Regulation of the RelA (p65) transactivation domain

The Generation of ROS by Exposure to Trihalomethanes Promotes the IκBα/NF-κB/p65 Complex Dissociation in Human Lung Fibroblast

Background: Disinfection by-products used to obtain drinking water, including halomethanes (HMs) such as CH2Cl2, CHCl3, and BrCHCl2, induce cytotoxicity and hyperproliferation in human lung fibroblasts (MRC-5). Enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) modulate these damages through their biotransformation processes, potentially generating toxic metabolites. However, the role of the oxidative stress response in cellular hyperproliferation, modulated by nuclear factor-kappa B (NF-κB), remains unclear. Methods: In this study, MRC-5 cells were treated with these compounds to evaluate reactive oxygen species (ROS) production, lipid peroxidation, phospho-NF-κB/p65 (Ser536) levels, and the activities of SOD, CAT, and GPx. Additionally, the interactions between HMs and ROS with the IκBα/NF-κB/p65 complex were analyzed using molecular docking. Results: Correlation analysis among biomarkers revealed positive relationships between pro-oxidant damage and antioxidant responses, particularly in cells treated with CH2Cl2 and BrCHCl2. Conversely, negative relationships were observed between ROS levels and NF-κB/p65 levels in cells treated with CH2Cl2 and CHCl3. The estimated relative free energy of binding using thermodynamic integration with the p65 subunit of NF-κB was -3.3 kcal/mol for BrCHCl2, -3.5 kcal/mol for both CHCl3 and O2•, and -3.6 kcal/mol for H2O2. Conclusions: Chloride and bromide atoms were found in close contact with IPT domain residues, particularly in the RHD region involved in DNA binding. Ser281 is located within this domain, facilitating the phosphorylation of this protein. Similarly, both ROS interacted with the IPT domain in the RHD region, with H2O2 forming a side-chain oxygen interaction with Leu280 adjacent to the phosphorylation site of p65. However, the negative correlation between ROS and phospho-NF-κB/p65 suggests that steric hindrance by ROS on the C-terminal domain of NF-κB/p65 may play a role in the antioxidant response.

The role of actin cytoskeleton CFL1 and ADF/cofilin superfamily in inflammatory response

Actin remodeling proteins are important in immune diseases and regulate cell cytoskeletal responses. These responses play a pivotal role in maintaining the delicate balance of biological events, protecting against acute or chronic inflammation in a range of diseases. Cofilin (CFL) and actin depolymerization factor (ADF) are potent actin-binding proteins that cut and depolymerize actin filaments to generate actin cytoskeleton dynamics. Although the molecular mechanism by which actin induces actin cytoskeletal reconstitution has been studied for decades, the regulation of actin in the inflammatory process has only recently become apparent. In this paper, the functions of the actin cytoskeleton and ADF/cofilin superfamily members are briefly introduced, and then focus on the role of CFL1 in inflammatory response.

Targeted transcriptional upregulation of SENP1 by CRISPR activation enhances deSUMOylation pathways to elicit antinociception in the spinal nerve ligation model of neuropathic pain

