Signal transduction through NF-kappa B

Analysis of expression of nuclear factor kappa B (NF-kappa B) in multiple myeloma: downregulation of NF-kappa B induces apoptosis

Nuclear factor-kappa B (NF-kappa B) is an important transcription factor that regulates survival in many cells. Activated NF-kappa B has been shown to protect some haematopoietic neoplastic cells from apoptosis. In the present study, we analysed NF-kappa B status in 13 primary samples from patients with multiple myeloma (MM) and in four myeloma cell lines including U266, RPMI 8226, HS-Sultan and K620. Constitutive activation of NF-kappa B was evaluated by either immunohistochemistry or immunofluorescence using a monoclonal mouse anti-human p65 (Rel A) antibody, which recognizes the unbound, active form of p65 (Rel A). Constitutively active NF-kappa B was present in all MM patient samples as well as in all four myeloma cell lines. Inhibition of constitutively active NF-kappa B, by either proteasome inhibitors (MG132, gliotoxin) or inhibitors of I kappa B phosphorylation (Bay117082, and Bay117085), induced apoptosis as demonstrated by both flow cytometric analysis and light microscopic morphological evaluation. This chemically induced apoptosis was associated with decreased DNA binding of nuclear NF-kappa B as determined by the electrophoretic mobility shift assay. In addition, adenovirus vector with dominant negative I kappa B alpha (Ad5I kappa B) was used for inhibition of NF-kappa B in the U266 cell line. Compared with wild-type, super-repressor-treated cells showed an increased level of apoptosis. These results suggest that constitutive expression of NF-kappa B plays an important role in plasma cell survival in MM.

Transcriptional mechanisms of acute lung injury

Acute lung injury occurs as a result of a cascade of cellular events initiated by either infectious or noninfectious inflammatory stimuli. An elevated level of proinflammatory mediators combined with a decreased expression of anti-inflammatory molecules is a critical component of lung inflammation. Expression of proinflammatory genes is regulated by transcriptional mechanisms. Nuclear factor-kappa B (NF-kappa B) is one critical transcription factor required for maximal expression of many cytokines involved in the pathogenesis of acute lung injury. Activation and regulation of NF-kappa B are tightly controlled by a complicated signaling cascade. In acute lung injury caused by infection of bacteria, Toll-like receptors play a central role in initiating the innate immune system and activating NF-kappa B. Anti-inflammatory cytokines such as interleukin-10 and interleukin-13 have been shown to suppress inflammatory processes through inhibiting NF-kappa B activation. NF-kappa B can interact with other transcription factors, and these interactions thereby lead to greater transcriptional selectivity. Modification of transcription is likely to be a logical therapeutic target for acute lung injury.

Tubular NF-kappaB and AP-1 activation in human proteinuric renal disease

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) and activated protein-1 (AP-1) are transcription factors that regulate many genes involved in the progression of renal disease. Recent data have shown that NF-kappaB is activated in tubules and glomeruli in various experimental models of renal injury. In vitro studies also suggest that proteinuria could be an important NF-kappaB activator. We therefore approached the idea that NF-kappaB may be an indicator of renal damage progression.

METHODS

Paraffin-embedded renal biopsy specimens from 34 patients with intense proteinuria [14 with minimal change disease (MCD) and 20 with idiopathic membranous nephropathy (MN)] and from 7 patients with minimal or no proteinuria (IgA nephropathy) were studied by Southwestern histochemistry for the in situ detection of activated transcription factors NF-kappaB and AP-1. In addition, by immunohistochemistry, we performed staining for the NF-kappaB subunits (p50 and p65) and AP-1 subunits (c-fos, c-jun). By immunohistochemistry and/or in situ hybridization, the expression of some chemokines [monocyte chemoattractant protein-1 (MCP-1), RANTES, osteopontin (OPN)] and profibrogenic cytokines [transforming growth factor-beta (TGF-beta)], whose genes are regulated by NF-kappaB and/or AP-1, were studied further.

RESULTS

NF-kappaB was detected mainly in the tubules of proteinuric patients, but rarely in nonproteinuric IgA nephropathy (IgAN) patients. In addition, there was a significant relationship between the intensity of proteinuria and NF-kappaB activation in MCD (r = 0.64, P = 0.01) and MN patients (r = 0.64, P < 0.01). Unexpectedly, patients with MCD had a significantly higher NF-kappaB tubular activation than those with MN (P < 0.01). To assess whether there was a different composition of NF-kappaB protein components, immunostaining was performed for the NF-kappaB subunits p50 and p65. However, no differences were noted between MCD and MN patients. In those patients, there was a lower tubular activation of AP-1 compared with NF-kappaB. Moreover, a strong correlation in the expression of both transcription factors was observed only in MN (r = 0.7, P = 0.004). Patients with progressive MN had an overexpression of MCP-1, RANTES, OPN, and TGF-beta, mainly in the proximal tubules, while no significant expression was found in MCD patients.

CONCLUSIONS

On the whole, our results show that a tubular overactivation of NF-kappaB and AP-1 and a simultaneous up-regulation of certain proinflammatory and profibrogenic genes are markers of progressive renal disease in humans. Increased activation of solely NF-kappaB and/or AP-1 may merely indicate the response of tubular renal cells to injury.

Nuclear factor-kappaB (NF-kappaB) regulates proliferation and branching in mouse mammary epithelium

The nuclear factor-kappaB (NF-kappaB) family of transcription factors has been shown to regulate proliferation in several cell types. Although recent studies have demonstrated aberrant expression or activity of NF-kappaB in human breast cancer cell lines and tumors, little is known regarding the precise role of NF-kappaB in normal proliferation and development of the mammary epithelium. We investigated the function of NF-kappaB during murine early postnatal mammary gland development by observing the consequences of increased NF-kappaB activity in mouse mammary epithelium lacking the gene encoding IkappaBalpha, a major inhibitor of NF-kappaB. Mammary tissue containing epithelium from inhibitor kappaBalpha (IkappaBalpha)-deficient female donors was transplanted into the gland-free mammary stroma of wild-type mice, resulting in an increase in lateral ductal branching and pervasive intraductal hyperplasia. A two- to threefold increase in epithelial cell number was observed in IkappaBalpha-deficient epithelium compared with controls. Epithelial cell proliferation was strikingly increased in IkappaBalpha-deficient epithelium, and no alteration in apoptosis was detected. The extracellular matrix adjacent to IkappaBalpha-deficient epithelium was reduced. Consistent with in vivo data, a fourfold increase in epithelial branching was also observed in purified IkappaBalpha-deficient primary epithelial cells in three-dimensional culture. These data demonstrate that NF-kappaB positively regulates mammary epithelial proliferation, branching, and functions in maintenance of normal epithelial architecture during early postnatal development.

Role of nitric oxide in inflammation

A number of laboratories have sought to elucidate the role of nitric oxide (NO) in both acute and chronic inflammatory diseases. It is now well appreciated that NO can influence many aspects of the inflammatory cascade ranging from its own expression to recruitment of leucocytes to the effected tissue. With the advent of mice selectively deficient in the various isoforms of nitric oxide synthase (NOS), the role that NO may play in various disease states can now be examined in vivo. One such syndrome that has gained much attention in recent years is ischaemia and reperfusion-induced tissue injury. Ischaemia-reperfusion (I/R) injury is an important clinical consideration in situations such as transplantation, trauma, liver or bowel resection and haemorrhagic shock. A hallmark of I/R is the production of reactive oxygen species (ROS) during the reperfusion phase and it is thought that the production of ROS mediate much of the post-ischaemic tissue injury. This review will examine the current state of knowledge regarding the regulatory mechanisms by which NO can influence various aspects of the inflammatory cascade as well as its role in a model of I/R injury in vivo.

TNF-alpha-induced cell death in feline immunodeficiency virus-infected cells is mediated by the caspase cascade

TNF-alpha induced apoptosis in a feline fibroblastic cell line (CRFK) infected with FIV but not in its uninfected control. In this study, to understand the molecular basis of the different susceptibilities to TNF-alpha between FIV-infected and uninfected cells, we examined the expression of TNF receptors and the activation of the caspase and NF-kappaB pathways. Expression levels of TNFR I and TNFR II mRNAs were similar between uninfected and FIV-infected CRFK cells. To understand the role of caspases in TNF-alpha-induced apoptosis, we examined the effect of three different classes of caspase inhibitors, Z-VAD-FMK, Ac-YVAD-CMK, and Z-DEVD-FMK, on the TNF-alpha-induced apoptosis in FIV-infected cells. Pretreatment with each of these caspase inhibitors protected FIV-infected CRFK cells from TNF-alpha-induced cell death. Moreover, one of the caspase substrates, poly(ADP-ribose) polymerase, was shown to be cleaved after TNF-alpha treatment in FIV-infected CRFK cells but not in uninfected CRFK cells. Electrophoretic mobility shift assay using an NF-kappaB motif oligonucleotide and promoter assay using an NF-kappaB luciferase reporter construct indicated that TNF-alpha treatment had induced activation of NF-kappaB in both FIV-infected and uninfected CRFK cells. The present study indicates that TNF-alpha-induced apoptosis in FIV-infected CRFK cells is mediated by the activation of the caspase cascade, but not by either upregulation of TNF receptor or inhibition of NF-kappaB.

