Nuclear factor kappa B inhibition improves conductance artery function in type 2 diabetic mice

BACKGROUND

We previously reported that enhanced nuclear factor kappa B (NFκB) activity is responsible for resistance arteries dysfunction in type 2 diabetic mice.

METHODS

In this study, we aimed to determine whether augmented NFκB activity also impairs conductance artery (thoracic aorta) function in type 2 diabetic mice. We treated type 2 diabetic (db(-) /db(-) ) and control (db(-) /db(+) ) mice with two NFκB inhibitors (dehydroxymethylepoxyquinomicin, 6 mg/kg, twice a week and IKK-NBD peptide, 500 µg/kg/day) for 4 weeks.

RESULTS

As expected, the NFκB inhibition did not affect blood glucose level and body weight. Thoracic aorta vascular endothelium-dependent relaxation (EDR), determined by the wire myograph, was impaired in diabetic mice compared with control and was significantly improved after NFκB inhibition. Interestingly, thoracic EDR was also rescued in db(-) /db(-p50NFκB-/-) and db(-) /db(-PARP-1-/-) double knockout mice compared with db(-) /db(-) mice. Similarly, the acute in vitro down regulation of NFκB-p65 using p65 shRNA lentiviral particles in arteries from db(-) /db(-) mice also improved thoracic aorta EDR. Western blot analysis showed that the p65NFκB phosphorylation, cleaved PARP-1 and COX-2 expression were increased in thoracic aorta from diabetic mice, which were restored after NFκB inhibition and in db(-) /db(-p-50NFκB-/-) and db(-) /db(-PARP-1-/-) mice.

CONCLUSIONS

The present results indicate that in male type 2 diabetic mice, the augmented NFκB activity also impairs conductance artery function through PARP-1 and COX-2-dependent mechanisms.

Nicotine reduces TNF-α expression through a α7 nAChR/MyD88/NF-ĸB pathway in HBE16 airway epithelial cells

AIMS

To explore the signaling mechanism associated with the inhibitory effect of nicotine on tumor necrosis factor (TNF)- α expression in human airway epithelial cells.

METHODS

HBE16 airway epithelial cells were cultured and incubated with either nicotine or cigarette smoke extract (CE). Cells were then transfected with α1, α5, or α7 nicotinic acetylcholine receptor (nAChR)-specific small interfering RNAs (siRNAs). The effects of nicotine on the production of proinflammatory factors TNF-α, in transfected cells were analyzed. Furthermore, we assayed the expression levels of myeloid differentiation primary response gene 88 (MyD88) protein, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 protein, NF-κB activity and NF-κB inhibitor alpha (I-κBα) expression in cells after treatment with nicotine or α7 nAChR inhibitor, α -bungarotoxin (α-BTX).

RESULTS

The production of TNF-α was lower in cells pretreated with nicotine before lipopolysaccharide (LPS) stimulation, compared with LPS-only-treated cells. In contrast, in α7 siRNA-transfected cells incubated with nicotine and LPS, TNF-α expression was higher than that in non-transfected cells or in α1 or α5 siRNA-transfected cells. Addition of MyD88 siRNA or the NF-κB inhibitor pyridine-2,6-dithiocarboxylic acid (PDTC) also reduced TNF-α expression. Furthermore, we found that nicotine decreased MyD88 protein, NF-κB p65 protein, NF-κB activity and phospho-I-κBα expression induced by CE or LPS. The inhibitor α-BTX could reverse these effects.

CONCLUSION

Nicotine reduces TNF-α expression in HBE16 airway epithelial cells, mainly through an α7 nAChR/MyD88/NF-κB pathway.

Two homologues of inhibitor of NF-kappa B (IκB) are involved in the immune defense of the Pacific oyster, Crassostrea gigas

A novel homologue of IκB was cloned from a hemocyte cDNA of Crassostrea gigas (designed as CgIκB2). The complete cDNA of CgIκB2 includes an open reading frame (ORF) of 1032 bp, and 3' and 5'untranslated regions (UTR's) of 141 bp and 279 bp, respectively. The ORF encodes a putative protein of 343 amino acids with a calculated molecular weight of approximately 37.8 kDa. Alignment analysis reveals that CgIκB2 contains a conserved degradation motif and six ankyrin repeats. A phylogenetic analysis suggests that a gene duplication event prior to the gastropod-bivalve divergence resulted in the emergence of two IκB homologues in C. gigas. Distinct maximal expression patterns of CgIκB1 in hemocytes and CgIκB2 in the gonad were observed. CgIκB1 and CgIκB2 expression in response to bacterial challenge is similar and inducible. Moreover, both CgIκB1 and CgIκB2 are able to inhibit NF-κb/Rel activating transcription in S2 or HEK293 cells. Our findings demonstrate that both CgIκB1 and CgIκB2 are involved in immune defense in C. gigas through regulation of NF-κB/Rel activity.

Selective blockade of NF-kappaB by novel mutated IkappaBalpha suppresses CD3/CD28-induced activation of memory CD4+ T cells in asthma

BACKGROUND

Nuclear factor kappaB (NF-kappaB) overactivation plays a crucial role in T-helper 2 (Th2)-biased allergic airway inflammation by increased activation and decreased apoptosis of CD4(+) T cells. We have shown that targeted NF-kappaB suppression in dendritic cells by adenoviral gene transfer of a novel mutated inhibitor of NF-kappaB (IkappaBalpha) (AdIkappaBalphaM) contributes to T-cell tolerance, but the immunosuppressive action of AdIkappaBalphaM on memory (CD45RO(+)) CD4(+) T cells remains enigmatic.

METHODS

CD45RO(+) T cells from Dermatophagoides farinaei-sensitized asthmatic patients, untransfected or transfected with AdIkappaBalphaM or AdLacZ (beta-galactosidase) for 24 h, were stimulated with anti-CD3 (1.0 microg/ml) plus anti-CD28 (0.5 microg/ml) monoclonal antibody for an additional 24 h. IkappaBalphaM transgene expression and NF-kappaB activation were detected by polymerase chain reaction (PCR), reverse transcription-PCR (RT-PCR), Western blot analysis, and electrophoretic mobility shift assay. Phenotype and apoptosis were measured by flow cytometry, annexin V binding, and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling analyses. Cytokine production and cell proliferation were determined using enzyme-linked immunosorbent assay and [(3)H] thymidine incorporation.

RESULTS

A unique 801-bp IkappaBalphaM cDNA and a dose-dependent increase in IkappaBalphaM transgene expression were observed in AdIkappaBalphaM-transfected CD45RO(+) T cells. Significantly, AdIkappaBalphaM inhibited CD3/CD28-mediated NF-kappaB activation in CD45RO(+) T cells, leading to evident apoptosis, reduction of eotaxin, RANTES, Th1 [interferon (IFN)-gamma and interleukin (IL)-2], and Th2 (IL-4, IL-5, and IL-13 despite a slight decrease in IL-10) cytokines and secondary proliferative response. AdIkappaBalphaM also upregulated cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and downregulated CD69 besides no change in CD28.

CONCLUSION

IkappaBalphaM might be beneficial to augment memory CD4(+) T-cell tolerance through modulating B7-CD28/CTLA-4 co-stimulatory pathways and NF-kappaB-dependent cytokine profiles in allergic inflammatory diseases including asthma.

Current topics in prevention of human T-cell leukemia virus type i infection: NF-kappa B inhibitors and APOBEC3

Human T-cell leukemia virus type I (HTLV-I) is the first human retrovirus and causes adult T-cell leukemia/lymphoma (ATL). Constitutive activation of nuclear factor-kappa B (NF-kappa B) in the leukemic cells is essential for their growth and survival. Thus, NF-kappa B inhibitors have been attracting attention as a potential strategy to treat ATL. Recently, the field of retrovirus research has been stimulated by the discovery of an innate host defense factor, APOBEC3, against the retroviruses. HTLV-I is relatively resistant to the antiviral effects of APOBEC3. To clarify the resistance of HTLV-I against APOBEC3 might contribute to the design of effective therapeutic approaches.

Piperine inhibits TNF-alpha induced adhesion of neutrophils to endothelial monolayer through suppression of NF-kappaB and IkappaB kinase activation

Piperine displays antipyretic, analgesic, insecticidal and anti-inflammatory activities. It is the first amide to be isolated from Piper species. In the process of identifying non-steroidal anti-inflammatory small molecules from the natural sources, we demonstrate here that piperine inhibits adhesion of neutrophils to endothelial monolayer. The inhibition of neutrophils to endothelial monolayer by piperine is due to its ability to block the tumor necrosis factor-alpha (TNF-alpha) induced expression of cell adhesion molecules i.e. ICAM-1 (intercellular adhesion molecule-1), VCAM-1 (vascular cell adhesion molecule-1) and E-selectin as analyzed by cell-ELISA and confirmed by flow cytometry. Further, we demonstrate that inhibition of ICAM-1 by piperine is reversible. As nuclear factor-kappaB (NF-kappaB) is known to control the transcriptional regulation of cell adhesion molecules hence, we measured the effect of piperine on NF-kappaB in the cytoplasm and in the nucleus of endothelial cells. We observed that pretreatment of endothelial cells with piperine blocks the nuclear translocation and activation of NF-kappaB via blocking the phosphorylation and degradation of its inhibitory protein, IkappaBalpha. Piperine blocks the phosphorylation and degradation of IkappaBalpha by attenuating TNF-alpha induced IkappaB kinase activity. These results suggest a possible mechanism of anti-inflammatory activity of piperine. Therefore, piperine or its structural analogues could be used for the development of new anti-inflammatory molecules.

