NF-κB Gene Transcription Research Articles

The BTK Inhibitor ARQ 531 Targets Ibrutinib-Resistant CLL and Richter Transformation.

Targeted inhibition of Bruton tyrosine kinase (BTK) with the irreversible inhibitor ibrutinib has improved outcomes for patients with hematologic malignancies, including chronic lymphocytic leukemia (CLL). Here, we describe preclinical investigations of ARQ 531, a potent, reversible inhibitor of BTK with additional activity against Src family kinases and kinases related to ERK signaling. We hypothesized that targeting additional kinases would improve global inhibition of signaling pathways, producing more robust responses. In vitro treatment of patient CLL cells with ARQ 531 decreases BTK-mediated functions including B-cell receptor (BCR) signaling, viability, migration, CD40 and CD86 expression, and NF-κB gene transcription. In vivo, ARQ 531 was found to increase survival over ibrutinib in a murine Eμ-TCL1 engraftment model of CLL and a murine Eμ-MYC/TCL1 engraftment model resembling Richter transformation. Additionally, ARQ 531 inhibits CLL cell survival and suppresses BCR-mediated activation of C481S BTK and PLCγ2 mutants, which facilitate clinical resistance to ibrutinib.Significance: This study characterizes a rationally designed kinase inhibitor with efficacy in models recapitulating the most common mechanisms of acquired resistance to ibrutinib. Reversible BTK inhibition is a promising strategy to combat progressive CLL, and multikinase inhibition demonstrates superior efficacy to targeted ibrutinib therapy in the setting of Richter transformation. Cancer Discov; 8(10); 1300-15. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

Abnormal expression of circulating nuclear factor-κB in hepatocellular carcinoma and reversal of multidrug resistance through intervening its gene transcription

To investigate the expressions of nuclear factor-κB (NF-κB) and P-glycoprotein (P-gp) in patients with liver diseases and the effects and mechanism of intervening NF-κB activation on multiple drug resistance (MDR) reversal. The levels of circulating NF-κB and P-gp expression were quantitatively detected in 294 patients with liver diseases by using enzyme-linked immunosorbent assay. NF-κB gene transcription in human HepG2 cells was intervened by specific siRNA with/without doxorubicin treatment. Levels of protein or gene expression were analyzed by Western blotting or fluorescence quantitative polymerase chain reaction (PCR). The dynamic increase of circulating NF-κB and P-gp expressions were observed during patients from chronic hepatitis to cirrhosis to hepatocellular carcinoma (HCC) development. The levels of serum NF-κB and P-gp expression in HCC were significantly higher (P<0.001) than those in cirrhosis, chronic hepatitis, and normal controls. The expression levels of serum NF-κB and P-gp were significantly associated with HBV infection (P<0.05), elevated after interventional chemotherapy with higher frequency or prolonged therapy, and significantly decreased in the post-operative HCC (P<0.001). Both expressions in HepG2 cells were significantly higher after adding doxorubicin in the cell cultures. After the cells were transfected with siRNA, the NF-κB expression was down-regulated at mRNA or protein level with higher sensitivity to doxorubicin. The over-expressions of NF-κB and P-gp are closely associated with MDR formation; intervention of NF-κB activation can inhibit P-gp expression, and enhance the sensitivity to anti-cancer drug and reverse MDR of HCC.

Reversal of multidrug resistance of hepatocellular carcinoma cells by metformin through inhibitingNF-κBgene transcription

