Inhibition Of NF-kappaB DNA Binding Research Articles

Abstract 5005: Combined targeting of IKKα and β effectively suppresses NF-κB activation, cell survival and migration in head and neck squamous cell cancers

Abstract Activation of the transcription factor NF-kappaB (NF-kB) has been found to be a key promoter of tumorigenesis and a contributor of chemotherapy resistance in many cancers, including head and neck squamous cell carcinomas (HNSCC). The NK-kB pathway is regulated through both canonical and noncanonical pathways involving the IkB kinases (IKK) α and β which together, have been implicated in cancer pathogenesis. However, the individual roles of the IKK subunits have not been previously elucidated and potential therapeutic targets still largely remain to be characterized. Endogenous IKKα and β expression and phosphorylation were analyzed by IHC staining and western blot in HNSCC tumor specimens and cell lines (UM-SCC 11A and 11B). Individual and dual overexpression and knockdown of IKKα and β were assessed for their effects on NF-kB activation by a luciferase reporter assay, and on tumor cell proliferation and migration in vitro via MTT and wound healing assays, respectively. HNSCC tissue and cell lines exhibited aberrant expression with increased nuclear localization and phosphorylation of IKKα and β when compared to normal controls. In a panel of 9 HNSCC cell lines, endogenous IKKα was more abundantly expressed than IKKβ. While individual overexpression of wt or constitutively activated IKKβ was more potent than IKKα, dual overexpression of IKKα and β exhibited the strongest induction of NF-kB activation. siRNA knockdown of either kinase resulted in decreased cell proliferation and migration and NF-kB activation, and a combinatorial effect was seen with double IKKα and β knockdown. Additionally, chemical inhibitors targeting IKKα and β were used to evaluate their potential for suppressing NF-kB activation and targeting the HNSCC malignant phenotype in vitro. Four small molecule inhibitors were studied that preferentially targeted IKKα>β (17-DMAG), IKKβ (MLN120b and SC514), or both IKKα and β (wedelolactone). Compared to the IKKβ specific inhibitor, MLN120b, 17-DMAG more potently inhibited NF-kB DNA binding in electromobility shift assays (EMSA) and NF-kB reporter gene activation. MTT proliferation assays and flow cytometric DNA cell cycle analysis demonstrated more potent effects of 17-DMAG and wedelolactone in inhibiting cell proliferation. We conclude that overexpression and signaling mediated by both IKKα and β contribute to NF-kB activation, and pathogenesis of proliferation and migration of HNSCC cells in vitro. Furthermore, dual siRNA silencing or chemical inhibition of IKKα and β kinases resulted in combinatorial inhibitory effects on NF-kB activation and the malignant phenotype. In the face of intrinsic and acquired chemoresistance limiting treatment options, IKKα/β represent promising novel therapeutic targets for fighting HNSCC. 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 5005. doi:10.1158/1538-7445.AM2011-5005

Phase I Trial of Bortezomib (NSC 681239) and Flavopiridol (NSC 649890) in Patients with Recurrent or Refractory Indolent B-Cell Neoplasms.

Preclinical studies suggest that neoplastic cells may be particularly sensitive to simultaneous interruption of cell-cycle and survival signaling pathways. In accord with this concept, we have shown that flavopiridol (F), a CDK inhibitor, interacts with bortezomib (B), a proteasome inhibitor, to induce mitochondrial injury and apoptosis in human leukemia, myeloma, and lymphoma cells (Dai et al, Oncogene 22:7108, 2003; Dai et al, Blood 104:509, 2004). These actions were associated with inhibition of NF-kappaB DNA binding, increased expression of phospho-JNK, and downregulation of XIAP and Mcl-1. Based on these findings, a phase I trial has been initiated to identify appropriate doses of B+F for further investigation. Eligible patients (pts) include those with multiple myeloma or indolent B-cell neoplasms, and recurrent or refractory disease following at least 1 prior systemic therapy (excluding allogeneic stem cell transplantation). In the initial stage of the trial, pts received B (iv push) immediately followed by F bolus (1- hour infusion) on d1, 4, 8, and 11 out of a 21-day (d) cycle. Dose levels were, in mg/m2 (B/F): 1.0/15, 1.3/15, 1.3/22, 1.3/30, 1.3/40, 1.3/50, and 1.3/60. Subsequently, a “hybrid” F infusion schedule (30 minute load followed by a 4-hour infusion) was adopted based on evidence of activity of this schedule in chronic lymphocytic leukemia. With the hybrid schedule, all pts receive B (iv push) 1.3 mg/m2 on d1, 4, 8 and 11. Targeted F dose levels using the hybrid schedule are (Fload/Finfusion; mg/m2): 20/20 on d1 and 8; 30/30 on d1 and 8; 30/50 on d1 and 8; 30/30 on d1, 4, 8 and 11; 30/50 on d1, 4, 8 and 11. Dose limiting toxicity (DLT) is defined as NCI CTCAE grade 4 ANC/platelets for > 1 week or grade ≥ 3 non-heme toxicity. 38 pts have been enrolled. 29 pts were treated at 7 dose levels with the bolus schedule, after which development of the hybrid schedule was begun. With the hybrid schedule, 11 pts have been treated at 3 dose levels. To date, one DLT (grade 3 lower back pain) was observed at level 5 of the bolus schedule and one DLT (grade 3 fatigue) was seen at the 1st hybrid dose level. The MTD of the hybrid schedule has not been reached. Non-DLT toxicities include herpes zoster (2 disseminated), peripheral neuropathy, fatigue, postural hypotension, syncope, diarrhea and ≤ grade 3 cytopenias. Of 35 pts evaluable for response, there have been 2 complete responses (1 lymphoma and 1 mantle cell lymphoma), 7 partial responses (5 myeloma and 2 lymphoma), 3 minor responses (2 myeloma and 1 extramedullary plasmacytoma), 15 patients with stable disease (5 myeloma, 7 lymphoma, 1 Waldenstrom's and 2 mantle cell lymphomas). Of the 3 pts who had received prior bortezomib, 2 had minor responses and 1 had disease progression. To date, hyperacute tumor lysis has not occurred with the hybrid schedule, but aggressive prophylaxis and monitoring are integral to the treatment plan. Correlative laboratory studies involving bone marrow CD138+ cells from patients with myeloma revealed a reduction in post-treatment NF-kappaB nuclear localization in 4 of 5 evaluable patients. Variable effects on myeloma cell expression of phospho-JNK, Mcl-1, and XIAP have been observed. Collectively, these findings indicate that a regimen combining bortezomib and flavopiridol, including the use of a hybrid flavopiridol schedule, is well tolerated in patients with progressive B-cell malignancies, and has clear activity in some patients refractory to standard therapy. Pending identification of the MTD and RPTD (recommended phase II dose), phase II evaluation of this therapeutic strategy should define its activity more definitively.