Fisetin, an Inhibitor of Cyclin-Dependent Kinase 6, Down-Regulates Nuclear Factor-κB-Regulated Cell Proliferation, Antiapoptotic and Metastatic Gene Products through the Suppression of TAK-1 and Receptor-Interacting Protein-Regulated IκBα Kinase Activation

Fisetin (3,7,3',4'-tetrahydroxyflavone) exhibits anti-inflammatory and antiproliferative effects through a mechanism that is poorly understood. Although fisetin has been cocrystalized with cyclin-dependent kinase 6 and inhibits its activity, this inhibition is not sufficient to explain various activities assigned to this flavonol. Because of the critical role of the NF-kappaB pathway in regulation of inflammation and proliferation of tumor cells, we postulated that fisetin modulates this pathway. To test this hypothesis, we examined the effect of fisetin on NF-kappaB and NF-kappaB-regulated gene products in vitro. We found that among nine different flavones tested, fisetin was potent in suppressing tumor necrosis factor (TNF)-induced NF-kappaB activation. Fisetin also suppressed the NF-kappaB activation induced by various inflammatory agents and carcinogens, and it blocked the phosphorylation and degradation of IkappaBalpha by inhibiting IkappaBalpha (IKK) activation, which in turn led to suppression of the phosphorylation and nuclear translocation of p65. NF-kappaB-dependent reporter gene expression was also suppressed by fisetin, as was NF-kappaB reporter activity induced by TNFR1, TRADD, TRAF2, NIK, and IKK but not that induced by p65 transfection. Fisetin also inhibited TNF-induced TAK1 and receptor-interacting protein activation, events that lie upstream of IKK activation. The expression of NF-kappaB-regulated gene products involved in antiapoptosis (cIAP-1/2, Bcl-2, Bcl-xL, XIAP, Survivin, and TRAF1), proliferation (cyclin D1, c-Myc, COX-2), invasion (ICAM-1 and MMP-9), and angiogenesis (vascular endothelial growth factor) were also down-regulated by fisetin. This correlated with potentiation of apoptosis induced by TNF, doxorubicin, and cisplatin. Thus, overall, our results indicate that fisetin mediates antitumor and anti-inflammatory effects through modulation of NF-kappaB pathways.

Glucocorticoid receptor and nuclear factor-kappa B interactions in restraint stress-mediated protection against acoustic trauma

The role of glucocorticoid receptors (GRs) in the protective effect of restraint stress (RS) before acoustic trauma was studied in spiral ganglion neurons of CBA mice. RS increased corticosterone and protected against elevated auditory brain stem thresholds caused by acoustic trauma. This protection was inhibited by the pretreatment with a corticosterone synthesis inhibitor, metyrapone (MET), and a GR antagonist (RU486). RS followed by acoustic trauma caused an immediate increase in corticosterone that triggered nuclear translocation of GR, without a change in the expression of GR protein. RU486 + MET before RS and acoustic trauma caused an immediate increase in GR mRNA followed by increased GR protein expression (24 h after trauma). GR signaling was further characterized by analyzing nuclear factor-kappaB (NF kappaB) nuclear translocation and protein expression. NF kappaB nuclear translocation was reduced after acoustic trauma or pretreatment with RU486 + MET before RS and acoustic trauma. On the contrary, RS protected against the trauma-induced NF kappaB reduction of its nuclear translocation in inhibitory-kappaB (I kappaB)-dependent manner. RU486 + MET caused a simultaneous decreased I kappaB expression and NF kappaB nuclear translocation, demonstrating an interference with the I kappaB-mediated activation of NF kappaB. In summary, RS protects the cochlea from acoustic trauma by increasing corticosterone and activating GRs. These results emphasis how GR activity modulates hearing sensitivity and its importance for the rationale use of glucocorticoids in inner ear diseases.

Mechanisms of endothelial response to oxidative aggression: protective role of autologous VEGF and induction of VEGFR2 by H2O2

The defense mechanisms of endothelial cells (EC) against reactive oxygen species (ROS) are insufficiently characterized. We have addressed the hypothesis that vascular endothelial growth factor (VEGF) and its receptors are relevant elements in this response. Cell viability, VEGF and VEGF receptor (VEGFR1 and VEGFR2) expression, and transcription factor activation were studied on transient exposure of monolayer EC to H2O2. Wild-type and mutant inhibitors of κBα (IκBα) constructions were used to further assess the role of NF-κB in the induction of VEGFR2 expression. A concentration of H2O2 ≥60 μM elicited clear-cut damaging effects on EC, whereas lower concentrations (2–4 μM) were cytoprotective. The cytoprotective effect was shifted to an EC-damaging pattern by means of specific VEGF blockade, therefore revealing a major role of autologous VEGF. Exposure to H2O2 increased VEGF and VEGFR2 mRNA and protein in EC, without affecting VEGFR1 expression. Also, H2O2 challenge was accompanied by increased NF-κB, activator protein-1, and specific protein-1 nuclear binding. A role of NF-κB as the mediator of the H2O2 induction of VEGFR2 mRNA expression was supported by inhibition by the ROS scavenger pyrrolidine dithiocarbamate and by the blocking effect of transfected IκBα. Exposure to exogenous VEGF also increased VEGFR2 and induced NF-κB in EC. In summary, autologous VEGF is instrumental for EC protection induced by low concentrations of ROS. ROS induce expression not only of VEGF but also of VEGFR2. VEGFR2 increase by ROS is mainly driven through a NF-κB-dependent pathway.

Inhibition of nuclear factor kappa B (NFkappaB) activity in oral tumor cells prevents depletion of NK cells and increases their functional activation

The aim of this study is to identify candidate factors which may be responsible for the functional inactivation and depletion of NK cells by tumor cells. Inhibition of NFkappaB activity by an IkappaB super-repressor in HEp2 cells, a cell line commonly used as an oral tumor model, blocked tumor-induced NK cell death, and increased the function of NK cells significantly. Increased expression of CD69 early activation antigen on NK cells as well as augmented proliferation and secretion of IFN-gamma by NK cells were observed when these cells were co-incubated with IkappaB super-repressor transfected HEp2 cells (HEp2-IkappaB((S32AS36A))). More importantly, the secretion of IL-6 was significantly inhibited when NK cells were co-cultured with HEp2-IkappaB((S32AS36A)) cells. In addition, the survival and function of cytotoxic effector cells remained significantly elevated in the presence of IFN-gamma-treated HEp2-IkappaB((S32AS36A)) cells when compared to either untreated or IFN-gamma-treated vector-alone transfected HEp2 cells. Similar findings to those obtained using purified peripheral blood NK cells were also observed when non-fractionated peripheral blood mononuclear cells were used in the co-cultures of immune effectors with HEp2 cell transfectants. Addition of recombinant human IL-6 to the co-cultures of immune effectors with the NFkappaB knockdown HEp2 tumor cells substantially decreased the levels of secreted IFN-gamma. Thus, the results presented in this paper suggest that the inhibition of NFkappaB function in oral tumors may serve to activate and expand the function and numbers of NK cells. Moreover, NFkappaB-mediated increase in IL-6 secretion by oral tumors may in part be responsible for the observed inactivation and death of the immune effectors.

Integrin-Mediated Transcriptional Activation of Inhibitor of Apoptosis Proteins Protects Smooth Muscle Cells Against Apoptosis Induced by Degraded Collagen

Apoptosis of smooth muscle cells (SMC) and degradation of the extracellular matrix (ECM) have both been implicated in atherosclerotic plaque rupture. We have previously reported that degraded type I collagen fragments induce a rapid but transient apoptotic burst initiated by calpains in SMC. The aim of the current study was to identify the pathway responsible for consecutive SMC survival. We show that exposure of SMC to collagen fragments resulted in a sustained activation of nuclear factor (NF)-κB via phosphorylation and degradation of IκBα. Its prevention through retroviral expression of superrepressor IκBα or proteasome inhibition potently induced apoptosis. In the presence of blocking antibodies to α v β 3 integrin and RGD peptides, collagen fragments no longer activated NF-κB and apoptosis was enhanced. The mechanism by which NF-κB was protecting SMC against collagen fragment-induced apoptosis was a transcriptional activation of several endogenous caspase inhibitors of the inhibitor of apoptosis protein (IAP) family as: (1) the expression of xIAP, c-IAP2, and survivin was potently induced by collagen fragments; (2) IAP expression was abrogated by superrepressor IκBα; and (3) knockdown of each of the 3 IAPs by small interfering RNA (siRNA) resulted in enhanced apoptosis after collagen fragment treatment. Our data suggest that SMC exposed to degraded collagen are protected against apoptosis by a mechanism involving α v β 3 -dependent NF-κB activation with consequent activation of IAPs. This may constitute a novel antiapoptotic pathway ensuring SMC survival in settings of enhanced ECM degradation such as cell migration, vascular remodeling, and atherosclerotic plaque rupture.

Eriocalyxin B induces apoptosis of t(8;21) leukemia cells through NF-κB and MAPK signaling pathways and triggers degradation of AML1-ETO oncoprotein in a caspase-3-dependent manner

Diterpenoids isolated from Labiatae family herbs have strong antitumor activities with low toxicity. In this study, Eriocalyxin B (EriB), a diterpenoid extracted from Isodon eriocalyx, was tested on human leukemia/lymphoma cells and murine leukemia models. Acute myeloid leukemia cell line Kasumi-1 was most sensitive to EriB. Significant apoptosis was observed, concomitant with Bcl-2/Bcl-XL downregulation, mitochondrial instability and caspase-3 activation. AML1-ETO oncoprotein was degraded in parallel to caspase-3 activation. EriB-mediated apoptosis was associated with NF-kappaB inactivation by preventing NF-kappaB nuclear translocation and inducing IkappaBalpha cleavage, and disturbance of MAPK pathway by downregulating ERK1/2 phosphorylation and activating AP-1. Without affecting normal hematopoietic progenitor cells proliferation, EriB was effective on primary t(8;21) leukemia blasts and caused AML1-ETO degradation. In murine t(8;21) leukemia models, EriB remarkably prolonged the survival time or decreased the xenograft tumor size. Together, EriB might be a potential treatment for t(8;21) leukemia by targeting AML1-ETO oncoprotein and activating apoptosis pathways.

