Cytoplasmic IkappaB Research Articles

Decidualized Human Endometrial Stromal Cells Are Sensors of Hormone Withdrawal in the Menstrual Inflammatory Cascade1

Menstruation is a complex process dependent on premenstrual release of inflammatory mediators and proteolytic enzymes from endometrial cells. Endometrial leukocytes are traditionally considered to be the major source of the inflammatory factors. However, evidence is emerging to suggest a role for decidualized endometrial stromal cells in the premenstrual inflammatory cascade. We sought to determine if withdrawal of hormone support (estrogen and progesterone) from decidualized endometrial stromal cells, in a model mimicking the precise timing leading to menstruation, activated inflammatory signaling pathways and downstream release of inflammatory mediators. Human endometrial stromal cells decidualized gradually over 12 days of estradiol and progestin treatment as evidenced by an increase in prolactin secretion. Withdrawal of hormone support from decidualized stromal cells resulted in a decrease in cytoplasmic IkappaB and a progressive increase in nuclear accumulation of NF-kappaB, as demonstrated by Western immunoblot and immunocytochemical analyses. Concomitant with nuclear translocation of NF-kappaB, hormone withdrawal led to production of a host of inflammatory mediators by the decidualized stromal cells, including IFN-alpha, IL-6, CCL11, GM-CSF, CCL2, IL1-RA, CXCL10, CXCL8, IL-12, IL-15, VEGF, and CCL5. Elevation of inflammatory mediators was not observed, however, upon hormone withdrawal in cells treated with the NF-kappaB inhibitor BAY 11-7085. Decidualized stromal cells are likely highly sensitive sensors of changing hormone levels. This provides a mechanism by which decidualized stromal cells may recruit inflammatory leukocytes into the premenstrual endometrium and contribute to the intense inflammation underlying this unique physiological process.

NS-398 Induces Apoptosis in Human Esophageal Cancer Cells Through Inhibition of NF-kappaB Downstream Regulation of Cyclooxygenase-2

Although non-steroidal anti-inflammatory drugs (NSAIDs) have been demonstrated to have cancer-preventive effects and induce apoptosis of cancer cells, the mechanism of their effects is not clearly known. We studied the mechanism in human esophageal cancer cell line TE13. The esophageal squamous cell carcinoma cell line TE-13 was cultured with NS-398 at different concentrations or for different times. Proliferation and apoptosis were measured by MTT reduction and flow cytometry. Prostaglandin F1α was determined with radioimmunoassay. Expression of COX-2 mRNA was measured by RT-PCR and COX-2 protein levels with Western blot analysis. Nuclear NF-kappaB and cytoplasmic IkappaB protein levels were determined by electrophoretic mobility shift assay and Western blot, respectively. NS-398 significantly inhibited cell proliferation and induced apoptosis at concentrations of 0.001, 0.01, 1, and 100 μ mol/L. NS-398 dose-dependently decreased the levels of COX-2 mRNA, COX-2 protein, nuclear NF-kappaB protein and production of PGF1α and increased the cytoplasmic IkappaB protein. In conclusion, NS-398 inhibits the proliferation of, and induced apoptosis in, the cultured TE-13 SCC cell line. These changes correlate with a reduction in COX-2 mRNA and protein expression, prostaglandin synthesis, an inhibition of NF-kappaB nuclear translocation, and an increase in cytoplasmic IkappaB.

Role of nuclear IκB proteins in the regulation of host immune responses

A variety of microbial components activate a transcription factor called nuclear factor-kappaB (NF-kappaB) that plays an essential role in the optimal activation of host immune systems. The transcriptional activity of NF-kappaB is tightly regulated at multiple steps in immune signaling pathways, because excessive activation is detrimental to the host. One mechanism to prevent NF-kappaB activation is mediated by cytoplasmic IkappaB family proteins. Although cytoplasmic IkappaBs interact with NF-kappaB subunits in the cytoplasm of unstimulated cells, IkappaBs are rapidly degraded on stimulation, allowing free NF-kappaB to translocate into the nucleus and activate the transcription of genes encoding various immune mediators. After the translocation of NF-kappaB from the cytoplasm to the nucleus, nuclear proteins that are structurally similar to cytoplasmic IkappaBs take part in the regulation of NF-kappaB transcriptional activity, as activators or inhibitors, by associating with NF-kappaB subunits. Therefore, the regulatory IkappaB-like nuclear molecules are described as "nuclear IkappaB proteins." In this review, the in vivo function of the nuclear IkappaB proteins, Bcl-3, IkappaBzeta, and IkappaBNS in the context of host immune responses and diseases will be discussed.