Down‐regulation of collagen and connective tissue growth factor expression with hepatocyte growth factor in lung fibroblasts from white scleroderma patients via two signaling pathways

To study the mechanisms by which hepatocyte growth factor (HGF) down-regulates collagen and connective tissue growth factor (CTGF) in scleroderma (systemic sclerosis [SSc]) lung fibroblasts. CTGF, type I collagen, and IkappaBalpha expression, together with MAPK phosphorylation, were studied by immunoblotting of lung fibroblasts derived from white SSc patients. Matrix metalloproteinase 1 (MMP-1) expression in cell culture medium samples was measured by enzyme-linked immunosorbent assay, MMP-1 activity was studied using an MMP-1 assay, and NF-kappaB DNA binding activity was determined using a transcription factor assay. In lung fibroblasts from white SSc patients, HGF activated MAPK (ERK-1/2) signaling pathways and MMP-1, while it inhibited NF-kappaB and significantly down-regulated CTGF and collagen in a time- and dose-dependent manner. Small interfering RNA (siRNA)-mediated depletion of Grb2 expression disrupted c-Met receptor downstream signaling, which resulted in diminished HGF-induced ERK-1/2 phosphorylation and the recovery of HGF-inhibited expression of MMP-1, NF-kappaB, collagen, and CTGF. The MAPK inhibitor, U0126, blocked MMP-1 activity and restored HGF-inhibited collagen and CTGF accumulation. Inhibition of MMP activity by MMP inhibitor GM1489 and inhibition of MMP-1 expression by siRNA did not prevent HGF-induced ERK-1/2 phosphorylation and NF-kappaB activity, but significantly restored HGF-inhibited collagen and CTGF accumulation. NF-kappaB inhibitor BAY 11-7082 did not interfere with MAPK phosphorylation or MMP-1 expression and activation, but significantly inhibited NF-kappaB DNA binding activity and acted synergistically with HGF to completely diminish the expression of CTGF. In lung fibroblasts from white SSc patients, HGF down-regulates the accumulation of CTGF via MAPK/MMP-1 and NF-kappaB signaling pathways, whereas collagen down-regulation is mediated mainly by a MAPK/MMP-1-dependent pathway.

The Phase 2 Enzyme Inducers Ethacrynic Acid, DL-Sulforaphane, and Oltipraz Inhibit Lipopolysaccharide-Induced High-Mobility Group Box 1 Secretion by RAW 264.7 Cells