Tumour necrosis factor-alpha blockers in rheumatoid arthritis: review of the clinical experience

Tumour necrosis factor (TNF)-alpha has been found to play a central role in the pathogenesis of rheumatoid arthritis, leading to development of novel drug therapies that neutralise the deleterious effects of this cytokine. This new concept of immunobiological treatment of rheumatoid arthritis has yielded successful results. Although the 2 currently available TNFalpha blockers, infliximab and etanercept, differ in structure, mechanism of action and pharmacokinetics, they have provided similar benefits both in clinical improvement and in slowing and even arresting the progression of radiographic damage. This therapeutic response seems to be unequalled by "conventional" treatments in rheumatoid arthritis, and is incontestably a turning point in the therapeutic management of this disease.

Effect of benzoyl peroxide on antioxidant status, NF-kappaB activity and interleukin-1alpha gene expression in human keratinocytes

Benzoyl peroxide (BP) is used as a topical treatment for acne. Besides its anti-bacterial activity, the exact molecular mechanisms underlying its mode of action are not fully understood. In the current study, the effects of BP on cell viability, antioxidant status and, IL-1 and IL-8 gene expression were investigated in HaCaT keratinocytes. Keratinocytes incubated for 24 h with BP exhibited a dose-dependent cytotoxicity at concentrations above 250 microM. Furthermore, in the presence of 300 microM BP about 50% of the cellular vitamin E was depleted within the first 30 min. The intracellular ratio of oxidized to reduced glutathione (GSSG/GSH) was increased significantly starting 6 h after BP treatments indicating that BP reacts rapidly with targets in the cell membrane and more slowly with those in the cytosol. NF-kappaB transactivation was not significantly affected by BP. However, BP treatment of HaCaT keratinocytes resulted in a dose-dependent increase in IL-1alpha gene expression whereas no changes in IL-8 mRNA levels were observed. These results demonstrate that BP induces an inflammatory reaction mediated by oxidative stress by a pathway independent of the redox-sensitive transcription factor NF-kappaB.

Proteinase-activated receptor-2-mediated activation of stress-activated protein kinases and inhibitory kappa B kinases in NCTC 2544 keratinocytes

In this study we examined the regulation of the stress-activated protein (SAP) kinases and inhibitory kappa B kinases (IKKs) through stimulation of the novel G-protein-coupled receptor proteinase-activated receptor-2 in the human keratinocyte cell line NCTC2544. Trypsin and the peptide SLIGKV stimulated a time-dependent increase in both c-Jun N-terminal kinase and p38 mitogen-activated protein kinase activity. Trypsin also stimulated NF kappa B-DNA binding and the activation of the upstream kinases IKK alpha and -beta. Phorbol 12-myristate 13-acetate also strongly activated both SAP kinases and IKK isoforms, suggesting the potential for a protein kinase C-mediated regulatory mechanism underlying the effects of trypsin. Pre-incubation with selective protein kinase C (PKC) inhibitors GF109203X and Gö6983, or transfection of dominant negative (DN)-PKC alpha, abolished phorbol 12-myristate 13-acetate-mediated c-Jun N-terminal kinase activity, although it only partially inhibited the response to trypsin. In contrast, Gö6983 reduced trypsin-stimulated p38 mitogen-activated protein kinase activity to a greater extent than GF109203X, although DN-PKC alpha or PKC zeta had no substantial effect. Additionally, inhibitors of PKC partially reduced trypsin-stimulated IKK alpha activity but abolished that of IKK beta, whereas DN-PKC alpha but not DN-PKC zeta substantially reduced trypsin-stimulated Flag-IKK beta activity. This study shows for the first time proteinase-activated receptor-2-mediated stimulation of both SAP kinase and IKK signaling and differing roles for PKC isoforms in the regulation of each pathway.

Hiv-1 Tat can substantially enhance the capacity of NIK to induce IkappaB degradation

The human immunodeficiency virus type 1 (HIV-1) Tat is a virally encoded protein that dramatically up-regulates viral replication through interactions with the HIV-1 5' long terminal repeat (LTR) and cellular transcription factors. The HIV-1 LTR is divided into three major regions: modulatory, core and TAR. The modulatory region contains numerous cis-acting sequences for the binding of transcription factors including NF-kappaB, NF-AT, and AP-1. In several reports, Tat has been found to induce NF-kappaB activation of the HIV-1 LTR, while in other studies Tat has been reported to have no effect on activation of NF-kappaB. These discrepancies may arise from differences in experimental conditions such as the source of Tat (exogenous versus endogenous), the detection methods for NF-kappaB activation (DNA binding capability versus IkappaB degradation), and the types of reporters used (HIV-1 versus non-HIV-1 derived). To reconcile these differences we examined the effect of endogenous Tat on NF-kappaB activation, on IkappaB degradation and its interaction with upstream MAP3Ks. We demonstrate that although an 80% reduction in Tat-induced HIV-1 LTR activity can be detected if the kappaB binding sites are mutated, surprisingly endogenous Tat (expressed intracellularly by transfection) lacks direct effect on IkappaB degradation. Further analysis demonstrates that although Tat alone lacks direct effect on IkappaBalpha degradation or dissociation from NF-kappaB, Tat can substantially enhance the capacity of NF-kappaB-inducing kinase (NIK), but not MEKK1, to accelerate degradation of IkappaB. We propose a model to explain these collective experimental findings.

Homocysteine inhibits tumor necrosis factor-induced activation of endothelium via modulation of nuclear factor-kappa b activity

Homocystinuria is a metabolic disorder associated with an increased incidence of vascular disease. Here, we analyzed the effects of homocysteine on endothelial cell activation that is a prerequisite for the recruitment of leukocytes to sites of evolving atherosclerotic plaques. Exposure of human umbilical vein endothelial cells to homocysteine alone did not modulate expression of the adhesion molecules E-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, and the chemokines monocyte chemotactic protein-1 and interleukin-8. In contrast, tumor necrosis factor (TNF)-induced upregulation of these molecules was almost completely inhibited by homocysteine, but not by related thiol amino acids. Using electrophoretic mobility shift and reporter gene assays, the inhibitory effect of homocysteine could be attributed to inhibition of DNA binding and transcriptional activity of NF-kappa B. TNF-induced phosphorylation and degradation of I kappa B-alpha, however, were not affected. Neither was NF-kappa B-independent activation of endothelial cells by interferon-gamma influenced by homocysteine. In summary, our data indicate that homocysteine alters the response to injury of endothelial cells which may have fundamental impacts on mechanisms of leukocyte recruitment to sites of inflammation. Our findings might refer to a novel pathway by which homocysteine is involved in vascular disorders associated with homocystinuria.

Taurine chloramine inhibits inducible nitric oxide synthase and TNF-alpha gene expression in activated alveolar macrophages: decreased NF-kappaB activation and IkappaB kinase activity

Taurine prevents tissue damage in a variety of models that involve inflammation, including oxidant-induced lung damage. The mechanism of protection is uncertain, but is postulated to involve the actions of taurine chloramine (Tau-Cl) derived via halide-dependent myeloperoxidase associated with neutrophils. Understanding the influence of Tau-Cl on the production of inflammatory mediators by alveolar macrophages provides an opportunity for determining the mechanism of Tau-Cl action. The effects of Tau-Cl were evaluated on the production of NO and TNF-alpha in NR8383, a cloned cell line derived from rat alveolar macrophages (RAM), and in primary cultures of RAM. Production of NO and TNF-alpha, and expression of inducible NO synthase was inhibited by Tau-Cl in activated NR8383 cells as well as in RAM. Temporal (2, 4, 8, 24 h) expression of inducible NO synthase and TNF-alpha mRNAs was reduced by Tau-Cl in NR8383 cells. Tau-Cl depressed NF-kappaB migration into the nucleus of activated NR8383 cells and caused a more sustained presence of IkappaB in the cytoplasm. Stabilization of cytoplasmic IkappaB-alpha in Tau-Cl-treated cells resulted from decreased phosphorylation of IkappaB-alpha serine-32 and a lower activity of IkappaB kinase (IKK). Additional experiments demonstrated that Tau-Cl does not directly inhibit IKK activity. These results suggest that Tau-Cl exerts its effects at some level upstream of IKK in the signaling pathway and inhibits production of inflammatory mediators through a mechanism that, at least in part, involves inhibition of NF-kappaB activation.

