Taurodeoxycholate Stimulates Intestinal Cell Proliferation and Protects Against Apoptotic Cell Death Through Activation of NF-κB

We hypothesized that the NF-kappaB pathway would be operative in the proliferative effect of bile salts on enterocytes. To determine this, we studied the effect of the bile salt taurodeoxycholate on cultured rat enterocyte proliferation and apoptosis and examined the role of NF-kappaB activation in these growth regulatory processes. Intestinal epithelial cells were grown for 6 days with or without taurodeoxycholate. Proliferation was measured. The cells were exposed to a known apoptotic stimulus, TNF-alpha and cyclohexamide. Apoptosis was quantified using cell number and the TUNEL stain. NF-kappaB activation was determined by an electrophoretic mobility shift assay. NF-kappaB activation was inhibited by an IkappaB superrepressor. Taurodeoxycholate stimulated cell proliferation (P < 0.01) and induced resistance to TNF-alpha induced apoptosis (P < 0.01). Taurodeoxycholate induced NF-kappaB activation. Inhibition of NF-kappaB prevented taurodeoxycholate-induced IEC-6 cell proliferation and rendered cells sensitive to TNF-alpha-induced apoptosis. Taurodeoxycholate stimulates intestinal epithelial cell proliferation and protects intestinal epithelial cells from TNF-alpha-induced apoptosis through NF-kappaB. These data support an important beneficial role of bile salts in regulation of mucosal growth and repair. Decreased enterocyte exposure to luminal bile salts, as occurs during starvation and parenteral nutrition, may have a detrimental effect on mucosal integrity.     

Inhibition of Lipid Peroxidation, NF-κB Activation and IL-8 Production by Rebamipide in Helicobacter pylori-Stimulated Gastric Epithelial Cells

The present study aimed to investigate whether rebamipide, a novel antiulcer agent that has an oxygen radical scavenging activity, would inhibit lipid peroxidation, NF-B activation, and IL-8 production by H. pylori. Human gastric epithelial cells (AGS and KATO III), treated with rebamipide or not were incubated in the absence or the presence of H. pylori. As a result, H. pylori significantly stimulated IL-8 production, which was similar to time course stimulation of lipid peroxidation. Other cytokines (IL-1, IL-1, IL-6, TNF-) were not stimulated by H. pylori. Treatment with H. pylori resulted in the activation of two species of NF-B dimers (a p50/p65 heterodimer and a p50 homodimer). Rebamipide significantly inhibited lipid peroxidation as an indicative of oxidative damage, NF-B complex formation, and IL-8 production by H. pylori. In conclusion, rebamipide may attenuate H. pylori-induced gastric inflammation by inhibiting lipid peroxidation and oxidant-mediated activation of NF-B and thereby decreasing IL-8 production.     

Inhibition of NF-κB Renders Human Juvenile Costal Chondrocyte Cell Lines Sensitive to TNF-α-Mediated Cell Death

Background. Recently, therapeutics employing knowledge on various signaling pathways are being developed, with NF-B being one of the most promising targets. NF-B has been suggested to play a role not only in the induction of inflammatory mediators, but also in the protection from cell death. Objectives. This study pursued the role of the NF-B pathway in the regulation of chondrocyte death induced by tumor necrosis factor alpha (TNF-) and of the pertinent target molecules involved. Methods. The human chondrocyte cell line C28/I2 was used for the experiment. Chondrocytes were transduced with adenovirus-encoding IkappaB (IB) superrepressor which inhibits NF-B activation, and treated with TNF-. The proportion of cell death was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazdium bromide (MTT) assay. Activation of p38 mitogen activated protein (MAP) kinase and phosphatidylinositol 3-kinase (PI3K) by TNF- was inhibited with SB202190 and Ly 294002 respectively. The expression of apoptosis related protein was analyzed with western blot assay, and the activation of c-Jun N-terminal kinase (JNK) by solid-phase kinase assay. Results. Treatment with TNF- led to cell death in 23% and 50% of ad-IB-SR infected chondrocytes after 24 and 72 h respectively. The expression of Bcl-XL, Bcl-2, and XIAP significantly decreased, and activation of JNK was prolonged for up to 6 h in infected cells treated with TNF-. Preincubation with p38 inhibitor or PI3K inhibitor before TNF- led to a significant increase in cell death in ad-IB-SR transduced chondrocytes, resulting in 53% and 30% cell death after 24 h for p38 inhibitor and PI3K inhibitor respectively. Conclusion. In our experimental system, specific inhibition of NF-B activation rendered chondrocytes susceptible to cell death induced by TNF-. The cell death was enhanced by inhibition of another signaling pathway such as p38 MAP kinase or PI3K. The expression of Bcl-XL, Bcl-2 and XIAP and activation of JNK were affected by ad-IB-SR transduction, implying a role in the NF-B regulated cell survival signaling in human chondrocytes.     