Pentoxifylline Attenuates Lung Injury and Modulates Transcription Factor Activity in Hemorrhagic Shock

Evidence exists that resuscitation with Ringer's lactate (RL) contributes to postshock inflammation and lung injury. We hypothesized that the anti-inflammatory agent pentoxifylline (PTX) attenuates postresuscitative lung injury through modulation of transcription factors after hemorrhagic shock. Male Sprague Dawley rats underwent a 1 h period of hypotension and resuscitation with RL (32 mL/kg) or RL + PTX (25 mg/kg). Lung sections were graded for histological injury and myeloperoxidase content. Cytokine-induced neutrophil chemoattractant concentration was determined by enzyme immunoassay. Matrix metalloproteinase-2 and -9 (MMP) activity was evaluated by zymography. Heme oxygenase-1, nuclear factor kappa B (NF-kappaB) p65 nuclear translocation, and cytoplasmic I-kappaB phosphorylation were assessed by Western blot. NF-kappaB and cAMP response element binding protein (CREB) DNA binding were determined by light shift chemiluminescent electrophoretic mobility shift assay. RL resuscitation led to statistically significant increases in all parameters of lung injury when compared with the negative control. The addition of PTX significantly decreased histology lung injury, myeloperoxidase content, cytokine-induced neutrophil chemoattractant by 48% (P < 0.05), heme oxygenase-1 expression by 50% (P < 0.05), MMP-2 activity by 70% (P < 0.05), MMP-9 activity by 44% (P < 0.05), cytoplasmic I-kappaB phosphorylation by 66% (P < 0.01), nuclear NF-kappaB p65 phosphorylation by 51% (P < 0.05), and NF-kappaB DNA binding by 42% (P < 0.05). In contrast, PTX increased CREB DNA binding by 69% when compared with RL alone (P < 0.04). The addition of PTX to conventional RL infusion after shock significantly reduced histological lung injury and pulmonary neutrophil activity when compared to treatment with RL alone. The administration of PTX was also associated with diminished NF-kappaB and enhanced CREB activation. Therefore, the administration of PTX may serve as a novel therapeutic adjunct after hemorrhagic shock.

Interleukin-10 Blocked Endoplasmic Reticulum Stress in Intestinal Epithelial Cells: Impact on Chronic Inflammation

The initiation of endoplasmic reticulum (ER)-mediated stress responses in intestinal epithelial cells (IEC) may contribute to the pathogenesis of chronic intestinal inflammation. The aim of the study was to use functional epithelial cell proteomics to characterize anti-inflammatory mechanisms of interleukin 10 (IL-10). Primary IEC were isolated from Enterococcus faecalis-monoassociated IL-10-deficient (IL-10-/-) and wild-type mice to perform 2D-gel sodium-dodecyl-sulfate polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. In addition, IEC from 6 patients with active Crohn's disease, ulcerative colitis, and sigmoid diverticulitis as well as noninflamed controls were purified. Molecular protective mechanisms of IL-10 were characterized in tumor necrosis factor (TNF)-stimulated IL-10 receptor (IL-10R) reconstituted epithelial cells. Primary IEC from IL-10-/- mice as well as inflammatory bowel disease patients revealed increased expression levels of the glucose-regulated ER stress protein (grp)-78 under conditions of chronic inflammation. Consistent with the observation that TNF induced ER stress responses through grp-78 redistribution from the ER lumen to the cytoplasmic IkappaB kinase complex, grp-78 knockdown completely abolished TNF-induced nuclear factor-kappaB RelA phosphorylation in epithelial cell cultures. Interestingly, IL-10 inhibited grp-78 protein and messenger RNA expression in IL-10R reconstituted IEC. Chromatin immunoprecipitation analysis and immunofluorescence microscopy revealed that IL-10-mediated p38 signaling inhibited TNF-induced recruitment of the ER-derived activating transcription factor (ATF)-6 to the grp-78 promoter likely through the blockade of ATF-6 nuclear translocation. Primary IEC from inflamed IL-10-/- mice and inflammatory bowel disease patients revealed activated ER stress responses in the intestinal epithelium. IL-10 inhibits inflammation-induced ER stress response mechanisms by modulating ATF-6 nuclear recruitment to the grp-78 gene promoter.

