of monocytic U937 cells to human umbilical vein endothelial cells (HUVEC), as well as the expression of adhesion and chemoattractant molecules, the translocation of NF-kappaB, the degradation of IkappaB-alpha and the production of reactive oxygen species (ROS) in HUVEC. Adhesion of U937 cells to DHEA-treated HUVEC was evaluated by co-culture experiments using [(3)H]-thymidine-labeled U937 cells. The expression of adhesion and chemoattractant molecules was evaluated by flow cytometry and RT-PCR, respectively; NF-kappaB translocation was determined by Electrophoretic Mobility Shift Assay (EMSA) and IkappaB-alpha degradation by Western blot. ROS production was determined by the reduction of fluorescent DCFDA. TNF-alpha was used to induce inflammatory responses in HUVEC. One hundred micromolar of DHEA-treatment inhibited the TNF-alpha-induced expression of ICAM-1, E-selectin, ROS production and U937 cells adhesion to HUVEC, and interfered with NF-kappaB translocation and IkappaB-alpha degradation. DHEA at the above mention concentration also inhibited the mRNA expression of MCP-1 and IL-8 in basal conditions but not in TNF-alpha-stimulated conditions. Our results suggest that DHEA inhibits the expression of molecules involved in the inflammatory process, therefore it could be used as an alternative in the treatment of chronic inflammatory diseases such as atherosclerosis.

Regions of IkappaBalpha that are critical for its inhibition of NF-kappaB.DNA interaction fold upon binding to NF-kappaB

Nuclear factor kappaB (NF-kappaB) transcription factors regulate genes responsible for critical cellular processes. IkappaBalpha, -beta, and -epsilon bind to NF-kappaBs and inhibit their transcriptional activity. The NF-kappaB-binding domains of IkappaBs contain six ankyrin repeats (ARs), which adopt a beta-hairpin/alpha-helix/loop/alpha-helix/loop architecture. IkappaBalpha appears compactly folded in the IkappaBalpha.NF-kappaB crystal structure, but biophysical studies suggested that IkappaBalpha might be flexible even when bound to NF-kappaB. Amide H/(2)H exchange in free IkappaBalpha suggests that ARs 2-4 are compact, but ARs 1, 5, and 6 are conformationally flexible. Amide H/(2)H exchange is one of few techniques able to experimentally identify regions that fold upon binding. Comparison of amide H/(2)H exchange in free and NF-kappaB-bound IkappaBalpha reveals that the beta-hairpins in ARs 5 and 6 fold upon binding to NF-kappaB, but AR 1 remains highly solvent accessible. These regions are implicated in various aspects of NF-kappaB regulation, such as controlling degradation of IkappaBalpha, enabling high-affinity interaction with different NF-kappaB dimers, and preventing NF-kappaB from binding to its target DNA. Thus, IkappaBalpha conformational flexibility and regions of IkappaBalpha folding upon binding to NF-kappaB are important attributes for its regulation of NF-kappaB transcriptional activity.