The diuretic ethacrynic acid (EA) has been shown to inhibit signaling by the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB). Accordingly, we sought to determine whether this compound is capable of inhibiting the release of cytokines [interleukin (IL)-6 and IL-10] and NO from RAW 264.7 murine macrophage-like cells stimulated with lipopolysaccharide (LPS). Additionally, we sought to determine whether EA can inhibit secretion of high-mobility group box 1 (HMGB1), a nuclear protein that is secreted by immunostimulated macrophages and functions in the extracellular milieu as a proinflammatory mediator. In a concentration-dependent manner, EA inhibited secretion of IL-6, IL-10, nitric oxide, and HMGB1. As expected, EA inhibited NF-kappaB DNA binding in LPS-stimulated RAW 264.7 cells. Treating these cells with pyrrolidine dithiocarbamate, SN50 (amino acid sequence AAVALLPAVLLALLAPVQRKRQKLMP) or 5-(thien-3-yl)-3-aminothiophene-2-carboxamide (SC-514) also inhibited LPS-induced NF-kappaB DNA binding, but these compounds failed to inhibit LPS-induced HMGB1 secretion. These findings suggested that inhibition of HMGB1 secretion by EA might occur via a mechanism unrelated to the NF-kappaB signaling pathway. Because EA is an electrophilic compound that is known to be capable of inducing expression of so-called phase 2 proteins, we sought to determine whether two other phase 2 enzyme inducers, oltipraz and DL-sulforaphane, also are capable of inhibiting HMGB1 release from immunostimulated macrophages. Incubating RAW 264.7 cells with either oltipraz or DL-sulforaphane inhibited LPS-induced HMGB1 secretion. Moreover, both EA and DL-sulforaphane inhibited relocalization of nuclear HMGB1 into the cytoplasm of LPS-stimulated RAW 264.7 cells. These data suggest that phase 2 inducers may exert anti-inflammatory effects by inhibiting secretion of the cytokine-like nuclear protein HMGB1.

Phase I Trial of Bortezomib (NSC 681239) and Flavopiridol (NSC 649890) in Patients with Recurrent or Refractory Indolent B-Cell Neoplasms.

Preclinical studies suggest that neoplastic cells may be particularly sensitive to simultaneous interruption of cell-cycle and survival signaling pathways. In accord with this concept, we have shown that flavopiridol (F), a CDK inhibitor, interacts with Bortezomib (B), a proteasome inhibitor, to induce mitochondrial injury and apoptosis in human leukemia, myeloma, and lymphoma cells (Dai et al, Oncogene 22:7108, 2003; Dai et al, Blood 104,509, 2004). These actions were associated with inhibition of NF-kappaB DNA binding, and diminished expression of phospho-JNK, XIAP, and Mcl-1. Based on these findings, we have initiated a phase I trial to identify appropriate doses of B+F for further investigation. Eligible patients (pts) include those with multiple myeloma, indolent B-cell lymphoma, or a related disorder, and must have recurrent or refractory disease following at least 1 prior systemic therapy (excluding allogeneic stem cell transplantation). Pts receive B (iv bolus) immediately followed by F (1 hour infusion) on days 1, 4, 8, and 11; courses are repeated every 21 days. Targeted dose levels are (B/F; mg/m2): 1.0/15, 1.3/15, 1.3/22, 1.3/30, and 1.3/40. Dose limiting toxicity (DLT) is defined as NCI CTCAE grade 4 ANC/platelet for > 1 week or grade ≥ 3 non-heme toxicity. 14 pts have been treated at 4 dose levels. There have been no DLT to date. There have been 3 episodes of herpes zoster (2 disseminated), 4 cases of exacerbation of pre-existing peripheral neuropathy, and 8 pts have discontinued study treatment after 1 to 5 cycles due to non-DLT toxicities. Among 11 patients evaluable for response and who are Bortezomib-naive, there has been 1 complete response (mantle cell lymphoma; MCL), 3 partial responses (2 myeloma, 1 lymphoma), and 5 patients with stable disease (3 myeloma, 1 lymphoma, 1 Waldenstrom's). The patient with MCL who achieved a CR had previously received CHOP, Rituximab-CHOP, and fludarabine-Rituximab x 2. Correlative laboratory studies involving bone marrow CD138+ cells from patients with myeloma revealed a reduction in post-treatment NF-kappaB nuclear localization in 4/5 evaulable patients. Variable effects on myeloma cell expression of phospho-JNK, Mcl-1, and XIAP have been observed. Additional patients who previously received Bortezomib have now been entered on the study, but it is too early to evaluate their responses. Collectively, these findings indicate that a regimen combining Bortezomib and flavopiridol is well tolerated in patients with progressive B-cell malignancies, and has clear activity in some patients refractory to standard therapy. Pending identification of the MTD and RPTD (recommended phase II dose), Phase II evaluation of this therapeutic strategy should define its activity more definitively.

Nuclear Factor-κB Mediates Kupffer Cell Apoptosis Through Transcriptional Activation of Fas/FasL 1,2

