Lipopolysaccharide induces phosphorylation of MAD3 and activation of c-Rel and related NF-kappa B proteins in human monocytic THP-1 cells

Topical Sustained-Release Dexamethasone-Loaded Chitosan Nanoparticles: Assessment of Drug Delivery Efficiency in a Rabbit Model of Endotoxin-Induced Uveitis

Uveitis is an ocular illness that if not treated properly can lead to a total loss of vision. In this study, we evaluated the utility of HA-coated Dexamethasone-sodium-phosphate (DEX)-chitosan nanoparticles (CSNPs) coated with hyaluronic acid (HA) as a sustained ocular delivery vehicle for the treatment of endotoxin-induced-uveitis (EIU) in rabbits. The CSNPs were characterized for particle size, zeta potential, polydispersity, surface morphology, and physicochemical properties. Drug encapsulation, in vitro drug release, and transcorneal permeation were also evaluated. Finally, eye irritation, ocular pharmacokinetics, and pharmacodynamics were in vivo. The CSNPs ranged from 310.4 nm and 379.3 nm pre-(uncoated) and post-lyophilization (with HA-coated), respectively. The zeta potentials were +32 mV (uncoated) and -5 mV (HA-uncoated), while polydispersity was 0.178-0.427. Drug encapsulation and loading in the CSNPs were 73.56% and 6.94% (uncoated) and 71.07% and 5.54% (HA-coated), respectively. The in vitro DEX release over 12 h was 77.1% from the HA-coated and 74.2% from the uncoated NPs. The physicochemical properties of the CSNPs were stable over a 3-month period when stored at 25 °C. Around a 10-fold increased transcorneal-flux and permeability of DEX was found with HA-CSNPs compared to the DEX-aqueous solution (DEX-AqS), and the eye-irritation experiment indicated its ocular safety. After the ocular application of the CSNPs, DEX was detected in the aqueous humor (AH) till 24 h. The area under the concentrations curve (AUC0-24h) for DEX from the CSNPs was 1.87-fold (uncoated) and 2.36-fold (HA-coated) higher than DEX-AqS. The half-life (t1/2) of DEX from the uncoated and HA-coated NPs was 2.49-and 3.36-fold higher, and the ocular MRT0-inf was 2.47- and 3.15-fold greater, than that of DEX-AqS, respectively. The EIU rabbit model showed increased levels of MPO, TNF-α, and IL-6 in AH. Topical DEX-loaded CSNPs reduced MPO, TNF-α, and IL-6 levels as well as inhibited NF-κB expression. Our findings demonstrate that the DEX-CSNPs platform has improved the delivery properties and, hence, the promising anti-inflammatory effects on EIU in rabbits.

Interleukin-1 and Nuclear Factor Kappa B Signaling Promote Breast Cancer Progression and Treatment Resistance

While meant for wound healing and immunity in response to injury and infection, inflammatory signaling is usurped by cancerous tumors to promote disease progression, including treatment resistance. The interleukin-1 (IL-1) inflammatory cytokine family functions in wound healing and innate and adaptive immunity. Two major, closely related IL-1 family members, IL-1α and IL-1β, promote tumorigenic phenotypes and contribute to treatment resistance in cancer. IL-1 signaling converges on transactivation of the Nuclear Factor Kappa B (NF-κB) and Activator protein 1 (AP-1) transcription factors. NF-κB and AP-1 signaling are also activated by the inflammatory cytokine Tumor Necrosis Factor Alpha (TNFα) and microbe-sensing Toll-Like Receptors (TLRs). As reviewed elsewhere, IL-1, TNFα, and TLR can promote cancer progression through NF-κB or AP-1. In this review, we focus on what is known about the role of IL-1α and IL-1β in breast cancer (BCa) progression and therapeutic resistance, and state evidence for the role of NF-κB in mediating IL-1-induced BCa progression and therapeutic resistance. We will present evidence that IL-1 promotes BCa cell proliferation, BCa stem cell expansion, angiogenesis, and metastasis. IL-1 also regulates intracellular signaling and BCa cell hormone receptor expression in a manner that confers a growth advantage to the tumor cells and allows BCa cells to evade therapy. As such, the IL-1 receptor antagonist, anakinra, is in clinical trials to treat BCa and multiple other cancer types. This article presents a review of the literature from the 1990s to the present, outlining the evidence supporting a role for IL-1 and IL-1-NF-κB signaling in BCa progression.

Anti-psoriatic and anti-inflammatory effects of Kaempferia parviflora in keratinocytes and macrophage cells

Kaempferia parviflora (KP) has been used as folk medicine for curing various conditions, including anti-inflammatory diseases. However, anti-psoriatic effects in an aspect of suppression of NF-κB activation have not been explored. Therefore, our current study aimed to elucidate the anti-inflammation of KP in lipopolysaccharide (LPS)-induced RAW264.7 cells and anti-psoriatic effects of KP in cytokine-induced human keratinocytes, HaCaT cells. We discovered that KP extract significantly suppressed LPS-induced inflammation at both gene expression and protein production. Specifically, dramatic reduction of nitric oxide (NO) was explored by using Griess method. Consistently, data from RT-qPCR, ELISA, and western blot analysis confirmed that crucial inflammatory and psoriatic markers including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, IL-17, IL-22, and IL-23 were significantly decreased by the action of KP. These events were associated with the results from immunofluorescence study and western blot analysis where the activation of NF-κB upon LPS stimulation was clearly inhibited by KP through its ability to suppress IκB-α degradation resulting in inhibition of NF-κB nuclear translocation. Furthermore, KP extract significantly inhibited LPS-stimulated phosphorylation of ERK1/2, JNK, and p38 in a dose-dependent manner, along with inhibition of ERK1/2 activation in both TNF-α- and EGF-induced HaCaT cells. Interestingly, HaCaT cells exposed to 15 μg/mL of KP also exhibited significant decrease of cell migration and proliferation. Our results revealed that KP extract has a potential to be developed as a promising agent for treating inflammation and psoriasis, in part through targeting the proliferation and the NF-κB pathways.

NF-κB signaling promotes castration-resistant prostate cancer initiation and progression

Prostate Cancer (PCa) is the second leading cause of cancer-related death in men. Adenocarcinoma of the prostate is primarily composed of Androgen Receptor-positive (AR⁺) luminal cells that require AR transcriptional activity for survival and proliferation. As a consequence, androgen deprivation and anti-androgens are used to treat PCa patients whose disease progresses following attempted surgical or radiation interventions. Unfortunately, patients with advanced PCa can develop incurable castration-resistant PCa (CRPCa) due to mutated, variant, or overexpressed AR. Conversely, low or no AR accumulation or activity can also underlie castration resistance. Whether CRPCa is due to aberrant AR activity or AR independence, NF-κB signaling is also implicated in the initiation and maintenance of CRPCa and, thus, the NF-κB pathway may be a promising alternative therapeutic target. In this review, we present evidence that NF-κB signaling promotes CRPCa initiation and progression, describe the dichotomic role of NF-κB in the regulation of AR expression and activity and outline studies that explore NF-κB inhibitors as PCa therapies.

Time and dose-dependent impairment of neonatal respiratory motor activity after systemic inflammation

Neonatal respiratory impairment during infection is common, yet its effects on respiratory neural circuitry are not fully understood. We hypothesized that the timing and severity of systemic inflammation is positively correlated with impairment in neonatal respiratory activity. To test this, we evaluated time- and dose-dependent impairment of in vitro fictive respiratory activity. Systemic inflammation (induced by lipopolysaccharide, LPS, 5 mg/kg, i.p.) impaired burst amplitude during the early (1 h) inflammatory response. The greatest impairment in respiratory activity (decreased amplitude, frequency, and increased rhythm disturbances) occurred during the peak (3 h) inflammatory response in brainstem-spinal cord preparations. Surprisingly, isolated medullary respiratory circuitry within rhythmic slices showed decreased baseline frequency and delayed onset of rhythm only after higher systemic inflammation (LPS 10 mg/kg) early in the inflammatory response (1 h), with no impairments at the peak inflammatory response (3 h). Thus, different components of neonatal respiratory circuitry have differential temporal and dose sensitivities to systemic inflammation, creating multiple windows of vulnerability for neonates after systemic inflammation.