Mouse monoclonal anti–human thrombomodulin antibodies bind to and activate endothelial cells through NF‐κB activation in vitro

To clarify whether mouse monoclonal antibodies (mAb) against human thrombomodulin (TM), which react with human TM present on the endothelial cell (EC) surface, have anti-endothelial cell antibody (AECA) activity and influence antiinflammatory properties of human TM expressed on the EC surface in vitro. Three preparations of mouse mAb against human TM that react with different sites of the human TM epidermal growth factor-like domain were tested for their ability to 1) bind to ECs, 2) modulate cytokine secretion from ECs, EC adhesion molecule expression, and neutrophil adhesion to ECs, and 3) stimulate nuclear translocation of NF-kappaB through the degradation of cytoplasmic IkappaB in ECs. Recombinant human interleukin-1beta (IL-1beta) was used as a positive control, and mouse IgG1 and mouse IgG2a were used as negative controls. The 3 preparations of mouse mAb against human TM that bind to unfixed EC monolayers enhanced IL-6 and IL-8 secretion from ECs, up-regulated expression of endothelial leukocyte adhesion molecule 1, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1 on EC monolayers, and enhanced neutrophil adhesion to ECs to a degree similar to that observed with IL-1beta stimulation, but they did not induce the secretion of tumor necrosis factor alpha or IL-1beta from ECs throughout the incubation period. The 3 preparations stimulated nuclear translocation of NF-kappaB through the degradation of cytoplasmic IkappaB. Mouse IgG1 and mouse IgG2a did not exhibit such effects. These results suggest the possibility that AECA can react with antigens such as TM that are present on the EC surface and activate ECs. Such events on ECs may lead to vascular inflammation and damage in patients with connective tissue diseases and vasculitis in which AECA are present.

Aspirin induces apoptosis in oesophageal cancer cells by inhibiting the pathway of NF‐kappaB downstream regulation of cyclooxygenase‐2

Aspirin has potential in the prevention or treatment of oesophageal cancer, the seventh most common cancer in the world, but its mechanism of action is still not certain. The oesophageal squamous cell carcinoma cell line TE-13 was cultured with aspirin at different concentrations or for different times. Proliferation and apoptosis were measured by MTT reduction and flow cytometry. Expression of COX-2 mRNA was measured by RT-PCR and COX-2 protein levels with Western blot analysis. Nuclear NF-kappaB and cytoplasmic IkappaB protein levels were determined by electrophoretic mobility shift assay and Western blot, respectively. Aspirin significantly inhibited cell proliferation and induced apoptosis at concentrations of 1, 4, 8 mmol/L. Aspirin dose-dependently decreased the levels of COX-2 mRNA, COX-2 protein and nuclear NF-kappaB protein and increased the cytoplasmic IkappaB protein. We conclude that aspirin inhibits the proliferation of, and induced apoptosis in, the cultured TE-13 SCC cell line. These changes correlate with a reduction in COX-2 mRNA and protein expression, prostaglandin synthesis, an inhibition of NF-kappaB nuclear translocation, and an increase in cytoplasmic IkappaB. These results support the further investigation of the cyclooxygenase pathway in investigating the potential of aspirin and similar drugs in cancer prevention and therapy.