ABSTRACT

The voltage-gated sodium channel Na V 1.7 is an essential component of human pain signaling. Changes in Na V 1.7 trafficking are considered critical in the development of neuropathic pain. SUMOylation of collapsin response mediator protein 2 (CRMP2) regulates the membrane trafficking and function of Na V 1.7. Enhanced CRMP2 SUMOylation in neuropathic pain correlates with increased Na V 1.7 activity. Pharmacological and genetic interventions that interfere with CRMP2 SUMOylation in rodents with neuropathic pain have been shown to reverse mechanical allodynia. Sentrin or SUMO-specific proteases (SENPs) are vital for balancing SUMOylation and deSUMOylation of substrates. Overexpression of SENP1 and/or SENP2 in CRMP2-expressing cells results in increased deSUMOylation and decreased membrane expression and currents of Na V 1.7. Although SENP1 is present in the spinal cord and dorsal root ganglia, its role in regulating Na V 1.7 function and pain is not known. We hypothesized that favoring SENP1 expression can enhance CRMP2 deSUMOylation to modulate Na V 1.7 channels. In this study, we used a clustered regularly interspaced short palindromic repeats activation (CRISPRa) SENP1 lentivirus to overexpress SENP1 in dorsal root ganglia neurons. We found that SENP1 lentivirus reduced CRMP2 SUMOylation, Na V 1.7-CRMP2 interaction, and Na V 1.7 membrane expression. SENP1 overexpression decreased Na V 1.7 currents through clathrin-mediated endocytosis, directly linked to CRMP2 deSUMOylation. Moreover, enhancing SENP1 expression did not affect the activity of TRPV1 channels or voltage-gated calcium and potassium channels. Intrathecal injection of CRISPRa SENP1 lentivirus reversed mechanical allodynia in male and female rats with spinal nerve injury. These results provide evidence that the pain-regulating effects of SENP1 overexpression involve, in part, the modulation of Na V 1.7 channels through the indirect mechanism of CRMP2 deSUMOylation.

CRISPR/dCas9 Tools: Epigenetic Mechanism and Application in Gene Transcriptional Regulation

CRISPR/Cas9-mediated cleavage of DNA, which depends on the endonuclease activity of Cas9, has been widely used for gene editing due to its excellent programmability and specificity. However, the changes to the DNA sequence that are mediated by CRISPR/Cas9 affect the structures and stability of the genome, which may affect the accuracy of results. Mutations in the RuvC and HNH regions of the Cas9 protein lead to the inactivation of Cas9 into dCas9 with no endonuclease activity. Despite the loss of endonuclease activity, dCas9 can still bind the DNA strand using guide RNA. Recently, proteins with active/inhibitory effects have been linked to the end of the dCas9 protein to form fusion proteins with transcriptional active/inhibitory effects, named CRISPRa and CRISPRi, respectively. These CRISPR tools mediate the transcription activity of protein-coding and non-coding genes by regulating the chromosomal modification states of target gene promoters, enhancers, and other functional elements. Here, we highlight the epigenetic mechanisms and applications of the common CRISPR/dCas9 tools, by which we hope to provide a reference for future related gene regulation, gene function, high-throughput target gene screening, and disease treatment.

Critical Role of Novel O-GlcNAcylation of S550 and S551 on the p65 Subunit of NF-κB in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, with a mere 5-year survival of ~10%. This highlights the urgent need for innovative treatment options for PDAC patients. The nuclear factor κB (NF-κB) is a crucial transcription factor that is constitutively activated in PDAC. It mediates the transcription of oncogenic and inflammatory genes that facilitate multiple PDAC phenotypes. Thus, a better understanding of the mechanistic underpinnings of NF-κB activation holds great promise for PDAC diagnosis and effective therapeutics. Here, we report a novel finding that the p65 subunit of NF-κB is O-GlcNAcylated at serine 550 and 551 upon NF-κB activation. Importantly, the overexpression of either serine-to-alanine (S-A) single mutant (S550A or S551A) or double mutant (S550A/S551A) of p65 in PDAC cells impaired NF-κB nuclear translocation, p65 phosphorylation, and transcriptional activity, independent of IκBα degradation. Moreover, the p65 mutants downregulate a category of NF-κB-target genes, which play a role in perpetuating major cancer hallmarks. We further show that overexpression of the p65 mutants inhibited cellular proliferation, migration, and anchorage-independent growth of PDAC cells compared to WT-p65. Collectively, we discovered novel serine sites of p65 O-GlcNAcylation that drive NF-κB activation and PDAC phenotypes, thus opening new avenues by inhibiting the NF-κB O-GlcNAcylation enzyme, O-GlcNAc transferase (OGT), for PDAC treatment in the future.