Functional coupling between secretory and cytosolic phospholipase A2 modulates tumor necrosis factor-alpha- and interleukin-1beta-induced NF-kappa B activation

Tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta are potent activators of the transcription factor NF-kappaB, induced during inflammatory conditions. We have previously shown that both secretory and cytosolic phospholipase A(2) (PLA(2)) are involved in TNF-alpha- and IL-1beta-induced NF-kappaB activation. In this study, we have addressed the mechanism of PLA(2) involvement with respect to downstream arachidonic acid (AA) metabolites and the functional coupling between PLA(2)s mediating NF-kappaB activation. We show that in addition to inhibitors of secretory and cytosolic PLA(2)s, 5-lipoxygenase inhibitors attenuate TNF-alpha- and IL-1beta-stimulated NF-kappaB activation. Exogenous addition of leukotriene B(4) (LTB(4)) restored NF-kappaB activation reduced by 5-lipoxygenase inhibitors or an LTB(4) receptor antagonist, thus identifying LTB(4) as a mediator in signaling to NF-kappaB. TNF-alpha- and IL-1beta-induced AA release from cellular membranes was accompanied by phosphorylation of cytosolic PLA(2). Inhibitors of secretory PLA(2) and of 5-lipoxygenase/LTB(4) functionality markedly reduced AA release and nearly completely abolished cytosolic PLA(2) phosphorylation. This demonstrates that secretory PLA(2), through 5-lipoxygenase metabolites, is an essential upstream regulator of cytosolic PLA(2) and AA release. Our results therefore suggest the existence of a functional link between secretory and cytosolic PLA(2) in cytokine-activated keratinocytes, providing a molecular explanation for the participation of both secretory and cytosolic PLA(2) in arachidonic acid signaling and NF-kappaB activation in response to proinflammatory cytokines.

Evidence that HAX-1 is an interleukin-1 alpha N-terminal binding protein

During studies aimed at understanding the function of the N-terminal peptide of interleukin-1 alpha (IL-1 NTP, amino acids 1-112), which is liberated from the remainder of IL-1 alpha during intracellular processing, we identified by yeast two-hybrid analysis a putative interacting protein previously designated as HAX-1. In vitro binding studies and transient transfection experiments confirmed that HAX-1 can associate with the IL-1 NTP. HAX-1 was first identified as a protein that associates with HS1, a target of non-receptor protein tyrosine kinases within haematopoietic cells. Recent data have also revealed interactions between HAX-1 and three disparate proteins, polycystin-2 (derived from the PKD2 gene), a protein linked to polycystic kidney disease, cortactin, and Epstein-Barr virus nuclear antigen leader protein (EBNA-LP). Sequence analysis of different HAX-1 binding domains revealed a putative consensus binding motif that is present in various intracellular proteins. Overlapping peptides comprising the IL-1 NTP were synthesized, and binding experiments revealed that discrete peptides were capable of interacting with HAX-1. HAX-1 may serve to retain the IL-1 NTP in the cytoplasm, and complex formation between the IL-1 NTP and HAX-1 may play a role in motility and/or adhesion of cells.

Targeted mutation of TNF receptor I rescues the RelA-deficient mouse and reveals a critical role for NF-kappa B in leukocyte recruitment

NF-kappaB binding sites are present in the promoter regions of many acute phase and inflammatory response genes, suggesting that NF-kappaB plays an important role in the initiation of innate immune responses. However, targeted mutations of the various NF-kappaB family members have yet to identify members responsible for this critical role. RelA-deficient mice die on embryonic day 15 from TNF-alpha-induced liver degeneration. To investigate the importance of RelA in innate immunity, we genetically suppressed this embryonic lethality by breeding the RelA deficiency onto a TNFR type 1 (TNFR1)-deficient background. TNFR1/RelA-deficient mice were born healthy, but were susceptible to bacterial infections and bacteremia and died within a few weeks after birth. Hemopoiesis was intact in TNFR1/RelA-deficient newborns, but neutrophil emigration to alveoli during LPS-induced pneumonia was severely reduced relative to that in wild-type or TNFR1-deficient mice. In contrast, radiation chimeras reconstituted with RelA or TNFR1/RelA-deficient hemopoietic cells were healthy and demonstrated no defect in neutrophil emigration during LPS-induced pneumonia. Analysis of RNA harvested from the lungs of mice 4 h after LPS insufflation revealed that the induction of several genes important for neutrophil recruitment to the lung was significantly reduced in TNFR1/RelA-deficient mice relative to that in wild-type or TNFR1-deficient mice. These results suggest that TNFR1-independent activation of RelA is essential in cells of nonhemopoietic origin during the initiation of an innate immune response.

Nuclear factor-kappa B is upregulated in colorectal cancer

BACKGROUND

Chemoresistance may involve the anti-apoptotic transcriptional regulator, nuclear factor-kappa B (NF-kappa B). The purpose of this study was to determine whether chemotherapy induces NF-kappa B activation in a human colon cancer cell line (SW48) and whether NF-kappa B is constitutively activated in colorectal cancer.

METHODS

SW48 cells were incubated with gemcitabine hydrochloride (Gemzar) in the presence and absence of the 26s proteasome inhibitor, MG132, and NF-kappa B binding (electrophoretic mobility shift assay), DNA synthesis (tritiated thymidine uptake), cell viability (3-[4,5-dimethylthiazol-2-yl]-diphenyl-tetrazolium bromide assay), and apoptosis (caspase-3 activity) were measured at 24 hours. NF-kappa B binding (electrophoretic mobility shift assay) was also assayed in 10 colorectal cancer tumors.

RESULTS

SW48 cells demonstrated constitutive NF-kappa B binding that was enhanced by gemcitabine hydrochloride in a dose-dependent manner. MG132 inhibited NF-kappa B binding and enhanced gemcitabine hydrochloride's inhibition of DNA synthesis (gemcitabine hydrochloride = 73% +/- 1.4% vs gemcitabine hydrochloride + MG132 = 6% +/- 0.4%, P <.05), cell killing (gemcitabine hydrochloride = 87% +/- 2.0 vs gemcitabine hydrochloride + MG132 = 25% +/- 1.3%, P <.05), and caspase-3 activity (gemcitabine hydrochloride = 870 +/- 17.4 vs gemcitabine hydrochloride + MG132 = 1075 +/- 20.4, P <.05). NF-kappa B binding was increased in 8 of 10 colorectal cancer tumors compared with adjacent normal mucosa.

CONCLUSIONS

Gemcitabine hydrochloride enhances NF-kappa B binding in a colorectal cancer cell line, whereas inhibition of NF-kappa B enhances gemcitabine hydrochloride's antitumor activity. NF-kappa B is also activated in human colorectal cancer. NF-kappa B may identify chemoresistant tumors, whereas inhibition of NF-kappa B may be a novel, biologically based therapy. (Surgery 2001;130:363-9).

Cytoplasmic localization is important for transcription factor nuclear factor-kappa B activation by hepatitis C virus core protein through its amino terminal region

We previously reported that hepatitis C virus core protein (core) activates the transcription factor nuclear factor-kappa B (NF-kappa B) when expressed transiently. In the present study, we investigated the relationship between the NF-kappa B activation capacity and subcellular localization of the core. By changing the subcellular localization of the C-terminally truncated core from the nucleus to the cytoplasm, NF-kappa B was activated. In addition, NF-kappa B activity was augmented by forcing the mutated core to move to the endoplasmic reticulum. It was also suggested that the region from aa 21 to 80 of the core is involved in the activation of NF-kappa B.

N-substituted benzamides inhibit nuclear factor-kappaB and nuclear factor of activated T cells activity while inducing activator protein 1 activity in T lymphocytes

N-substituted benzamides are compounds that have recently been reported to inhibit nuclear factor-kappaB (NF-kappaB) activity and induce apoptosis in a pre-B cell line. In this study, we focused on the effects of N-substituted benzamides on transcriptional regulation in Jurkat T cells. We used a model system where the cells can be stimulated either through TCR/CD28 or by treatment of the cells with PMA and ionomycin to induce transcription factors typical for T lymphocyte activation. Treatment of the Jurkat cells with procainamide did not influence the transcription factor profile of stimulated cells, while treatment with a derivative having an acetyl group in position 4 of the aromatic ring inhibited NF-kappaB and nuclear factor of activated T cells (NFAT) activity. Declopramide, which contains a chloride in position 3 of the aromatic ring, was inactive in this system, whereas also the acetylated derivative of this compound inhibited NF-kappaB and NFAT activity. In contrast, the transcriptional activity and nuclear expression of activator protein 1 induced by TCR/CD28 stimulation or PMA and ionomycin treatment was enhanced by the acetylated variants of the N-substituted benzamides. Finally, we investigated the effect of N-substituted benzamides on intact promoters for two genes central in immune regulation; the CD40 ligand (CD40L) and IL-2 promoters. The transcriptional activity of the CD40L promoter as well as surface expression of the CD40L induced by signaling through TCR/CD28 was inhibited by addition of acetylated N-substituted benzamides, while the transcriptional activity of the IL-2 promoter was enhanced. Taken together, these data indicate that derivatives of N-substituted benzamides are potential drug candidates for quantitative as well as qualitative modulation of immune functions.