Myxoma virus M013 protein antagonizes NF-κB and inflammasome pathways via distinct structural motifs

Among the repertoire of immunoregulatory proteins encoded by myxoma virus, M013 is a viral homologue of the viral pyrin domain-only protein (vPOP) family. In myeloid cells, M013 protein has been shown to inhibit both the inflammasome and NF-κB signaling pathways by direct binding to ASC1 and NF-κB1, respectively. In this study, a three-dimensional homology model of the M013 pyrin domain (PYD) was built based on similarities to known PYD structures. A distinctive feature of the deduced surface electrostatic map of the M013 PYD is the presence of a negatively region consisting of numerous aspartate and glutamate residues in close proximity. Single-site mutations of aspartate and glutamate residues reveal their role in interactions with ASC-1. The biological significance of charge complementarity in the M013-ASC-1 interaction was further confirmed by functional assays of caspase-1 activation and subsequent secretion of cytokines. M013 also has a unique 33-residue C-terminal tail that follows the N-terminal PYD, and it is enriched in positively charged residues. Deletion of the tail of M013 significantly inhibited the interactions between M013 and NF-κB1, thus compromising the ability of the viral protein to suppress the secretion of pro-inflammatory cytokines. These results demonstrate that vPOP M013 exploits distinct structural motifs to regulate both the inflammasome and NF-κB pathways.

ZNF580 - a brake on Interleukin-6

Background

Zinc finger protein 580 (ZNF580) was reported to modulate angiogenesis, endothelial homeostasis and blood pressure control. ZNF580 regulated genes include VEGF-A and IL-8. However, it is unknown if ZNF580 could play a role during inflammation. The aim of this study was to find out if ZNF580 affects the expression of IL-6, if it occurs in monocytic cells and responds to inflammatory mediators.

Results

Overexpression of ZNF580 reduced LPS-induced promotor activity of IL-6. Consistently, overexpression of ZNF580 reduced by half the LPS-induced expression of IL-6. ZNF580 was strongly expressed in the nucleus of MonoMac6, a human monocytic cell line. LPS-stimulated IL-6 secretion increased when ZNF580 was suppressed with siRNA. After stimulation of MonoMac6 with LPS for 24 h, ZNF580 negatively correlated with the amount of secreted IL-6. In response to LPS, ZNF580 was increased within the first 8 h, followed by a marked decrease after 16 h. This decrease coincided with sustained IL-6 production.

Conclusion

This study demonstrated that ZNF580 inhibits LPS-induced expression of IL-6. ZNF580 was highly expressed in monocytic cells and therefore may contribute to the modulation of its IL-6 production, at least in response to LPS. This suggests cooperation between ZNF580 and NFκB, which could play a role during sepsis.

Interleukin 2 Activates Brain Microvascular Endothelial Cells Resulting in Destabilization of Adherens Junctions

The pleiotropic cytokine interleukin 2 (IL2) disrupts the blood-brain barrier and alters brain microcirculation, underlying vascular leak syndrome that complicates cancer immunotherapy with IL2. The microvascular effects of IL2 also play a role in the development of multiple sclerosis and other chronic neurological disorders. The mechanism of IL2-induced disruption of brain microcirculation has not been determined previously. We found that both human and murine brain microvascular endothelial cells express constituents of the IL2 receptor complex. Then we established that signaling through this receptor complex leads to activation of the transcription factor, nuclear factor κB, resulting in expression of proinflammatory interleukin 6 and monocyte chemoattractant protein 1. We also discovered that IL2 induces disruption of adherens junctions, concomitant with cytoskeletal reorganization, ultimately leading to increased endothelial cell permeability. IL2-induced phosphorylation of vascular endothelial cadherin (VE-cadherin), a constituent of adherens junctions, leads to dissociation of its stabilizing adaptor partners, p120-catenin and β-catenin. Increased phosphorylation of VE-cadherin was also accompanied by a reduction of Src homology 2 domain-containing protein-tyrosine phosphatase 2, known to maintain vascular barrier function. These results unravel the mechanism of deleterious effects induced by IL2 on brain microvascular endothelial cells and may inform the development of new measures to improve IL2 cancer immunotherapy, as well as treatments for autoimmune diseases affecting the central nervous system.

Effects of protease inhibitors on LPS-mediated activation of a mouse macrophage cell line (J774)

Pretreatment (1 h) of a mouse macrophage-like cell line, J774, with the protease inhibitor, phenylalanine-chloromethyl ketone (PCK) or its structural analogue, tosylphenylalanine chloromethyl ketone (TPCK) was found to cause substantial inhibition of LPS-triggered activation of NF-κB. Pretreatment of cells with other types of protease inhibitors or their various structural analogues had no effect. PCK or TPCK appeared to exert its inhibitory effect by: (i) partially preventing LPS-triggered degradation of IκBα protein; (ii) preventing LPS-triggered nuclear translocation of NF-κB proteins (p50, RelA and Rel); and (iii) inhibiting the DNA-binding activities of NF-κB proteins. Pretreatment of cells with PCK or TPCK also resulted in the total or partial inhibition of LPS activatable (AP-1 or CREB) or constitutively-existing (Oct-1) transcription factors, but not of another constitutively-expressed transcription factor (SP-1). Pretreatment of J774 cells with PCK was found to substantially suppress LPS-induced expression of mRNAs specific for cytokine genes (TNFα, IL-1α and β, and IL-6), inducible nitric oxide synthase (iNOS) gene and IκBα gene, but not NF-κB1 p105 gene or β-actin gene. Furthermore, PCK pretreatment inhibited, in a dose-dependent manner, LPS-triggered production of nitric oxide production and tumoricidal activity.

Differential mechanisms of LPS-induced NFκB activation in macrophages and fibroblasts

Lipopolysaccharide is a prototypic stimulus of inflammatory gene expression which can act on a variety of cell types to produce different patterns of response. In the present report, the ability of LPS to stimulate NFKB activity was investigated in a fibroblast cell line (NIH3T3) and compared to LPS-induced response in a macrophage like cell line (RAW264.7). LPS was a potent stimulus of KB binding activity in both cell types though the protein composition of such binding activity varied. LPS caused nuclear translocation of KB binding activity in RAW 264.7 cells which contained NFKB1 (p50), RelA (p65), and high levels of c-Rel. Nuclei from LPS-stimulated NIH3T3 cells contained only NFKB1 and RelA but little c-Rel. Both cell types contain comparable levels of total c-Rel protein. Using two structurally distinct KB sequence motifs, LPS was shown to produce a different pattern of transacting activity in fibroblasts as compared to macrophages; both KB motifs were sensitive to LPS in RAW264.7 cells while only one of the two was functional in LPS-stimulated NIH3T3 cells. Thus LPS appears to utilize the NFKB family of transcription factors differentially depending upon the cell type being stimulated. Such differential activation of transcription factor family members may be an important determinant of the diverse nature of inflammatory response seen in different tissue settings.

Mycobacterium tuberculosis secretory proteins downregulate T cell activation by interfering with proximal and downstream T cell signalling events

Background

Mycobacterium tuberculosis (M. tuberculosis) modulates host immune response, mainly T cell responses for its own survival leading to disease or latent infection. The molecules and mechanisms utilized to accomplish immune subversion by M. tuberculosis are not fully understood. Understanding the molecular mechanism of T cell response to M. tuberculosis is important for development of efficacious vaccine against TB.

Methods

Here, we investigated effect of M. tuberculosis antigens Ag85A and ESAT-6 on T cell signalling events in CD3/CD28 induced Peripheral blood mononuclear cells (PBMCs) of PPD+ve healthy individuals and pulmonary TB patients. We studied CD3 induced intracellular calcium mobilization in PBMCs of healthy individuals and TB patients by spectrofluorimetry, CD3 and CD28 induced activation of mitogen activated protein kinases (MAPKs) in PBMCs of healthy individuals and TB patients by western blotting and binding of transcription factors NFAT and NFκB by Electrophorectic mobility shift assay (EMSA).

Results

We observed CD3 triggered modulations in free intracellular calcium concentrations in PPD+ve healthy individuals and pulmonary TB patients after the treatment of M. tuberculosis antigens. As regards the downstream signalling events, phosphorylation of MAPKs, Extracellular signal-regulated kinase 1 and 2 (ERK1/2) and p38 was curtailed by M. tuberculosis antigens in TB patients whereas, in PPD+ve healthy individuals only ERK1/2 phosphorylation was inhibited. Besides, the terminal signalling events like binding of transcription factors NFAT and NFκB was also altered by M. tuberculosis antigens. Altogether, our results suggest that M. tuberculosis antigens, specifically ESAT-6, interfere with TCR/CD28-induced upstream as well as downstream signalling events which might be responsible for defective IL-2 production which further contributed in T-cell unresponsiveness, implicated in the progression of disease.