IkappaBepsilon provides negative feedback to control NF-kappaB oscillations, signaling dynamics, and inflammatory gene expression

NF-κB signaling is known to be critically regulated by the NF-κB–inducible inhibitor protein IκBα. The resulting negative feedback has been shown to produce a propensity for oscillations in NF-κB activity. We report integrated experimental and computational studies that demonstrate that another IκB isoform, IκBɛ, also provides negative feedback on NF-κB activity, but with distinct functional consequences. Upon stimulation, NF-κB–induced transcription of IκBɛ is delayed, relative to that of IκBα, rendering the two negative feedback loops to be in antiphase. As a result, IκBɛ has a role in dampening IκBα-mediated oscillations during long-lasting NF-κB activity. Furthermore, we demonstrate the requirement of both of these distinct negative feedback regulators for the termination of NF-κB activity and NF-κB–mediated gene expression in response to transient stimulation. Our findings extend the capabilities of a computational model of IκB–NF-κB signaling and reveal a novel regulatory module of two antiphase negative feedback loops that allows for the fine-tuning of the dynamics of a mammalian signaling pathway.

Nuclear Factor-kappaB controls the reaggregation of 3D neurosphere cultures in vitro

The approach of reaggregation involves the regeneration and self-renewal of histotypical 3D spheres from isolated tissue kept in suspension culture. Reaggregated spheres can be used as tumour, genetic, biohybrid and neurosphere models. In addition the functional superiority of 3D aggregates over conventional 2D cultures developed the use of neurospheres for brain engineering of CNS diseases. Thus 3D aggregate cultures created enormous interest in mechanisms that regulate the formation of multicellular aggregates in vitro. Here we analyzed mechanisms guiding the development of 3D neurosphere cultures. Adult neural stem cells can be cultured as self-adherent clusters, called neurospheres. Neurospheres are characterised as heterogeneous clusters containing unequal stem cell sub-types. Tumour necrosis factor-alpha (TNF-alpha is one of the crucial inflammatory cytokines with multiple actions on several cell types. TNF-alpha strongly activates the canonical Nuclear Factor Kappa-B (NF- kappaB) pathway. In order to investigate further functions of TNF in neural stem cells (NSCs) we tested the hypothesis that TNF is able to modulate the motility and/or migratory behaviour of SVZ derived adult neural stem cells. We observed a significantly faster sphere formation in TNF treated cultures than in untreated controls. The very fast aggregation of isolated NSCs (<2h) is a commonly observed phenomenon, though the mechanisms of 3D neurosphere formation remain largely unclear. Here we demonstrate for the first time, increased aggregation and enhanced motility of isolated NSCs in response to the TNF-stimulus. Moreover, this phenomenon is largely dependent on activated transcription factor NF-kappaB. Both, the pharmacological blockade of NF-kappaB pathway by pyrrolidine dithiocarbamate (PDTC) or Bay11-7082 and genetic blockade by expression of a transdominant-negative super-repressor IkappaB-AA1 led to decreased aggregation.

Reciprocal and coordinate regulation of serum amyloid A versus apolipoprotein A-I and paraoxonase-1 by inflammation in murine hepatocytes

OBJECTIVE

During inflammation, the serum amyloid A (SAA) content of HDL increases, whereas apolipoprotein A-I (apoA-I) and paraoxonase-1 (PON-1) decrease. It remains unclear whether SAA physically displaces apoA-I or if these changes derive from coordinated but inverse transcriptional regulation of the HDL apolipoprotein genes. Because cytokines stimulate the hepatic expression of inflammatory markers, we investigated their role in regulating SAA, apoA-I, and PON-1 expression.

METHODS AND RESULTS

A cytokine mixture (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, and IL-6) simultaneously induced SAA and repressed apoA-I and PON-1 expression levels. These effects were partially inhibited in cells pretreated with either nuclear factor kappaB (NF-kappaB) inhibitors (pyrrolidine dithiocarbamate, SN50, and overexpression of super-repressor inhibitor kappaB) or after exposure to the peroxisome proliferator-activated receptor-alpha (PPARalpha) ligands (WY-14643 and fenofibrate). Consistent with these findings, the basal level of SAA was increased, whereas apoA-I and PON-1 decreased in primary hepatocytes from PPARalpha-deficient mice as compared with wild-type mice. Moreover, neither WY-14643 nor fenofibrate had any effect on SAA, apoA-I, or PON-1 expression in the absence of PPARalpha.

CONCLUSIONS

These results suggest that cytokines increase the expression of SAA through NF-kappaB transactivation, while simultaneously decreasing the expression of apoA-I and PON-1 by inhibiting PPARalpha activation. Inflammation may convert HDL de novo into a more proatherogenic form by coordinate but inverse transcriptional regulation in the liver, rather than by physical displacement of apoA-I by SAA.

Constitutive activation of NF-kappaB in human hepatocellular carcinoma: evidence of a cytoprotective role

Activation of nuclear factor-kappaB (NF-kappaB) can promote or inhibit apoptosis. Oxidative stress is an important mechanism by which certain anticancer drugs kill cancer cells, and is also one of the mechanisms that activate NF-kappaB. We therefore examined hepatic expression of the NF-kappaB monomer p65 in human hepatocellular carcinoma (HCC) tissue samples from eight patients and compared it with their respective samples of surrounding liver tissues. We also studied the effect of NF-kappaB inhibition in human HCC cells exposed to oxidative stress, by infecting HuH7 cells with a recombinant adenovirus carrying mutant IkappaBalpha (mIkappaBalpha). Cultured HuH7 cells were infected with mIkappaBalpha or beta-galactosidase (beta-Gal) for 24 hr followed by treatment with increasing concentrations of H2O2. Cytotoxicity, NF-kappaB translocation, NF-kappaB DNA binding, cell proliferation, and apoptosis were determined. The monomer p65 was overexpressed in six of eight human HCC tissues. In HuH7 cells, introduction of mIkappaBalpha potently inhibited the translocation, activation, and DNA binding of NF- kappaB. In control (beta-Gal-infected) HuH7 cells, exposure to H2O2 produced a dose-dependent increase in apoptosis, regardless of NF-kappaB status. mIkappaBalpha-mediated inhibition of NF-kappaB activation sensitized HuH7 cells to H2O2-induced inhibition of cell growth, and further promoted cell death. Addition of H2O2 (200-500 microM) to control or mIkappaBalpha-infected HuH7 cells enhanced caspase-3 activity and cleavage. Adenovirus-mediated transfer of mIkappaBalpha potently inhibits NF-kappaB activity in HuH7 cells, and this enhances oxidative stress-induced cell killing.

Interferon-induced sensitization to apoptosis is associated with repressed transcriptional activity of the hTERT promoter in multiple myeloma

The aim of the present study was to explore hTERT as a target for IFN-induced sensitization to apoptosis in multiple myeloma (MM). IFN-alpha and IFN-gamma downregulated telomerase activity in the IL-6-dependent MM cell line U-266-1970. In MM cells undergoing IFN-induced sensitization to Fas-mediated apoptosis, the repression of telomerase was increased as compared to IFN-alpha treatment alone. Similar to the sensitization effect of IFN, the use of a dominant negative IkappaBalpha vector inhibiting hTERT activity via transcriptional targeting resulted in augmentation of Fas-mediated apoptosis. The mechanism underlying the reduction of telomerase activity by IFN was shown to be transcriptional repression of the hTERT gene. The present study does not support a direct effect of IFN on NF-kappaB binding to the hTERT promoter as underlying the transcriptional repression. We conclude that one potential mechanism whereby IFNs induce apoptosis sensitization is by repressing hTERT transcription and telomerase activity, thereby constituting attractive targets for MM therapy.

Increased radiation-induced apoptosis of Saos2 cells via inhibition of NFκB: A role for c-Jun N-terminal kinase

To elucidate the possible effect of NFkappaB on radioresistance, we used the osteosarcoma cell line Saos2, stably expressing the NFkappaB constitutive inhibitor, mIkappaB (Saos2-mIkappaB) or stably transfected with the empty vector (Saos2-EV). Ionizing radiation induced "intrinsic" apoptosis in Saos2-mIkappaB cells but not in Saos2-EV control cells, with intact NFkappaB activity. We find as expected, that this NFkappaB activity was enhanced following irradiation in the Saos2-EV control cells. On the other hand, inhibition of NFkappaB signaling in Saos2-mIkappaB cells led to the upregulation of the pro-apoptotic systems, such as Bax protein and c-Jun N-terminal Kinase (JNK)/c-Jun/AP1 signaling. Inhibition of NFkappaB resulted in decreased expression of the DNA damage protein GADD45beta, a known inhibitor of JNK. Subsequently, JNK activation of c-Jun/AP-1 proteins increased radiation-induced apoptosis in these mutants. Radiation-induced apoptosis in Saos2-mIkappaB cells was inhibited by the JNK specific inhibitor SP600125 as well as by Bcl-2 over-expression. Furthermore, release of cytochrome-c from mitochondria was increased and caspase-9 and -3 were activated following irradiation in Saos2-mIkappaB cells. Antisense inhibition of GADD45beta in Saos2-EV cells significantly enhanced apoptosis following irradiation. Our results demonstrate that radioresistance of Saos2 osteosarcoma cells is due to NFkappaB-mediated inhibition of JNK. Our study brings new insight into the mechanisms underlying radiation-induced apoptosis of osteosarcoma, and may lead to development of new therapeutic strategies against osteosarcoma.