Nuclear factor (NF)-kappaB is a key transcriptional factor for cell survival, inflammation, and stress response. We demonstrated that Kupffer cell-derived FasL plays a central role in pancreatitis-induced hepatocyte injury. The aim of this study was to determine the role of NF-kappaB in regulating death ligand/receptor pathway in Kupffer cells during conditions that mimic acute pancreatitis. Tissue cultures of rat Kupffer cells were treated with elastase (1 U/L) to mimic pancreatitis before and after infection with AdIkappaB to block activation of NF-kappaB. Tumor necrosis factor (enzyme-linked immunoassay), Fas/FasL, and caspase-3 (Western), tumor necrosis factor and Fas/FasL mRNA (reverse-transcription polymerase chain reaction), and NF-kappaB DNA binding (electrophoretic mobility shift assay) were determined. Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) and DNA fragmentation. Gels were quantified by densitometry. Data (n=3) are mean+/-SEM; student's t test was used for statistical analysis. AdIkappaB infection up-regulated mutated IkappaBalpha that maintained its binding properties to NF-kappaB. Promoter-reporter assay demonstrated that FasL gene promoter was regulated by NF-kappaB. Infection with AdIkappaB attenuated the elastase-induced up-regulation of Fas/FasL (all P<0.01 versus elastase) and NF-kappaB DNA binding but did not affect elastase-induced up-regulation of TNF. AdIkappaB attenuated elastase-induced cleavage of caspase-3, DNA fragmentation and TUNEL staining (all P<0.01 versus elastase). Inhibition of NF-kappaB DNA binding down-regulates Fas/FasL and attenuates elastase-induced apoptosis; however, it has no effect on TNF production, suggesting that regulation of Fas/FasL and TNF may occur via different pathways. The ability of Kupffer cells to autoregulate their stress response by up-regulating their death ligand/receptor and apoptosis warrants further investigation.

Porcine arterivirus activates the NF-κB pathway through IκB degradation

Nuclear factor-kappaB (NF-κB) is a critical regulator of innate and adaptive immune function as well as cell proliferation and survival. The present study demonstrated for the first time that a virus belonging to the Arteriviridae family activates NF-κB in MARC-145 cells and alveolar macrophages. In porcine reproductive and respiratory syndrome virus (PRRSV)-infected cells, NF-κB activation was characterized by translocation of NF-κB from the cytoplasm to the nucleus, increased DNA binding activity, and NF-κB-regulated gene expression. NF-κB activation was increased as PRRSV infection progressed and in a viral dose-dependent manner. UV-inactivation of PRRSV significantly reduced the level of NF-κB activation. Degradation of IκB protein was detected late in PRRSV infection, and overexpression of the dominant negative form of IκBα (IκBαDN) significantly suppressed NF-κB activation induced by PRRSV. However, IκBαDN did not affect viral replication and viral cytopathic effect. PRRSV infection induced oxidative stress in cells by generating reactive oxygen species (ROS), and antioxidants inhibited NF-κB DNA binding activity in PRRSV-infected cells, suggesting ROS as a mechanism by which NF-κB was activated by PRRSV infection. Moreover, NF-κB-dependent expression of matrix metalloproteinase (MMP)-2 and MMP-9 was observed in PRRSV-infected cells, an observation which implies that NF-κB activation is a biologically significant aspect of PRRSV pathogenesis. The results presented here provide a basis for understanding molecular pathways of pathology and immune evasion associated with disease caused by PRRSV.

Antitumor agent parthenolide reverses resistance of breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand through sustained activation of c-Jun N-terminal kinase.

The antitumor activity of the sesquiterpene lactone parthenolide, an active ingredient of medicinal plants, is believed to be due to the inhibition of DNA binding of transcription factors NF-kappaB and STAT-3, reduction in MAP kinase activity and the generation of reactive oxygen. In this report, we show that parthenolide activates c-Jun N-terminal kinase (JNK), which is independent of inhibition of NF-kappaB DNA binding and generation of reactive oxygen species. Parthenolide reversed resistance of breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Cancer cells treated with a combination of TRAIL and parthenolide underwent massive typical apoptosis and atypical apoptosis involving the loss of plasma membrane integrity. JNK activity is necessary for the parthenolide-induced sensitization to TRAIL because a dominant-negative JNK or the JNK inhibitor SP600125 reduced TRAIL plus parthenolide-induced apoptosis. Parthenolide induced phosphorylation of Bid and increased TRAIL-dependent cleavage of Bid without affecting caspase 8 activities. Cytochrome c but not Smac/DIABLO was released from the mitochondria in cells treated with parthenolide alone. Parthenolide through JNK increased the TRAIL-mediated degradation of the antiapoptotic protein X-linked inhibitor of apoptosis (XIAP). Enhanced XIAP cleavage correlated with increased and prolonged caspase 3 activity and PARP cleavage, suggesting that the sensitization to TRAIL involves 'feed forward' activation of caspase 3. These results identify a new antitumor activity of parthenolide, which can be exploited to reverse resistance of cancer cells to TRAIL, particularly those with elevated XIAP levels.

Coordinate activation of HIF-1 and NF-kappaB DNA binding and COX-2 and VEGF expression in retinal cells by hypoxia.