Regulation and function of IKK and IKK-related kinases

Members of the nuclear factor kappa B (NF-kappaB) family of dimeric transcription factors (TFs) regulate expression of a large number of genes involved in immune responses, inflammation, cell survival, and cancer. NF-kappaB TFs are rapidly activated in response to various stimuli, including cytokines, infectious agents, and radiation-induced DNA double-strand breaks. In nonstimulated cells, some NF-kappaB TFs are bound to inhibitory IkappaB proteins and are thereby sequestered in the cytoplasm. Activation leads to phosphorylation of IkappaB proteins and their subsequent recognition by ubiquitinating enzymes. The resulting proteasomal degradation of IkappaB proteins liberates IkappaB-bound NF-kappaB TFs, which translocate to the nucleus to drive expression of target genes. Two protein kinases with a high degree of sequence similarity, IKKalpha and IKKbeta, mediate phosphorylation of IkappaB proteins and represent a convergence point for most signal transduction pathways leading to NF-kappaB activation. Most of the IKKalpha and IKKbeta molecules in the cell are part of IKK complexes that also contain a regulatory subunit called IKKgamma or NEMO. Despite extensive sequence similarity, IKKalpha and IKKbeta have largely distinct functions, due to their different substrate specificities and modes of regulation. IKKbeta (and IKKgamma) are essential for rapid NF-kappaB activation by proinflammatory signaling cascades, such as those triggered by tumor necrosis factor alpha (TNFalpha) or lipopolysaccharide (LPS). In contrast, IKKalpha functions in the activation of a specific form of NF-kappaB in response to a subset of TNF family members and may also serve to attenuate IKKbeta-driven NF-kappaB activation. Moreover, IKKalpha is involved in keratinocyte differentiation, but this function is independent of its kinase activity. Several years ago, two protein kinases, one called IKKepsilon or IKK-i and one variously named TBK1 (TANK-binding kinase), NAK (NF-kappaB-activated kinase), or T2K (TRAF2-associated kinase), were identified that exhibit structural similarity to IKKalpha and IKKbeta. These protein kinases are important for the activation of interferon response factor 3 (IRF3) and IRF7, TFs that play key roles in the induction of type I interferon (IFN-I). Together, the IKKs and IKK-related kinases are instrumental for activation of the host defense system. This Review focuses on the functions of IKK and IKK-related kinases and the molecular mechanisms that regulate their activities.

IKKalpha and IKKbeta function in TNFalpha-stimulated adhesion molecule expression in human aortic smooth muscle cells

The role of NFkappaB and it's upstream kinases in regulating adhesion molecule expression in the smooth muscle of the vasculature remains controversial. We therefore examined the effect of blocking the NFkappaB pathway on TNFalpha-stimulated ICAM-1 and VCAM-1 expression in primary cultures of human aortic smooth muscle cells using an adenoviral wild-type IkappaB alpha construct (Ad.IkappaB alpha) and dominant-negative IKKalpha (Ad.IKKalpha+/-) and IKKbeta (Ad.IKKbeta+/-) constructs. Ad.IkappaB alpha treatment was found to block NFkappaB DNA-binding, and thereby completely prevent TNFalpha-stimulated ICAM-1 and VCAM-1 expression without influencing IKK activity. Ad.IKKbeta+/- treatment completely inhibited TNFalpha-stimulated IKK kinase activity, IkappaB alpha degradation and NFkappaB DNA-binding in addition to completely blocking TNFalpha-stimulated ICAM-1 and VCAM-1 expression. Ad.IKKalpha+/- treatment however had no detectable effect on NFkappaB DNA-binding or ICAM-1 and VCAM-1 expression. Our results demonstrate that TNFalpha-stimulated ICAM-1 and VCAM-1 expression in human aortic smooth muscle cells is NFkappaB-dependent, that IKKbeta is a suitable target for drug therapy and Ad.IKKbeta+/- an effective inhibitor of TNFalpha-stimulated ICAM-1 and VCAM-1 expression.

Novel targets in gastric and esophageal cancer

Esophageal cancer (EC) and gastric cancer (GC) constitute a major cause of cancer deaths worldwide. Recent improvements in both surgical techniques and adjuvant/neoadjuvant chemotherapy, radiotherapy or both have increased the survival of patients with loco-regional disease. However, most patients with GC or EC have advanced disease either at diagnosis or during the follow-up, and despite recent advances, these patients still do poorly. Understanding of the molecular pathways that characterize cell growth, cell cycle, apoptosis, angiogenesis and invasion has provided novel targets in cancer therapy. In this review we describe the current status of targeted therapies in the treatment of EC and GC, including EGFR inhibitors, antiangiogenic agents, cell cycle inhibitors, apoptosis promoters and matrix metalloproteinases inhibitors. The emerging data from the clinical development of these compounds has provided novel opportunities in the treatment of EC and GC that will probably translate into clinical benefit for patients with these common malignancies.