To interfere with the activation of nuclear factor-κB (NF-κB) with metformin and explore its effect in reversing multidrug resistance (MDR) of hepatocellular carcinoma (HCC) cells. Expression of P-glycoprotein (P-gp) and NF-κB in human HepG2 or HepG2/adriamycin (ADM) cells treated with pCMV-NF-κB-small interference RNA (siRNA) with or without metformin, was analyzed by Western blot or fluorescence quantitative PCR. Cell viability was tested by CCK-8 assay. Cell cycle and apoptosis were measured by flow cytometry and Annexin-V-PE/7-AnnexinV apoptosis detection double staining assay, respectively. P-gp overexpression in HepG2 and HepG2/ADM cells was closely related to mdr1 mRNA (3.310 ± 0.154) and NF-κB mRNA (2.580 ± 0.040) expression. NF-κB gene transcription was inhibited by specific siRNA with significant down-regulation of P-gp and enhanced HCC cell chemosensitivity to doxorubicin. After pretreatment with metformin, HepG2/ADM cells were sensitized to doxorubicin and P-gp was decreased through the NF-κB signaling pathway. The synergistic effect of metformin and NF-κB siRNA were found in HepG2/ADM cells with regard to proliferation inhibition, cell cycle arrest and inducing cell apoptosis. Metformin via silencing NF-κB signaling could effectively reverse MDR of HCC cells by down-regulating MDR1/P-gp expression.

Nuclear FAM21 participates in NF-κB-dependent gene regulation in pancreatic cancer cells.

The pentameric WASH complex is best known for its role in regulating receptor trafficking from retromer-rich endosomal subdomains. FAM21 functions to stabilize the WASH complex through its N-terminal head domain and localizes it to endosomes by directly binding the retromer through its extended C-terminal tail. Herein, we used affinity purification combined with mass spectrometry to identify additional FAM21-interacting proteins. Surprisingly, multiple components of the nuclear factor κB (NF-κB) pathway were identified, including the p50 and p65 (RelA) NF-κB subunits. We show that FAM21 interacts with these components and regulates NF-κB-dependent gene transcription at the level of p65 chromatin binding. We further demonstrate that FAM21 contains a functional monopartite nuclear localization signal sequence (NLS) as well as a CRM1/exportin1-dependent nuclear export signal (NES), both of which work jointly with the N-terminal head domain and C-terminal retromer recruitment domain to regulate FAM21 cytosolic and nuclear subcellular localization. Finally, our findings indicate that FAM21 depletion sensitizes pancreatic cancer cells to gemcitabine and 5-fluorouracil. Thus, FAM21 not only functions as an integral component of the cytoplasmic WASH complex, but also modulates NF-κB gene transcription in the nucleus.

Abstract 19038: Epigenetic Regulation of Canonical TNFa Pathway by HDAC1 Determines Survival of Cardiac Myocytes

Gene transcription is regulated by post-translation modifications. Histone deacetylases (HDACs) remove acetyl-groups from histone and non-histone factors inhibiting transcription. Pro-inflammatory cytokines such as TNFα activate the canonical Nuclear Factor -κB (NF-κB) pathway. Earlier we established a cytoprotective role for NF-κB in the heart. Though a causal relationship for HDAC1 and NF-κB has been established, the impact of HDAC1 on TNFα signaling is unknown. Herein, we demonstrate HDAC1 provides a molecular switch for determining cell survival in the TNFα pathway. In contrast to vehicle treated control cells, TNFα treated cells displayed a marked increase in NF-κB gene transcription. Notably, cells treated with TNFα were indistinguishable from vehicle controls cells with respect to viability. Interestingly, HDAC activity was reduced in cells treated with TNFα. Conversely, in the presence of HDAC1, NF-κB gene transcription by TNFα was repressed, resulting in mitochondrial perturbations and widespread cell death. Heterologous fusion proteins comprised of yeast Gal4 DNA binding domain fused in frame to the NF-κB p65 transactivation domain were preferentially repressed by HDAC1. Moreover, transcription mediated by Gal4VP16 protein from herpes virus was unaffected by HDAC1 in cardiac myocytes. Mutations that abrogate known catalytic activities of HDAC1, small interference RNA or pharmacological inhibition of HDAC1, restored NF-κB signaling and suppressed cell death induced by TNFα. These data provide the first evidence for an obligate link between HDAC1 and canonical TNFα pathway for cell survival of cardiac myocytes.