NF-κB and IRF7 Pathway Activation by Epstein-Barr Virus Latent Membrane Protein 1

The principal Epstein-Barr virus (EBV) oncoprotein, Latent Membrane Protein 1 (LMP1), is expressed in most EBV-associated human malignancies. LMP1 mimics CD40 receptor signaling to provide infected cells with constitutive NF-κB, MAP kinase, IRF7, and PI3 kinase pathway stimulation. EBV-transformed B-cells are particularly dependent on constitutive NF-κB activity, and rapidly undergo apoptosis upon NF-κB blockade. Here, we review LMP1 function, with special attention to current understanding of the molecular mechanisms of LMP1-mediated NF-κB and IRF7 pathway activation. Recent advances include the elucidation of transmembrane motifs important for LMP1 trafficking and ligand-independent signaling, analysis of genome-wide LMP1 gene targets, and the identification of novel cell proteins that mediate LMP1 NF-κB and IRF7 pathway activation.     

KRAS Mutation and NF-κB Activation Indicates Tolerance of Chemotherapy and Poor Prognosis in Colorectal Cancer

Background

Evidence shows a strong relationship between KRAS mutations and the NF-κB signaling pathway. In colorectal cancer, however, the study of this subject has been very limited and results are inconsistent.

Aims

To examine the relationship between KRAS mutations and NF-κB activation and their effect on chemotherapy response and survival of colorectal cancer patients.

Materials and Methods

NF-κB activation was analyzed by immunohistochemistry in 167 primary colorectal cancer specimens in which the KRAS mutation status was confirmed. Clinical and pathologic data were extracted from the medical records and reviewed.

Results

Of 167 tumors screened, 63 (37.7?%) had NF-κB activation, 59 (35.3?%) had KRAS mutations, and 30 (18.0?%) had both NF-κB activation and KRAS mutations. The frequency of NF-κB activation in tumors with KRAS mutations was significantly higher than in tumors with wild type KRAS; 50.8 versus 30.6?%, P?=?0.012. Patients with both KRAS mutations and NF-κB activation had a lower objective response to first-line chemotherapy than patients with other tumors, 23.8 versus 49.4?% (P?=?0.035). Compared to patients with both KRAS mutations and NF-κB activation, overall survival of patients in other groups was significantly higher; median overall survival was 28.4?months (95?% CI 21.0–35.8) versus 46.3?months (95?% CI 39.4–53.2), hazard ratio 0.259 (95?% CI 0.125–0.538), P?=?0.005.

Conclusions

NF-κB activation was associated with KRAS mutation, and both KRAS mutation and NF-κB activation were indicative of high tolerance of chemotherapy and poor prognosis for colorectal cancer patients. Tumors with KRAS mutations and NF-κB activation may be a unique subtype of colorectal cancer.     

Taurocholate Potentiates Ethanol-Induced NF-κB Activation and Inhibits Caspase-3 Activity in Cultured Rat Gastric Mucosal Cells

We have previously shown that ethanol (EtOH) induces protective NF-κB activation in gastric surface epithelial cells. This study investigates the defense systems in rat gastric mucosal cells (RGM-1) exposed simultaneously to EtOH and taurocholate (TC) or acetylsalicylic acid (ASA). Simultaneous exposure to ASA and EtOH increased EtOH-induced caspase-3 activity and decreased cell viability, indicating synergetic damaging action. Simultaneous exposure to TC (5 mM) with EtOH (5%) increased EtOH-induced NF-κB activation, opposing EtOH-induced decrease in cell membrane integrity and in cell viability as shown by decreasing RelA expression with siRNA technique. Low doses of TC decreased the EtOH (5%) induced caspase-3 activity independently from NF-κB pathway and inhibited EtOH-induced decrease in caspase-3 precursor protein levels, also indicating the inhibition of caspase-3 pathway. The TC (5 mM)-induced protection in EtOH exposed tissues seems to have two distinct pathways, inhibition of apoptosis and enhancement of NF-κB signaling.     

Tcl1 interacts with Atm and enhances NF-κB activation in hematologic malignancies

The T-cell leukemia/lymphoma 1 (TCL1) oncogene is a target of chromosomal translocations and inversions at 14q31.2, and its rearrangement in T cells causes T-cell prolymphocytic leukemias. TCL1 dysregulation in B cells is responsible for the development of an aggressive form of chronic lymphocytic leukemia (CLL), the most common human leukemia. We have investigated the mechanisms underlying the oncogenic functions of Tcl1 protein using a mass spectrometry approach and have identified Atm (ataxia-telangiectasia mutated) as a candidate Tcl1-interacting protein. The Tcl1-Atm complex formation was validated by coimmunoprecipitation experiments. Importantly, we show that the association of Atm with Tcl1 leads to enhanced IκBα phosphorylation and ubiquitination and subsequent activation of the NF-κB pathway. Our findings reveal functional cross-talk between Atm and Tcl1 and provide evidence for a novel pathway that could be targeted in leukemias and lymphomas.     