Escherichia coli enterotoxin B subunit triggers apoptosis of CD8(+) T cells by activating transcription factor c-myc

Heat-labile enterotoxin from enterotoxinogenic Escherichia coli is not only an important cause of diarrhea in humans and domestic animals but also possesses potent immunomodulatory properties. Recently, the nontoxic, receptor-binding B subunit of heat-labile enterotoxin (EtxB) was found to induce the selective death of CD8(+) T cells, suggesting that EtxB may trigger activation of proapoptotic signaling pathways. Here we show that EtxB treatment of CD8(+) T cells but not of CD4(+) T cells triggers the specific up-regulation of the transcription factor c-myc, implicated in the control of cell proliferation, differentiation, and death. A concomitant elevation in Myc protein levels was also evident, with peak expression occurring 4 h posttreatment. Preincubation with c-myc antisense oligodeoxynucleotides demonstrated that Myc expression was necessary for EtxB-mediated apoptosis. Myc activation was also associated with an increase of IkappaBalpha turnover, suggesting that elevated Myc expression may be dependent on NF-kappaB. When CD8(+) T cells were pretreated with inhibitors of IkappaBalpha turnover and NF-kappaB translocation, this resulted in a marked reduction in both EtxB-induced apoptosis and Myc expression. Further, a non-receptor-binding mutant of EtxB, EtxB(G33D), was shown to lack the capacity to activate Myc transcription. These findings provide further evidence that EtxB is a signaling molecule that triggers activation of transcription factors involved in cell survival.

Cyclopentenone prostaglandins inhibit cytokine-induced nf-kappab activation and chemokine production by human mesangial cells

In the kidney an uncontrolled inflammatory response to an acute insult may lead to chronic inflammation, permanent tissue damage, and progressive renal insufficiency. Resolution of acute inflammation likely is dependent on endogenous regulatory mechanisms activated in parallel with mediators of renal inflammation. These mechanisms are postulated to attenuate the renal expression of proinflammatory cytokines, including the chemokines responsible for recruiting leukocytes to the kidney, thus facilitating the transition from inflammation to healing. To understand the regulation of the inflammatory response within the kidney, the effects of anti-inflammatory J series cyclopentenone prostaglandins on chemokine production by human mesangial cells were examined. Treatment of mesangial cells with prostaglandin J(2) and 15-deoxy-Delta(12,14)-prostaglandin J(2) blocked interleukin-1beta-induced monocyte chemoattractant protein-1 mRNA expression and protein production. This correlated with failure of the transcription factor nuclear factor-kappaB (NF-kappaB) to translocate to the nucleus and bind to its recognition motif, a step required for cytokine-induced monocyte chemoattractant protein-1 gene activation. NF-kappaB failed to translocate because the cyclopentenone prostaglandins attenuated degradation of the NF-kappaB inhibitor IkappaB-alpha. These data suggest that certain prostaglandins can limit the extent of renal chemokine expression and thus may have an important role in resolving renal inflammation.

Hepatitis C virus core protein potentiates TNF-alpha-induced NF-kappaB activation through TRAF2-IKKbeta-dependent pathway

Previous work has implicated that the core protein of hepatitis C virus (HCV) may play a modulatory effect on NF-kappaB activation induced by TNF-alpha. However, it is unclear how HCV core protein modulates TNF-alpha-induced NK-kappaB activation. Here we show that overexpression of HCV core protein potentiates NF-kappaB activation induced by TNF-alpha. Expression of dominant negative form of TRAF2 inhibits the synergistic effects of HCV core protein on NF-kappaB activation, suggesting that HCV core protein potentiates NF-kappaB activation through TRAF2. Moreover, we demonstrate that HCV core protein potentiates TRAF2-mediated NF-kappaB activation via IKKbeta. In addition, HCV core protein associates with TNF-R1-TRADD-TRAF2 signaling complex, resulting in synergistically activation of NF-kappaB induced by TNF-alpha. Thus, these observations indicate that HCV core protein may play an important role in the regulation of the cellular inflammatory and immune responses through NF-kappaB.

Persistent activation of NF-kappa B by the tax transforming protein involves chronic phosphorylation of IkappaB kinase subunits IKKbeta and IKKgamma

The Tax transforming protein encoded by human T-cell leukemia virus type 1 (HTLV1) persistently activates transcription factor NF-kappaB and deregulates the expression of downstream genes that mediate cell cycle entry. We recently found that Tax binds to and chronically stimulates the catalytic function of IkappaB kinase (IKK), a cellular enzyme complex that phosphorylates and inactivates the IkappaB inhibitory subunit of NF-kappaB. We now demonstrate that the IKKbeta catalytic subunit and IKKgamma regulatory subunit of IKK are chronically phosphorylated in HTLV1-infected and Tax-transfected cells. Alanine substitutions at Ser-177 and Ser-181 in the T loop of IKKbeta protect both of these IKK subunits from Tax-directed phosphorylation and prevent the induction of IkappaB kinase activity. Each of these inhibitory effects is recapitulated in Tax transfectants expressing the bacterial protein YopJ, a potent in vivo agonist of T loop phosphorylation. Moreover, ectopically expressed forms of IKKbeta that contain glutamic acid substitutions at Ser-177 and Ser-181 have the capacity to phosphorylate a recombinant IKKgamma substrate in vitro. We conclude that Tax-induced phosphorylation of IKKbeta is required for IKKbeta activation, phosphoryl group transfer to IKKgamma, and acquisition of the deregulated IKK phenotype.

Green tea polyphenol extract attenuates inflammation in interleukin-2-deficient mice, a model of autoimmunity

Green tea polyphenols (GrTP) have been previously shown to decrease endotoxin-induced tumor necrosis factor-alpha production and lethality in mice. Our present studies demonstrate that GrTP inhibit inflammatory responses and may be useful in treating chronic inflammatory states, such as inflammatory bowel disease. In this preliminary study, we examined whether GrTP decrease disease activity in interleukin-2-deficient (IL-2(-/-) mice. Eight-week old IL-2(-/-) C57BL/6J mice who were fed nonpurified diet were randomly assigned to receive water with GrTP (5 g/L) or water alone (control) for up to 6 wk. After 1 wk, explant colon and lamina propria lymphocyte (LPL) cultures were established from a subgroup of mice and supernatants collected. Culture supernatants from GrTP-treated mice showed decreased spontaneous interferon-gamma and tumor necrosis factor-alpha secretion compared with that of controls. At 6 wk, the GrTP group had less severe colitis as demonstrated by lower histologic scores and wet colon weights. This was associated with lower plasma levels of serum amyloid A, increased weight gain and improved hematocrits. These results show that GrTP attenuated inflammation in IL-2(-/-) mice and suggest a role for GrTP in treating chronic inflammatory diseases such as inflammatory bowel disease.

Microarray analysis reveals previously unknown changes in Toxoplasma gondii-infected human cells

Cells infected with the intracellular protozoan parasite Toxoplasma gondii undergo up-regulation of pro-inflammatory cytokines, organelle redistribution, and protection from apoptosis. To examine the molecular basis of these and other changes, gene expression profiles of human foreskin fibroblasts infected with Toxoplasma were studied using human cDNA microarrays consisting of approximately 22,000 known genes and uncharacterized expressed sequence tags. Early during infection (1-2 h), <1% of all genes show a significant change in the abundance of their transcripts. Of the 63 known genes in this group, 27 encode proteins associated with the immune response. These genes are also up-regulated by secreted, soluble factors from extracellular parasites indicating that the early response does not require parasite invasion. Later during infection, genes involved in numerous host cell processes, including glucose and mevalonate metabolism, are modulated. Many of these late genes are dependent on the direct presence of the parasite; i.e. secreted products from either the parasite or infected cells are insufficient to induce these changes. These results reveal several previously unknown effects on the host cell and lay the foundation for detailed analysis of their role in the host-pathogen interaction.