Protein methyltransferase 2 inhibits NF-kappaB function and promotes apoptosis

The protein arginine methyltransferases (PRMTs) include a family of proteins with related putative methyltransferase domains that modify chromatin and regulate cellular transcription. Although some family members, PRMT1 and PRMT4, have been implicated in transcriptional modulation or intracellular signaling, the roles of other PRMTs in diverse cellular processes have not been fully established. Here, we report that PRMT2 inhibits NF-kappaB-dependent transcription and promotes apoptosis. PRMT2 exerted this effect by blocking nuclear export of IkappaB-alpha through a leptomycin-sensitive pathway, increasing nuclear IkappaB-alpha and decreasing NF-kappaB DNA binding. The highly conserved S-adenosylmethionine-binding domain of PRMT2 mediated this effect. PRMT2 also rendered cells susceptible to apoptosis by cytokines or cytotoxic drugs, likely due to its effects on NF-kappaB. Mouse embryo fibroblasts from PRMT2 genetic knockouts showed elevated NF-kappaB activity and decreased susceptibility to apoptosis compared to wild-type or complemented cells. Taken together, these data suggest that PRMT2 inhibits cell activation and promotes programmed cell death through this NF-kappaB-dependent mechanism.

A novel member of the IkappaB family, human IkappaB-zeta, inhibits transactivation of p65 and its DNA binding

A novel member of the IkappaB family, human IkappaB-zeta, was identified by a differential screening approach of apoptosis-sensitive and -resistant tumor cells. The protein consists of 6 ankyrin repeats at its COOH terminus and shares about 30% identity with other IkappaB members. IkappaB-zeta associates with both the p65 and p50 subunit of NF-kappaB and inhibits the transcriptional activity as well as the DNA binding of the transcription factor. Interestingly, IkappaB-zeta is localized in the nucleus where it aggregates in matrix-associated deacetylase bodies, indicating that IkappaB-zeta regulates nuclear NF-kappaB activity rather than its nuclear translocation from the cytoplasm. IkappaB-zeta expression itself was regulated by NF-kappaB, suggesting that its activity is controlled in a negative feedback loop. Unlike classical IkappaB proteins, IkappaB-zeta was not degraded upon cell stimulation. Treatment with tumor necrosis factor-alpha, interleukin-1beta, and lipopolysaccharide induced a strong induction of IkappaB-zeta transcripts. Expression of IkappaB-zeta was detected in different tissues including lung, liver, and in leukocytes but not in the brain. Suppression of endogenous IkappaB-zeta by RNA interference rendered cells more resistant to apoptosis, whereas overexpression of IkappaB-zeta was sufficient to induce cell death. Our results, therefore, suggest that IkappaB-zeta functions as an additional regulator of NF-kappaB activity and, hence, provides another control level for the activation of NF-kappaB-dependent target genes.

Inhibition of human immunodeficiency virus type 1 replication in latently infected cells by a novel IkappaB kinase inhibitor

In human immunodeficiency virus type 1 (HIV-1) latently infected cells, NF-kappaB plays a major role in the transcriptional induction of HIV-1 replication. Hence, downregulation of NF-kappaB activation has long been sought for effective anti-HIV therapy. Tumor necrosis factor alpha (TNF-alpha) stimulates IkappaB kinase (IKK) complex, a critical regulator in the NF-kappaB signaling pathway. A novel IKK inhibitor, ACHP {2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl-nicotinonitrile}, was developed and evaluated as a potent and specific inhibitor for IKK-alpha and IKK-beta. In this study, we examined the ability of this compound to inhibit HIV-1 replication in OM10.1 cells latently infected with HIV. When these cells were pretreated with ACHP, TNF-alpha-induced HIV-1 replication was dramatically inhibited, as measured by the HIV p24 antigen levels in the culture supernatants. Its 50% effective concentration was approximately 0.56 microM, whereas its 50% cytotoxic concentration was about 15 microM. Western blot analysis revealed inhibition of IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 nuclear translocation, and p65 phosphorylation. ACHP was also found to suppress HIV-1 long terminal repeat (LTR)-driven gene expression through the inhibition of NF-kappaB activation. Furthermore, ACHP inhibited TNF-alpha-induced NF-kappaB (p65) recruitment to the HIV-1 LTR, as assessed by chromatin immunoprecipitation assay. These findings suggest that ACHP acts as a potent suppressor of TNF-alpha-induced HIV replication in latently infected cells and that this inhibition is mediated through suppression of IKK activity.