Inhibition of SRC tyrosine kinases suppresses activation of nuclear factor-kappaB, and serine and tyrosine phosphorylation of IkappaB-alpha in lipopolysaccharide-stimulated raw 264.7 macrophages

Involvement of protein tyrosine kinases (PTK) in lipopolysaccharide (LPS)-induced nuclear factor-kappa B (NF-kappaB) activation has been demonstrated. Studies investigated the role of PTK and the underlying mechanisms by which PTK play a role in LPS induction of pathways leading to NF-kappaB activation in macrophages. Inhibitors of PTK-genistein, herbimycin A, or AG126-blocked LPS-induced NF-kappaB activation. Genistein also blocked pervanadate-induced NF-kappaB activation. Furthermore, Src TK selective inhibitors-damnacanthal or PP1-blocked LPS-induced NF-kappaB activation over a range of nanomolar concentrations. Genistein, damnacanthal, or PP1 blocked the LPS-induced serine phosphorylation, the degradation of IkappaB-alpha, and the consequent translocation of the p65 subunit of NF-kappaB to the nucleus. In addition to serine phosphorylation of IkappaB-alpha, LPS-induced NF-kappaB activation also required tyrosine phosphorylation of IkappaB-alpha. These TK inhibitors blocked substantially LPS induction of tyrosine phosphorylation of IkappaB-alpha. Furthermore, cSrc and Lck were physically associated with IkappaB-alpha. These results suggest that the LPS-induced NF-kappaB pathways are dependent on both serine and tyrosine phosphorylation of IkappaB-alpha, and that Src TK, such as cSrc and Lck, are key components of the LPS signaling pathway through at least two different mechanisms associated with NF-kappaB activation.

Expression of activated transcription factor nuclear factor-kappaB in periodontally diseased tissues

BACKGROUND

Chronic periodontitis is an inflammatory disease found mainly in adults. Little is known about molecular level changes associated with host response in this condition. Nuclear factor-kappaB (NF-kappaB) is a transcription factor implicated in immune and inflammatory responses. NF-kappaB activation has also been reported to be associated with many chronic inflammatory diseases. The purpose of this paper was to compare the nuclear and cytoplasmic expression of NF-kappaB transcription factor (p50/p65) and cytoplasmic expression of IkappaB in periodontal tissues of periodontitis patients and controls.

METHODS

Twenty patients with chronic periodontitis and 20 healthy controls were included in the study. Gingival tissues taken during extraction were processed for immunohistochemical staining and evaluation.

RESULTS

Nuclear (activated) p50 was found in 90% of periodontal patient tissues compared to only 30% of healthy tissues. A more significant result was obtained with p65 (75% versus 5%). Intense cytoplasmic immunoreactivity was also observed in periodontitis tissues. IkappaB, the inhibitor of NF-kappaB, was expressed only in 5% of periodontally diseased tissues.

CONCLUSION

Activation of NF-kappaB (p50/p65) is significant in periodontally diseased tissues, suggesting the potential of inhibitors of NF-kappaB in managing periodontitis.

Inhibition of nuclear factor κB by IκB superrepressor gene transfer ameliorates ischemia-reperfusion injury after experimental lung transplantation

OBJECTIVES

Ischemia-reperfusion injury after lung transplantation is associated with significant morbidity and mortality. The activation of the transcription factor nuclear factor kappaB is central to the 2 important pathways that characterize ischemia-reperfusion injury, namely the inflammatory response and apoptosis. The purpose of this study was to determine the effects of nuclear factor kappaB inhibition on experimental lung transplant ischemia-reperfusion injury with gene transfer of the nuclear factor kappaB inhibitor IkappaB in a superrepressor form (IkappaBSR).

METHODS

An orthotopic left lung transplant model in isogeneic rats was used, with 18 hours of prolonged cold storage of donor lung grafts used to create severe ischemia-reperfusion injury. Donor rats underwent endobronchial gene transfection with saline alone or adenovirus encoding either beta-galactosidase control or IkappaBSR 48 hours before harvest. The function of transplanted lung grafts was assessed on the basis of isolated graft oxygenation, wet/dry lung weight ratio, and myeloperoxidase activity. Nuclear factor kappaB activation was assessed by means of enzyme-linked immunosorbent assay. Apoptotic cell death was assessed by evaluating the levels of histone-associated DNA fragments and caspase-3 activity.

RESULTS

Treatment of donor lung grafts with IkappaBSR resulted in significantly improved oxygenation compared with that seen in control tissue 24 hours after transplantation. IkappaBSR-treated lungs also demonstrated less pulmonary edema and reduced neutrophil infiltration 24 hours after reperfusion. Nuclear factor kappaB activation and apoptotic cell death induction 2 hours after transplantation was significantly reduced in IkappaBSR-treated lungs compared with in control lungs.

CONCLUSIONS

Inhibition of nuclear factor kappaB activation by IkappaBSR gene transfer improves transplanted lung graft oxygenation, decreases pulmonary edema and neutrophil sequestration, and reduces apoptotic cell death after experimental lung transplantation.

Growth inhibition of multiple myeloma cells by a novel IkappaB kinase inhibitor

Involvement of nuclear factor-kappaB (NF-kappaB) in cell survival and proliferation of multiple myeloma has been well established. In this study we observed that NF-kappaB is constitutively activated in all human myeloma cell lines, thus confirming the previous studies. In addition, we found the phosphorylation of p65 subunit of NF-kappaB in addition to the phosphorylation of IkappaBalpha and the activation of NF-kappaB DNA binding and that various target genes of NF-kappaB including bcl-x(L), XIAP, c-IAP1, cyclin D1, and IL-6 are up-regulated. We then examined the effect of a novel IkappaB kinase inhibitor, 2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl nicotinonitrile (ACHP). When myeloma cells were treated with ACHP, the cell growth was efficiently inhibited with IC(50) values ranging from 18 to 35 mumol/L concomitantly with inhibition of the phosphorylation of IkappaBalpha/p65 and NF-kappaB DNA-binding, down-regulation of the NF-kappaB target genes, and induction of apoptosis. In addition, we observed the treatment of ACHP augmented the cytotoxic effects of vincristine and melphalan (l-phenylalanine mustard), conventional antimyeloma drugs. These findings indicate that IkappaB kinase inhibitors such as ACHP can sensitize myeloma cells to the cytotoxic effects of chemotherapeutic agents by blocking the antiapoptotic nature of myeloma cells endowed by the constitutive activation of NF-kappaB.

Nuclear factor {kappa}B inactivation in the rat liver ameliorates short term total warm ischaemia/reperfusion injury

BACKGROUND

In hepatic ischaemia/reperfusion injury, activated liver macrophages (Kupffer cells) are dominantly regulated by a transcription factor, nuclear factor kappaB (NFkappaB), with respect to expression of inflammatory cytokines, acute phase response proteins, and cell adhesion molecules.

AIMS

We assessed whether inactivation of NFkappaB in the liver could attenuate total hepatic warm ischaemia/reperfusion injury.

METHODS

We studied rats with hepatic overexpression of inhibitor kappaBalpha super-repressor (IkappaBalpha SR) caused by a transgene introduced using an adenoviral vector. Hepatic ischaemia/reperfusion injury was induced under warm conditions by total occlusion of hepatoduodenal ligament structures for 20 minutes, followed by reperfusion. Controls included uninfected and control virus (AdLacZ) infected rats.

RESULTS

IkappaBalpha SR was overexpressed in Kupffer cells as well as in hepatocytes, blocking nuclear translocation of NFkappaB (p65) into the nucleus after reperfusion. Gene transfection with IkappaBalpha SR, but not with LacZ, markedly attenuated ischaemia/reperfusion injury, suppressing inducible nitric oxide synthase and nitrotyrosine expression in the liver. Moreover, no remarkable hepatocyte apoptosis was detected under IkappaBalpha SR overexpression.

CONCLUSIONS

Adenoviral transfer of the IkappaBalpha SR gene in the liver ameliorates short term warm ischaemia/reperfusion injury, possibly through attenuation of hepatic macrophage activation.

Cytokine-stimulated GTP cyclohydrolase I expression in endothelial cells requires coordinated activation of nuclear factor-kappaB and Stat1/Stat3

Endothelial production of nitric oxide (NO) is dependent on adequate cellular levels of tetrahydrobiopterin (BH4), an important cofactor for the nitric oxide synthases. Vascular diseases are often characterized by vessel wall inflammation and cytokine treatment of endothelial cells increases BH4 levels, in part through the induction of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for BH4 biosynthesis. However, the molecular mechanisms of cytokine-mediated GTPCH I induction in the endothelium are not entirely clear. We sought to investigate the signaling pathways whereby cytokines induce GTPCH I expression in human umbilical vein endothelial cells (HUVECs). Interferon-gamma (IFN-gamma) induced endothelial cell GTPCH I protein and BH4 modestly, whereas high-level induction required combinations of IFN-gamma and tumor necrosis factor-alpha (TNF-alpha). In the presence of IFN-gamma, TNF-alpha increased GTPCH I mRNA in a manner dependent on nuclear factor-kappaB (NF-kappaB), as this effect was abrogated by overexpression of a dominant-negative IkappaB construct. HUVEC IFN-gamma treatment resulted in signal transducer and activator of transcription 1 (Stat1) activation and DNA binding in a Jak2-dependent manner, as this was inhibited by AG490. Conversely, overexpression of Jak2 effectively substituted for IFN-gamma in supporting TNF-alpha-mediated GTPCH I induction. The role of IFN-gamma was also Stat1-dependent as Stat1-null cells exhibited no GTPCH I induction in response to cytokines. However, Stat1 activation with oncostatin M failed to support TNF-alpha-mediated GTPCH I induction because of concomitant Stat3 activation. Consistent with this notion, siRNA-mediated Stat3 gene silencing allowed oncostatin M to substitute for IFN-gamma in this system. These data implicate both NF-kappaB and Stat1 in endothelial cell cytokine-stimulated GTPCH I induction and highlight the role of Stat3 in modulating Stat1-supported gene transcription. Thus, IFN-gamma and TNF-alpha exert distinct but cooperative roles for BH4 biosynthesis in endothelium that may have important implications for vascular function during vascular inflammation.