Inhibition of NF-kappa B activity by thalidomide through suppression of IkappaB kinase activity

The sedative and anti-nausea drug thalidomide, which causes birth defects in humans, has been shown to have both anti-inflammatory and anti-oncogenic properties. The anti-inflammatory effect of thalidomide is associated with suppression of cytokine expression and the anti-oncogenic effect with inhibition of angiogenesis. It is presently unclear whether the teratogenic properties of thalidomide are connected in any way to the beneficial, anti-disease characteristics of this drug. The transcription factor NF-kappaB has been shown to be a key regulator of inflammatory genes such as tumor necrosis factor-alpha and interleukin-8. Inhibition of NF-kappaB is associated with reduced inflammation in animal models, such as those for rheumatoid arthritis. We show here that thalidomide can block NF-kappaB activation through a mechanism that involves the inhibition of activity of the IkappaB kinase. Consistent with the observed inhibition of NF-kappaB, thalidomide blocked the cytokine-induced expression of NF-kappaB-regulated genes such as those encoding interleukin-8, TRAF1, and c-IAP2. These data indicate that the therapeutic potential for thalidomide may be based on its ability to block NF-kappaB activation through suppression of IkappaB kinase activity.

High constitutive level of NF-kappaB is crucial for viability of adenocarcinoma cells

Most of cells exhibit low nuclear level of NF-kappaB. However, in some cell lines and tissues aberrantly activated NF-kappaB is playing an important role in cell motility, growth control and survival. Here we describe the result of decrease of constitutive NF-kappaB level in different adenocarcinoma cell lines. Treatment of mouse adenocarcinoma cell line CSML-100 with both synthetic (TPCK or PDTC) or natural (I(kappaB)-alpha) NF-kappaB inhibitors caused apoptotic death. Low doses of TPCK were harmless for CSML100 cells but sensitized them to TNF-induced apoptosis. Death of CSML100 cells in the presence of high concentration TPCK was not accompanied with significant changes in c-myc activity but strongly correlated with rapid decrease in p53 level. Thus, mutual behavior p53 and NF-kappaB represented a unique feature of TPCK-induced apoptosis in CSML-100 adenocarcinoma cells.

Ergolide, sesquiterpene lactone from Inula britannica, inhibits inducible nitric oxide synthase and cyclo-oxygenase-2 expression in RAW 264.7 macrophages through the inactivation of NF-kappaB

We investigated the mechanism of suppression of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2) by ergolide, sesquiterpene lactone from Inula britannica. iNOS activity in cell-free extract of LPS/IFN-gamma-stimulated RAW 264.7 macrophages was markedly attenuated by the treatment with ergolide. Its inhibitory effect on iNOS was paralleled by decrease in nitrite accumulation in culture medium of LPS/IFN-gamma-stimulated RAW 264.7 macrophages in a concentration-dependent manner. However, its inhibitory effect does not result from direct inhibition of the catalytic activity of NOS. Ergolide markedly decreased the production of prostaglandin E(2) (PGE(2)) in cell-free extract of LPS/IFN-gamma-stimulated RAW 264.7 macrophages in a concentration-dependent manner, without alteration of the catalytic activity of COX-2 itself. Ergolide decreased the level of iNOS and COX-2 protein, and iNOS mRNA caused by stimulation of LPS/IFN-gamma in a concentration-dependent manner, as measured by Western blot and Northern blot analysis, respectively. Ergolide inhibited nuclear factor-kappaB (NF-kappaB) activation, a transcription factor necessary for iNOS and COX-2 expression in response to LPS/IFN-gamma. This effect was accompanied by the parallel reduction of nuclear translocation of subunit p65 of NF-kappaB as well as IkappaB-alpha degradation. In addition, these effects were completely blocked by treatment of cysteine, indicating that this inhibitory effect of ergolide could be mediated by alkylation of NF-kappaB itself or an upstream molecule of NF-kappaB. Ergolide also directly inhibited the DNA-binding activity of active NF-kappaB in LPS/IFN-gamma-pretreated RAW 264.7 macrophages. These results demonstrate that the suppression of NF-kappaB activation by ergolide might be attributed to the inhibition of nuclear translocation of NF-kappaB resulted from blockade of the degradation of IkappaB and the direct modification of active NF-kappaB, leading to the suppression of the expression of iNOS and COX-2, which play important roles in inflammatory signalling pathway.

Novel NEMO/IkappaB kinase and NF-kappa B target genes at the pre-B to immature B cell transition

The IkappaB kinase (IKK) signaling complex is responsible for activating NF-kappaB-dependent gene expression programs. Even though NF-kappaB-responsive genes are known to orchestrate stress-like responses, critical gaps in our knowledge remain about the global effects of NF-kappaB activation on cellular physiology. DNA microarrays were used to compare gene expression programs in a model system of 70Z/3 murine pre-B cells versus their IKK signaling-defective 1.3E2 variant with lipopolysaccharide (LPS), interleukin-1 (IL-1), or a combination of LPS + phorbol 12-myristate 13-acetate under brief (2 h) or long term (12 h) stimulation. 70Z/3-1.3E2 cells lack expression of NEMO/IKKgamma/IKKAP-1/FIP-3, an essential positive effector of the IKK complex. Some stimulated hits were known NF-kappaB target genes, but remarkably, the vast majority of the up-modulated genes and an unexpected class of repressed genes were all novel targets of this signaling pathway, encoding transcription factors, receptors, extracellular ligands, and intracellular signaling factors. Thirteen stimulated (B-ATF, Pim-2, MyD118, Pea-15/MAT1, CD82, CD40L, Wnt10a, Notch 1, R-ras, Rgs-16, PAC-1, ISG15, and CD36) and five repressed (CCR2, VpreB, lambda5, SLPI, and CMAP/Cystatin7) genes, respectively, were bona fide NF-kappaB targets by virtue of their response to a transdominant IkappaBalphaSR (super repressor). MyD118 and ISG15, although directly induced by LPS stimulation, were unaffected by IL-1, revealing the existence of direct NF-kappaB target genes, which are not co-induced by the LPS and IL-1 Toll-like receptors.

Transcriptional regulation of intracellular IL-1 receptor antagonist gene by IL-1 alpha in primary mouse keratinocytes

The inflammatory cytokine IL-1alpha mediates inflammatory reactions in skin and up-regulates the expression of other proinflammatory genes. We previously found that IL-1alpha also increases steady state mRNA levels for intracellular IL-1 receptor antagonist (icIL-1Ra) in primary mouse keratinocytes; however, the mechanism for this was unknown. Here we show that increased expression in primary keratinocytes is due to increased rates of transcription. To study the transcriptional regulation of icIL-1Ra expression induced by IL-1alpha, we functionally characterized 4.5 kb of the 5'-flanking region of the human icIL-1Ra gene. Deletion analysis showed that regulatory elements were contained in the -598- and -288-bp region upstream of the transcription start site. Then we investigated cis- and trans-acting factors required for icIL-1Ra expression and found that a NF-IL-6 site and a NF-kappaB site in the icIL-1Ra promoter were responsible for IL-1alpha-induced icIL-1Ra expression. Moreover, gel shift assays and cotransfection experiments showed that CCAAT/enhancer-binding proteins alpha, beta, and p65 bind to the NF-IL-6 site and NF-kappaB site, respectively, and functionally trans-activate the icIL-1Ra promoter. Finally, mutational analysis confirmed that these elements were both essential for maximal transcription induced by IL-1alpha.

Oxidative stress causes nuclear factor-kappaB activation in acute hypovolemic hemorrhagic shock

Nuclear Factor kappaB (NFkappaB) is an ubiquitous rapid response transcription factor involved in inflammatory reactions and exerts its action by expressing cytokines, chemokines, and cell adhesion molecules. We investigated the role of NF-kappaB in acute hypovolemic hemorrhagic (Hem) shock. Hem shock was induced in male anesthetized rats by intermittently withdrawing blood from an iliac catheter over a period of 20 min (bleeding period) until mean arterial blood pressure (MAP) fell and stabilized within the range of 20-30 mmHg. Hemorrhagic shocked rats died in 26.3 +/- 2.1 min following the discontinuance of bleeding, experienced a marked hypotension (mean arterial blood pressure = 20-30 mmHg) and had enhanced plasma levels of Tumor Necrosis Factor-alpha (200 +/- 15 pg/ml, 20 min after the end of bleeding). Furthermore, aortas taken 20 min after bleeding from hemorrhagic shocked rats showed a marked hypo-reactivity to phenylephrine (PE; 1nM to 10 microM) compared with aortas harvested from sham shocked rats. Hem shocked rats also had increased levels of TNF-alpha mRNA in the liver (15-20 min after the end of bleeding) and enhanced plasma levels of 2,5-dihydroxybenzoic acid (2,5-DHBA; 6 +/- 2.2 microm), 2,3-dihydroxybenzoic acid (2,3-DHBA; 13 +/- 2.1 microm), both studied to evaluate OH(*) production. Electrophoretic mobility shift assay showed that liver NF-kappaB binding activity increased in the nucleus 10 min after the end of hemorrhage and remained elevated until the death of animals. Western blot analysis suggested that the levels of inhibitory IkappaBalpha protein in the cytoplasm became decreased at 5 min after the end of bleeding. IRFI-042, a vitamin E analogue (20 mg/kg intraperitoneally 2 min after the end of bleeding), inhibited the loss of IkappaBalpha protein from the cytoplasm and blunted the increase in NF-kappaB binding activity. Furthermore IRFI-042 increased survival time (117.8 +/- 6.51 min; p <.01) and survival rate (vehicle = 0% and IRFI-042 = 80%, at 120 min after the end of bleeding), reverted the marked hypotension, decreased liver mRNA for TNF-alpha, reduced plasma TNF-alpha (21 +/- 4.3 pg/ml), and restored to control values the hypo-reactivity to PE. Our results suggest that acute blood loss (50% of the estimated total blood volume over a period of 20 min) causes early activation of NF-kappaB, likely through an increased production of reactive oxygen species. This experiment indicates that NF-kappaB-triggered inflammatory cascade becomes early activated during acute hemorrhage even in the absence of resuscitation procedures.