Functional inactivation of p53 by human T-cell leukemia virus type 1 Tax protein: mechanisms and clinical implications

Human T-cell leukemia virus type 1 (HTLV-I) has been implicated with the etiology of adult T-cell leukemia (ATL) and certain other clinical disorders. Although the leukemogenic mechanism of HTLV-1 is not fully understood yet, the viral Tax protein is widely regarded as a key factor in this mechanism. Tax can modulate the synthesis or function of many regulatory factors which control a wide range of normal and oncogenic cellular processes and therefore, it acts as a potent oncoprotein. In the last few years, special attention has been attracted to Tax interference with the transactivation function of p53, a tumor-suppressor protein that is involved in regulation of the cell-cycle and apoptosis and in maintaining the cellular genome integrity. p53 is mutated in approximately 60% of all human tumors. In contrast, mutant p53 is found in only small percentage of ATL patients. Nevertheless, p53 is inactive in the leukemic cells of most ATL patients and in most HTLV-1 transformed cells. By inactivating p53, Tax can immortalize the HTLV-1-infected cells and destabilize their genome. Consequently, such cells can progress toward the ultimate leukemic state by a stepwise accumulation of oncogenic mutations and other types of chromosomal aberrations. Furthermore, since p53 exists in most ATL patients in its wild-type form, its reactivation by therapeutic drugs might be an effective approach for ATL therapy. Several mechanisms have been proposed so far for Tax-induced p53 inactivation. Understanding the exact mechanism of this Tax effect is essential for designing effective means for this therapeutic approach. In this review article, we discuss the various mechanisms proposed for Tax interference with p53 functions and their clinical and therapeutic implications.

Saikosaponin-d inhibits T cell activation through the modulation of PKCtheta, JNK, and NF-kappaB transcription factor

The effects of saikosaponin-d, a triterpene saponin derived from Bupleurum falcatum L. (Umbelliferae), on the signaling pathways of T cell activation were examined. The results showed that saikosaponin-d potently suppressed both early (CD69) and late (CD71) expressions of mouse T cells stimulated with Con A or PMA. It interfered with PKCtheta translocation from cytosol to membrane fraction and inhibited the phosphorylations of IkappaBalpha and JNK, but not ERK, in PMA-activated mouse T cells. Additionally, it inhibited PMA and ionomycin-stimulated IL-2 production in mouse T cells. In summary, these results indicate that the mechanism by which saikosaponin-d inhibits T cell activation would involve the suppression of CD69 and CD71 expressions and IL-2 production, and the modulation of PKC pathway through PKCtheta, JNK, and NF-kappaB transcription factor. This may herald a novel approach for further studies of saikosaponin-d as a candidate for use in the treatment of inflammatory and autoimmune diseases.