Conclusion

To the best of our knowledge, this is the first study to investigate effect of Ag85A and ESAT-6 on TCR- and TCR/CD28- induced upstream and downstream signalling events of T-cell activation in TB patients. This study showed the effect of secretory antigens of M. tuberculosis in the modulation of T cell signalling pathways. This inflection is accomplished by altering the proximal and distal events of signalling cascade which could be involved in T-cell dysfunctioning during the progression of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-015-0128-6) contains supplementary material, which is available to authorized users.

Identification and expression analysis of immune-related genes linked to Rel/NF-κB signaling pathway under stresses and bacterial challenge from the small abalone Haliotis diversicolor

Inhibitor of NF-κB (IκB), nuclear factor-κB (NF-κB), and Akirin2 are all important members of Rel/NF-κB signaling pathway, which plays a pivotal role in regulating the innate immune response of vertebrates and invertebrates. In this study, the IκB (SaIκB) and Akirin2 (SaAkirin2) cDNAs of small abalone Haliotis diversicolor were cloned and characterized. The full length cDNA of SaIκB and SaAkirin2 were 1748 bp and 1452 bp respectively, encoding a protein of 401 aa and 187 aa respectively. A conserved degradation motif (DS56GIYS60) and six ankyrin repeats were identified in the SaIκB by SMART analysis. Meanwhile, a typical nuclear localization signal (NLS) was found at the N-terminal region of the SaAkirin2 protein. Also, the mRNA expression level of SaIκB, SaAkirin2, and AbNF-κB were detected by quantitative real-time PCR. The results revealed that all these three genes were ubiquitously expressed in 7 selected tissues. The expression level of SaIκB in gills was higher than that in other tissues (P < 0.05) while the expression level of AbNF-κB was significantly higher in hepatopancreas and haemocytes. The highest expression level of SaAkirin2 was detected in hepatopancreas, followed by mantle. The mRNA expression levels in either gills or haemocytes of SaIκB, SaAkirin2, and AbNF-κB were significantly up-regulated (P < 0.05) post thermal stress, hypoxia exposure, thermal plus hypoxia stress and the injection of Vibrio parahaemolyticus. These results indicated that these three NF-κB signaling pathway-related genes are involved in response to bacterial infection and play essential roles in response to thermal and hypoxia stress.

Two NF-κB inhibitor-alpha (IκBα) genes from rock bream (Oplegnathus fasciatus): molecular characterization, genomic organization and mRNA expression analysis after immune stimulation

IkBa is a member of IkB family, which sequesters NF-kB in an inactivate form in the cytoplasm and blocks the translocation of NF-kB to nucleus. The IkBa paralogs of rock bream (OfIkBa-A and OfIkBa-B) encoded IkBa proteins with typical features including, highly conserved IkB degradation motif, six ankyrin repeats and a PEST sequence. However, their amino acid identity and similarity were only 55.6 and 69.7%, respectively suggesting that these two genes could be the two different isoforms of IkBa. The number and size of the exons of OfIkBa-A and OfIkBa-B were conserved well with all the compared vertebrate species, although they have significantly different genomic sizes. Phylogenetic analysis revealed that OfIkBa-A and OfIkBa-B proteins cluster with IkBa family members; however, they were grouped with different subclades in IkBa family. Tissue specific expression of OfIkBa mRNA was constitutively detected in all the tested tissues, and they showed the higher transcription level in heart, liver, gill and peripheral blood cells, respectively. The injection of flagellin stimulated the mRNA expression of OfIkBa paralogs in head kidney and intestine. Moreover, the OfIkBa mRNA expression in gill and liver was significantly upregulated by LPS, poly I:C and Edwardsiella tarda challenges. The transcription of OfIkBa was up-regulated in early-phase of injection and then rapidly restored. These results suggest that the OfIkBa paralogs might be involved in rapid immune responsive reactions in rock bream against bacterial and viral pathogens.

Glutathione transferase omega 1 is required for the lipopolysaccharide-stimulated induction of NADPH oxidase 1 and the production of reactive oxygen species in macrophages

Bacterial lipopolysaccharide (LPS) stimulation of macrophages and inflammation via the Toll-like receptor 4 (TLR4) signaling pathway through NF-κΒ generates reactive oxygen species (ROS) and proinflammatory cytokines such as IL-1β, IL-6, and TNFα. Because glutathione transferase Omega 1-1 (GSTO1-1) can catalyze redox reactions such as the deglutathionylation of proteins and has also been implicated in the release of IL-1β we investigated its role in the development of LPS-mediated inflammation. Our data show that shRNA knockdown of GSTO1-1 in macrophage-like J774.1A cells blocks the expression of NADPH oxidase 1 and the generation of ROS after LPS stimulation. Similar results were obtained with a GSTO1-1 inhibitor. To maintain high ROS levels during an inflammatory response, LPS stimulation causes the suppression of enzymes such as catalase and glutathione peroxidase that protect against oxidative stress. The knockdown of GSTO1-1 also attenuates this response. Our data indicate that GSTO1-1 needs to be catalytically active and mediates its effects on the LPS/TLR4 inflammatory pathway upstream of NF-κΒ. These data suggest that GSTO1-1 is a novel target for anti-inflammatory intervention.

Identification of Bruton’s tyrosine kinase as a therapeutic target in acute myeloid leukemia

Inhibition of Bruton’s tyrosine kinase is as effective in vitro against AML as chronic lymphocytic leukemia. Ibrutinib shows activity in AML because Bruton’s tyrosine kinase is constitutively active.

Regulation of IL-8 promoter activity by verrucarin A in human monocytic THP-1 cells

Macrocyclic trichothecenes have been frequently detected in fungi in water-damaged buildings and exhibited higher toxicity than the well-studied trichothecenes; however, the mechanism underlying their toxicity has been poorly understood. In this study, transcriptional regulation of the cytokine interleukin (IL)-8 by a macrocyclic trichothecene, verrucarin A (VA), in human monocytic THP-1 cells is reported. Consistent with previous findings, VA was 100-fold more cytotoxic than deoxynivalenol (DON), while ochratoxin A (OA) was not cytotoxic. In cells transduced with the wild-type IL-8 promoter luciferase construct, VA induced a biphasic dose response composed of an upregulation of luciferase expression at low concentrations of 0.01-1 ng/ml and a downregulation at high levels of 10 ng/ml and higher. In contrast, DON induced a sigmoid-shaped dose response with the EC50 of 11.6 ng/ml, while OA did not markedly affect the IL-8 expression. When cells were transduced with IL-8 promoter with a mutation of transcription factor nuclear factor-κB (NF-κB)-binding site, VA (1 ng/ml), DON (1000 ng/ml), and tumor necrosis factor (TNF) α (20 ng/ml)-induced luciferase expression were impaired. In addition, the NF-κB inhibitor caffeic acid phenethyl ester inhibited VA-, DON-, and TNFα-induced luciferase expression. Mutation of the CCAAT/enhancer-binding protein (CEBP) β binding site of the IL-8 promoter affected only DON-, but not VA- and TNFα-induced luciferase expression. Taken together, these results suggested that VA activated IL-8 promoter via an NF-κB-dependent, but not CEBPβ-dependent, pathway in human monocytes.

The high Nrf2 expression in human acute myeloid leukemia is driven by NF-κB and underlies its chemo-resistance

NF-E2-related factor 2 (Nrf2) transcription factor regulates a range of cytoprotective transcriptional responses, preventing further cellular injury by removing biochemical damage and renewing tissue. Here we show that acute myeloid leukemia (AML) cells possess greater constitutive nuclear levels of Nrf2 than normal control CD34(+) cells because of an imbalance between mRNA expression levels of Nrf2 and its inhibitor Keap1 but not through their somatic mutation. Elevated Nrf2 was reduced by NF-κB inhibitors. Using promoter assays, ChIP and siRNA knockdown, we demonstrated NF-κB subunits p50 and p65 induce transcription of Nrf2 in AML cells at a specific promoter κB-site and that long-term lentiviral miRNA-knockdown of Nrf2 significantly reduced clonogenicity of AML patient cells and improved their chemotherapeutic responsiveness. Normal physiologic Nrf2 protects cells from damage, but here we have exposed aberrant continuous nuclear activation of Nrf2 in AML that allows cell survival, even against cytotoxic chemotherapeutics. We show for the first time that Nrf2, an important regulator of several biologic processes involved in the progression of cancer, has abnormal NF-κB-driven constitutive expression in AML. Such a mechanism allows for a greater cytoprotective response in human AML cells and encourages their evasion of chemotherapy-induced cytotoxicity, which is necessary for improved clinical outcomes.