Regulation of CHK1 inhibitor resistance by a c-Rel and USP1 dependent pathway

Previously, we discovered that deletion of c-Rel in the Eµ-Myc mouse model of lymphoma results in earlier onset of disease, a finding that contrasted with the expected function of this NF-κB subunit in B-cell malignancies. Here we report that Eµ-Myc/cRel-/- cells have an unexpected and major defect in the CHK1 pathway. Total and phospho proteomic analysis revealed that Eµ-Myc/cRel-/- lymphomas highly resemble wild-type (WT) Eµ-Myc lymphomas treated with an acute dose of the CHK1 inhibitor (CHK1i) CCT244747. Further analysis demonstrated that this is a consequence of Eµ-Myc/cRel-/- lymphomas having lost expression of CHK1 protein itself, an effect that also results in resistance to CCT244747 treatment in vivo. Similar down-regulation of CHK1 protein levels was also seen in CHK1i resistant U2OS osteosarcoma and Huh7 hepatocellular carcinoma cells. Further investigation revealed that the deubiquitinase USP1 regulates CHK1 proteolytic degradation and that its down-regulation in our model systems is responsible, at least in part, for these effects. We demonstrate that treating WT Eµ-Myc lymphoma cells with the USP1 inhibitor ML323 was highly effective at reducing tumour burden in vivo. Targeting USP1 activity may thus be an alternative therapeutic strategy in MYC-driven tumours.

Interleukin-10 Deficiency Impacts on TNF-Induced NFκB Regulated Responses In Vivo

Interleukin-10 (IL-10) is an anti-inflammatory cytokine that has a major protective role against intestinal inflammation. We recently revealed that intestinal epithelial cells in vitro regulate NFκB-driven transcriptional responses to TNF via an autocrine mechanism dependent on IL-10 secretion. Here in this study, we investigated the impact of IL-10 deficiency on the NFκB pathway and its downstream targets in the small intestinal mucosa in vivo. We observed dysregulation of TNF, IκBα, and A20 gene and protein expression in the small intestine of steady-state or TNF-injected Il10-/- mice, compared to wild-type C57BL6/J counterparts. Upon TNF injection, tissue from the small intestine showed upregulation of NFκB p65[RelA] activity, which was totally diminished in Il10-/- mice and correlated with reduced levels of TNF, IκBα, and A20 expression. In serum, whilst IgA levels were noted to be markedly downregulated in IL-10-deficient- mice, normal levels of mucosal IgA were seen in intestine mucosa. Importantly, dysregulated cytokine/chemokine levels were observed in both serum and intestinal tissue lysates from naïve, as well as TNF-injected Il10-/- mice. These data further support the importance of the IL-10-canonical NFκB signaling pathway axis in regulating intestinal mucosa homeostasis and response to inflammatory triggers in vivo.

ROR activation by Nobiletin enhances antitumor efficacy via suppression of IκB/NF-κB signaling in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous disease characterized by poor response to standard therapies and therefore unfavorable clinical outcomes. Better understanding of TNBC and new therapeutic strategies are urgently needed. ROR nuclear receptors are multifunctional transcription factors with important roles in circadian pathways and other processes including immunity and tumorigenesis. Nobiletin (NOB) is a natural compound known to display anticancer effects, and our previous studies showed that NOB activates RORs to enhance circadian rhythms and promote physiological fitness in mice. Here, we identified several TNBC cell lines being sensitive to NOB, by itself or in combination. Cell and xenograft experiments showed that NOB significantly inhibited TNBC cell proliferation and motility in vitro and in vivo. ROR loss- and gain-of-function studies showed concordant effects of the NOB–ROR axis on MDA-MB-231 cell growth. Mechanistically, we found that NOB activates ROR binding to the ROR response elements (RRE) of the IκBα promoter, and NOB strongly inhibited p65 nuclear translocation. Consistent with transcriptomic analysis indicating cancer and NF-κB signaling as major pathways altered by NOB, p65-inducible expression abolished NOB effects, illustrating a requisite role of NF-κB suppression mediating the anti-TNBC effect of NOB. Finally, in vivo mouse xenograft studies showed that NOB enhanced the antitumor efficacy in mammary fat pad implanted TNBC, as a single agent or in combination with the chemotherapy agent Docetaxel. Together, our study highlights an anti-TNBC mechanism of ROR-NOB via suppression of NF-κB signaling, suggesting novel preventive and chemotherapeutic strategies against this devastating disease.