Proinflammatory signaling mechanisms are implicated in the induction of retinal neovascularization (NV) during ischemic retinopathies. This study examined transcription factor (TF) AP-1, HIF-1, and NF-kappaB DNA-binding in relation to cyclooxygenase (COX)-2 and VEGF RNA and protein levels in hypoxia-triggered monkey choroidal retinal (RF/6A) endothelial cells. Effects of the carboxamide CGP43182 were tested on COX-2 and VEGF activation and prostaglandin (PG)E(2) release. RF/6A cells were subjected to hypoxia for 1 and 3 hours, at which times RNA and proteins were isolated. Potential AP-1, hypoxia-inducible factor (HIF)-1 and NF-kappaB DNA-binding sites were identified using DNA sequence search algorithms and were analyzed using gel-shift assay. COX-2 and VEGF RNA, protein, and PGE(2) levels were quantified by RT-PCR, Western analysis, and enzyme immunoassay, respectively. Tubular morphogenesis was analyzed with phase-contrast imaging microscopy. Nuclear AP-1, HIF-1 and NF-kappaB promoter DNA binding increased 1.5-, 4-, and 3-fold, respectively, after 1 hour of hypoxia. COX-2 RNA was elevated five- and fourfold after 1 and 3 hours of hypoxia, respectively. VEGF RNA and protein abundance lagged behind COX-2 induction but were each increased two- to threefold 3 hours after hypoxia. CGP43182 was found to inhibit NF-kappaB DNA binding, COX-2 and VEGF gene expression, PGE(2) release, and hypoxia-induced tubular morphogenesis. Maximum HIF-1 and NF-kappaB DNA binding immediately before COX-2 expression suggests that these TFs are important regulators of COX-2 induction in hypoxic RF/6A cells. IL-1beta emulated AP-1, HIF-1, and NF-kappaB DNA binding during hypoxia and may be a novel cytokine trigger for NV. CGP43182 appears to be an effective inhibitor of NV. VEGF expression appears to be regulated through dual interdependent mechanisms involving HIF-1 directly and indirectly through NF-kappaB-mediated COX-2 expression and PGE(2) production.

Increased NF-κB DNA binding but not transcriptional activity during apoptosis induced by the COX-2-selective inhibitor NS-398 in colorectal carcinoma cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit colorectal neoplasia, an effect that is associated with their ability to induce apoptosis. Although NSAIDs have been reported to inhibit NF-κB, more recent studies show activation of NF-κB by NSAIDs. NF-κB commonly shows antiapoptotic activity and is implicated in the therapeutic resistance of cancer cells. The effects of highly COX-2-selective NSAIDs such as NS-398 on NF-κB in colorectal tumour cells have not been reported. Therefore, we addressed whether NF-κB has a role in NS-398-induced apoptosis of colorectal cancer cells. Treatment of HT-29 colorectal carcinoma cells with doses of NS-398 (50–75 μM) known to induce apoptosis had no effect on NF-κB for up to 48 h. However after 72 and 96 h NF-κB DNA-binding activity was increased by NS-398, in parallel with apoptosis induction. NS-398-treated HT-29 cells showed increased p50 homodimer binding and an induction of p50/p65 heterodimers, as demonstrated by supershift assay. However, although NS-398 increased NF-κB DNA binding it did not increase NF-κB-dependent reporter activity and inhibition of NF-κB DNA binding did not enhance NS-398-induced apoptosis. This indicates that NF-κB activated by NS-398 is transcriptionally inactive and is an encouraging result for the use of COX-2-selective NSAIDs not only in chemoprevention but also as novel therapies for colon cancer.

Nuclear factor kappa B: a potential target for anti-HIV chemotherapy.

The Nuclear Factor Kappa B (NF-kappaB) is a lymphoid-specific transcription factor, which is sequestered in the cytoplasm by the protein IkappaB. NF-kappaB plays a major role in the regulation of HIV-1 gene expression. Upon activation, NF-kappaB is released from IkappaB, moves to the nucleus, and binds to its sites on the HIV long terminal repeat to start transcription of integrated HIV genome. The present review focuses on the NF-kappaB as a potential target for the development of chemotherapy against HIV-1. Beginning from the viral-binding to reverse transcription, integration, and gene expression, to the virion maturation, the life cycle of HIV presents drug-targets at all the stages. As a result, many drugs have been developed and have entered clinical trials. Some of the most important of these are reverse transcriptase and protease inhibitors, which have been used mostly in clinical studies in the form of combined therapy. But, this combined therapy has presented the problem of resistance, due to mutations in the virus. However, targeting NF-kappaB for the suppression of virus does not present the problem of resistance, as NF-kappaB is a normal part of the human T-4 cell, and is not subject to mutations, as is the virus. An overview of the NF-kappaB system and its role in HIV-1 is presented, followed by a critical review of its current and potential synthetic inhibitors. The drugs studied against NF-kappaB fall mainly into three categories: (1) Antioxidants, against oxidative stress conditions, which aid in NF-kappaB activation, (2) IkappaB phosphorylation and degradation inhibitors (the phosphorylation and degradation of IkappaB is necessary to make NF-kappaB free and move to the nucleus), and (3) NF-kappaB DNA binding inhibitors. The antioxidants include N-Acetyl-L-cysteine (NAC), alpha-Lipoic acid, glutathione monoester, pyrrolidine dithiocarbamate, and tepoxalin, of which NAC is the best studied. The IkappaB phosphorylation and degradation inhibitors, which have been studied in the context of HIV-1 include the salicylates (sodium salicylate, and acetylsalicylic acid (aspirin)). Finally, the NF-kappaB DNA binding inhibitors, which have received attention only recently, are reviewed. These include the most potential, aurine tricarboxylic acid (ATA), a chelating agent, which has been found to inhibit NF-kappaB DNA binding at a low concentration of 30 micro M. The probable mechanism of action of these drugs is discussed alongwith relevant suggestions and conclusions.