Co-operative functions between nuclear factors NFkappaB and CCAT/enhancer-binding protein-beta (C/EBP-beta) regulate the IL-6 promoter in autocrine human prostate cancer cells

BACKGROUND

IL-6 is a growth and survival factor for prostate cancer cells through autocrine pathways. Here, we have systematically examined the transcriptional regulation mechanisms of IL-6 in autocrine prostate cancer cells.

METHODS

RT-PCR and immunohistochemical staining were used to determine IL-6 production in the cells. Serial mutant IL-6 promoter luciferase reporters were generated and their transcriptional activities were examined. The transcription factors involved in IL-6 regulation were identified with super-shift EMSA. Overexpression of NFkappaB p65 and C/EBP-beta, and blockade of NFkappaB with IkappaBalpha or CAPE were performed to demonstrate the cooperation between NFkappaB p65 and C/EBP-beta in activation of IL-6.

RESULTS

Transcription factor regulatory sites IL6-NFkappaB, IL6-C/EBP, IL6-CREB, and IL6-AP1, are responsive to constitutively activated IL-6 production in autocrine prostate cancer cell lines. Among these sites, IL6-AP1 and IL6-C/EBP appear most important, while IL6-NFkappaB shows the least effect for IL-6 promoter activity as determined by mutant IL-6 promoter luciferase reporter assay. Nevertheless, nuclear factor NFkappaB is activated and required. Such activation is minimally dependent upon the IL6-NFkappaB site, occurring through cooperation with other transcription factors that bind the IL-6 promoter. Cooperation between NFkappaB p65 and C/EBP-beta did not require a functional IL6-NFkappaB binding site.

CONCLUSIONS

These data support a unique role for NFkappaB p65 as the primary trigger in autocrine production of IL-6 in prostate cancer cells. Furthermore, we describe a novel transcriptional activation mechanism for NFkappaB that is independent of its regulatory binding site, occurring through cooperation with other transcription factors that facilitate the neighboring regulatory site.

RelB regulates human dendritic cell subset development by promoting monocyte intermediates

In humans, epithelial Langerhans cells (LCs) and monocyte-derived/interstitial dendritic cells (DCs) constitute 2 myeloid DC sublineages. Molecular mechanisms involved in their development from common myeloid progenitors remain poorly defined. Here we demonstrate that the nuclear factor-κB (NF-κB) transcription factor RelB regulates the generation of monocytic CD14+CD11b+ precursors of interstitial DCs from human hematopoietic progenitors. RelB overexpression promoted, whereas endogenous RelB inhibition (by p100ΔN) blocked, precursor cell development along this DC subset pathway. RelB inhibition specifically arrested precursor progression from CD14loCD11b- to CD14+CD11b+ stages. Precursors were still capable of LC and granulocyte differentiation but were defective in macrophage–colony-stimulating factor (M-CSF)–dependent monocyte/macrophage differentiation. RelB inhibition markedly differed from classical NF-κB signaling inhibition because IκBα superrepressor (IκBα-SR), but not p100ΔN, impaired LC/DC differentiation, DC adhesion, and progenitor cell proliferation. Although RelB up-regulation and nuclear translocation are regarded as hallmarks of human myeloid DC maturation, ectopic RelB overexpression failed to promote DC maturation. Our results suggest that RelB regulates human monopoiesis and monocyte-derived DC subset development.

Inhibitory effects of epicatechin on interleukin-1beta-induced inducible nitric oxide synthase expression in RINm5F cells and rat pancreatic islets by down-regulation of NF-kappaB activation

Cytokines that are released by infiltrating inflammatory cells around the pancreatic islets are involved in the pathogenesis of type 1 diabetes mellitus. Specifically, interleukin-1beta (IL-1beta) stimulates inducible nitric oxide synthase (iNOS) expression and nitric oxide overproduction, leading to the beta-cell damage. In activating this pathway, nuclear factor-kappaB (NF-kappaB) plays a crucial role, and many of the IL-1beta-sensitive genes contain NF-kappaB binding sites in their promoter regions. We have recently shown that epicatechin, which is a flavonoid, had a protective effect on pancreatic beta-cells in both streptozotocin-treated rats and islets. In the present study, the effects of epicatechin on IL-1beta-induced beta-cell damage were examined. RINm5F cells and islets were pretreated with epicatechin and next incubated with IL-1beta. The released nitrite, iNOS protein and mRNA expression levels were then measured. IkappaBalpha protein, nuclear translocation of NF-kappaB, and NF-kappaB DNA binding activity were also determined. Following the transient transfection of an iNOS promoter into the cells, the iNOS promoter activity was measured. ATP- or D-glucose-induced insulin release was measured in RINm5F cells and islets, respectively. Epicatechin significantly reduced IL-1beta-induced nitrite production, iNOS protein and mRNA expressions, and it also inhibited IL-1beta-induced IkappaBalpha protein degradation, NF-kappaB activation, and iNOS promoter activity. Epicatechin partly restored the IL-1beta-induced inhibition of insulin release. These results suggest that epicatechin inhibits the IL-1beta-induced iNOS expression by down-regulating NF-kappaB activation, and protecting beta-cells from IL-1beta.

Pivotal role of nuclear factor kappaB signaling in anti-CD40-induced liver injury in mice

Nuclear factor kappaB (NF-kappaB) has a central role in coordinating the expression of a wide variety of genes that control immune responses and is also recognized as an antiapoptotic transcription factor. Here, we focused on the role of the NF-kappaB signaling pathway in the interaction between inflammatory cells and hepatocytes in liver inflammation. We found that pretreatment of mice with adenoviruses expressing a mutant form of the inhibitor kappaB superrepressor (Ad5IkappaB), a NF-kappaB inhibitor, reduced the migration of inflammatory cells and cytokine and chemokine expression in the liver 12 hours after a single intravenous injection of an anti-CD40 antibody (alphaCD40) compared with mice infected with control adenoviruses (Ad5LacZ). We also confirmed reductions in cytokine production by macrophages, T cells, and natural killer (NK) cells in the liver of Ad5IkappaB-treated mice by FACS analysis. However, alphaCD40 treatment in Ad5IkappaB-infected mice induced elevation of serum alanine aminotransferase at 24 hours, and the liver injury was associated with massive hepatocyte apoptosis. Furthermore, interferon gamma (IFN-gamma) production by NK cells and T cells was increased and stimulated tumor necrosis factor alpha (TNF-alpha) production by macrophages in the Ad5IkappaB-infected liver. Moreover, the liver injury was completely suppressed by the administration of anti-IFN-gamma and anti-TNF-alpha. These results suggest that inhibition of NF-kappaB activity suppressed alphaCD40-induced liver inflammation at an early phase, resulting in a reduction in cytokine and chemokine production, whereas it sensitized hepatocytes to TNF-alpha-induced apoptosis and exacerbated liver injury at the late phase. In conclusion, NF-kappaB exerts pivotal activities at inflammatory sites, and caution should be exercised in NF-kappaB-targeted therapy of liver disease.

Reduced infiltration and increased apoptosis of leukocytes at sites of inflammation by systemic administration of a membrane-permeable IkappaBalpha repressor

OBJECTIVE

NF-kappaB activation is associated with several inflammatory disorders, including rheumatoid arthritis (RA), making this family of transcription factors a good target for the development of antiinflammatory treatments. Although inhibitors of the NF-kappaB pathway are currently available, their specificity has not been adequately determined. IkappaBalpha is a physiologic inhibitor of NF-kappaB and a potent repressor experimentally when expressed in a nondegradable form. We describe here a novel means for specifically regulating NF-kappaB activity in vivo by administering a chimeric molecule comprising the super-repressor IkappaBalpha (srIkappaBalpha) fused to the membrane-transducing domain of the human immunodeficiency virus Tat protein (Tat-srIkappaBalpha).

METHODS

The Wistar rat carrageenan-induced pleurisy model was used to assess the effects of in vivo administration of Tat-srIkappaBalpha on leukocyte infiltration and on cytokine and chemokine production.

RESULTS

Systemic administration of Tat-srIkappaBalpha diminished infiltration of leukocytes into the site of inflammation. Analysis of the recruited inflammatory cells confirmed uptake of the inhibitor and reduction of the NF-kappaB activity. These cells exhibited elevated caspase activity, suggesting that NF-kappaB is required for the survival of leukocytes at sites of inflammation. Analysis of exudates, while showing decreases in the production of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-1beta, also revealed a significant increase in the production of the neutrophil chemoattractants cytokine-induced neutrophil chemoattractant 1 (CINC-1) and CINC-3 compared with controls. This result could reveal a previously unknown feedback mechanism in which infiltrating leukocytes may down-regulate local production of these chemokines.

CONCLUSION

These results provide new insights into the etiology of inflammation and establish a strategy for developing novel therapeutics by regulating the signaling activity of pathways known to function in RA.