Activation of RelA homodimers by tumour necrosis factor alpha: a possible transcriptional activator in human vascular endothelial cells

In vascular endothelial cells, cytokines induce genes that are expressed in inflammatory lesions partly through the activation of transcription factor NF-kappaB (nuclear factor-kappaB). Among the members of the NF-kappaB/rel protein family, homodimers of the RelA subunit of NF-kappaB can also function as strong transactivators when expressed in cells. However, the functional role of endogenous RelA homodimers has not been clearly elucidated. We investigated whether RelA homodimers are induced in cytokine-treated vascular endothelial cells. Gel mobility-shift and supershift assays revealed that a cytokine TNFalpha (tumour necrosis factor alpha) activated both NF-kappaB1/RelA heterodimers and RelA homodimers that bound to a canonical kappaB sequence, IgkappaB (immunoglobulin kappaB), in SV40 (simian virus 40) immortalized HMEC-1 (human dermal microvascular endothelial cell line 1). In HMEC-1 and HUVEC (human umbilical-vein endothelial cells), TNFalpha also induced RelA homodimers that bound to the sequence 65-2kappaB, which specifically binds to RelA homodimers but not to NF-kappaB1/RelA heterodimers in vitro. Deoxycholic acid, a detergent that can dissociate the NF-kappaB-IkappaB complex (where IkappaB stands for inhibitory kappaB), induced the binding of the RelA homodimers to 65-2kappaB from the cytosolic fraction of resting HMEC-1. Furthermore, TNFalpha induced the transcriptional activity of a reporter gene that was driven by 65-2kappaB in HMEC-1. These results suggest that in addition to NF-kappaB1/RelA heterodimers, TNFalpha also induces RelA homodimers that are functionally active. Thus RelA homodimers may actively participate in cytokine regulation of gene expression in human vascular endothelial cells.

Mixed-disulfide folding intermediates between thyroglobulin and endoplasmic reticulum resident oxidoreductases ERp57 and protein disulfide isomerase

We present the first identification of transient folding intermediates of endogenous thyroglobulin (Tg; a large homodimeric secretory glycoprotein of thyrocytes), which include mixed disulfides with endogenous oxidoreductases servicing Tg folding needs. Formation of disulfide-linked Tg adducts with endoplasmic reticulum (ER) oxidoreductases begins cotranslationally. Inhibition of ER glucosidase activity blocked formation of a subgroup of Tg adducts containing ERp57 while causing increased Tg adduct formation with protein disulfide isomerase (PDI), delayed adduct resolution, perturbed oxidative folding of Tg monomers, impaired Tg dimerization, increased Tg association with BiP/GRP78 and GRP94, activation of the unfolded protein response, increased ER-associated degradation of a subpopulation of Tg, partial Tg escape from ER quality control with increased secretion of free monomers, and decreased overall Tg secretion. These data point towards mixed disulfides with the ERp57 oxidoreductase in conjunction with calreticulin/calnexin chaperones acting as normal early Tg folding intermediates that can be "substituted" by PDI adducts only at the expense of lower folding efficiency with resultant ER stress.

The role of nuclear factor kappa B in human labour

Preterm birth remains the leading cause of perinatal mortality and morbidity, largely as a result of a poor understanding of the precise mechanisms controlling labour onset in humans. Inflammation has long been recognised as a key feature of both preterm and term labour, with an influx of inflammatory cells into the uterus and elevated levels of pro-inflammatory cytokines observed during parturition. Nuclear factor kappa B (NF-κB) is a transcription factor family classically associated with inflammation. Accumulating evidence points to a role for NF-κB in the physiology and pathophysiology of labour. NF-κB activity increases with labour onset and is central to multiple prolabour pathways. Premature or aberrant activation of NF-κB may thus contribute to preterm labour. The current understanding of NF-κB in the context of human labour is discussed here.