Abstract 268: Epigenetic Regulation Of Canonical Tnfa Pathway By Hdac1 Determines Survival Of Cardiac Myocytes

Gene transcription is regulated by post-translation modifications. Histone deacetylases (HDACs) remove acetyl-groups from histone and non-histone factors inhibiting transcription. Pro-inflammatory cytokines such as TNFα activate the canonical Nuclear Factor -κB (NF-κB) pathway. Earlier we established a cytoprotective role for NF-κB in the heart. Though a causal relationship for HDAC1 and NF-κB has been established, the impact of HDAC1 on TNFα signaling is unknown. Herein, we demonstrate HDAC1 provides a molecular switch for determining cell survival in the TNFα pathway. In contrast to vehicle treated control cells, TNFα treated cells displayed a marked increase in NF-κB gene transcription. Notably, cells treated with TNFα were indistinguishable from vehicle controls cells with respect to viability. Interestingly, HDAC activity was reduced in cells treated with TNFα. Conversely, in the presence of HDAC1, NF-κB gene transcription by TNFα was repressed, resulting in mitochondrial perturbations and widespread cell death. Heterologous fusion proteins comprised of yeast Gal4 DNA binding domain fused in frame to the NF-κB p65 transactivation domain were preferentially repressed by HDAC1. Moreover, transcription mediated by Gal4VP16 protein from herpes virus was unaffected by HDAC1 in cardiac myocytes. Mutations that abrogate known catalytic activities of HDAC1, small interference RNA or pharmacological inhibition of HDAC1, restored NF-κB signaling and suppressed cell death induced by TNFα. These data provide the first evidence for an obligate link between HDAC1 and canonical TNFα pathway for cell survival of cardiac myocytes.

Epigenetic regulation of canonical TNFα pathway by HDAC1 determines survival of cardiac myocytes

Gene transcription is regulated by post-translation modifications. Histone deacetylases (HDACs) remove acetyl groups from histone and non-histone factors inhibiting transcription. Proinflammatory cytokines such as TNFα activate the canonical nuclear factor-κB (NF-κB) pathway. Earlier we established a cytoprotective role for NF-κB in the heart. Though a causal relationship for HDAC1 and NF-κB has been established, the impact of HDAC1 on TNFα signaling is unknown. Herein, we demonstrate that HDAC1 provides a molecular switch for determining cell survival in the TNFα pathway. In contrast to vehicle-treated control cells, TNFα-treated cells displayed a marked increase in NF-κB gene transcription. Notably, cells treated with TNFα were indistinguishable from vehicle controls cells with respect to viability. Interestingly, HDAC activity was reduced in cells treated with TNFα. Conversely, in the presence of HDAC1, NF-κB gene transcription by TNFα was repressed, resulting in mitochondrial perturbations and widespread cell death. Heterologous fusion proteins comprised of yeast Gal4 DNA binding domain fused in frame to the NF-κB p65 transactivation domain were preferentially repressed by HDAC1. Moreover, transcription mediated by Gal4VP16 protein from herpes virus was unaffected by HDAC1 in cardiac myocytes. Mutations that abrogate known catalytic activities of HDAC1, small interference RNA, or pharmacological inhibition of HDAC1 restored NF-κB signaling and suppressed cell death induced by TNFα. These data provide the first evidence for an obligate link between HDAC1 and canonical TNFα pathway for cell survival of cardiac myocytes.

Ethanol extract of Adiantum capillus-veneris L. suppresses the production of inflammatory mediators by inhibiting NF-κB activation