Prevention of diabetes in NOD mice by administration of dendritic cells deficient in nuclear transcription factor-kappaB activity.

Abnormalities of dendritic cells (DCs) have been identified in type 1 diabetic patients and in nonobese diabetic (NOD) mice that are associated with augmented nuclear transcription factor (NF)-kappaB activity. An imbalance that favors development of the immunogenic DCs may predispose to the disease, and restoration of the balance by administration of DCs deficient in NF-kappaB activity may prevent diabetes. DCs propagated from NOD mouse bone marrow and treated with NF-kappaB-specific oligodeoxyribonucleotide (ODN) in vitro (NF-kappaB ODN DC) were assessed for efficacy in prevention of diabetes development in vivo. Gel shift assay with DC nuclear extracts confirmed specific inhibition of NF-kappaB DNA binding by NF-kappaB ODN. The costimulatory molecule expression, interleukin (IL)-12 production, and immunostimulatory capacity in presenting allo- and islet-associated antigens by NF-kappaB ODN DC were significantly suppressed. NF-kappaB ODN renders DCs resistant to lipopolysaccharide stimulation. Administration of 2 x 10(6) NF-kappaB ODN DCs into NOD mice aged 6-7 weeks effectively prevented the onset of diabetes. T-cells from pancreatic lymph nodes of NF-kappaB ODN DC-treated animals exhibited hyporesponsiveness to islet antigens with low production of interferon-gamma and IL-2. These findings provide novel insights into the mechanisms of autoimmune diabetes and may lead to development of novel preventive strategies.

Activation of Protein Kinase Cζ Is Essential for Cytokine-induced Metalloproteinase-1, -3, and -9 Secretion from Rabbit Smooth Muscle Cells and Inhibits Proliferation

Several matrix metalloproteinases (MMPs), including MMP-1, -3, and -9, mediate matrix destruction during chronic inflammatory diseases such as arthritis and atherosclerosis. MMP up-regulation by inflammatory cytokines involves interactions between several transcription factors, including activator protein-1 and nuclear factor kappaB (NF-kappaB). The upstream regulatory pathways are less well understood. We investigated the role of isoforms of protein kinase C (PKC) in basic fibroblast growth factor- and interleukin-1alpha-mediated MMP production from cultured rabbit aortic smooth muscle cells. A synthetic PKC inhibitor, RO318220, inhibited MMP-1, -3, and -9 production by 89 +/- 3, 75 +/- 18, and 89 +/- 9%, respectively. However, down-regulation of conventional and novel isoforms did not inhibit but rather increased MMP-9 production by 48 +/- 16%, implicating an atypical PKC isoform. Consistent with this, PKCzeta protein levels and activity were stimulated 3.3- and 13-fold, respectively, by basic fibroblast growth factor plus interleukin-1alpha and antisense oligonucleotides to PKCzeta significantly decreased MMP-9 formation by 62 +/- 18% compared with scrambled sequences. Moreover, adenovirus-mediated overexpression of a dominant-negative (DN) PKCzeta reduced MMP-1, -3, and -9 production by 78 +/- 9, 76 +/- 8, and 76 +/- 5%, respectively. DN-PKCzeta inhibited NF-kappaB DNA binding but did not affect ERK1/2 activation or AP-1 binding. Antisense PKCzeta oligonucleotides and DN-PKCzeta stimulated cell proliferation by 89 +/- 14% (n = 4) and 305 +/- 74% (n = 3), respectively (both p < 0.05). Our results show that PKCzeta is essential for cytokine-induced up-regulation of MMP-1, -3, and -9, most likely by activating NF-kappaB. Selective inhibition of PKCzeta is therefore a possible strategy to inhibit MMP production in inflammatory diseases such as atherosclerosis.

Butyrate Suppression of Colonocyte NF-κB Activation and Cellular Proteasome Activity