Activation of NF-kappaB by HTLV-I and implications for cell transformation

T-cell transformation by the human T-cell leukemia virus type I (HTLV-I) involves deregulation of cellular transcription factors, including members of the NF-kappaB family. In normal T cells, NF-kappaB activation occurs transiently in response to immune stimuli, which is required for antigen-stimulated T-cell proliferation and survival. However, HTLV-I induces persistent activation of NF-kappaB, causing deregulated expression of a large array of cellular genes, which in turn contributes to the induction of T-cell transformation. The HTLV-I transforming protein Tax functions as an intracellular stimulator of IkappaB kinase (IKK), a cellular kinase mediating NF-kappaB activation by diverse stimuli. Tax physically interacts with IKK and renders this inducible kinase constitutively active. By assembling different Tax/IKK complexes, Tax targets the persistent activation of both canonical and noncanonical NF-kappaB signaling pathways. Whereas Tax plays a primary role in HTLV-I-mediated NF-kappaB activation, recent studies reveal that the IKK/NF-kappaB signaling pathway is also activated in freshly isolated adult T-cell leukemia (ATL) cells that often lack detectable Tax expression. The mechanism underlying this Tax-independent pathway of NF-kappaB activation remains poorly understood. Clarifying the precise nature and consequences of the constitutive NF-kappaB activation in ATL cells is important for developing rational therapeutic strategies for this T-cell malignancy.

Involvement of spinal cord nuclear factor κB activation in rat models of proinflammatory cytokine-mediated pain facilitation

Proinflammatory cytokines, such as interleukin-1beta and tumour necrosis factor-alpha, are released by activated glial cells in the spinal cord and play a major role in pain facilitation. These cytokines exert their actions, at least partially, through the activation of the transcription factor, nuclear factor kappaB (NF-kappaB). In turn, NF-kappaB regulates the transcription of many inflammatory mediators, including cytokines. We have previously shown that intrathecal injection of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein, gp120, induces mechanical allodynia via the release of proinflammatory cytokines. Here, we investigated whether NF-kappaB is involved in gp120-induced pain behaviour in Sprague-Dawley rats. Intrathecal administration of NF-kappaB inhibitors, pyrrolidinedithiocarbamate (PDTC) and SN50, prior to gp120 partially attenuated gp120-induced allodynia. In addition, PDTC delayed and reversed allodynia in a model of neuropathic pain induced by sciatic nerve inflammation. These observations suggest that intrathecal gp120 may lead to activation of NF-kappaB within the spinal cord. To reveal NF-kappaB activation, we assessed inhibitory factor kappaBalpha (IkappaBalpha) mRNA expression by in situ hybridization, as NF-kappaB activation up-regulates IkappaBalpha gene expression as part of an autoregulatory feedback loop. No or low levels of IkappaBalpha mRNA were detected in the lumbar spinal cord of vehicle-injected rats, whereas IkappaBalpha mRNA expression was markedly induced in the spinal cord following intrathecal gp120 in predominantly astrocytes and endothelial cells. Moreover, IkappaBalpha mRNA expression positively correlated with proinflammatory cytokine protein levels in lumbosacral cerebrospinal fluid. Together, these results demonstrate that spinal cord NF-kappaB activation is involved, at least in part, in exaggerated pain states.

Achieving stability of lipopolysaccharide-induced NF-kappaB activation

The activation dynamics of the transcription factor NF-kappaB exhibit damped oscillatory behavior when cells are stimulated by tumor necrosis factor-alpha (TNFalpha) but stable behavior when stimulated by lipopolysaccharide (LPS). LPS binding to Toll-like receptor 4 (TLR4) causes activation of NF-kappaB that requires two downstream pathways, each of which when isolated exhibits damped oscillatory behavior. Computational modeling of the two TLR4-dependent signaling pathways suggests that one pathway requires a time delay to establish early anti-phase activation of NF-kappaB by the two pathways. The MyD88-independent pathway required Inferon regulatory factor 3-dependent expression of TNFalpha to activate NF-kappaB, and the time required for TNFalpha synthesis established the delay.