Ethnopharmacological relevanceAdiantum capillus-veneris L. is a wildly distributed plant species and has been extensively used in south of China as traditional folk medicine for the treatment of inflammatory diseases. Aim of the studyTo investigate the anti-inflammatory effect of ethanolic extracts of Adiantum capillus-veneris L. and the involvement of NF-κB signaling in the regulation of inflammation. Materials and methodsThe plant ethanolic extracts were initially tested against lipopolysaccharide (LPS)-induced prostaglandin E2 (PGE2) production in RAW264.7 mouse macrophages, and interleukin 6 (IL-6) and tumor necrosis factor (TNF) production in human U937 monocytes. The effect of the plant extracts on the transcription factor nuclear factor kappa B (NF-κB) pathway was evaluated in TNF-α stimulated HepG2 cells by luciferase gene reporter assay and Western blotting at the transcriptional and translational levels. Subsequently, the inhibition of NF-κB downstream gene expression (IL-8 and ICAM-1) by the plant extracts was assessed via quantitative real time polymerase chain reaction (qPCR). Lastly, the anti-inflammatory activities of the plant extracts in vivo were evaluated by testing spleen index and NF-κB related protein expression in LPS-stimulated CD1 mice. ResultsThe plant ethanolic extracts effectively suppressed PGE2, IL-6 and TNF release with an IC50 less than 50μg/ml. Moreover, luciferase expression could be specifically blocked in HepG2 cells, not in HEK293 cells, showing that the plant extracts displayed a cell-specific pattern on NF-κB gene transcription. The assayed biological activity also depended on the order of adding TNF-α and the plant extracts because the plant extracts could only block the NF-κB activation if added earlier but were unable to stop the signal when added after TNF-α. However, the plant extracts did not exert any effect on ubiquitination which regulates several steps in the NF-κB pathway. Additionally, the plant extracts down-regulated phosphorylation of IKKα/β at S176/180, p38 at T180/Y182 and p65 at S536, but not p65 at S276. This was confirmed by their ability to selectively abrogate the induction of IL-8 transcription, whereas the ICAM-1 gene, which is not transcribed selectively by an NF-κB complex containing a form of p65 phosphorylated on Ser536, did not change. Finally, the plant extracts at 200μg/mg could normalize the LPS-induced elevation of spleen index as well as NF-κB and p38 activations in CD1 mice. ConclusionThe present studies presents the potential utilization of this plant extracts, as a natural resources for the development of an anti-inflammatory medicine.

Identification of an N-terminal Truncation of the NF-κB p65 Subunit That Specifically Modulates Ribosomal Protein S3-dependent NF-κB Gene Expression

NF-κB is a pleiotrophic transcription factor that plays a prominent regulatory role in various cellular processes. Although previous efforts have focused on its activation, how NF-κB selects specific target genes in response to discrete signals remains puzzling. In addition to the well defined Rel protein components of NF-κB, the ribosomal protein S3 (RPS3) was identified to be an essential component of specific NF-κB complexes. RPS3 synergistically interacts with the NF-κB p65 subunit to achieve optimal binding and transactivation of a subset of NF-κB target genes, thus providing regulatory specificity. Emerging evidence suggests an important role for the RPS3-p65 interaction in context-specific NF-κB gene transcription. The food-borne pathogen Escherichia coli O157:H7 impacts the transcription of a subset of NF-κB target genes encoding proinflammatory cytokines and chemokines in host cells by preventing the nuclear translocation of RPS3, but not p65. The N terminus of p65 is crucial for RPS3 binding. Although several p65 N-terminal fragments are generated by either protease cleavage or alternative mRNA splicing under certain pathophysiological conditions, the role of these fragments in modulating NF-κB signaling, in particular RPS3-dependent selective gene transcription, has not been fully characterized. Here we report that an N-terminal fragment of p65 (amino acids 21-186) can selectively modulate NF-κB gene transcription by competing for RPS3 binding to p65. This 21-186 fragment preferentially localizes in the cytoplasm where it delays stimuli-induced RPS3 nuclear translocation, without affecting the nuclear translocation of p65. Our findings thus uncover a new cytoplasmic function for the N-terminal domain of p65 and provide a novel strategy for selective inhibition of NF-κB gene transcription.