Lobolide, a diterpene, blockades the NF-κB pathway and p38 and ERK MAPK activity in macrophages in vitro

AIM

Recent studies have shown that constitutive activation of the nuclear factor κB (NF-κB) plays a key role in chronic inflammation and cancers. The aim of this study was to characterize lobolide, a cembrane diterpene, as a drug candidate targeting the NF-κB signaling pathway.

METHODS

A HEK 293/NF-κB-Luc stable cell line was constructed to evaluate the effect of lobolide on NF-κB activation. THP-1 human monocytes and peripheral blood mononuclear cells (PBMCs) from healthy volunteers were tested. Lipopolysaccharide (LPS)-induced TNFα and IL-1β production and activation of the TAK1-IKK-NF-κB pathway were studied using ELISA and Western blot analysis.

RESULTS

In HEK 293/NF-κB-Luc stable cells, lobolide (0.19-50 μmol/L) inhibited NF-κB activation in a concentration-dependent manner with an IC(50) value of 4.2 ± 0.3 μmol/L. Treatment with lobolide (2.5-10 μmol/L) significantly suppressed LPS-induced production of TNFα and IL-1β in both THP-1 cells and PBMCs. In THP-1 cells, the suppression was partially caused by blockade of the translocation of NF-κB from the cytoplasm to the nucleus via affecting the TAK1-IKK-NF-κB pathway and p38 and ERK MAPK activity.

CONCLUSION

Lobolide is a potential inhibitor of the NF-κB pathway, which blocks the translocation of NF-κB from the cytoplasm to the nucleus. Lobolide inhibits LPS-stimulated TNFα and IL-1β release, suggesting that the compound might be an anti-inflammatory compound.

It takes two to tango: IκBs, the multifunctional partners of NF-κB

The inhibitory IκB proteins have been discovered as fundamental regulators of the inducible transcription factor nuclear factor-κB (NF-κB). As a generally excepted model, stimulus-dependent destruction of inhibitory IκBs and processing of precursor molecules, both promoted by components of the signal integrating IκB kinase complex, are the key events for the release of various NF-κB/Rel dimers and subsequent transcriptional activation. Intense research of more than 20 years provides evidence that the extending family of IκBs act not simply as reversible inhibitors of NF-κB activation but rather as a complex regulatory module, which assures feedback regulation of the NF-κB system and either can inhibit or promote transcriptional activity in a stimulus-dependent manner. Thus, IκB and NF-κB/Rel family proteins establish a complex interrelationship that allows modulated NF-κB-dependent transcription, tailored to the physiological environment.

NF-κB and the link between inflammation and cancer

The nuclear factor-κB (NF-κB) transcription factor family has been considered the central mediator of the inflammatory process and a key participant in innate and adaptive immune responses. Coincident with the molecular cloning of NF-κB/RelA and identification of its kinship to the v-Rel oncogene, it was anticipated that NF-κB itself would be involved in cancer development. Oncogenic activating mutations in NF-κB genes are rare and have been identified only in some lymphoid malignancies, while most NF-κB activating mutations in lymphoid malignancies occur in upstream signaling components that feed into NF-κB. NF-κB activation is also prevalent in carcinomas, in which NF-κB activation is mainly driven by inflammatory cytokines within the tumor microenvironment. Importantly, however, in all malignancies, NF-κB acts in a cell type-specific manner: activating survival genes within cancer cells and inflammation-promoting genes in components of the tumor microenvironment. Yet, the complex biological functions of NF-κB have made its therapeutic targeting a challenge.

TNF mediates the sustained activation of Nrf2 in human monocytes

Modulation of monocyte function is a critical factor in the resolution of inflammatory responses. This role is mediated mainly by the production of TNF-α. Investigations of the actions of TNF have mostly focused on acute activation of other cell types such as fibroblasts and endothelial cells. Less is known about the effects of TNF on monocytes themselves, and little is known about the regulation of cell responses to TNF beyond the activation of NF-κB. In this study, we investigated the regulation of NF-E2-related factor 2 (Nrf2) cyctoprotective responses to TNF in human monocytes. We found that in monocytes TNF induces sustained Nrf2 activation and Nrf2 cytoprotective gene induction in a TNFR1-dependent manner. Under TNF activation, monocytes increased their expression of Nrf2-dependent genes, including NAD(P)H:quinone oxidoreductase 1 and glutamyl cysteine ligase modulatory, but not heme oxygenase-1. We also showed that autocrine TNF secretion was responsible for this sustained Nrf2 response and that Nrf2 activation by TNF was mediated by the generation of reactive oxygen species. Moreover, we showed that Nrf2-mediated gene induction can modulate TNF-induced NF-κB activation. These results show for the first time, to our knowledge, that TNF modulates prolonged Nrf2-induced gene expression, which in turn regulates TNF-induced inflammatory responses.

High basal nuclear levels of Nrf2 in acute myeloid leukemia reduces sensitivity to proteasome inhibitors

Proteasome inhibitors such as bortezomib exhibit clinical efficacy in multiple myeloma, but studies in acute myeloid leukemia (AML) have been disappointing to date. The apparent failure in AML likely reflects a lack of biological understanding that might clarify applications of proteosome inhibitors in this disease. Here we show that AML cells are considerably less sensitive than control noncancerous cells to bortezomib-induced cytotoxicity, permitting most bortezomib-treated AML cells to survive treatment. We traced reduced bortezomib sensitivity to increased basal levels of nuclear Nrf2, a transcription factor that stimulates protective antioxidant enzymes. Bortezomib stimulates cytotoxicity through accumulation of reactive oxygen species (ROS) but elevated basal levels of nuclear Nrf2 present in AML cells reduced ROS levels, permitting AML cells to survive drug treatment. We further found that the Nrf2 transcriptional repressor Bach1 is rapidly inactivated by bortezomib, allowing rapid induction of Nrf2-regulated cytoprotective and detoxification genes that protect AML cells from bortezomib-induced apoptosis. By contrast, nonmalignant control cells lacked constitutive activation of Nrf2, such that bortezomib-mediated inactivation of Bach1 led to a delay in induction of Nrf2-regulated genes, effectively preventing the manifestation of apoptotic protection that is seen in AML cells. Together, our findings argue that AML might be rendered sensitive to proteasome inhibitors by cotreatment with either an Nrf2-inhibitory or Bach1-inhibitory treatment, rationalizing a targeted therapy against AML.

Enzymatic extract from Ecklonia cava induces the activation of lymphocytes by IL-2 production through the classical NF-κB pathway

Activated nuclear factor-kappa B (NF-κB), a well-known transcription factor, leads to the development, differentiation, and proliferation of T and B lymphocytes and the secretion of cytokines by the classical pathway. We have examined here whether an enzymatic extract (ECK) from the brown seaweed, Alariaceae Laminariales Ecklonia cava may contribute to activating lymphocytes through the NF-κB pathway for participation in immune responses. In our study, ECK dose-dependently enhanced the proliferation of lymphocytes. ECK significantly increased the phosphorylation of inhibitors of κB at 0.25 and 0.5 h of exposure, followed by its gradual decrease. In addition, NF-κB p65 was gradually activated, and its binding to nuclear deoxyribonucleic acid was observed from 0.25 h after stimulation (up to 0.5 h). Further experiments showed that the application of N-p-tosyl-L: -phenylalanine chloromethyl ketone, an NF-κB inhibitor, significantly blocked ECK-induced lymphocyte's proliferation and the interleukin (IL)-2 productions. Accordingly, our results suggest that ECK increases the production of IL-2 through the activation of NF-κB then induces the proliferation of lymphocytes with the coordinated stimulation of IL-2.