Inhibition of NF-Kappa B augments sensitivity to 5-Fluorouracil/Folinic acid in colon cancer1

BACKGROUND

5-fluorouracil (5-FU), the most common antimetabolite used for the treatment of colorectal cancer, exerts its cytotoxic effects through the induction of apoptosis. Folinic acid potentiates the effect of 5-FU. Drug activity is currently limited as a result of inducible chemoresistance. Limited research suggests that the transcription factor nuclear factor kappa-B (NF-kappaB), which has antiapoptotic properties, may play a major role in inducible chemoresistance.

MATERIALS AND METHODS

SW48 colon cancer cells were used for all experiments. Cell growth was determined by cell proliferation assay. Apoptosis was assessed by measuring caspase 3 activity. Activation of NF-kappaB was ascertained by electrophoretic mobility shift assay, luciferase reporter assay, and Western blot analysis.

RESULTS

Treatment with 5-FU (0.001-10 mm), not only inhibited growth and induced apoptosis but significantly activated NF-kappaB in SW48 cells. Folinic acid alone (0.01-100 mg/L) did not inhibit growth but improved the cytotoxic effect of 5-FU in a dose-dependent manner. Likewise, folinic acid alone did not activate NF-kappaB or induce apoptosis but enhanced 5-FU-mediated NF-kappaB activation and cell apoptosis. Transfection with adenovirus IkappaBalpha super-repressor strongly inhibited constitutive activation of NF-kappaB and significantly enhanced 5-FU and 5-FU/Folinic acid-mediated growth inhibition (P < 0.05).

CONCLUSIONS

Treatment with 5-FU activates NF-kappaB. Folinic acid enhances 5-FU-mediated activation of NF-kappaB. Inhibition of NF-kappaB enhances the cytotoxic effect of 5-FU with or without Folinic acid in colon cancer cells.

Induction of transcription by p21Waf1/Cip1/Sdi1: role of NFkappaB and effect of non-steroidal anti-inflammatory drugs

p21(Waf1/Cip1/Sdi1) is the primary mediator of cell cycle arrest in response to different forms of stress and in the programs of senescence and differentiation. p21 interacts with many regulatory proteins and has broad effects on cellular gene expression. p21 was previously shown to stimulate NFkappaB transcriptional activity through its effect on the p300/CBP transcription cofactor family. p21 expression in human cells increases mRNA levels of different genes, some of which have been implicated in carcinogenesis and age-related diseases. Here we report that p21 expression stimulates promoters of six p21-responsive human genes and the cytomegalovirus promoter, as well as an artificial promoter containing NFkappaB response elements. The IkappaBalpha super-repressor blocked the effect of p21 on all but one of the promoters, and the response to p21 was abrogated by the mutagenesis of an NFkappaB element. p21 inducibility of all the tested promoters and of the endogenous p21-responsive genes was strongly inhibited by adenoviral E1A protein and its deletion mutants that bind p300/CBP but not p21 or Rb. Sulindac and some other non-steroidal anti-inflammatory drugs that inhibit NFkappaB decrease the effects of p21 on the responsive promoters and endogenous genes. These findings suggest the feasibility of developing agents that will counteract p21-mediated induction of disease-associated genes.

TNFα-induced hepatocyte apoptosis is associated with alterations of the cell cycle and decreased stem loop binding protein

BACKGROUND

Inhibition of nuclear factor kappa B (NF kappa B) during liver regeneration induces hepatocyte apoptosis associated with normal DNA synthesis but decreased mitosis, suggesting that inhibition of NF kappa B impairs progression from S-phase through the G(2)/M phase of the cell cycle. Our aim was to determine if inhibition of NF kappa B alters cell cycle characteristics in hepatocytes treated with tumor necrosis factor alpha (TNF alpha).

METHODS

Primary hepatocytes from BALB/c mice were infected with adenoviruses expressing luciferase (control; AdLuc) or the I kappa B super-repressor (AdI kappa B) and treated with or without TNF alpha (30 ng/ml). Flow cytometry was performed (0 to 40 hours) to determine apoptosis and cell cycle progression. Reverse transcriptase-polymerase chain reaction and immunoblots assessed changes in cell cycle mediators and antiapoptotic factors.

RESULTS

Primary hepatocytes treated with AdI kappa B and TNF alpha demonstrated significantly more S-phase cells (14% +/- 3% vs 6% +/- 2%, P<.05) at 14 hours compared with controls. Inhibition of NF kappa B with or without TNFalpha was associated with decreased expression of stem loop bind protein, a marker of cell cycle progression through S-phase. The NF kappa B-induced antiapoptotic proteins, iNOS and TRAF2, had decreased message at 9 and 12 hours, respectively, in TNF alpha- and AdI kappa B-treated cells.

CONCLUSION

Inhibition of NF kappa B in TNF alpha-treated primary mouse hepatocytes is associated with increased S-phase cell cycle retention and decreased stem loop bind protein.

Hepatitis B virus X antigen promotes transforming growth factor-beta1 (TGF-beta1) activity by up-regulation of TGF-beta1 and down-regulation of alpha2-macroglobulin

Hepatitis B virus (HBV) X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) by activation of signalling pathways such as NF-kappaB. To identify NF-kappaB target genes differentially expressed in HBxAg-positive compared to -negative cells, HepG2 cells consistently expressing HBxAg (HepG2X cells) were stably transfected with pZeoSV2 or pZeoSV2-IkappaBalpha. mRNA from each culture was isolated and compared by PCR select cDNA subtraction. The results showed lower levels of alpha(2)-macroglobulin (alpha(2)-M) in HepG2X-pZeoSV2 compared to HepG2X-pZeoSV2-IkappaBalpha cells. This was confirmed by Northern and Western blotting, and by measurement of extracellular alpha(2)-M levels. Elevated transforming growth factor-beta1 (TGF-beta1) levels were also seen in HepG2X compared to control cells. Serum-free conditioned medium (SFCM) from HepG2X cells suppressed DNA synthesis in a TGF-beta-sensitive cell line, Mv1Lu. The latter was reversed when the SFCM was pretreated with exogenous, activated alpha(2)-M or with anti-TGF-beta. Since elevated TGF-beta1 promotes the development of many tumour types, these observations suggest that the HBxAg-mediated alteration in TGF-beta1 and alpha(2)-M production may contribute importantly to the pathogenesis of HCC.

IG20, in contrast to DENN-SV, (MADD splice variants) suppresses tumor cell survival, and enhances their susceptibility to apoptosis and cancer drugs

We identified seven putative splice variants of the human IG20 gene. Four variants namely, IG20, MADD, IG20-SV2 and DENN-SV are expressed in human tissues. While DENN-SV is constitutively expressed in all tissues, expression of IG20 appears to be regulated. Interestingly, overexpression of DENN-SV enhanced cell replication and resistance to treatments with TNFalpha, vinblastine, etoposide and gamma-radiation. In contrast, IG20 expression suppressed cell replication and increased susceptibility to the above treatments. Moreover, cells that were resistant and susceptible to TNFalpha-induced apoptosis exclusively expressed endogenous DENN-SV and IG20, respectively. When PA-1 ovarian cancer cells that are devoid of endogenous IG20 variant, but express higher levels of DENN-SV, were transfected with IG20, they showed reduced cell proliferation and increased susceptibility to apoptosis induced by TNFalpha, TRAIL and gamma-radiation. This indicated that overexpression of IG20 can override endogenous DENN-SV function. CrmA reversed the effects of IG20, but not DENN-SV. In contrast, dominant-negative-I-kappa B reversed the effects of DENN-SV, but not IG20, and showed that DENN-SV most likely exerted its effects through NFkappaB activation. Together, our data show that IG20 gene can play a novel and significant role in regulating cell proliferation, survival and death through alternative mRNA splicing.

Direct inhibition of NF-kappa B blocks bone erosion associated with inflammatory arthritis

Inflammatory arthritis is associated with devastating joint tissue destruction and periarticular bone erosion. Although secreted products of infiltrating immune cells perpetuate the inflammatory response, the osteolytic component of this disease is a direct result of localized recruitment and activation of osteoclasts. Given that NF-kappaB plays a central role in both processes, the function of this transcription factor was examined. Using a mouse model of autoreactive Ig transfer that engenders inflammatory arthritis, we show numerous osteoclasts in the articular joint tissue associated with progressive periarticular osteolytic lesions. Moreover, cells retrieved from these joints exhibit heightened NF-kappaB activity. Importantly, direct administration of dominant negative*I-kappaB or tyrosine 42-mutated I-kappaB (Y42F*I-kappaB) proteins into mice before induction of the disease attenuates in vivo activation of the transcription factor. More importantly, these I-kappaB mutant forms significantly inhibit in vivo production of TNF and receptor activator of NF-kappaB ligand, and block joint swelling, osteoclast recruitment, and osteolysis. Thus, NF-kappaB appears to be the centerpiece of inflammatory-osteolytic arthritis and direct inhibition of this transcription factor by unique and novel I-kappaB mutant proteins blocks manifestation of the disease.