A calpain inhibitor elevated expressions of NF-κB in atrial fibrillation canine atria

This aim of this study is to observe the alterations of calpain proteolytic system and effect of a calpain I inhibitor on NF-κB expressions in rapid pacing canine atrial fibrillation (AF) models. Twenty-one dogs were divided equally into three groups: a sham operation group, a control AF group and a calpain inhibitor group. Rapid right atrium pacing at 600 beats per min was applied in the control AF group and the calpain inhibitor group. N-Acetyl-Leu-Leu-Met (1.0 mg/kg/day) was administered in the calpain inhibitor group for three weeks. The protein expressions of NF-κB, calpain I, calpain II and calpastatin were assessed by immunohistochemistry and gene amplification of NF-κB and calpain I were detected by quantitative real time polymerase chain reaction. The highest density of calpain I was shown in the control AF group (p < 0.01, vs. calpain inhibitor group and sham operation group). Protein expression of calpain II and calpastatin had no significant difference among the three groups. Gene amplification results of calpain I unveiled the most active transcription was in the calpain inhibitor group (p < 0.01, vs. control AF group and sham operation group). The mRNA expression of NF-κB were elevated in the calpain inhibitor group, the cycle of threshold means were (20.1±5.1), while were (33.4±6.1) and (30.4±5.8) in the sham operation group and control AF group, respectively. NF-κB protein expressions in calpain inhibitor group were positive, while were negative in the other two groups. In canine heart muscle cells, atrial fibrillation elevated calpain I gene transcription, promoted protein expression and enhanced protease activity. The calpain I inhibitor N-Acetyl-Leu-Leu-Met promoted NF-κB gene transcription and protein expressions in AF canine models. Key words: Calpain I inhibitor, atrial fibrillation, NF-κB.

IL-33/ST2 axis in inflammation and immunopathology

Interleukin-33 (IL-33), a member of the IL-1 family of cytokines, binds to its plasma membrane receptor, heterodimeric complex consisted of membrane-bound ST2L and IL-1R accessory protein, inducing NFkB and MAPK activation. IL-33 exists as a nuclear precursor and may act as an alarmin, when it is released after cell damage or as negative regulator of NFκB gene transcription, when acts in an intracrine manner. ST2L is expressed on several immune cells: Th2 lymphocytes, NK, NKT and mast cells and on cells of myeloid lineage: monocytes, dendritic cells and granulocytes. IL-33/ST2 axis can promote both Th1 and Th2 immune responses depending on the type of activated cell and microenvironment and cytokine network in damaged tissue. We previously described and discuss here the important role of IL-33/ST2 axis in experimental models of type 1 diabetes, experimental autoimmune encephalomyelitis, fulminant hepatitis and breast cancer. We found that ST2 deletion enhance the development of T cell-mediated autoimmune disorders, EAE and diabetes mellitus type I. Disease development was accompanied by dominantly Th1/Th17 immune response but also higher IL-33 production, which suggest that IL-33 in receptor independent manner could promote the development of inflammatory autoreactive T cells. IL-33/ST2 axis has protective role in Con A hepatitis. ST2-deficient mice had more severe hepatitis with higher influx of inflammatory cells in liver and dominant Th1/Th17 systemic response. Pretreatment of mice with IL-33 prevented Con A-induced liver damage through prevention of apoptosis of hepatocytes and Th2 amplification. Deletion of IL-33/ST2 axis enhances cytotoxicity of NK cells, production of IFN-γ in these cells and systemic production of IFN-γ, IL-17 and TNF-α, which leads to attenuated tumor growth. IL-33 treatment of tumor-bearing mice suppresses activity of NK cells, dendritic cell maturation and enhances alternative activation of macrophages. In conclusion, we observed that IL-33 has attenuated anti-inflammatory effects in T cell-mediated responses and that both IL-33 and ST2 could be further explored as potential therapeutic targets in treatment of immune-mediated diseases.