NF-kappaB-inhibited acute myeloid leukemia cells are rescued from apoptosis by heme oxygenase-1 induction

Despite high basal NF-kappaB activity in acute myeloid leukemia (AML) cells, inhibiting NF-kappaB in these cells has little or no effect on inducing apoptosis. We previously showed that heme oxygenase-1 (HO-1) underlies this resistance of AML to tumor necrosis factor-induced apoptosis. Here, we describe a mechanism by which HO-1 is a silent antiapoptotic factor only revealed when NF-kappaB is inhibited, thus providing a secondary antiapoptotic mechanism to ensure AML cell survival and chemoresistance. We show that inhibition of NF-kappaB increased HO-1 expression in primary AML cells compared with that of nonmalignant cells. In addition, we observed this suppressed HO-1 level in AML cells compared with CD34(+) nonmalignant control cells. Using chromatin immunoprecipitation assay and small interfering RNA knockdown, we showed that the NF-kappaB subunits p50 and p65 control this suppression of HO-1 in AML cells. Finally, we showed that inhibition of HO-1 and NF-kappaB in combination significantly induced apoptosis in AML cells but not in noncancerous control cells. Thus, NF-kappaB inhibition combined with HO-1 inhibition potentially provides a novel therapeutic approach to treat chemotherapy-resistant forms of AML.

Therapeutic efficacy of Kangen-karyu against H2O2-induced premature senescence

The anti-aging potential of Kangen-karyu extract was investigated using the mechanisms of the cellular aging model of stress-induced premature senescence (SIPS) in TIG-1 human fibroblasts. SIPS was induced by a sublethal dose of H2O2 and chronic oxidative stress with repeat treatment of low-dose H2O2. Reactive oxygen species generation, lipid peroxidation, and senescence-associated β-galactosidase activity were elevated in TIG-1 cells under SIPS induced by H2O2. However, Kangen-karyu extract led to significant declines in these parameters, suggesting its role in ameliorating oxidative stress-related aging. It was also observed that SIPS due to H2O2 treatment led to the loss of cell viability, whereas Kangen-karyu extract improved cell viability by attenuating H2O2-induced oxidative damage. TIG-1 cells under the condition of SIPS caused by sublethal and chronic low doses of H2O2 showed nuclear factor-κB (NF-κB) translocation to the nucleus from the cytosol, while Kangen-karyu extract inhibited NF-κB nuclear translocation, implying that Kangen-karyu extract could exert an anti-aging effect through NF-κB modulation. In addition, treatment with Kangen-karyu extract under H2O2-induced chronic oxidative stress normalized the cell cycle by reducing the number of cells in the G0/G1 phase and elevating the proportion of those in the S phase, indicating the role of Kangen-karyu extract in cell cycle regulation. On the other hand, Kangen-karyu extract did not exert such an effect on cell cycle regulation under acute oxidative stress induced by sublethal H2O2. Furthermore, treatment with Kangen-karyu extract prolonged the lifespan of TIG-1 cells under SIPS. The present study suggests that Kangen-karyu might play a therapeutic role against the aging process caused by oxidative stress.

The mechanisms underlying the anti-aging activity of the Chinese prescription Kangen-karyu in hydrogen peroxide-induced human fibroblasts

Our previous study showed that Kangen-karyu extract protected against cellular senescence by reducing oxidative damage through the inhibition of reactive oxygen species generation and regulation of the antioxidative status. Although these findings suggest that Kangen-karyu could delay the aging process, the mechanisms responsible for protection against aging have rarely been elucidated. Therefore, this study was focussed on the mechanisms responsible for the anti-aging activity of Kangen-karyu extract using hydrogen peroxide (H2O2)-induced human diploid fibroblasts, a well-established experimental model of cellular aging. Kangen-karyu extract exerted a protective effect against the morphological changes induced by H2O2 treatment and inhibited senescence-associated β-galactosidase activity. In addition, the beneficial effects of Kangen-karyu extract on cell viability and lifespan indicated that Kangen-karyu extract could delay the cellular aging process. The observation that Kangen-karyu extract prevented nuclear factor kappa B (NF-κB) translocation in response to oxidative stress suggested that Kangen-karyu exerted its anti-aging effect through NF-κB modulation and prevention of H2O2-induced overexpression of haem oxygenase-1 protein. Moreover, pretreatment with Kangen-karyu extract reduced overexpression of bax protein and prevented the mitochondrial membrane potential decline, suggesting that Kangen-karyu extract may protect mitochondria from mitochondrial oxidative stress and dysfunction. These findings indicate that Kangen-karyu is a promising potential anti-aging agent that may delay, or normalize, the aging process by virtue of its protective activity against oxidative stress-related conditions.

Interaction of the IkappaBalpha C-terminal PEST sequence with NF-kappaB: insights into the inhibition of NF-kappaB DNA binding by IkappaBalpha

The transcription factor NF-kappaB (p50/p65) binds either a kappaB DNA element or its inhibitor protein, IkappaBalpha, but these two binding events are mutually exclusive. The reason for this exclusivity is not obvious from the available crystal structure data. The C-terminal PEST-like sequence of IkappaBalpha appears to be involved in the process, but it is located in both of the published X-ray structures of the IkappaBalpha/NF-kappaB complex at a significant distance away from the DNA contact loop in the NF-kappaB DNA-binding domain. We have used nuclear magnetic resonance spectroscopy and differential isotopic labeling to probe the interactions between the p50/p65 NF-kappaB heterodimer and IkappaBalpha in solution. Our measurements are able to resolve a local structural discrepancy between the two crystal structures, and we confirm that the primary interaction of the IkappaBalpha PEST domain is with the DNA-binding domain of the p65 subunit. Mutagenesis of key arginine residues in the DNA contact sequence results in the loss of specific interaction of the PEST sequence with the p65 subdomain. We conclude that the local structure of the IkappaBalpha/NF-kappaB complex in the region of the PEST sequence is consistent with a direct interaction of this acidic sequence with the basic DNA contact sequence in p65, thus reducing the affinity of NF-kappaB for DNA by a competitive mechanism that is still to be elucidated fully.

Lipopolysaccharide-induced expression of NAD(P)H:quinone oxidoreductase 1 and heme oxygenase-1 protects against excessive inflammatory responses in human monocytes

Monocytes play a central role in the immunopathological effects of sepsis. This role is mediated by production of the cytokines TNF-alpha and IL-1beta. The transcription factor NF-E2-related factor 2 (Nrf2) regulates innate immune responses in various experimental disease models. Presently, the role of Nrf2-regulated genes in LPS-treated human monocytes is not well defined. Herein we show that Nrf2 mediates a significant regulation of LPS-induced inflammatory responses. Analysis of Nrf2-regulated gene expression in human monocytes showed that LPS induced the expression of the phase II detoxification gene NAD(P)H:quinone oxidoreductase 1 (NQO1). Furthermore, NQO1 mRNA or protein expression in response to LPS was regulated by Nrf2. Silencing Nrf2 expression in human monocytes inhibited LPS-induced NQO1 expression; however, in contrast, it significantly increased TNF and IL-1beta production. Silencing expression of NQO1 alone, or in combination with heme oxygenase-1 (HO-1) silencing, markedly increased LPS-induced TNF and IL-1beta expression. Additionally, overexpression of NQO1 and/or HO-1 inhibited LPS-induced TNF and IL-1beta expression. These results show for the first time that LPS induces NQO1 and HO-1 expression in human monocytes via Nrf2 to modulate their inflammatory responsiveness, thus providing novel potential therapeutic strategies for the treatment of sepsis.

Cloning and characterization of the IkappaBalpha gene from Japanese flounder, Paralichthys olivaceus

We identified and characterized the Japanese flounder (Paralichthys olivaceus) inhibitor kappa B alpha (JFIKBA) cDNA. The JFIKBA cDNA contains an open reading frame of 960bp encoding 320 amino acid residues. JFIKBA contains 6 ankyrin repeats in the central coding region. Expression studies by RT-PCR showed constitutive expression of the JFIKBA gene in several Japanese flounder tissues (brain, muscle, gill, heart, kidney, liver, spleen and intestine). Moreover, expression of JFIKBA mRNA was induced in kidney by LPS stimulation. To investigate the role of JFIKBA, we constructed a recombinant plasmid expressing the JFIKBA coding region under the control of the cytomegalovirus (CMV) promoter. Over-expression of the JFIKBA gene in the Japanese flounder cultured cell line derived from kidney, suppressed the expression of the TNF alpha gene with lipopolysaccharide stimulation. These results indicated that JFIKBA has an important role in the innate immune system, especially in the signaling of the cytokine network.