Activation of NF-kappaB by extracellular matrix is involved in spreading and glucose-stimulated insulin secretion of pancreatic beta cells

Laminin-5-rich extracellular matrix derived from 804G cells (804G-ECM) engages beta1 integrins to induce spreading, improve glucose-stimulated insulin secretion (GSIS), and increase survival of pancreatic beta cells. The present study examines whether 804G-ECM activates the transcriptional activity of NF-kappaB and the involvement of NF-kappaB in those effects of 804G-ECM on pancreatic beta cells. 804G-ECM induces nuclear translocation and the DNA binding activity of the p65 subunit of NF-kappaB. 804G-ECM-induced nuclear translocation of NF-kappaB was weak as compared with that induced by interleukin-1beta. Transient 804G-ECM-induced DNA binding activity of NF-kappaB (peak at 2 h) and overexpression of NF-kappaB target genes IkappaB alpha and NF-kappaB1(p105) (peak at 4 h) were observed. When NF-kappaB was inhibited by an inhibitor of IkappaB alpha phosphorylation (Bay 11-7082) or by a recombinant adenovirus expressing the nonphosphorylatable form of IkappaB alpha, 804G-ECM-induced cell spreading and actin cytoskeleton organization were reduced. GSIS from cells on 804G-ECM was inhibited 5-fold, whereas cell survival was not affected. In summary, the results indicate that 804G-ECM induces a transient and moderate NF-kappaB activity. This study shows for the first time that ECM-induced NF-kappaB activity is necessary in maintaining GSIS, although it does not affect survival of pancreatic beta cells. The effects of ECM-induced NF-kappaB activity contrast with the deleterious effects of cytokine-induced NF-kappaB activity. It is proposed that transient and moderate NF-kappaB activity is essential for proper function of the pancreatic beta cell.

HDAC inhibition prevents NF-kappa B activation by suppressing proteasome activity: down-regulation of proteasome subunit expression stabilizes I kappa B alpha

The short chain fatty acid (SCFA) butyrate (BA) and other histone deacetylase (HDAC) inhibitors can rapidly induce cell cycle arrest and differentation of colon cancer cell lines. We found that butyrate and the specific HDAC inhibitor trichostatin A (TSA) can reprogram the NF-(kappa)B response in colon cancer cells. Specifically, TNF-alpha activation is suppressed in butyrate-differentiated cells, whereas IL-1beta activation is largely unaffected. To gain insight into the relationship between butyrate-induced differentiation and NF-(kappa)B regulation, we determined the impact of butyrate on proteasome activity and subunit expression. Interestingly, butyrate and TSA reduced the cellular proteasome activity in colon cancer cell lines. The drop in proteasome activity results from the reduced expression of the catalytic beta-type subunits of the proteasome at both the protein and mRNA level. The selective impact of HDAC inhibitors on TNF-alpha-induced NF-(kappa)B activation appears to relate to the fact that the TNF-alpha-induced activation of NF-(kappa)B is mediated by the proteasome, whereas NF-kappaB activation by IL-1beta is largely proteasome-independent. These findings indicate that cellular differentation status and/or proliferative capacity can significantly impact proteasome activity and selectively alter NF-(kappa)B responses in colon cancer cells. This information may be useful for the further development and targeting of HDAC inhibitors as anti-neoplastic and anti-inflammatory agents.

Novel targeted therapies in the treatment of gastric and esophageal cancer

Esophageal cancer (EC) and gastric cancer (GC) constitute a major cause of cancer deaths worldwide. Recent improvements in both surgical techniques and adjuvant/neoadjuvant radiotherapy and chemotherapy approaches have increased the survival of patients with loco-regional disease. However, most of the patients with GC or EC have advanced disease either at diagnosis or at follow-up. Despite recent advances in the treatment of advanced disease, these patients still do poorly. An emerging understanding of the molecular pathways that characterize cell growth, cell cycle, apoptosis, angiogenesis and invasion has provided novel targets in cancer therapy. In this review we describe the current status of targeted therapies in the treatment of EC and GC. These therapeutic strategies include EGFR inhibitors, antiangiogenic agents, cell cycle inhibitors, apoptosis promoters and matrix metalloproteinases inhibitors. The emerging data from the clinical development of these compounds has provided novel opportunities in the treatment of EC and GC that will probably translate into efficacy advantage in the treatment of these common malignancies.