Abstract 17470: NF-κB Activation Down Stream of Tuber Sclerosis Complex -mTOR Signaling pathway is Suppressed in Doxorubicin-Induced Cardiotoxicity

The signaling networks that coordinate cell survival and cell death are poorly defined in the heart. The mammalian target of rapamycin (mTOR) is a highly conserved serine threonine kinase centrally involved in vital processes including growth, proliferation, and gene transcription. However, mTOR's role in regulating cell survival under normal or disease conditions has not been undetermined. Previously we established a cytoprotective role for the cellular factor NF-κB in ventricular myocytes. Notably, we demonstrated that NF-κB activation was necessary and sufficient for basal cell survival and suppressing mitochondrial perturbations during hypoxic injury. Herein, we provide new compelling evidence that activation of IKK-NF-κB signaling pathway down-stream of mTOR suppresses mitochondrial perturbations and cell death during metabolic stress imposed by nutrient deprivation or hypoxia. In contrast to wild type cells, constitutive activation of mTOR in tuber sclerosis complex (TSC) 2 -/- cells displayed marked increased mTOR targets p-P70S6, p-4EBP-1 and S6 protein. Interestingly, a significant increase in nuclear NF-κB activity and NF-κB gene transcription was also observed in TSC 2 -/- cells. Interestingly, in in vivo and in vitro models of Doxorubicin (Dox) -induced cardiotoxicity we observed a marked reduction in mTOR and NF-κB activity. However, basal NF-κB activity and cell viability were significantly reduced upon mTOR inactivation following metabolic stress or hypoxia. Moreover, basal Bnip3 gene transcription and cell death were significantly increased in cells treated with DOX and defective for mTOR activity. IKKβ- mediated activation of NF-κB restored mTOR activity and suppressed cell death induced by Bnip3 in DOX treated cells. To our knowledge our data provide the first direct evidence that operationally links mTOR and cell survival via IKKβ-NF-κB mediated repression of Bnip3.

Abstract 2891: Gastrin signaling and Par-4 in pancreatic cancer

Abstract Background: The gastrointestinal peptide, gastrin, has been identified as a growth factor in pancreatic cancer. Gastrin stimulates growth of pancreatic cancer through the cholecystokinin (CCK)-2 receptor. Prostate apoptosis response-4 (Par-4) is a tumor-suppressor protein that induces apoptosis in cancer cells but not in normal cells. Par-4 is down-regulated in a variety of cancers, including pancreatic where it is correlated with lower rate of survival. The anti-apoptotic activity of Par-4 is reduced when active Akt1 binds and phosphorylates it. In colon cancer cells, Par-4 also binds to NFκB and repressed NFκB gene transcription. Gastrin stimulation mediated through the CCK-2R regulates NFκB and Akt activity. Hypothesis: Stimulation of human pancreatic cancer cells with gastrin affects Par-4 activity which may be mediated through Akt. Methods: PANC-1 cells were serum starved for 16-hours, pretreated with a CCK-2R specific inhibitor (YM022) or vehicle for 1hr, and then stimulated with 10-8 M gastrin-17 for 20min. Cells were immediately lysed and the whole cell lysate was subjected to immunoprecipitation with magnetic Dynabeads bound to antibodies specific for Par-4 or NFκB(p65). Immunoprecipitation samples were probed for Par-4, and NFκB(p65), and cell lysates were probed for Par-4, NFκB(p65), Akt, phospho-p65 (Ser536), and phospho-Akt (Ser473). PANC-1 cells were transfected with siRNA specific to the CCK-2R or appropriate scrambled control delivered by Lipofectamine 2000. Protein was isolated 72 hours after transfection. Results: Pretreatment of PANC-1 cells with YM022 before gastrin stimulation blocked phosphorylation of Akt while total levels of Akt remained unchanged. siRNA knock-down of CCK-2R also resulted in a decrease of Akt activation. Phosphorylation of NFκB(p65) was increased in cells pretreated with YM022 compared to cells treated with gastrin alone; total levels of NFκB(p65) remained unchanged. Binding of Par-4 to NFκB(p65) was enhanced in cells treated with both gastrin and YM022, compared to cells treated with gastrin alone. Total levels of Par-4 remained unchanged. Conclusion: For the first time we provide evidence supporting that gastrin stimulation of pancreatic cancer cells alters activity of Par-4. Gastrin stimulation decreases binding of Par-4 to NFκB(p65) in PANC-1 cells while pretreatment with YM022 blocks this decrease in binding. The change in Par-4 activity may be mediated through Akt because YM022 and gastrin stimulation alters their activity and they are known binding partners of Par-4. Since Par-4 sensitizes cells to apoptosis induction as exemplified by sensitization of colon cancer cells to the chemotherapeutic agent, 5-fluorouracil, when Par-4 is delivered in vivo, understanding of the mechanism by which Par-4 is down-regulated is important in developing therapies to take advantage of Par-4 induced sensitization to apoptosis. Supported by: R01 CA117926 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2891. doi:10.1158/1538-7445.AM2011-2891