RNA-dependent protein kinase PKR is required for activation of NF-kappa B by IFN-gamma in a STAT1-independent pathway

The IFN-inducible dsRNA-activated protein kinase PKR regulates protein synthesis through phosphorylation of eukaryotic initiation factor-2alpha. It also acts as a signal transducer for transcription factors NF-kappaB, IFN regulatory factor-1, and activating transcription factor-2. IFN-gamma, a pleiotropic cytokine, elicits gene expression by activating the Janus kinase-STAT signaling pathway. IFN-gamma can synergize with TNF-alpha to activate NF-kappaB in a number of cell lines. Here we show that IFN-gamma alone can activate NF-kappaB, by a Janus kinase-1-mediated, but Stat1-independent, mechanism. NF-kappaB activation by IFN-gamma is associated with degradation of IkappaB beta. The IFN-gamma response can be blocked by 2',5'-oligoadenylate-linked antisense chimeras against PKR mRNA. There was no activation of NF-kappaB by IFN in PKR-null cells, indicating that PKR is required for IFN-gamma signaling to NF-kappaB.

Regulation of nuclear factor kappa B transactivation. Implication of phosphatidylinositol 3-kinase and protein kinase C zeta in c-Rel activation by tumor necrosis factor alpha

Transactivation by c-Rel (nuclear factor kappaB) was dependent on phosphorylation of several serines in the transactivation domain, indicating that it is a phosphorylation-dependent Ser-rich domain. By Ser --> Ala mutational and deletion analysis, we have identified two regions in this domain: 1) a C-terminal region (amino acids 540-588), which is required for basal activity; and 2) the 422-540 region, which responds to external stimuli as tumor necrosis factor (TNF) alpha or phorbol myristate acetate plus ionomycin. Ser from 454 to 473 were shown to be required for TNFalpha-induced activation, whereas Ser between 492 and 519 were required for phorbol myristate acetate plus ionomycin activation. Phosphatidylinositol 3-kinase (PI3K) and protein kinase C (PKC) zeta were identified as downstream signaling molecules of TNFalpha-activation of c-Rel transactivating activity. Interestingly, dominant negative forms of PI3K inhibited PKCzeta activation and dominant negative PKCzeta inhibited PI3K-mediated activation of c-Rel transactivating activity, indicating a cross-talk between both enzymes. We have identified the critical role of different Ser for PKCzeta- and PI3K-mediated responses. Interestingly, those c-Rel mutants not only did not respond to TNFalpha but also acted as dominant negative forms of nuclear factor kappaB activation.

Macrophages in renal inflammation

This review describes recent advances in macrophage biology in the context of renal inflammation. It highlights the importance of the activated macrophage for the progression and resolution of renal disease, and discusses recent and potential future approaches to modify macrophage function selectively within the kidney to activate them specifically to promote the healing of kidney disease.

Failure of alpha-melanocyte stimulating hormone to attenuate cerebral complications in experimental pneumococcal meningitis

Alpha-melanocyte-stimulating hormone (alpha-MSH) is an endogenous neuroimmunomodulatory peptide that can inhibit a broad range of inflammatory mediators known to be involved in the pathophysiology of bacterial meningitis. We evaluated the effect of alpha-MSH in a rat model of pneumococcal meningitis. Rats were intracisternally infected with Streptococcus pneumoniae and treatment was started 6 h after infection. Both systemic and intracisternal alpha-MSH failed to influence blood-brain barrier disruption, increased intracranial pressure, brain cytokine concentrations (IL-1beta, IL-6, TNF-alpha, MIP-2, and IL-10), CSF bacterial titers, and clinical parameters of disease severity (weight loss, body temperature, and blood pressure), although the treatment strongly increased the CNS concentrations of alpha-MSH. However, systemic but not intracisternal alpha-MSH slightly reduced the CNS leukocyte accumulation, indicating that leukocyte extravasation is inhibited by alpha-MSH from the blood side. Our results show that alpha-MSH reduces the CNS leukocyte accumulation by its systemic action, but does not attenuate meningitis-associated intracranial complications.

Identification of genes induced by inflammatory cytokines in airway epithelium

Epithelial cells lining the airways are thought to play a prominent role in respiratory diseases. We utilized cDNA representational difference analysis to identify the genes in which expression is induced by the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1beta in primary human bronchial epithelial cells and hence are relevant to airway inflammation. Hybridization of the subtraction product to arrayed cDNAs indicated that known tumor necrosis factor-alpha- and interleukin-1beta-inducible genes such as B94, Zfp36, and regulated on activation normal T cell expressed and secreted were represented, confirming the success of the subtraction experiment. A 1,152-clone library potentially representing genes with higher transcript levels in cytokine-treated human bronchial epithelial cells was generated and sequenced. Sequence similarity searches indicated that these clones represented 57 genes of known function, 1 gene of unknown function, 6 expressed sequence tags, and 2 novel sequences. The expression of 19 of these clones was studied by a combination of Northern blotting and RT-PCR analyses and confirmation of differential expression for 10 known genes, 2 expressed sequence tags, and a novel sequence not represented in any of the public databases was obtained. Thus cDNA representational difference analysis was utilized to isolate known and novel differentially expressed genes, which putatively play a role in airway inflammation.

Ionizing radiation affects 26s proteasome function and associated molecular responses, even at low doses

BACKGROUND AND PURPOSE

Ionizing radiation is known to activate certain signal transduction pathways, the regulation of which could involve post-transcriptional as well as transcriptional mechanisms. One of the most important post-transcriptional pathways in eukaryotic cells is the ATP- and ubiquitin-dependent degradation of proteins by the 26s proteasome. This process controls initiation of many cellular stress responses, as well as inflammatory responses under control of the transcription factor NF-kappaB. The literature on the relationship between radiation and inflammation seems somewhat paradoxical. At high doses, radiation is generally pro-inflammatory. On the other hand, low dose radiation has a long history of use in the treatment of inflammatory disease. This suggests the involvement of multiple mechanisms that may operate differentially at different dose levels.

MATERIALS AND METHODS

In this paper, the ability of different doses of ionizing radiation to directly affect 26s proteasome activity was tested in ECV 304 cells. Proteasome activity, IkappaBalpha protein levels, and NF-kappaB activation were monitored.

RESULTS

Inhibition of chymotrypsin-like 20s and 26s proteasome activity was observed immediately after low- and high-dose irradiation either of cells or purified proteasomes. The inhibitory effect was independent of the availability of the known endogenous proteasome inhibitor heat shock protein 90 (hsp90). Levels of IkappaBalpha, a physiological 26s proteasome substrate, were increased only at low doses (0.25 Gy) and unaltered at higher doses whereas only the highest doses (8 and 20 Gy) activated NF-kappaB.

CONCLUSIONS

We conclude that the proteasome is a direct target of ionizing radiation and suggest that inhibition of proteasome function provides a molecular framework within which low dose anti-inflammatory effects of radiation, and radiation-induced molecular responses in general, should be considered.