Role of NF-κB and cytokine in experimental cancer cachexia

AIM: To assess the putative involvement of NF-κB and pronflammatory cytokines in the pathogenesis of cancer cachexia and the therapeutic efficacy of indomethadn (IND)on cachexia. METHODS: Thirty young male BABL/c mice were divided randomly into five groups: (a) control, (b) tumor-bearingplus saline, (c) tumor-bearing plus IND (0.25 mg.kg-1), (d)tumor-bearing plus IND (0.5 mg.kg-1), and (e) tumor-bearingplus IND (2 mg.kg-1). Colon 26 adenocarcinoma cells of murine were inoculated subcutaneously to induce cachexia. Saline and IND were given intraperitoneally daily for 7 days from the onset of cachexia to sacrifice. Food intake and body composition were documented, serum levels of TNF-α and IL-6 and activity of NF-κB in the spleen wereinvestigated in all animals .RESULTS: Weight loss was observed in all tumor-bearingmice. By day 16, body weights of non-tumor mice were about 72 % of healthy controls (P&lt;0.01), and the weight of gastrocnemius was decreased by 28.7 % (P&lt;0.01). No difference was found between groups in food intake (P&gt;0.05). Gastrocnemius weight was increased markedly (P&lt;0.01) after treatment of IND (0.5 mg.kg-1), while the non-tumor body weights were not significantly elevated. Tumor-bearing caused a 2-3 fold increase in serum levels of both TNF-α and IL-6 (P&lt;0.01). The concentration of TNF-α (P&lt;0.05)and IL-6 (P&lt;0.01) in tumor-bearing mice was reduced after administration of 0.5 mg.kg-1 IND for 7 days. But the level of IL-6 was slightly elevated following treatment of IND 2.0mg-kg-1. NF-κB activation in the spleen was increased in tumor-bearing mice in comparison with controls in electrophoretic mobility shift assay (EMSA). NF-κB activity was reduced in mice treated with 0.5 mg.kg-2 of IND, whereas a hiaher NF-κB activity was observed in mice treated with 2.0 mg,kg-1 of IND . CONCLUSION: Colon 26 adenocarcinoma cells can induce severe cancer cachexia experimentally, and the mechanism may be partially due to the enhanced TNF-α and IL-6 in tumor-bearing animals, which is controlled by NF-κB, Low dose of indomethacin alleviates the cachexia,decreases the activation of NF-κB and the serum levelsof TNF-α and IL-6, and prevents body weight loss andmuscle atrophy, while no further effect is gained by ahigher dosage,     

Butyrate Inhibits NF-κB Activation in Lamina Propria Macrophages of Patients with Ulcerative Colitis

Background: In ulcerative colitis (UC) the activation (i.e. nuclear translocation) of nuclear factor kappa B (NF- &#115 B) is an important step in the regulation of cytokines secreted by lamina propria macrophages. Clinical trials suggest anti-inflammatory effects of locally administered butyrate in UC. The potential effects of butyrate on NF- &#115 B activation in lamina propria macrophages of UC patients were investigated. Methods: Eleven patients with distal UC were treated for up to 8 weeks with butyrate at 100 mM ( n = 6) or placebo ( n = 5) enemas. At entry and after 4 and 8 weeks, clinical status was noted and intestinal inflammation was graded endoscopically and histologically. Double-staining with antibodies against NF &#115 B (p65) and CD68 was employed to detect NF- &#115 B and macrophages, respectively. Results: In untreated patients, nuclear translocation of NF- &#115 B was detectable in virtually all macrophages. Butyrate treatment for 4 and 8 weeks resulted in a significant reduction in the number of macrophages being positive for nuclear translocated NF- &#115 B. In addition, butyrate significantly reduced both the number of neutrophils in crypt and surface epithelia and of the lamina propria lymphocytes/plasma cells. These findings correlated with a significant decrease in the Disease Activity Index (DAI). Conclusions: The decrease in DAI and mucosal inflammation in butyrate-treated patients is associated with a reduction of NF- &#115 B translocation in lamina propria macrophages. Since the inflammatory process in UC is mainly sustained by macrophage-derived cytokines, the known anti-inflammatory effects of butyrate may in part be mediated by an inhibition of NF- &#115 B activation in these macrophages.