Role of protein kinase C delta in curcumin-induced antioxidant response element-mediated gene expression in human monocytes

The Nrf2/antioxidant response element (ARE) signaling pathway plays a key role in activating cellular antioxidants, including heme oxygenase-1 (HO-1), NADPH quinone oxidoreductase-1 (NQO1), and glutathione. Protein kinase C (PKC) may also regulate these antioxidants, as PKC phosphorylates Nrf2 in vitro. This study examined the role of PKC in ARE-mediated gene regulation in human monocytes by curcumin, a potent inducer of the Nrf2/ARE pathway. Curcumin increased HO-1 and glutamyl cysteine ligase modulator (GCLM) expression and stimulated Nrf2 binding to the ARE. Curcumin also rapidly stimulated PKC phosphorylation and Ro-31-8220, a pan-PKC inhibitor, decreased curcumin-induced GCLM and HO-1 mRNA expression and ARE binding. Rottlerin (a PKC delta inhibitor) and PKC delta antisense oligonucleotides significantly inhibited curcumin-induced GCLM and HO-1 mRNA expression and ARE binding. Furthermore, a p38 MAP kinase inhibitor reduced GCLM and HO-1 expression and rottlerin inhibited curcumin-induced p38 phosphorylation. In summary, curcumin activates ARE-mediated gene expression in human monocytes via PKC delta, upstream of p38 and Nrf2.

Involvement of reactive oxygen species in cyclic stretch-induced NF-kappaB activation in human fibroblast cells

1 Uniaxial cyclic stretch leads to an upregulation of cyclooxygenase (COX)-2 through increases in the intracellular Ca(2+) concentration via the stretch-activated (SA) channel and following nuclear factor kappa B (NF-kappaB) activation in human fibroblasts. However, the signaling mechanism as to how the elevated Ca(2+) activates NF-kappaB is unknown. In this study, we examined the involvement of reactive oxygen species (ROS) as an intermediate signal, which links the elevated Ca(2+) with NF-kappaB activation. 2 4-Hydroxy-2-nonenal (HNE) was produced and modified IkappaB peaking at 2 min. The phosphorylation of IkappaB peaked at 8 min. HNE modification and IkappaB phosphorylation, NF-kappaB translocation to the nucleus, and following COX-2 production were inhibited by extracellular Ca(2+) removal or Gd(3+) application, as well as by the antioxidants. The stretch-induced Ca(2+) increase was inhibited by extracellular Ca(2+) removal, or Gd(3+) application. 3 IkappaB kinase (IKK) activity peaked at 4 min, which was inhibited by extracellular Ca(2+) removal, Gd(3+) or the antioxidants. IKK was also HNE-modified and, similarly to IkappaB, peaked at 2 min. IKK under static conditions was activated by exogenously applied HNE at a relatively low dose (1 microM), while it was inhibited at higher concentrations, suggesting that HNE could be one of the candidate signals in the stretch-induced NF-kappaB activation. 4 The present study suggests that the NF-kappaB activation by cyclic stretch is mediated by the following signal cascade: SA channel activation --> intracellular Ca(2+) increase --> production of ROS --> activation of IKK --> phosphorylation of IkappaB --> NF-kappaB translocation to the nucleus.

Lipopolysaccharide-Induced Heme Oxygenase-1 Expression in Human Monocytic Cells Is Mediated via Nrf2 and Protein Kinase C

Monocytes play a key role in mobilization of the immune response during sepsis. In response to LPS, monocytes produce both proinflammatory mediators and regulatory proteins that counteract the inflammation and oxidative stress. In murine macrophages, LPS stimulates expression of heme oxygenase 1 (HO-1), a cytoprotective enzyme that catalyzes the degradation of heme. The HO-1 5'-untranslated region, similarly to other cytoprotective genes, contains antioxidant-response elements (AREs) that can bind the transcription factor NF-E2-related factor 2 (Nrf2). At present, the role of Nrf2 in LPS-induced HO-1 expression in monocytic cells has not been investigated. In this study, LPS induced HO-1 mRNA and protein expression in human monocytes and THP-1 cells. Nrf2 translocated from the cytosol to the nucleus in response to LPS and bound to the ARE site in the human HO-1 promoter. In addition, a dominant negative Nrf2 mutant inhibited LPS-induced HO-1 mRNA expression but not TNF-alpha mRNA expression in THP-1 cells. Ro-31-8220, a pan-protein kinase C (PKC) inhibitor, and Go6976, a classical PKC inhibitor, blunted LPS-induced HO-1 mRNA expression in monocytes and THP-1 cells. Both PKC inhibitors also blocked LPS-induced Nrf2 binding to the ARE. These results indicate that LPS-induced HO-1 expression in human monocytic cells requires Nrf2 and PKC.

Functional analysis of tumor necrosis factor gene promoter from Japanese flounder, Paralichthys olivaceus, using fish cell lines

The expression vector pTNF-GFP containing the 2351 bp 5' flanking region of Japanese flounder tumor necrosis factor (TNF) gene was linked with the green fluorescence protein (GFP) gene and was introduced into YO-K cells derived from Japanese flounder kidney and HINAE cells derived Japanese flounder embryos. YO-K cells and HINAE cells were incubated with three concentrations (250, 500, 1000 microg/ml) of lipopolysaccharide (LPS) at 20 degrees C for 24 h. The number of cells expressing GFP, as well as the amount of GFP protein was increased by LPS stimulation in both cell lines. GFP mRNA transcription was also induced by LPS stimulation in both YO-K cells and HINAE cells after 1 h stimulation. In YO-K cells, expression level of GFP decreased gradually from 3 to 6 h post-stimulation, while a reverse trend was observed in HINAE cells. A deletion assay of TNF gene promoter showed that the 5' flanking region, -1783 to -1300 bp, containing cis-acting regulatory elements mediated LPS induction. An electrophoretic mobility shift assay using 2 fragments (-1783 to -1541 bp and -1540 to -1300 bp) revealed that only LPS-stimulated nuclear extracts bound to the -1540 to -1300 bp fragment. These results suggest that transcription of the TNF gene promoter in homologous cultured cells exhibited an inducible pattern and was regulated under the control of the immune system.

Akt-induced promotion of cell-cycle progression at G2/M phase involves upregulation of NF-Y binding activity in PC12 cells

Akt is a key downstream effector of the PI3K signaling pathway and plays a role in cell growth and survival. Expression of a myristoylated constitutively active form of Akt (myr-Akt) in PC12 cells could override cell-growth arrest at G2/M phase and apoptosis that were induced by etoposide treatment. On the other hand, inactivation of Akt by expression of its dominant negative mutant form (km-Akt) inhibited cell proliferation by arresting the cells at G2/M phase. Expression of myr-Akt also led to an increase in the protein and mRNA levels of CDK1 and cyclin B1. Furthermore, EMSA data revealed that expression of myr-Akt promoted the binding of NF-Y to the consensus CCAAT promoter sequence, whereas expression of km-Akt almost completely abolished it. Moreover, the Akt activity was minimal in the cells that were arrested at G2/M phase by nocodazole treatment, but reached to a maximal level as the cells progressed to mitosis and G1 phase upon removal of the drug. Treatment with Akt inhibitors, but not with those of MEK or p70S6K, blocked the release of the cells from the nocodazole-induced G2/M arrest, further revealing that the Akt activity is required for G2/M phase transition. These results suggest that Akt facilitate cell-cycle progression at G2/M phase in PC12 cells and this Akt activity is correlated with upregulation of NF-Y DNA-binding activity and cyclin B1/CDK1 gene expression.

Gonococcal porin IB activates NF-kappaB in human urethral epithelium and increases the expression of host antiapoptotic factors

Infection of human urethral epithelial cells (UECs) with Neisseria gonorrhoeae increases the transcription of several host antiapoptotic genes, including bfl-1, cox-2, and c-IAP-2. In order to identify the bacterial factor(s) responsible for eliciting these changes, the transcriptional status of apoptotic machinery was monitored in UECs challenged with certain gonococcal membrane components. Initially, we observed that infection of UECs with gentamicin-killed gonococci increased the expression of the antiapoptotic Bcl-2 family member, bfl-1. This observation indicated that viable, replicating bacteria are not required for induction of antiapoptotic gene expression. Confirming this observation, treatment of UECs with purified gonococcal membrane increased the expression of bfl-1, cox-2, and c-IAP-2. This finding suggested that a factor or multiple factors present in the outer membrane (OM) are responsible for altering UEC antiapoptotic gene expression. Interestingly, treatment of UECs with gonococcal porin IB (PorB IB), a major constituent of the OM, significantly increased the transcription of bfl-1, cox-2, and c-IAP-2. The upregulation of these genes by PorB IB was determined to be dependent on NF-kappaB activation, as inhibiting NF-kappaB blocked induced expression of these genes. This work demonstrates the altered expression of host apoptotic factors in response to gonococcal PorB IB and supports a model whereby UEC cell death may be modulated as a potential mechanism of bacterial survival and proliferation.