Immunostimulation by the synthetic lipopeptide P3CSK4: TLR4-independent activation of the ERK1/2 signal transduction pathway in macrophages

Synthetic lipopeptides based on bacterial lipoprotein are efficient activators for monocytes/macrophages inducing the release of interleukin (IL)-1, IL-6, tumour necrosis factor-alpha (TNF-alpha), reactive oxygen/nitrogen intermediates, and the translocation of nuclear factor kappaB (NFkappaB). In this report we investigate the signal transduction pathways involved in leucocyte activation by the synthetic lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)3-lysine (P3CSK4). We show that P3CSK4 activates mitogen-activated protein (MAP)-kinases ERK1/2 and MAP kinase (MAPK)-kinases MEK1/2 in bone-marrow-derived macrophages (BMDM) and in the macrophage cell line RAW 264.7. Additionally, we could detect differences between the P3CSK4 and lipopolysaccharide (LPS)-induced phosphorylation of MAP kinases: Different levels in phosphorylation were found both in kinetics and dose-response using RAW 264.7 cells or BMDM from BALB/c and LPS responder mice (C57BL/10ScSn) or LPS non-responder mice (C57BL/10ScCr). The lipopeptide activated the MAPK-signalling cascade in both LPS responder and non-responder macrophages, whereas LPS induced the MAPK signalling pathway only in macrophages derived from LPS responder mice. An approximately 70% decrease of lipopeptide induced NFkappaB translocation and an about 50% reduction of nitric oxide (NO) release was observed in the presence of anti-CD14. These data correspond to the reduction of phosphorylation of ERK1/2 after stimulation with P3CSK4 in the presence of anti-CD14 antibodies. Inhibition of MEK1/2 by PD98059 completely reduced the lipopeptide-induced phosphorylation of ERK1/2 indicating that MEK1/2 are solely responsible for the phosphorylation of the downstream-located MAP kinases ERK1/2.

Involvement of Rel/NF-kappaB in regulation of ascidian notochord formation

The Rel/NF-kappaB family is known to be involved in a wide variety of biological processes, including morphogenesis. In the present study, two protochordate cDNA clones encoding Rel/NF-kappaB proteins, named As-rel1 and As-rel2, were isolated from a fertilized egg cDNA library of the ascidian Halocynthia roretzi. The As-rel1 protein is a typical Rel/NF-kappaB family member, containing a Rel homology domain, a nuclear localization sequence and a C-terminal putative transcription activation domain, while the As-rel2 protein is a novel Rel/NF-kappaB family member that lacks a nuclear localization sequence and the C-terminal domain. Northern blot analyses showed that both transcripts were maternally expressed and that their expression changed during development of H. roretzi embryos. Although injection of the As-rel2 mRNA into H. roretzi fertilized eggs had little effect on embryonic development, injection of the As-rel1 mRNA interfered greatly with notochord formation, resulting in a shortened tail with a reduced number of notochord cells. In contrast, embryos co-injected with As-rel1 and As-rel2 mRNA developed normally, indicating that the As-rel2 protein rescued the defect in notochord formation induced by the injection of As-rel1 mRNA alone. These results strongly suggest that the As-rel1 protein functions as a suppressor in ascidian notochord formation, while the As-rel2 protein has an antagonistic effect on the action of the As-rel1 protein.

Inhibition of the initial wave of NF-kappaB activity in rat muscle reduces ischemia/reperfusion injury

Nuclear factor kappaB (NF-kappaB) is thought to play an important role in the expression of genes expressed in response to ischemia/reperfusion (I/R) injury. In this report, the activation of NF-kappaB in rat skeletal muscle during reperfusion following a 4-h ischemic period was studied. NF-kappaB activation displayed a biphasic pattern, showing peak activities from 30 min to 3 h postperfusion and 6 h to 16 h postperfusion, with a decline to baseline binding activity levels between 3 h and 6 h. Inhibition of NF-kappaB activation was investigated using proline dithiocarbamate (Pro-DTC). NF-kappaB binding activity during reperfusion was significantly reduced by intravenous administration of Pro-DTC. Additionally, Pro-DTC resulted in decreased muscle edema and neutrophil activity, with an increased percentage of muscle survival compared with vehicle controls. These results demonstrate that NF-kappaB is activated during reperfusion in a biphasic manner and that the regulation of the initial phase of NF-kappaB activation affords physiological protection against a severe ischemic stress. Selective inhibition of NF-kappaB during early reperfusion may therefore be a therapeutic intervention for I/R injury.

Characterization of NF-kappaB expression in Hodgkin's disease: inhibition of constitutively expressed NF-kappaB results in spontaneous caspase-independent apoptosis in Hodgkin and Reed-Sternberg cells

Although the neoplastic cells of classical Hodgkin's disease (CHD) demonstrate high levels of constitutively active nuclear NF-kappaB, the precise physiologic and clinical significance of NF-kappaB expression is currently undefined. Expression of active NF-kappaB p65(Rel A) was evaluated in patient samples of CHD and nodular lymphocyte predominance Hodgkin's disease. The action of the chemical NF-kappaB inhibitors gliotoxin and MG132 and the effect of NF-kappaB inhibition utilizing an adenovirus vector carrying a dominant-negative IkappaBalpha mutant (Ad5IkappaB) were then demonstrated in CHD cell lines (L428, KMH2, and HS445). Hodgkin and Reed-Sternberg (HRS) cells from all patient and cell line specimens showed strong immunopositivity for active p65(Rel A). Expression was also seen in lymphocytic/histiocytic cells from all cases of nodular lymphocyte predominance Hodgkin's disease. After chemical NF-kappaB inhibition, p65(Rel A) was significantly reduced in nuclear extracts from cultured HRS cells as revealed by electrophoretic mobility shift assays. Furthermore, chemical NF-kappaB inhibition resulted in time- and concentration-dependent apoptosis in HRS cells. With the exception of MG132-induced apoptosis in HS445, apoptosis by chemical NF-kappaB inhibition was not significantly altered by preincubation with various caspase inhibitors (z-DQMD-FMK, z-DEVD-FMK, z-VAD-FMK, z-VEID-FMK, and z-IETD-FMK). Regardless of the chemical inhibitor used, no significant change in caspase-3 functional activity was found in CHD cell lines. HRS cells infected with Ad5IkappaB also showed a marked increase in spontaneous apoptosis compared with wild type adenovirus-infected and control cells. Overall, the inhibition of active NF-kappaB in HRS cells resulting in spontaneous caspase-independent apoptosis demonstrates a critical role for NF-kappaB in HRS cell survival and resistance to apoptosis.

Identification of genes induced by a macrophage activator, S-28463, using gene expression array analysis

S-28463 and imiquimod are imidazoquinoline compounds which stimulate microbicidal activity by inducing a local immune response at the site of application. Imiquimod-containing cream is an effective clinical treatment against cervical warts caused by human papillomavirus infection. Imiquimod also induces leishmanicidal activity both in vitro in macrophages and in vivo in a mouse model for cutaneous leishmaniasis. The major target cells of S-28463 and imiquimod are macrophages. To explore the molecular basis in which imidazoquinolines generate macrophage microbicidal activity, a cDNA gene array analysis was undertaken to identify genes induced by S-28463. Out of 588 genes screened in this assay, only 13 genes were significantly induced by S-28463. Remarkably, virtually all of the induced genes are involved in macrophage activation and inflammatory response. This experimental approach defines the mechanism of action of this clinically relevant compound in the induction of microbicidal activity in macrophages and also potentially identifies novel genes associated with microbicidal activity in this cell type.

Tyrosine phosphorylation-dependent activation of NF-kappa B. Requirement for p56 LCK and ZAP-70 protein tyrosine kinases

Phosphorylation of the N-terminal domain of I kappa B inhibitory subunits induces activation of the transcription factor NF-kappa B. Although serine phosphorylation has been shown to induce ubiquitination and subsequent proteasome-mediated degradation of I kappa B-alpha, little is known about the mechanisms that lead to release of active NF-kappa B in T cells as a consequence of tyrosine phosphorylation of I kappa B-alpha [Imbert, V., Rupec, R.A., Livolsi, A., Pahl, H.L., Traenckner, B.M., Mueller-Dieckmann, C., Farahifar, D., Rossi, B., Auberger, P., Baeuerle, P. & Peyron, J.F. (1996) Cell 86, 787--798]. The involvement of the tyrosine kinases p56(lck) and ZAP-70 in this reaction is demonstrated here using specific pharmacological inhibitors and Jurkat mutants unable to express these kinases. Although the inhibitors prevented both pervanadate-induced phosphorylation of I kappa B-alpha on Tyr42 and NF-kappa B activation, we observed that, in p56(lck)-deficient Jurkat mutants, NF-kappa B could still associate with I kappa B-alpha despite phosphorylation on Tyr42. Furthermore, the SH2 domain of p56(lck) appeared to be required for pervanadate-induced NF-kappa B activation but not for Tyr42 phosphorylation. These results show that p56(lck) and ZAP-70 are key components of the signaling pathway that leads to phosphotyrosine-dependent NF-kappa B activation in T cells and confirm that tyrosine kinases must control at least two different steps to induce activation of NF-kappa B. Finally, we show that H(2)O(2), which stimulates p56(lck) and ZAP-70 in T cells, is an activator of NF-kappa B through tyrosine phosphorylation of I kappa B-alpha.