Butyrate is derived from the microbial metabolism of dietary fiber in the colon where it plays an important role in linking colonocyte turnover and differentiation to luminal content. In addition, butyrate appears to have both anti-inflammatory and cancer chemopreventive activities. Using confocal microscopy and cell fractionation studies, butyrate pretreatment of a human colon cell line (HT-29 cells) inhibited the tumor necrosis factor-alpha (TNF-alpha)-induced nuclear translocation of the proinflammatory transcription factor NF-kappaB. Butyrate inhibited NF-kappaB DNA binding within 30 min of TNF-alpha stimulation, consistent with an inhibition of nuclear translocation. IkappaB.NF-kappaB complexes extracted from butyrate-treated cells were relatively resistant to in vitro dissociation by deoxycholate, suggesting a change in cellular IkappaB composition. Butyrate treatment increased p100 expression, an IkappaB that was not degraded upon TNF-alpha treatment. Butyrate also reduced the extent of TNF-alpha-induced IkappaB-alpha degradation and enhanced the presence of ubiquitin-conjugated IkappaB-alpha. The suppression of IkappaB-alpha degradation corresponded with a reduction in cellular proteasome activity as determined by in vitro proteasome assays and the increased presence of ubiquitin-conjugated proteins. The butyrate suppression of IkappaB-alpha degradation and proteasome activity may derive from its ability to inhibit histone deacetylases since the specific deacetylase inhibitor trichostatin A had similar effects. These results suggest a potential mechanism for the anti-inflammatory activity of butyrate and demonstrate the interplay between short chain fatty acids and cellular proteasome activity.

IL-4 abrogates osteoclastogenesis through STAT6-dependent inhibition of NF-kappaB.

IL-4, an anti-inflammatory cytokine, inhibits osteoclast differentiation, but the basis of this effect has been unclear. Osteoclastogenesis requires activation of RANK, which exerts its biologic effect via activation of NF-kappaB. NF-kappaB activation is manifested by nuclear translocation and binding to DNA, events secondary to phosphorylation and dissociation of IkappaBalpha. It is shown here that IL-4 reduces NF-kappaB nuclear translocation by inhibiting IkappaB phosphorylation, thus markedly inhibiting NF-kappaB DNA binding activity and blocking osteoclastogenesis entirely. Residual translocation of NF-kappaB in the presence of IL-4, however, suggests that nuclear mechanisms must primarily account for inhibition of NF-kappaB DNA binding and blockade of osteoclastogenesis. To address this issue, this study examined whether IL-4-induced STAT6 transcription factor blocks NF-kappaB transactivation. The results show that excess unlabeled consensus sequence STAT6, but not its mutated form, inhibits NF-kappaB binding. Furthermore, exogenously added STAT6 protein inhibits NF-kappaB/DNA interaction. Further supporting a role for STAT6 in this process are the findings that IL-4 fails to block osteoclastogenesis in STAT6(-/-) mice but that this blockade can be restored with addition of exogenous STAT6. Thus, IL-4 obliterates osteoclast differentiation by antagonizing NF-kappaB activation in a STAT6-dependent manner.

Tumor Necrosis Factor Induces Bcl-2 and Bcl-x Expression through NFκB Activation in Primary Hippocampal Neurons

Emerging data indicate that tumor necrosis factor (TNF) exerts a neuroprotective effect in response to brain injury. Here we examined the mechanism of TNF in preventing neuronal death in primary hippocampal neurons. TNF protected neurons against hypoxia- or nitric oxide-induced injury, with an increase in the anti-apoptotic proteins Bcl-2 and Bcl-x as determined by Western blot and reverse transcriptase-polymerase chain reaction analysis. Treatment of neurons with an antisense oligonucleotide to bcl-2 mRNA or that to bcl-x mRNA blocked the up-regulation of Bcl-2 or Bcl-x expression, respectively, and partially inhibited the neuroprotective effect induced by TNF. Moreover, adenovirus-mediated overexpression of Bcl-2 significantly inhibited hypoxia- or nitric oxide-induced neuronal death. To examine the possible involvement of a transcription factor, NFkappaB, in the regulation of Bcl-2 and Bcl-x expression in TNF-treated neurons, an adenoviral vector capable of expressing a mutated form of IkappaB was used to infect neurons prior to TNF treatment. Expression of the mutant NFkappaB completely inhibited NFkappaB DNA binding activity and inhibited both TNF-induced up-regulation of Bcl-2 and Bcl-x expression and neuroprotective effect. These findings indicate that induction of Bcl-2 and Bcl-x expression through NFkappaB activation is involved in the neuroprotective action of TNF against hypoxia- or nitric oxide-induced injury.

Signal transduction during liver regeneration.