RelA/p65 regulation of IkappaBbeta

IkappaB inhibitor proteins are the primary regulators of NF-kappaB. In contrast to the defined regulatory interplay between NF-kappaB and IkappaBalpha, much less is known regarding the regulation of IkappaBbeta by NF-kappaB. Here, we describe in detail the regulation of IkappaBbeta by RelA/p65. Using p65(-/-) fibroblasts, we show that IkappaBbeta is profoundly reduced in these cells, but not in other NF-kappaB subunit knockouts. This regulation prevails during embryonic and postnatal development in a tissue-specific manner. Significantly, in both p65(-/-) cells and tissues, IkappaBalpha is also reduced, but not nearly to the same extent as IkappaBbeta, thus highlighting the degree to which IkappaBbeta is dependent on p65. This dependence is based on the ability of p65 to stabilize IkappaBbeta protein from the 26S proteasome, a process mediated in large part through the p65 carboxyl terminus. Furthermore, IkappaBbeta was found to exist in both a basally phosphorylated and a hyperphosphorylated form. While the hyperphosphorylated form is less abundant, it is also more stable and less dependent on p65 and its carboxyl domain. Finally, we show that in p65(-/-) fibroblasts, expression of a proteolysis-resistant form of IkappaBbeta, but not IkappaBalpha, causes a severe growth defect associated with apoptosis. Based on these findings, we propose that tight control of IkappaBbeta protein by p65 is necessary for the maintenance of cellular homeostasis.

High levels of cytoplasmic HTLV-1 Tax mutant proteins retain a Tax-NF-κB-CBP ternary complex in the cytoplasm

The oncogenic potential of HTLV-1 Tax protein is partially ascribed to its capacity to activate NF-kappaB. The current view is that Tax acts first in the cytoplasm to dissociate NF-kappaB factors from the IkappaB proteins and enable their nuclear translocation, then Tax links p65(RelA), within the nucleus, to CBP/p300 and P/CAF, which are essential for its optimal transcriptional activity. Our present study challenges the paradigm that Tax-p65(RelA)-CBP/p300 assembly occurs in the nucleus. Using Tax mutants defective for nuclear localization we show that at low levels these mutants induce the nuclear translocation of NF-kappaB factors but not their transcriptional activity, whereas at high levels they trap CBP and free p65(RelA) in the cytoplasm and block, thereby, their transcriptional function. In contrast, wild-type (w.t.) Tax strongly stimulated NF-kappaB-dependent gene expression in all tested experimental settings. These data suggest that the Tax-p65(RelA)-CBP ternary complex is established in the cytoplasm rather than in the nucleus. When this complex is formed with w.t. Tax, the entire moiety translocates into the nucleus and exerts high transcriptional activity. However, if the complex is formed with the cytoplasmic Tax mutants, the resulting moiety is retained in the cytoplasm and is, therefore, devoid of transcriptional activity.

Tissue inhibitor of metalloproteinases-2 growth-stimulatory activity is mediated by nuclear factor-kappa B in A549 lung epithelial cells

Tissue inhibitors of metalloproteinases (TIMPs) are pleiotropic factors that function as key regulators of extracellular matrix remodeling. They exhibit multifunctional roles including cell growth-stimulating activities and protection from apoptosis. In the present study, we showed that human recombinant TIMP-2 (hrTIMP-2) promotes growth of A549 lung cells. This effect was accompanied by increase in nuclear factor-kappa B (NF-kappaB) activity 24h after exposure as determined by electrophoretic mobility shift assay (EMSA) analysis. This effect was correlated with downregulation of IkappaBalpha and beta proteins and later increases in Bcl-3, IkappaB, and cyclin D1 proteins. Blocking induction of NF-kappaB activity using a dominant-negative mutated version of IkappaBalpha abrogated NF-kappaB activation and cell proliferation.