Chemoprotective effect of caffeic acid phenethyl ester on promotion in a medium-term rat hepatocarcinogenesis assay

Caffeic acid phenethyl ester (CAPE), a natural honeybee product exhibits a spectrum of biological activities including anti-microbial, anti-inflammatory, antioxidant and anti-tumoral actions. CAPE is also chemopreventive against intestinal, colon and skin cancer. Our aim was to extend the study of its chemoprotective features to the promotion of hepatocarcinogenesis. Male Wistar rats were subjected to a protocol under a modified promotion regimen of the resistant hepatocyte model. The altered hepatic foci (AHF) were quantitatively analyzed by histochemistry and image processing. When given during promotion, CAPE (20 mg/kg) decreased the expression of number and area gamma-glutamyl transpeptidase (GGT) positive AHF by 91% and 97%, respectively. When GGT expression was analyzed by RT-PCR, CAPE drastically decreased and prevented expression of almost all GGT transcripts at this stage of the carcinogenic process. Glutathione S-transferase placental form (GST-P), another protein marker for preneoplastic lesions was measured by Western blot and a decrease of 82% was observed. Additionally, we evaluated the effect of CAPE on the expression of nuclear factor NF-kappaB and found an 85% decrease in nuclear localization of the p65 subunit of NF-kappaB; however, their repressor, IkappaBalpha was not modified. Our results showed that CAPE given during promotion in hepatocarcinogenesis protects against induction of GGT-positive AHF, GST-P protein, GGT mRNA expression and translocation of p65. This phenomenon was independent of IkappaBalpha degradation.

An NF-kappaB-specific inhibitor, IkappaBalpha, binds to and inhibits cyclin-dependent kinase 4

IkappaBalpha, a protein composed of six ankyrin repeats, is a specific inhibitor of nuclear factor kappaB (NF-kappaB) and functions in signal transductions in many different cell types. Using both in vivo yeast two-hybrid assays and in vitro activity and binding assays, we showed that IkappaBalpha binds to cyclin-dependent kinase 4 (CDK4) specifically and inhibits its kinase activity. The potencies of binding and inhibition of IkappaBalpha are comparable to those of INK4 proteins, the specific CDK4 inhibitors that also contain ankyrin repeats. Furthermore, we showed that INK4 proteins and IkappaBalpha compete with each other for binding to CDK4. These results led us to propose a hypothesis that there is cross talk between the NF-kappaB/IkappaBalpha pathway and the p16/CDK4/Rb pathway in cells, and that IkappaBalpha could substitute for the CDK4-inhibiting function of p16, a tumor suppressor frequently inactivated in human tumors. To further understand the structural basis of IkappaBalpha-CDK binding, we used different mutants of CDK4 to show that there are notable differences between IkappaBalpha and INK4 proteins in CDK4 binding since the binding is affected differently by different CDK4 mutations. We also demonstrated that the interaction of IkappaBalpha with CDK4 is different from that with its NF-kappaB. While most of the contacts contributing to NF-kappaB binding are located within the last two C-terminal ankyrin repeats and the loop region bridging them, the first four ankyrin repeats at the N-terminus are responsible for CDK4 binding and inhibition.

Attenuation of renal fibrosis by proteasome inhibition in rat obstructive nephropathy: possible role of nuclear factor kappaB

We previously reported that pyrrolidine dithiocarbamate blocked nuclear factor-kappaB (NF-kappaB) activation and attenuated interstitial inflammation and tubulointerstitial fibrosis in the rat obstructive nephropathy. Since pyrrolidine dithiocarbamate is an anti-oxidant and possesses additional biological properties, present experiment was conducted to clarify further the role of NF-kappaB in the development of tubulointerstitial fibrosis in obstructed kidney using a proteasome inhibitor that blocks NF-kappaB through stabilizing IkappaB, an endogenous inhibitor of NF-kappaB. At 5 days following unilateral ureteral obstruction (UUO) in rats, obstructed kidney exhibited tubulointerstitial fibrosis that was associated with macrophage infiltration. UUO decreased renal cortical IkappaB protein contents with concomitant increases in NF-kappaB DNA-binding activity and gene expression of monocyte chemoattractant protein-1. Administration of PSI, N-benzyloxy-carbonyl-Ile-Glu (O-t-Bu)-Ala-leucinal, a proteasome inhibitor, (3 mg/kg/day, s.c., b.i.d) to UUO rats inhibited proteasome activity and attenuated the changes in IkappaB content, NF-kappaB activity and MCP-1 mRNA expression observed in UUO rats. PSI also decreased macrophage influx and attenuated the development of fibrosis. Furthermore, up-regulated gene expression of pro-fibrogenic molecules observed in the obstructed kidney was attenuated by PSI. These results further support the notion that NF-kappaB plays an important role in the development of renal fibrosis in the obstructive nephropathy.

Inhibition of nuclear factor kappaB and phosphatidylinositol 3-kinase/Akt is essential for massive hepatocyte apoptosis induced by tumor necrosis factor alpha in mice

BACKGROUND/AIMS

Tumor necrosis factor (TNF)-alpha itself does not induce liver injury in normal mice or hepatocytes. Rather, this event, especially in vitro, is explained by the fact that the TNF-alpha/TNF receptor system not only triggers downstream signals leading to apoptosis but also induces an antiapoptotic pathway through the activation of nuclear factor (NF)-kappaB. The aim of this study was to determine whether inhibition of antiapoptotic pathways influences the susceptibility of mice to TNF-alpha. Here, we focused on the roles of NF-kappaB and phosphatidylinositol 3-kinase (PI3K)-regulated serine/threonine kinase Akt.

METHODS

TNF-alpha was administered to BALB/c mice after treatment with an adenovirus expressing a mutant form IkappaBalpha (Ad5IkappaB), the PI3K inhibitor wortmannin, or both. Liver injury was assessed biochemically and histologically. The expression of Bcl-2 family members and caspase activity were examined.

RESULTS

In the mice livers, treatment with Ad5IkappaB or the wortmannin suppressed the activation of NF-kappaB or Akt, respectively. Suppression of either NF-kappaB or Akt showed a slight increase in transaminase levels and focal liver cell death after TNF-alpha administration. However, in mice treated with both Ad5IkappaB and wortmannin, TNF-alpha administration resulted in massive hepatocyte apoptosis and hemorrhagic liver destruction in mice. The combination of Ad5IkappaB, wortmannin, and TNF-alpha markedly increased the activation of caspase-3 and -9, and activated caspase-8 to a lesser degree, suggesting that TNF-alpha-induced hepatocyte apoptosis is dependent on type II cell death signaling pathway, probably through the mitochondria. Inhibition of the NF-kappaB and PI3K/Akt pathways had no effect on expression of Bcl-2 families.

CONCLUSION

The inducible activation of NF-kappaB and constitutive activation of Akt regulate hepatocyte survival against TNF-alpha, which occurs independent of Bcl-2 families.

Adenovirus-mediated inhibition of NF-kappaB confers chemo-sensitization and apoptosis in prostate cancer cells

Acquirement of multi-drug resistance by tumor cells represents a major obstacle in the management of prostate cancer. Such resistance was demonstrated in the androgen-independent DU-145 cells in response to paclitaxel and the mechanisms by which these cell develops resistance was not understood. The objective of this study was to examine whether abrogation of the constitutively active NF-kappaB in the chemoresistant, androgen independent DU-145 prostate cancer cells will enhance their sensitivity to cytototoxic agents. Inhibition of NF-kappaB by a dominant negative super-repressor IkappaB mutant adenoviral construct enhanced the apoptotic potentials of paclitaxel and rhTNF-alpha in these cells. Using reporter assays and RT-PCR analysis, we demonstrate that paclitaxel-induced cell death was associated with an increase in NF-kappaB activation and MDR-1 gene expression. Abrogation of these effects by the dominant negative IkappaB adenoviral construct suggests that induction and/or constitutive activation of NF-kappaB can block the paclitaxel-induced apoptotic signaling pathways in this cell line, possibly by increasing the expression of anti-apoptotic and MDR-1 gene products, leading to development of chemoresistance in these cells. We conclude that inhibition of NF-kappaB activation may have therapeutic implications for prostate cancer.

Manganese superoxide dismutase-mediated gene expression in radiation-induced adaptive responses

Antioxidant enzymes are critical in oxidative stress responses. Radioresistant variants isolated from MCF-7 human carcinoma cells following fractionated ionizing radiation (MCF+FIR cells) or overexpression of manganese superoxide dismutase (MCF+SOD cells) demonstrated dose-modifying factors at 10% isosurvival of 1.8 and 2.3, respectively. MCF+FIR and MCF-7 cells (exposed to single-dose radiation) demonstrated 5- to 10-fold increases in MnSOD activity, mRNA, and immunoreactive protein. Radioresistance in MCF+FIR and MCF+SOD cells was reduced following expression of antisense MnSOD. DNA microarray analysis and immunoblotting identified p21, Myc, 14-3-3 zeta, cyclin A, cyclin B1, and GADD153 as genes constitutively overexpressed (2- to 10-fold) in both MCF+FIR and MCF+SOD cells. Radiation-induced expression of these six genes was suppressed in fibroblasts from Sod2 knockout mice (-/-) as well as in MCF+FIR and MCF+SOD cells expressing antisense MnSOD. Inhibiting NF-kappa B transcriptional activity in MCF+FIR cells, by using mutant I kappa B alpha, inhibited radioresistance as well as reducing steady-state levels of MnSOD, 14-3-3 zeta, GADD153, cyclin A, and cyclin B1 mRNA. In contrast, mutant I kappa B alpha was unable to inhibit radioresistance or reduce 14-3-3 zeta, GADD153, cyclin A, and cyclin B1 mRNAs in MCF+SOD cells, where MnSOD overexpression was independent of NF-kappa B. These results support the hypothesis that NF-kappa B is capable of regulating the expression of MnSOD, which in turn is capable of increasing the expression of genes that participate in radiation-induced adaptive responses.