Celastrol inhibits pro-inflammatory cytokine secretion in Crohn's disease biopsies

Crohn's disease is a chronic intestinal inflammatory process. In modern therapy, TNF-alpha inhibition is the main goal. The aim here is to characterize the effects of Celastrol, a pentacyclic-triterpene, on the secretion of inflammatory cytokines by LPS-activated human cells. Celastrol dose-dependently inhibited the secretion of all tested pro-inflammatory cytokines with IC(50) in the nanomolar range. Effect not related to glucocorticoid receptor activity is shown by competition experiments with the steroid antagonist RU486. Celastrol inhibited the pro-inflammatory cytokine secretion from mucosal inflammatory biopsies from Crohn's disease patients. Cytometry emphasized that for all tested pro-inflammatory cytokines, CD33(+) cells are the most sensitive. Quantitative-PCR and confocal analysis on a human monocytic cell line indicated that Celastrol acts at the transcriptional level by inhibiting LPS-induced NF-kappaB translocation. Celastrol might be a putative anti-inflammatory drug in the treatment of inflammatory diseases, given its inhibition of cytokine production by intestinal biopsies from Crohn's disease patients.

Downregulation of the DNA-binding activity of nuclear factor-kappaB p65 subunit in Porphyromonas gingivalis fimbria-induced tolerance

Porphyromonas gingivalis fimbriae induce high levels of nuclear factor-kappaB (NF-kappaB)-dependent cytokine release upon primary but not secondary stimulation of monocytic cells (FimA tolerance). In this study, fimbriae induced Toll-like receptor-mediated activation of both p50 and p65 subunits of NF-kappaB upon primary cellular activation. However, activation of the transactivating p65 subunit (but not of the transcriptionally inactive p50 subunit) was significantly inhibited in fimbria-restimulated cells. Moreover, expression of a NF-kappaB-dependent reporter gene was inhibited upon secondary stimulation with fimbriae. NF-kappaB p65 downregulation may thus contribute to induction of FimA tolerance.

Induced stabilization of IkappaBalpha can facilitate its re-synthesis and prevent sequential degradation

The transcription factor NF-kappaB is responsible for regulating genes that can profoundly impact cell proliferation, apoptosis, inflammation, and immune responses. The NF-kappaB inhibitor IkappaBalpha is rapidly degraded and then re-synthesized after an NF-kappaB stimulus. We have found that the re-synthesis of IkappaBalpha in a human colon-derived cell line (HT-29) includes the post-translational stabilization of newly synthesized IkappaBalpha. The TNF-alpha-induced stabilization of newly synthesized IkappaBalpha involves the C-terminal PEST region of the protein: N-terminal deletion mutants (lacking the IkappaB kinase phosphorylation sites) were readily stabilized by TNF-alpha, whereas deletion of the C-terminus resulted in a constitutively stable protein. The role of the C-terminus in stabilization was further supported by the finding that fusion of the IkappaBalpha C-terminus to GFP generated a protein that could also be stabilized by TNF-alpha. The p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 prevented stabilization of IkappaBalpha and delayed the re-emergence of IkappaBalpha following TNF-alpha-induced degradation. The IkappaBalpha stabilization pathway could prevent sequential rounds of IkappaBalpha degradation without preventing IkappaBalpha phosphorylation. Analysis of two other cell lines (SW480 and THP-1) revealed similarities and cell-specific differences in the regulation of IkappaBalpha stabilization. We propose that cytokine stabilization of newly synthesized IkappaBalpha in some cell types is a critical homeostatic mechanism that limits inflammatory gene expression.

Gold sodium thiomalate (GSTM) inhibits lipopolysaccharide stimulated tumor necrosis factor-alpha through ceramide pathway

TNF-alpha has emerged as the major pro-inflammatory cytokine involved in the pathogenesis of rheumatoid arthritis (RA). LPS is a potent stimulator of TNF-alpha production by human monocytes. Ceramide, a structural homolog of LPS and a second messenger in the sphingomyelin signal transduction pathway has been shown to stimulate TNF-alpha production from murine macrophages. We have previously shown that GSTM, an anti-rheumatic drug inhibits LPS stimulated TNF-alpha production by normal PBMCs. We studied the ability of ceramide to stimulate TNF-alpha production by human PBMCs and the mechanism of action of GSTM on ceramide and LPS induced TNF-alpha production. LPS induced significant TNF-alpha production in PBMCs and THP-1. However, C(2) ceramide stimulated TNF-alpha production in 5 of 10 PBMCs (ceramide responder); it did not do so in the other 5 PBMCs (ceramide non-responder) or the THP-1 cell line. GSTM inhibited LPS stimulated TNF-alpha productions in PBMCs of all 5 ceramide responders both at protein and mRNA expression level. We also found that GSTM inhibited LPS induced NF-kappaB level only in ceramide responder. Thus, we for the first time report that GSTM inhibits LPS stimulated TNF-alpha production through ceramide pathway and anti-inflammatory activity of GSTM in treatment of RA may depend on its ability to inhibit NF-kappaB activation and TNF-alpha production.

Radiosensitization by overexpression of the nonphosphorylation form of IkappaB-alpha in human glioma cells

To assess the role of NF-kappaB in cellular radiosensitivity, we constructed mutated IkappaB expression plasmids for SY-IkappaB (with mutations at residues of 32, 36 and 42) expression in human malignant glioma cells (radiosensitive MO54 and radioresistant T98 cells), giving respective cell types referred to as MO54-SY4 and T98-SY14. Both of the clones expressing SY-IkappaB became radiosensitive, compared with the parental MO54 and T98 cells. A treatment with herbimycin A or genistein did not change the radiosensitivity of cells expressing SY-IkappaB, but made both the MO54 and T98 parental cells more sensitive to ionizing radiation. A treatment with TNF-alpha induced DNA fragmentation and apoptosis in cells expressing SY-IkappaB, but not in MO54 and T98 cells. The survival after X-ray exposure of the parental MO54 cells was slightly increased by a TNF-alpha treatment, but that of the parental T98 cells did not change. The change in sensitivity to ultra-violet (UV) radiation and adriamycin in MO54-SY4 cells was very similar to that for X-ray sensitivity, but no change was observed in T98-SY14 cells. Significant sublethal damage repair was observed in T98 cells, whereas MO54 cells showed little repair activity. The expression of p53 was enhanced in the parental MO54 cells, while the p53 levels in the MO54-SY4, and in the parent and clonal T98 cells, did not change. Our data suggest that the serine and tyrosine phosphorylation of IkappaB-alpha may play a role in determining the radiosensitivity of malignant glioma cells.

[The Rel/NF-kappa-B transcription factors: complex role in cell regulation]

The transcription factor NF-kappa B has attracted widespread attention among researchers. NF-kappa B displays some original characteristics including rapid regulation, the wide range of genes that it controls and its probable involvement in several diseases. In resting cells, NF-kappa B is kept in an inactive form in the cytoplasm where it is bound to a member of the I kappa B family of inhibitory proteins. NF-kappa B can be activated by exposure of cells to physiological as well as non physiological stimuli. Upon cell activation, the inhibitors are modified through site specific phosphorylations which target them for subsequent ubiquitination and proteolytic degradation by the proteasome. Removal of the inhibitor unmasks the nuclear localization signals on subunits of NF-kappa B. Free NF-kappa B moves to the nucleus where it binds to target DNA elements and activate transcription of genes encoding proteins involved in immune responses, inflammation or cell proliferation. NF-kappa B could be considered as a co-ordinating element in the body's responses to situations of stress, infection or inflammation. A tight regulation of NF-kappa B seems to be crucial since a dysfunction could promote pathogenic processes including AIDS (acquired immunodeficiency syndrome), rheumatoid arthritis and cancer. Additionally, it will be important to understand the exact roles for NF-kappa B in regulating apoptosis. NF-kappa B is now regarded as a good therapeutic target and the development of specific inhibitors should lead in the next future to novel therapeutics.