Effects of Human RelA Transgene on Murine Macrophage Inflammatory Responses

The NFκB transcription factors are major regulators of innate immune responses, and NFκB signal pathway dysregulation is linked to inflammatory disease. Here, we utilised bone marrow-derived macrophages from the p65-DsRedxp/IκBα-eGFP transgenic strain to study the functional implication of xenogeneic (human) RelA(p65) protein introduced into the mouse genome. Confocal imaging showed that human RelA is expressed in the cells and can translocate to the nucleus following activation of Toll-like receptor 4. RNA sequencing of lipid A-stimulated macrophages, revealed that human RelA impacts on murine gene transcription, affecting both non-NFκB and NFκB target genes, including immediate-early and late response genes, e.g., Fos and Cxcl10. Validation experiments on NFκB targets revealed markedly reduced mRNA levels, but similar kinetic profiles in transgenic cells compared to wild-type. Enrichment pathway analysis of differentially expressed genes revealed interferon and cytokine signaling were affected. These immune response pathways were also affected in macrophages treated with tumor necrosis factor. Data suggests that the presence of xenogeneic RelA protein likely has inhibitory activity, altering specific transcriptional profiles of key molecules involved in immune responses. It is therefore essential that this information be taken into consideration when designing and interpreting future experiments using this transgenic strain.

Dissecting the Regulatory Strategies of NF-κB RelA Target Genes in the Inflammatory Response Reveals Differential Transactivation Logics

Nuclear factor κB (NF-κB) RelA is the potent transcriptional activator of inflammatory response genes. We stringently defined a list of direct RelA target genes by integrating physical (chromatin immunoprecipitation sequencing [ChIP-seq]) and functional (RNA sequencing [RNA-seq] in knockouts) datasets. We then dissected each gene’s regulatory strategy by testing RelA variants in a primary-cell genetic-complementation assay. All endogenous target genes require RelA to make DNA-base-specific contacts, and none are activatable by the DNA binding domain alone. However, endogenous target genes differ widely in how they employ the two transactivation domains. Through model-aided analysis of the dynamic time-course data, we reveal the gene-specific synergy and redundancy of TA1 and TA2. Given that post-translational modifications control TA1 activity and intrinsic affinity for coactivators determines TA2 activity, the differential TA logics suggests context-dependent versus context-independent control of endogenous RelA-target genes. Although some inflammatory initiators appear to require co-stimulatory TA1 activation, inflammatory resolvers are a part of the NF-κB RelA core response.

Ngo et al. developed a genetic complementation system for NF-κB RelA that reveals that NF-κB target-gene selection requires high-affinity RelA binding and transcriptional activation domains for gene induction. The synergistic and redundant functions of two transactivation domains define pro-inflammatory and inflammation-response genes.

BVDV-1 induces interferon-beta gene expression through a pathway involving IRF1, IRF7, and NF-κB activation

The bovine viral diarrhea virus (BVDV-1) is a pathogen with the capacity to modulate the interferon type I system. To further investigate the effects of BVDV-1 on the production of the immune response, the Madin-Darby bovine kidney cell line was infected with the cytopathic CH001 field isolate of BVDV-1, and the IFNbeta expression profiles were analyzed. The results showed that cpBVDV-1 was able to induce the production of IFNbeta in a way similar to polyinosinic-polycytidylic acid, but with less intensity. Interestingly, all cpBVDV-1 activities were blocked by pharmacological inhibitors of the IRF-1, IRF-7, and NF-κB signaling pathway, and the level of IFNbeta decreased at the level of transcript and protein. These results, together with in silico analyses showing the presence of several regulatory consensus target motifs, suggest that cpBVDV-1 regulates IFNbeta expression in bovines through the activation of several key transcription factors. Collectively, the results suggest that during cpBVDV-1 infection, cross talk is evident between various signaling pathways involved in transcriptional activation of IFNbeta in cattle.