Preconditioning of primary human endothelial cells with inflammatory mediators alters the “set point” of the cell

Endothelial cells are highly sensitive to changes in the extracellular milieu. Sepsis results in activation of inflammatory and coagulation pathways. We hypothesized that sepsis-associated mediators may alter the response capacity (so-called "set point") of endothelial cells. Human umbilical vein endothelial cells (HUVEC) were preincubated in the presence or absence of tumor necrosis factor (TNF)-alpha, lipopolysaccharide (LPS), hypoxia, hyperthermia, and/or high glucose; treated with or without thrombin for 4 h; and then processed for RNase protection assays of selected activation markers. Priming with TNF-alpha and LPS significantly inhibited thrombin-mediated induction of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, tissue factor, and E-selectin, but not platelet-derived growth factor-A or CD44. In electrophoretic mobility shift assays, thrombin-treated HUVEC demonstrated inducible binding of p65 NF-kappaB, an effect that was significantly blunted by pretreatment of cells with TNF-alpha and LPS. Consistent with these results, TNF-alpha and LPS attenuated the effect of thrombin on IkappaB phosphorylation, total cytoplasmic IkappaB, and nuclear translocation of p65 NF-kappaB. The inhibitory effect of TNF-alpha on thrombin signaling persisted for up to 24 h following removal of the cytokine. Taken together, these data suggest that inflammatory mediators prime endothelial cells to modulate subsequent thrombin response.

Preventive and therapeutic effects of NF-kappaB inhibitor curcumin in rats colitis induced by trinitrobenzene sulfonic acid

To ascertain the molecule mechanism of nuclear factor-kappaB (NF-kappaB) inhibitor curcumin preventive and therapeutic effects in rats' colitis induced by trinitrobenzene sulfonic acid (TNBS). Sixty rats with TNBS-induced colitis were treated with 2.0% curcumin in the diet. Thirty positive control rats were treated with 0.5% sulfasalazine (SASP). Thirty negative control rats and thirty model rats were treated with general diet. Changes of body weight together with histological scores were evaluated. Survival rates were also evaluated. Cell nuclear NF-kappaB activity in colonic mucosa was evaluated by using electrophoretic mobility shift assay. Cytoplasmic IkappaB protein in colonic mucosa was detected by using Western Blot analysis. Cytokine messenger expression in colonic tissue was assessed by using semiquantitative reverse-transcription polymerase chain reaction. Treatment with curcumin could prevent and treat both wasting and histopathologic signs of rats with TNBS-induced intestinal inflammation. In accordance with these findings, NF-kappaB activation in colonic mucosa was suppressed in the curcumin-treated groups. Degradations of cytoplasmic IkappaB protein in colonic mucosa were blocked by curcumin treatment. Proinflammatory cytokine messenger RNA expression in colonic mucosa was also suppressed. This study shows that NF-kappaB inhibitor curcumin could prevent and improve experimental colitis in murine model with inflammatory bowel disease (IBD). The findings suggest that NF-kappaB inhibitor curcumin could be a potential target for the patients with IBD.

Adenosine, prolonged wakefulness, and A1-activated NF-κB DNA binding in the basal forebrain of the rat

There is considerable evidence to suggest that adenosine is a modulator of behavioral state. Our previous reports showed that perfusion of adenosine into the basal forebrain decreased wakefulness. Furthermore, prolonged wakefulness resulted in increased levels of extracellular adenosine in the basal forebrain of cats and rats. However, the longer-term consequences of prolonged wakefulness and increased adenosine are largely unknown. We report here an increase in the DNA binding activity of the transcription factor, nuclear factor-kappa B (NF-kappaB) following 3 h of sustained wakefulness in the rat basal forebrain. Moreover, this treatment led to the appearance of the p65 subunit of NF-kappaB in the nucleus, as determined by western blot analysis of nuclear proteins. This contrasted with undetectable levels in the sleeping controls. A concomitant disappearance of I-kappaB in cytoplasm suggested the degradation of this inhibitor of NF-kappaB. In the acute in vitro basal forebrain slice preparation, perfusion of adenosine increased NF-kappaB DNA binding while pretreatment of the slices with the A1 adenosine receptor antagonist, cyclopentyl-1-3-dimethylxanthine, significantly reduced NF-kappaB DNA binding. These results are compatible with the hypothesis that increases in the levels of adenosine in the basal forebrain, that occur during prolonged wakefulness, act through an A1 adenosine receptor and a second messenger system to increase the activity of the transcription factor NF-kappaB. We further hypothesize that some of the long duration effects of prolonged wakefulness/sleep deprivation on performance and physiology, often termed 'sleep debt', might be mediated through adenosine and its activation of NF-kappaB, which is known to alter the expression of several behavioral state regulatory factors.