Antigen-specific T-cell downregulation by human dendritic cells following blockade of NF-kappaB

Dendritic cells (DCs) are important for presenting antigen to T cells, especially naïve T cells. It has recently been shown that blocking the transcription factor, nuclear factor kappa B (NF-kappaB) in human DCs inhibited the mixed leukocyte reaction. The aim of this study was to investigate the effect of blocking NF-kappaB in DCs during presentation of antigen to memory T cells in vitro. Peripheral blood monocytes were differentiated into immature DCs with interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor, and pulsed with an immunogenic tetanus toxoid peptide. Upon maturation, the antigen-pulsed DCs were highly effective in presenting antigen to autologous T cells. However, stimulation with antigen-pulsed DCs overexpressing IotakappaBetaalpha, the endogenous inhibitor of NF-kappaB, led to a significant reduction in T-cell proliferation, and decreased production of interferon-gamma, IL-4 and IL-10, whereas transforming growth factor-beta production was low throughout. There was a significant increase in apoptosis of antigen-specific T cells, even in the presence of IL-2, which was not found in resting T cells. Similar findings were observed using a proteasome inhibitor to block NF-kappaB. The effective downregulation of antigen-specific T-cell responses following blockade of NF-kappaB in DCs could be a useful approach for immunomodulating inflammatory T-cell responses.

Regulation of tissue factor expression in smooth muscle cells with nitric oxide

OBJECTIVE

This study was undertaken to determine the effect of nitric oxide (NO) on tissue factor (TF) expression in vascular smooth muscle cells.

STUDY DESIGN

Rat aortic smooth muscle cells (RASMCs) were exposed to NO delivered exogenously with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) or produced endogenously after infection with an adenoviral vector carrying human inducible NO synthase (AdiNOS). Functional TF activity was assessed with chromogenic TF assay. TF antigen was determined with immunohistochemistry. Northern blot analysis was used to determine steady- state TF messenger RNA (mRNA). Electrophoretic mobility gel shift assay was performed to determine the nuclear binding activity of nuclear factor kappa-B (NFkappaB). NFkappaB activity was inhibited by either prior transduction of RASMCs with mutant IkappaB or treatment with pyrrolidine dithiocarbamate.

RESULTS

RASMCs exposed to SNAP or infected with AdiNOS exhibited increased functional TF activity and antigen. Regardless of the source of NO, a time-dependent and concentration-dependent increase in TF activity was observed. Steady-state TF mRNA levels were also increased by NO delivered via either method. NFkappaB nuclear binding activity was also increased by NO. Inhibition of NFkappaB activity by either pyrrolidine dithiocarbamate treatment or mutant IkappaB transduction abrogated NO-induced enhancement of TF mRNA and functional activity.

CONCLUSION

In RASMC, NO exposure results in upregulation of TF functional activity, antigen, and mRNA. This effect appears to be mediated by an NFkappaB-dependent pathway.

Gene transfer of truncated IkappaBalpha prevents tubulointerstitial injury

BACKGROUND

Severe proteinuria not only indicates the presence of progressive glomerular disease, but also causes tubular epithelial cells to produce inflammatory mediators leading to tubulointerstitial (TI) injury. We investigated the role of nuclear factor-kappaB (NF-kappaB) in tubular epithelial cells in the development of proteinuria-induced TI injury.

METHODS

To specifically inhibit NF-kappaB activation, a recombinant adenovirus vector expressing a truncated form of IkappaBalpha (AdexIkappaBDeltaN) was injected into renal arteries of protein-overloaded rats, a model of TI injury characterized by infiltration of mononuclear cells and fibrosis.

RESULTS

Activation of NF-kappaB in the renal cortex, observed in protein-overloaded rats treated with a control vector, recombinant lacZ adenovirus, was prevented in AdexIkappaBDeltaN-injected rats. Microscopic examination revealed AdexIkappaBDeltaN treatment to markedly attenuate proteinuria-induced TI injury. Increased immunostaining of vascular cell adhesion molecule-1, transforming growth factor-beta, and fibronectin in TI lesions also was suppressed by AdexIkappaBDeltaN injection.

CONCLUSIONS

These findings provide evidence of the critical role of NF-kappaB activation in TI injury and suggest the therapeutic potential of adenovirus-mediated IkappaBDeltaN gene transfer into the kidney as a means of interrupting the process of TI damage.

Transfection of human endothelial cells with HIV-1 tat gene activates NF-kappa B and enhances monocyte adhesion

Human immunodeficiency virus (HIV)-1 Tat released from HIV-1-infected monocytes is believed to enter other cells via an integrin-facilitated pathway, resulting in altered gene expression. Indeed, exogenous Tat protein can increase cell adhesion molecule gene expression in human endothelial cells. Signaling pathways initiated by Tat in endothelial cells are not known. We evaluated the ability of endogenous tat to stimulate monocyte adhesion via activation of nuclear factor-kappaB (NF-kappaB) within human umbilical vein endothelial cells. Transfection with pcTat, but not control vector DNA, increased NF-kappaB binding activity, NF-kappaB luciferase reporter activity, and monocyte adhesion. pcTat also increased kappaB-dependent HIV-1-LTR-CAT reporter activity 28-fold compared with a 3-fold increase produced by transfection with an equivalent amount of pcTax (from human leukemia virus). The pcTat-induced increase in pNF-kappaB-Luc activity and monocyte adhesion to endothelial cells was blocked by cotransfection with dominant-negative mutant IkappaBalpha and by incubation with 10 mM aspirin. We conclude that monocyte adhesion to human endothelial cells stimulated by pcTat is mediated via an NF-kappaB-dependent mechanism. Furthermore, inhibition studies using aspirin suggest that pcTat-stimulated NF-kappaB activation and monocyte adhesion occur via a redox-sensitive mechanism.

Recombinant adenoviral expression of dominant negative IkappaBalpha protects brain from cerebral ischemic injury

Transcription factor NF-kappaB is associated with inflammatory response and cell survival. Under inactive condition, NF-kappaB is sequestered in the cytoplasm by an anchor protein, inhibitor of NF-kappaB (IkappaB). NF-kappaB was shown to be activated during ischemic brain injury. In the present study we have investigated the role of NF-kappaB in ischemic brain injury using a recombinant adenovirus expressing a dominant negative form of IkappaB (Adv/IkappaBdn) to specifically inhibit NF-kappaB activation. Our data demonstrated that cortical injection of Adv/IkappaBdn significantly reduced ischemic brain injury following permanent occlusion of the middle cerebral artery (MCAO) in rats, showing 55% reduction (p<0.01, n=8) in total ischemic lesion or 80% reduction (p<0.001) in the cortical area with Adv/IkappaBdn expression. Similarly, Adv/IkappaBdn expression significantly decreased neurological deficits (37% reduction over controls, p<0.01, n=8). These data provide further evidence for the role of NF-kappaB/IkappaB in ischemic brain injury and suggest that inhibition of NF-kappaB is neuroprotective in focal stroke.

Role of NF-kappaB on liver cold ischemia-reperfusion injury

The role of NF-kappaB, the rapid-response transcription factor for multiple genes, in cold ischemia-reperfusion (I/R) injury was examined after syngeneic transplantation of liver grafts. Lewis rat recipients were killed 1-48 h after reperfusion of three different liver grafts: 1) uninfected control, 2) infected ex vivo with control adenoviral vector (AdEGFP), and 3) infected ex vivo with AdIkappaB. In uninfected control livers, NF-kappaB was activated biphasically at 1-3 and 12 h after reperfusion with aspartate transaminase (AST) levels of 4,244 +/- 691 IU/l. The first peak of NF-kappaB activation associated with an increase of mRNA for TNF-alpha, IL-1beta, and IL-10. AdEGFP transfection resulted in similar outcomes. Interestingly, AdIkappaB-transfected liver grafts suffered more severe I/R injury (AST >9,000 IU/l). Transfected IkappaB was detected in transplanted livers as early as 6 h, and this correlated with the abrogation of the second, but not the first, peak of NF-kappaB activation at 12-48 h and increased apoptosis. Thus inhibition of the second wave of NF-kappaB activation in IkappaB-transfected livers resulted in an increase of liver injury, suggesting that NF-kappaB may have a dual role during liver I/R injury.

NF-kappaB activation by hepatitis B virus X (HBx) protein shifts the cellular fate toward survival

In this paper, we examined the cellular effect of hepatitits B virus X (HBx) in ChangX-34 cells, inducible HBx-expressing cells. High expression of HBx protein in ChangX-34 cells resulted in approximately three-fold increase in DNA synthesis and did not show apoptotic changes. Expression of HBx in these cells was accompanied by the NF-kappaB-mediated transcription. Interestingly, inhibition of NF-kappaB activity either by treatment with sulfasalazine, a specific inhibitor of NF-kappaB, or by expressing IkappaBalpha super-repressor significantly increased cell death in ChangX-34 cells but had no influence on parental Chang cells. Thus, the activation of NF-kappaB in HBx-expressing cells may play a critical role in shifting the balance toward cell survival.

Proteasome inhibitor MG-132 enhances the expression of interleukin-6 in human umbilical vein endothelial cells: Involvement of MAP/ERK kinase

Interleukin-6 (IL-6) is a multifunctional cytokine that plays an important role in inflammatory reactions. We have addressed the possible regulation of IL-6 expression by the ubiquitin-protease system in human umbilical vein endothelial cells. Cultured endothelial cells were treated with MG-132, a protease inhibitor, and the levels of IL-6 mRNA and protein were measured by reverse transcription-PCR and ELISA. MG-132 increased the expression of IL-6 mRNA and protein;and this effect was abolished by the pretreatment of the cells with U0126, an inhibitor of MAP or ERK kinases (MEK 1/2). MG-132 treatment was also found to enhance the level of phosphorylated MEK 1/2. Treatment of the cells with actinomycin D inhibited IL-6 expression in response to MG-132, suggesting the transcriptional upregulation of IL-6 under proteasomal inhibition. We conclude that a protease inhibitor MG-132 upregulates IL-6 expression in vascular endothelial cells, at least in part, through the activation of MEK 1/2.