Uni-axial cyclic stretch induces the activation of transcription factor nuclear factor kappaB in human fibroblast cells

The effect of uni-axial cyclic mechanical stretch on the activation of the transcription factor nuclear factor kappaB (NF-kappaB) was investigated in a human fibroblast cell line (TIG-1). In response to uni-axial cyclic stretch, NF-kappaB was found to be translocated into the nucleus. The NF-kappaB was first detectable 2 min after the onset of stretch and then peaked at 4 min and returned to the basal level within 10 min. To investigate whether NF-kappaB is activated following the translocation into the nucleus, we measured the luciferase activity in the cells transfected with pNF-kappaB-luciferase. The activity of luciferase increased 4 min after the initiation of cyclic stretch, peaked at 15 min (6.4-fold increase), and decreased gradually. We examined the involvement of the stretch-activated (SA) channel in the stretch-induced NF-kappaB activation. The application of Gd3+, a blocker of the SA channel, or the removal of extracellular Ca2+ inhibited both the translocation into the nucleus and the activation of NF-kB, which suggests that NF-kappaB is activated by uni-axial cyclic stretch via SA channel activation in human lung fibroblasts.

p21-activated kinase-1 (PAK1) inhibition of the human scavenger receptor class B, type I promoter in macrophages is independent of PAK1 kinase activity, but requires the GTPase-binding domain

Scavenger receptor class B, type I (SR-BI), is a high density lipoprotein receptor that mediates the flux of cholesterol between high density lipoprotein and cells. Recent evidence suggests that SR-BI plays a role in atherosclerosis and that inflammatory mediators down-regulate SR-BI in the macrophage. The purpose of this study was to evaluate the ability of lipopolysaccharide (LPS) to down-regulate the activity of the human SR-BI promoter in the macrophage and to delineate the mechanisms involved. Experiments with cultured cells and in vivo derived macrophages showed that LPS has a powerful suppressive effect on SR-BI expression both in vitro and in vivo. Transient transfection studies demonstrated that LPS represses SR-BI promoter activity in the macrophage cell line RAW 264.7. Cotransfection with either a constitutively active p21-activated protein kinase-1 (PAK1) construct (T423E) or a kinase-deficient PAK1 construct (K299R) resulted in repression of the SR-BI promoter, similar to LPS. These results demonstrate that PAK1-mediated down-regulation of the SR-BI promoter is independent of PAK1 kinase activity and suggest that PAK1 mediates the LPS-induced decrease in promoter activity. Cotransfection with constitutively active Cdc42 or Rac expression constructs also resulted in down-regulation of the promoter; whereas the dominant-negative Cdc42 and Rac constructs elevated basal promoter activity and blunted the LPS response. Cotransfection of PAK1 constructs containing mutations in both the kinase domain and the Cdc42/Rac-binding domain attenuated the PAK1-mediated down-regulation of the promoter, suggesting that Rac and Cdc42 are required for PAK1-mediated decreases in SR-BI promoter activity. 5'-Deletion analysis and gel shift data suggest that LPS inhibits binding of a novel transcription factor to a myeloid zing finger protein-1-like element (-476 to -456) in the human SR-BI promoter. These results demonstrate that the PAK1 pathway down-regulates the SR-BI promoter and suggest that activation of this pathway may play an important role in cholesterol trafficking in the vessel wall.

Leukocyte integrin Mac-1 recruits toll/interleukin-1 receptor superfamily signaling intermediates to modulate NF-kappaB activity

The leukocyte integrin Mac-1 (alphaMbeta2, CD11b/CD18) regulates important cell functions in inflammation, including adhesion, phagocytosis, and oxidative burst. Deficiency of Mac-1 reduces vessel wall inflammation and neointimal thickening after murine carotid artery injury. Although Mac-1 has been implicated in modulating AP-1 and NF-kappaB activity, the signal transduction pathways involved are undefined. cDNA array analysis of Mac-1-clustered compared with -nonclustered monocytic THP-1 cells showed increased expression of the signal transducer TRAF6 (TNF receptor-associated factor 6), leading us to consider the possibility that Mac-1 used a Toll/IL-1 receptor family-like signaling pathway. Mac-1-dependent activation of NF-kappaB was potentiated by wild-type, and attenuated by dominant negative, TRAF6- and TGF-beta-activated kinase (TAK1) constructs. IRAK1 (IL-1 receptor associated kinase), a kinase immediately upstream of TRAF6, coimmunoprecipitated with Mac-1. Taken together, these observations indicate that Mac-1 recruits a Toll/IL-1 receptor family-like cascade to modulate NF-kappaB activity. This represents a new pathway for integrin-dependent modulation of gene expression.

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors upregulate inducible NO synthase expression and activity in vascular smooth muscle cells

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase ameliorate atherosclerosis by both cholesterol-dependent and cholesterol-independent mechanisms. We examined whether HMG-CoA reductase inhibitors affect the expression and activity of inducible NO synthase (iNOS) in cultured rat aortic vascular smooth muscle (VSM) cells. Atorvastatin (34 to 68 micromol/L) markedly increased nitrite production, an increase that was essentially abrogated by the NO synthase inhibitor N(G)-monomethyl-L-arginine (500 micromol/L). Activity of iNOS, determined by the conversion of L-arginine to L-citrulline, increased 9-fold after atorvastatin treatment. Western blot and semiquantitative reverse transcriptase-polymerase chain reaction revealed that atorvastatin (34 to 68 micromol/L) strongly upregulated iNOS protein and mRNA levels, respectively. These concentrations of atorvastatin did not cause cytotoxicity, as judged by the cell survival rate. Similarly, simvastatin and lovastatin (34 micromol/L) caused robust upregulation of the iNOS protein level. Transfection experiments demonstrated that the -1034- to 88-bp human iNOS promoter was strongly induced by atorvastatin (34 micromol/L). Electromobility and supershift assays using a nuclear factor-kappaB (NF-kappaB) consensus oligonucleotide and nuclear extracts from VSM cells as well as transfection studies using an NF-kappaB reporter plasmid suggested that the transcriptional activation of the iNOS gene by atorvastatin is not mediated via the NF-kappaB pathway. We conclude that HMG-CoA reductase inhibitors potently upregulate iNOS expression and activity in VSM cells, at least in part, by transcriptional mechanisms that do not depend on transcription factor NF-kappaB. These effects might have important implications for the impact of HMG-CoA reductase inhibitors on atherosclerosis.

Hydrogen peroxide-mediated inhibition of lipopolysaccharide-stimulated inhibitory kappa B kinase activity in rat aortic smooth muscle cells

1. In rat aortic smooth muscle cells (RASMC), exposure to lipopolysaccharide (LPS) resulted in NF-kappaB-DNA binding, degradation of IkappaB-alpha, -beta and -epsilon and increased activity of both alpha and beta isoforms of inhibitory kappa B kinase (IKK). 2. Expression of dominant-negative (DN)-IKK-alpha, IKK-beta and NF-kappaB-inducing kinase (NIK) abolished LPS-stimulated NF-kappaB reporter activity, suggesting that activation of a NIK/IKK-dependent pathway is indispensable for NF-kappaB activation by LPS in this cell type. 3. The tyrosine phosphatase inhibitor, pervanadate, abolished LPS-stimulated NF-kappaB-DNA-binding activity. However, the effect of pervanadate was shown to be mediated by excess hydrogen peroxide (H(2)O(2)) present in the reaction mix. Preincubation of RASMC with H(2)O(2) inhibited LPS-stimulated IKK kinase activity and downstream NF-kappaB-DNA binding activity. 4. H(2)O(2) also strongly stimulated p38 MAP kinase activity in RASMCs. Effective inhibition of this pathway using SB203580 did not reverse the effects of H(2)O(2) on LPS-stimulated IKK/NF-kappaB signalling. 5. These studies show that hydrogen peroxide-mediated inhibition of LPS-stimulated NF-kappaB activation in RASMC occurs upstream of IKK. The inhibitory effect of H(2)O(2) is not due to tyrosine phosphatase inhibition, it is mediated by H(2)O(2) through a mechanism which is independent of any cross-talk involving MAP kinase homologues.