Interferon-tau suppresses prostaglandin F2alpha secretion independently of the mitogen-activated protein kinase and nuclear factor kappa B pathways

Pregnancy is established in ruminants through inhibitory actions of interferon (IFN)-tau on the release of prostaglandin F2alpha (PGF), which allows the corpus luteum to survive and continue to produce progesterone. Experiments were designed to 1) delineate the signal transduction pathway coordinating the synthesis of PGF, 2) determine how rapidly recombinant bovine (rb) IFN-tau attenuated phorbol ester (PDBu)-induced secretion of PGF, and 3) establish the site at which rbIFN-tau attenuates the secretion of PGF in cultured bovine endometrial (BEND) cells. BEND cells were untreated (control) or treated for 5, 10, 60, 180, or 300 min with PDBu (100 ng/ml), rbIFN-tau (50 or 500 ng/ml), PDBu + rbIFN-tau, or PDBu + PD98059 (MEK-1 inhibitor; 50 microM). Secretion of PGF was induced (P < 0.0001) by PDBu within 180 min, but induction was inhibited 74% by the addition of rbIFN-tau (P < 0.0001) and was ablated completely by PD98059. Parallel results were obtained for cyclooxygenase (COX)-2 protein expression. PDBu induced (P < 0.05) activation of the Raf-1/MEK-1/ERK-1/2 pathway, which was obligatory for the expression of COX-2 and secretion of PGF but was not altered by cotreatment with rbIFN-tau. PDBu induced (P < 0.05) transcription of c-jun and c-fos mRNAs within 30 min; induction was inhibited (P < 0.05) by cotreatment with PD98059 but not by cotreatment with rbIFN-tau. Treatment of BEND cells with rbIFN-tau also did not attenuate PDBu-induced degradation of IkappaBalpha, suggesting that the IkappaBalpha/NFkappaB pathway is not a site of IFN-tau inhibition of PGF. However, rbIFN-tau did block transcription of the COX-2 gene induced by PDBu within 30 min. In conclusion, COX-2 expression and PGF secretion induced by PDBu is mediated through the Raf-1/MEK-1/ERK-1/2 pathway, but this pathway is not disrupted by rbIFN-tau. Because rbIFN-tau inhibits COX-2 mRNA within 30 min, we hypothesized that transcription factors activated by rbIFN-tau rapidly and directly attenuate COX-2 gene expression, thereby suppressing secretion of PGF.

Inhibition of caspase 3 abrogates lipopolysaccharide-induced nitric oxide production by preventing activation of NF-kappaB and c-Jun NH2-terminal kinase/stress-activated protein kinase in RAW 264.7 murine macrophage cells

The effect of caspase inhibitors on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 267.4 murine macrophage cells was investigated. Pretreatment of RAW cells with a broad caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), resulted in a striking reduction in LPS-induced NO production. Z-VAD-FMK inhibited LPS-induced NF-kappaB activation. Furthermore, it blocked phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) but not that of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinases. Similarly, a caspase 3-specific inhibitor, Z-Asp-Glu-Val-Asp-fluoromethylketone, inhibited NO production, NF-kappaB activation, and JNK/SAPK phosphorylation in LPS-stimulated RAW cells. The attenuated NO production was due to inhibition of the expression of an inducible-type NO synthase (iNOS). The overexpression of the dominant negative mutant of JNK/SAPK and the addition of a JNK/SAPK inhibitor blocked iNOS expression but did not block LPS-induced caspase 3 activation. It was therefore suggested that the inhibition of caspase 3 might abrogate LPS-induced NO production by preventing the activation of NF-kappaB and JNK/SAPK. The caspase family, especially caspase 3, is likely to play an important role in the signal transduction for iNOS-mediated NO production in LPS-stimulated mouse macrophages.

cDNA array analysis of altered gene expression in human endothelial cells in response to Chlamydia pneumoniae infection

Strong epidemiological and pathological evidence supports a role for Chlamydia pneumoniae infection in atherosclerosis and human coronary heart disease. Animal models have shown that C. pneumoniae disseminates hematogenously in infected monocytes and macrophages, while in vitro data suggest that infected macrophages can transmit C. pneumoniae infection directly to endothelial cells. Endothelial cells may be key in vivo targets for C. pneumoniae infection; given that these cells are important in regulating the dynamics of the vessel wall, we used cDNA microarrays to study the transcriptional response of endothelial cells to infection with C. pneumoniae. cDNA arrays were used to characterize the mRNA expression profiles for 268 human genes following infection with C. pneumoniae, which were compared to mRNA profiles of uninfected cells. Selected genes of interest were further investigated by reverse transcription-PCR throughout a 24-h period of infection. C. pneumoniae infection upregulated mRNA expression for approximately 20 (8%) of the genes studied. Genes coding for cytokines (interleukin-1), chemokines (monocyte chemotactic protein 1 and interleukin-8), and cellular growth factors (heparin-binding epidermal-like growth factor, basic fibroblast growth factor, and platelet-derived growth factor B chain) were the most prominently upregulated. In addition to these families of genes, increases in mRNA levels for intracellular kinases and cell surface receptors with signal transduction activities were observed. Time course experiments showed that mRNA levels were upregulated within 2 h following infection. These results expand our knowledge of the response of endothelial cells to C. pneumoniae by further defining the repertoire of C. pneumoniae-inducible genes and provide new insight into potential mechanisms of atherogenesis. In addition, the use of cDNA microarrays may prove useful for the study of host cell responses to C. pneumoniae infection during latent and replicative stages of infection and related pathology.

Proteolysis-inducing factor regulates hepatic gene expression via the transcription factors NF-(kappa)B and STAT3

A novel protein, proteolysis-inducing factor (PIF), has been isolated from the urine of patients with pancreatic cancer and is capable of inducing muscle proteolysis in vitro. Only adult skeletal muscle and liver exhibit substantial binding of PIF. We have investigated the effect of PIF on hepatic gene expression. Primary cultures of human hepatocytes and the human cell line HepG2 were incubated in the presence of PIF to assess its effects on hepatic transcription factors, proinflammatory cytokine production, and acute phase proteins. PIF activates both the transcription factors NF-kB and STAT3, which result in the increased production of IL-8, IL-6, and C-reactive protein and the decreased production of transferrin. The function of PIF, beyond muscle degradation, is unknown but here we show that it is involved in hepatic gene expression, and is thus likely to be involved in the proinflammatory response observed in cachexia. These results may also suggest a potential role for PIF during embryonic development. The expression of PIF peaks during the embryonic period E8 to E9, a stage that is crucial in the development of skeletal muscle and liver and during which both NF-kB and STAT3 activation can also be observed.

Early activation of IKKbeta during in vivo myocardial ischemia

We have demonstrated that in vitro brief ischemia activates nuclear factor (NF)-kappaB in rat myocardium. We report in vivo ischemia-reperfusion (I/R)-induced NF-kappaB activation, IkappaB kinase -beta (IKKbeta) activity, and IkappaBalpha phosphorylation and degradation in rat myocardium. Rat hearts were subjected to occlusion of the coronary artery for up to 45 min or occlusion for 15 min followed by reperfusion for up to 3 h. Cytoplasmic and nuclear proteins were isolated from ischemic and nonischemic areas of each heart. NF-kappaB activation was increased in the ischemic area (680%) after 10 min of ischemia and in the nonischemic area (350%) after 15 min of ischemia and remained elevated during prolonged ischemia and reperfusion. IKKbeta activity was markedly increased in ischemic (1,800%) and nonischemic (860%) areas, and phosphorylated IkappaBalpha levels were significantly elevated in ischemic (180%) and nonischemic (280%) areas at 5 min of ischemia and further increased after reperfusion. IkappaBalpha levels were decreased in the ischemic (45%) and nonischemic (36%) areas after 10 min of ischemia and remained low in the ischemic area during prolonged ischemia and reperfusion. The results suggest that in vivo I/R rapidly induces IKKbeta activity and increases IkappaBalpha phosphorylation and degradation, resulting in NF-kappaB activation in the myocardium.

New perspectives in asthma treatment

The recent advances in the knowledge of the basic mechanisms underlying asthmatic inflammation have significantly contributed to the delineation of new therapeutic perspectives for asthma. There are currently three main approaches to the development of novel antiasthma treatments: 1) improvement in existing classes of drugs 2) identification of new compounds able to interfere with the complex network of proinflammatory mediators, cytokines, chemokines, and adhesion molecules involved in the pathogenesis of asthma 3) utilization of new forms of immunotherapy aimed at blocking the unbalanced Th2 response which characterizes the pathophysiology of asthma. Such a remarkable expansion in available therapeutic options will probably allow us, over the next decade, to treat asthma by more selectively targeting the pathogenetic events responsible for this widespread airway disease.