Comprehensive Targeted Sequencing Identifies Monogenic Disorders in Patients With Early-onset Refractory Diarrhea

OBJECTIVES

Causes of early-onset refractory diarrhea include exudative diarrhea associated with very early-onset inflammatory bowel diseases, osmotic or secretory diarrhea, and protein-losing enteropathy. Monogenic disorders are included in these diseases, yet a comprehensive genetic analysis has not been fully established.

METHODS

We established targeted gene panels covering all responsible genes for early-onset diarrhea. In total, 108 patients from 15 institutions were enrolled in this study. We collected clinical data from all patients. Seventy-three patients with exudative diarrhea, 4 with osmotic or secretory diarrhea and 8 with protein-losing enteropathy were subjected to genetic analysis.

RESULTS

A total of 15 out of the 108 enrolled patients (13.9%) were identified as monogenic. We identified 1 patient with RELA, 2 with TNFAIP3, 1 with CTLA4, 1 with SLCO2A1, 4 with XIAP, 3 with IL10RA, 1 with HPS1, 1 with FOXP3, and 1 with CYBB gene mutations. We also identified 1 patient with NFKB2 and 1 with TERT mutations from the gene panel for primary immunodeficiency syndromes. The patient with refractory diarrhea caused by heterozygous truncated RelA protein expression is the first case identified worldwide, and functional analysis revealed that the mutation affected nuclear factor kappa B signaling. Genotypes were significantly associated with the clinical and pathological findings in each patient.

CONCLUSIONS

We identified variable monogenic diseases in the patients and found that genes responsible for primary immunodeficiency diseases were frequently involved in molecular pathogenesis. Comprehensive genetic analysis was useful for accurate molecular diagnosis, understanding of underlying pathogenesis, and selecting the optimal treatment for patients with early-onset refractory diarrhea.An infographic for this article is available at: http://links.lww.com/MPG/B853.

Maturation of the Acute Hepatic TLR4/NF-κB Mediated Innate Immune Response Is p65 Dependent in Mice

Compared to adults, neonates are at increased risk of infection. There is a growing recognition that dynamic qualitative and quantitative differences in immunity over development contribute to these observations. The liver plays a key role as an immunologic organ, but whether its contribution to the acute innate immune response changes over lifetime is unknown. We hypothesized that the liver would activate a developmentally-regulated acute innate immune response to intraperitoneal lipopolysaccharide (LPS). We first assessed the hepatic expression and activity of the NF-κB, a key regulator of the innate immune response, at different developmental ages (p0, p3, p7, p35, and adult). Ontogeny of the NF-κB subunits (p65/p50) revealed a reduction in Rela (p65) and Nfkb1 (p105, precursor to p50) gene expression (p0) and p65 subunit protein levels (p0 and p3) vs. older ages. The acute hepatic innate immune response to LPS was associated by the degradation of the NF-κB inhibitory proteins (IκBα and IκBβ), and nuclear translocation of the NF-κB subunit p50 in all ages, whereas nuclear translocation of the NF-κB subunit p65 was only observed in the p35 and adult mouse. Consistent with these findings, we detected NF-κB subunit p65 nuclear staining exclusively in the LPS-exposed adult liver compared with p7 mouse. We next interrogated the LPS-induced hepatic expression of pro-inflammatory genes (Tnf, Icam1, Ccl3, and Traf1), and observed a gradually increase in gene expression starting from p0. Confirming our results, hepatic NF-κB subunit p65 nuclear translocation was associated with up-regulation of the Icam1 gene in the adult, and was not detected in the p7 mouse. Thus, an inflammatory challenge induces an NF-κB-mediated hepatic innate immune response activation across all developmental ages, but nuclear translocation of the NF-κB subunit p65 and associated induction of pro-inflammatory genes occurred only after the first month of life. Our results demonstrate that the LPS-induced hepatic innate immune response is developmentally regulated by the NF-κB subunit p65 in the mouse.