Tumor Necrosis Factor and Reactive Oxygen Species Cooperative Cytotoxicity Is Mediated via Inhibition of NF-κB

Tumor necrosis factor alpha (TNFalpha) plays a key role in pathogenesis of brain injury. However, TNFalpha exhibits no cytotoxicity in primary cultures of brain cells. This discrepancy suggests that other pathogenic stimuli that exist in the setting of brain injury precipitate TNFalpha cytotoxicity. The hypothesis was tested that reactive oxygen species (ROS), that are released early after brain injury, act synergistically with TNFalpha in causing cell death. Cultured human and rat brain capillary endothelial cells (RBEC), and cortical astrocytes were treated with TNFalpha alone or together with different doses of H2O2, and apoptotic cell death and DNA fragmentation were measured by means of 3'-OH-terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and Hoechst fluorescence assay, respectively. The effect of H2O2 on TNFalpha-induced activation of nuclear factor kappa B (NF-kappaB) was measured by Western blots of cytoplasmic and nuclear extracts of RBEC using anti-inhibitor of NF-kappaB (IkappaB) and anti-p65 subunit of NF-kappaB antibodies. Nuclear translocation of NF-kappaB was investigated by immunofluorescent staining of RBEC with anti-p65 antibodies. TNFalpha alone had no cytotoxic effect in brain endothelial cells and astrocytes at concentrations up to 100 ng/ml. Co-treatment with 5-10 microM of H2O2 caused a two-fold increase in the number of apoptotic cells 24 hr later. Similar doses (1-3 microM) of H2O2 initiated early DNA fragmentation. H2O2 inhibited TNFalpha-induced accumulation of p65 in the nucleus, although it had no effect on degradation of the IkappaB in cytoplasm. Immunostaining confirmed that H2O2 inhibited p65 transport to the nucleus. Reactive oxygen species could act synergistically with TNFalpha in causing cytotoxicity via inhibition of a cytoprotective branch of TNFalpha signaling pathways, which starts with NF-kappaB activation.

Inhibition of NFkappaB in activated rat hepatic stellate cells by proteasome inhibitors and an IkappaB super-repressor.

The hepatic stellate cell (HSC), following a fibrogenic stimulus, is transformed from a quiescent to an activated cell. Cytokines induce NFkappaB activity in activated but not in quiescent HSCs with subsequent expression of NFkappaB-responsive genes, such as intercellular adhesion molecule (ICAM)-1 and interleukin (IL)-6. We investigated the effect of proteasome inhibitors and an IkappaB super-repressor on the cytokine mediated activation of NFkappaB, ICAM-1, and IL-6 in activated HSCs. Culture-activated HSCs were stimulated with IL-1beta or tumor necrosis factor alpha (TNFalpha) in the presence or absence of proteasome inhibitors, ALLN or MG-132, or after infection with an adenovirus expressing the IkappaB super-repressor (Ad5IkappaB) or beta-galactosidase (Ad5LacZ) as a control. NFkappaB activity was evaluated by immunofluorescence and by electrophoretic mobility shift assay. The steady state level of cytoplasmic IkappaB protein was measured by Western Blot. ICAM-1 and IL-6 expression was measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbant assay. Proteasome inhibitors, which block the degradation of IkappaB, and the Ad5IkappaB, which provides an exogenous nondegradable IkappaB, block the stimulation of NFkappaB activity by TNFalpha and IL-1beta in activated HSCs. These reagents block the subsequent nuclear translocation of p65 NFkappaB and induction of ICAM-1 and IL-6 by cytokines. The specificities of the proteasome inhibitors and the IkappaB super-repressor are demonstrated by their failure to block c-Jun N-terminal kinase induction by cytokines. Cytokine-induced stimulation of NFkappaB, ICAM-1, and IL-6 is blocked by proteasome inhibitors and Ad5IkappaB in activated HSCs. Inhibition of IkappaBalpha degradation is a potential target for anti-inflammatory therapy in the liver and might influence the activation process of HSCs following fibrotic stimuli.