Morphine Impairs Host Innate Immune Response and Increases Susceptibility to Streptococcus pneumoniae Lung Infection

Chronic morphine use impairs host innate immune response and increases susceptibility to bacteria and virus. In this study a novel mouse model of chronic morphine treatment, followed by intranasal inoculation with Streptococcus pneumoniae, was used to investigate microbial events and host innate immune response. Our results show that chronic morphine treatment markedly delayed neutrophil recruitment and increased bacterial burden in the lung, spleen, and blood with a subsequent increase in mortality. In morphine-treated animals, before neutrophil recruitment, a significant decrease in TNF-alpha, IL-1, IL-6, MIP-2, and KC was observed both in bronchoalveolar lavage fluids and in lung tissue. In the early phase of infection, we found that accumulation of galectin-3 in the alveolar space of streptococcus-infected lungs was decreased after morphine treatment. The transcription factor NF-kappaB in lung resident cells was also inhibited after morphine treatment. Taken together, these results suggest that chronic morphine treatment in an S. pneumoniae infection model suppresses NF-kappaB gene transcription in lung resident cells, which, in turn, modulates the transcriptional regulation of MIP-2 and inflammatory cytokines. The decreased synthesis of MIP-2 and inflammatory cytokines coupled with the decreased release of galectin-3 result in reduced migration of neutrophils to the site of infection, thereby increasing susceptibility to S. pneumoniae infection after morphine treatment.

IKKβ Is Required for Bcl-2-mediated NF-κB Activation in Ventricular Myocytes

The transcription factor nuclear factor kappa B (NF-kappa B) is regulated by cytoplasmic inhibitor I kappa B alpha. An integral step in the activation of NF-kappa B involves the phosphorylation and degradation of I kappa B alpha. We have previously reported that I kappa B alpha activity is diminished in ventricular myocytes expressing Bcl-2 (de Moissac, D., Zheng, H., and Kirshenbaum, L. A. (1999) J. Biol. Chem. 274, 29505-29509). The underlying mechanism by which Bcl-2 activates NF-kappa B is undefined. In view of growing evidence that the I kappa B kinases (IKKs), notably IKK beta, are involved in signal induced phosphorylation of I kappa B alpha, we ascertained whether IKK beta is necessary and sufficient for Bcl-2 mediated NF-kappa B activation. Here we demonstrate that expression of Bcl-2 in ventricular myocytes resulted in an increase in NF-kappa B-dependent DNA binding, NF-kappa B gene transcription and reduced I kappa B alpha levels. An increase in the IKK beta kinase activity was observed in cells expressing full-length Bcl-2 but not in cells expressing the BH4 deletion mutant of Bcl-2 (Delta BH4; residues 10-30). Catalytically inactive mutants of IKK beta, but not IKK alpha, suppressed Bcl-2-mediated I kappa B alpha phosphorylation and NF-kappa B activation. Transfection of human embryonic 293 cells with a kinase-defective Raf-1 or a kinase-defective mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-1 (MEKK-1) suppressed Bcl-2-mediated IKK beta activity and NF-kappa B activation. Further, Bcl-2-mediated NF-kappa B activity was impaired in nullizygous mouse embryonic fibroblasts deficient for IKK beta. In this report, we provide the first direct evidence that Bcl-2 activates NF-kappa B by a signaling mechanism that involves Raf-1/MEKK-1 mediated activation of IKK beta.