Safrole-induced expression of proinflammatory responses is associated with phosphorylation of mitogen-activated protein kinase family and the nuclear factor-κB/inhibitor of κB pathway in macrophages

Objective:

Safrole, also called shikimol and Sassafras, is the carcinogenic and phenylpropanoid compound extracted from Sassafras tree and anise, betel, and camphor. Moreover, a high concentration of safrole can be occur in the saliva because of betel nut or areca quid chewing which a common habit observed in Southern and Southeastern Asia. Notably, macrophages are crucial phagocytic cells of the immune system. Nonetheless, to date, no evidence has been reported regarding safrole-induced proinflammatory response and the corresponding mechanism in macrophages.

Materials and Methods:

In the present study, the cytokines expression, NO generation, protein phosphorylation, and expression were assessed by enzyme-linked immunosorbent assay, Griess reagent, and Western blot assay, respectively.

Results:

In this study, we determined that safrole induces the generation of nitric oxide and proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and IL-6 in RAW264.7 macrophages in a concentration-dependent manner. Furthermore, inhibitor of κB (IκB) degradation was caused by safrole in a concentration-dependent manner. In addition, the phosphorylation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK) family, including p38 MAPK, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase, was induced by safrole began to increase at 10 μM and attained a plateau at 100 μM.

Conclusion:

These results indicated that safrole induces the expression of proinflammatory responses in macrophages through the NF-κB/IκB pathway and its upstream factor, MAPK family phosphorylation.

Small Molecule NF-κB Pathway Inhibitors in Clinic

Nuclear factor kappa B (NF-κB) signaling is implicated in all major human chronic diseases, with its role in transcription of hundreds of gene well established in the literature. This has propelled research into targeting the NF-κB pathways for modulating expression of those genes and the diseases mediated by them. In-spite of the critical, but often promiscuous role played by this pathway and the inhibition causing adverse drug reaction, currently many biologics, macromolecules, and small molecules that modulate this pathway are in the market or in clinical trials. Furthermore, many marketed drugs that were later found to also have NF-κB targeting activity were repurposed for new therapeutic interventions. Despite the rising importance of biologics in drug discovery, small molecules got around 76% of US-FDA (Food and Drug Administration-US) approval in the last decade. This encouraged us to review information regarding clinically relevant small molecule inhibitors of the NF-κB pathway from cell surface receptor stimulation to nuclear signaling. We have also highlighted the underexplored targets in this pathway that have potential to succeed in clinic.

Rosiglitazone Improves Glucocorticoid Resistance in a Sudden Sensorineural Hearing Loss by Promoting MAP Kinase Phosphatase-1 Expression

In this study, we investigated the role of MAP kinase phosphatase-1 (MKP-1) and rosiglitazone (RSG) in glucocorticoid resistance and glucocorticoid sensitivity, respectively, using a guinea pig model of lipopolysaccharide- (LPS-) induced sudden sensorineural hearing loss (SSHL). The pigs were divided into control, LPS, LPS+dexamethasone (DEX), LPS+RSG, and LPS+DEX+RSG groups. Their hearing was screened by auditory brainstem response measurement. Immunofluorescence staining was used to identify the location of MKP-1 in the inner ear. The expression levels of MKP-1 and the related proteins in the inner ear were detected using western blotting. The morphological changes in the cochlea were observed via hematoxylin-eosin staining. Severe hearing loss was observed in the LPS group, as opposed to the protection from hearing loss observed in the LPS+DEX+RSG group. A positive correlation was observed between MKP-1 expression levels and protection from hearing loss. RSG and DEX synergistically influenced inner ear inflammation. In conclusion, resistance of LPS-induced SSHL guinea pig models to glucocorticoids may result from impaired MKP-1 function in inner ear tissues, induced by glucocorticoids, impairing the inhibition of inflammation. Our findings present novel targets to develop potential therapeutics to treat inflammatory diseases of the inner ear.