Following partial hepatectomy (PH), there is a rapid and highly orchestrated series of biochemical events which occur prior to cellular proliferation. Some of these events are presumably intimately linked with the eventual regeneration of the liver, whereas others are likely to be stress related or required for the continued differentiated function of the liver while regeneration is occurring. The regulation of the AP-1 transcription factor c-Jun during hepatic regeneration has been studied here. There is a progressive increase in c-Jun-mRNA levels after sham operation, one-third PH, and two-thirds PH. A concomitant increase in activating protein 1 (AP-1) binding activity is also observed. The c-Jun protein is a major constituent of the AP-1 complex in quiescent and early regenerating liver. The activity of c-Jun amino-terminal kinase (JNK), which phosphorylates the activation domain of the c-Jun protein, is markedly stimulated after one-third and two-thirds PH. c-Jun amino-terminal kinase-1 is a constituent of this stimulated JNK activity after PH. When primary cultures of adult rat hepatocytes are incubated with epidermal growth factor or transforming growth factor-α, AP-1 transcriptional activity is increased and the activation domain of the c-Jun protein is further potentiated. Phosphopeptide mapping of the endogenous c-Jun protein in proliferating cultured hepatocytes demonstrates phosphorylation of the c-Jun activation domain. Pretreatment of animals prior to PH with a neutralizing antibody to tumour necrosis factor-α (TNFα), inhibits hepatocyte DNA synthesis and JNK activation. It is concluded that the stimulation of one-third or two-thirds PH activates JNK through a mechanism that requires TNFα, which phosphorylates the c-Jun activation domain in hepatocytes, resulting in enhanced transcription of AP-1-dependent genes. Although nuclear factor-kappa B (NFκB) binding activity is induced during liver regeneration following PH, the physiological consequence of this induction is unknown. The role of NFκB during liver regeneration has been assessed by delivering to the liver a super-repressor of NFκB activity using an adenoviral vector expressing a mutated form of IκB. This adenovirus (Ad5IκB) was almost exclusively expressed in the liver and inhibited NFκB DNA binding activity and transcriptional activity in cultured cells as well as in the liver in vivo. Following PH, Ad5IκB, but not a control adenovirus (Ad5βgal), resulted in the induction of apoptosis as demonstrated by histological staining and TUNEL analysis. In addition, infection with Ad5IκB but not Ad5βgal decreased the mitotic index following PH. These two phenomena, increased apoptosis and cell cycle arrest, were associated with liver failure in animals infected with the ad5IκB but not Ad5βgal as demonstrated by elevated serum bilirubin and ammonia levels. Thus, the induction of NFκB during liver regeneration following PH appears to be a required event to prevent apoptosis and to allow for normal cell cycle progression.

Effect of dexamethasone on interleukin-1beta-(IL-1beta)-induced nuclear factor-kappaB (NF-kappaB) and kappaB-dependent transcription in epithelial cells.

The production of inflammatory mediators by epithelial cells in inflammatory lung diseases may represent an important target for the anti-inflammatory effects of glucocorticoids. Nuclear factor-kappaB (NF-kappaB) is a major activator of inflammatory genes and has been proposed as a target for inhibition by glucocorticoids. We have used human pulmonary type-II A549 and airway epithelial BEAS-2B cells to investigate the effect of glucocorticoids on NF-kappaB regulation and kappaB-dependent transcription. In A549 cells following interleukin-1beta (IL-1beta) treatment, there was no effect of dexamethasone on the disappearance of I kappaB alpha protein, its subsequent reappearance 90-min later or the rapid induction of I kappaB alpha mRNA and transcription rate. Expression of p65 and p50/p105 proteins were also unaffected by dexamethasone. In addition, the rapid IL-1beta-induction of NF-kappaB DNA binding and p65 nuclear localisation was unaffected by short (1-6 hours) dexamethasone pre-treatments. Similarly, BEAS-2B cells showed no effect of dexamethasone on IL-1beta-induced NF-kappaB (p50/p65). Stable transfection of a kappaB-dependent reporter in A549 cells resulted in an 8-9-fold activation by IL-1beta or phorbol ester, that was repressed 30-40% by dexamethasone. However, in these cells, IL-1beta induction of inducible nitric oxide synthase, granulocyte-macrophage colony stimulating factor and cyclooxygenase-2 mRNA showed 70-90% repression by dexamethsone. We, therefore, conclude that in these epithelial cells, the repressive effects of glucocorticoids are not mediated by up-regulation of I kappaB alpha, decreased p50/p65 gene expression or inhibition of NF-kappaB DNA binding. Furthermore, since the maximal repression of IL-1beta or phorbol-ester-induced kappaB-dependent transcription by dexamethasone was less than 40%, simple inhibition of kappaB-dependent transcription cannot by itself account for the full repressive effects of glucocorticoids observed in these cells.

NFkappaB prevents apoptosis and liver dysfunction during liver regeneration.

Although NFkappaB binding activity is induced during liver regeneration after partial hepatectomy, the physiological consequence of this induction is unknown. We have assessed the role of NFkappaB during liver regeneration by delivering to the liver a superrepressor of NFkappaB activity using an adenoviral vector expressing a mutated form of IkappaBalpha. This adenovirus (Ad5IkappaB) was almost exclusively expressed in the liver and inhibited NFkappaB DNA binding activity and transcriptional activity in cultured cells as well as in the liver in vivo. After partial hepatectomy, infection with Ad5IkappaB, but not a control adenovirus (Ad5LacZ), resulted in the induction of massive apoptosis and hepatocytes as demonstrated by histological staining and TUNEL analysis. In addition, infection with Ad5IkappaB but not Ad5LacZ decreased the mitotic index after partial hepatectomy. These two phenomena, increased apoptosis and failure to progress through the cell cycle, were associated with liver dysfunction in animals infected with the Ad5IkappaB but not Ad5LacZ, as demonstrated by elevated serum bilirubin and ammonia levels. Thus, the induction of NFkappaB during liver regeneration after partial hepatectomy appears to be a required event to prevent apoptosis and to allow for normal cell cycle progression.