Considering Abundance, Affinity, and Binding Site Availability in the NF-κB Target Selection Puzzle

The NF-κB transcription regulation system governs a diverse set of responses to various cytokine stimuli. With tools from in vitro biochemical characterizations, to omics-based whole genome investigations, great strides have been made in understanding how NF-κB transcription factors control the expression of specific sets of genes. Nonetheless, these efforts have also revealed a very large number of potential binding sites for NF-κB in the human genome, and a puzzle emerges when trying to explain how NF-κB selects from these many binding sites to direct cell-type- and stimulus-specific gene expression patterns. In this review, we surmise that target gene transcription can broadly be thought of as a function of the nuclear abundance of the various NF-κB dimers, the affinity of NF-κB dimers for the regulatory sequence and the availability of this regulatory site. We use this framework to place quantitative information that has been gathered about the NF-κB transcription regulation system into context and thus consider questions it answers, and questions it raises. We end with a brief discussion of some of the future prospects that new approaches could bring to our understanding of how NF-κB transcription factors orchestrate diverse responses in different biological contexts.

Bioinformatics Based Therapeutic Effects of Sinomenium Acutum

OBJECTIVE

To decipher the possible mechanisms of Sinomenium Acutum (SA) in treating diseases by a bioinformatics method.

METHODS

SA ingredients were searched according to Chinese Pharmacopoeia, Chinese Medicine Dictionary and Traditional Chinese Medicines Database (TCMD). Active compounds and target proteins of SA were acquired through the Pubchem platform. Pathway, network and function analyses of SA were performed with ingenuity pathway analysis (IPA), a bioinformatics analysis platform. Disease, biofunction-target networks were established with Cytoscape.

RESULTS

Eighteen ingredients from SA were obtained. Seven active ingredients with 31 active target proteins were acquired according to PubChem Bioassay test. By IPA analysis, 277 canonical pathways belonging to 17 function categories were collected, 23 kinds of diseases, 21 categories bio-functions were obtained. Based on P value, calculated by IPA, the top 5 significant pathway of SA targets include phosphatidylinositol 3 kinase/Akt (PI3K/Akt) signaling, prostate cancer signaling, macrophage migration inhibitory factor (MIF) regulation of innate immunity, Guanosine-binding protein coupled receptor (GPCR) signaling, and ataxia telangiectasia mutated protein (ATM) signaling. Disease and bio-function network analysis indicated that mitogen activated protein kinase 1 (MAPK1), MAPK3, p65 nuclear factor κB (RELA), nuclear factor of κB inhibitor alpha (NFκBIA), interleukin 1β(IL-1β), prostaglandin G/H synthase 2 (PTGS2) and tumor protein 53 (TP53) were the critical targets in various diseases treated by SA.

CONCLUSION

In the different view of target, pathway, disease and bio-function, inflammation was found to be a central theme in many chronic conditions. SA could be used not only as an anti-inflammatory agent, but also for the treatment of cancers, neurological diseases, psychological disorders and metabolic diseases.

Mechanisms of NF-κB p65 and strategies for therapeutic manipulation

The transcription factor NF-κB is a critical regulator of immune and inflammatory responses. In mammals, the NF-κB/Rel family comprises five members: p50, p52, p65 (Rel-A), c-Rel, and Rel-B proteins, which form homo- or heterodimers and remain as an inactive complex with the inhibitory molecules called IκB proteins in resting cells. Two distinct NF-κB signaling pathways have been described: 1) the canonical pathway primarily activated by pathogens and inflammatory mediators, and 2) the noncanonical pathway mostly activated by developmental cues. The most abundant form of NF-κB activated by pathologic stimuli via the canonical pathway is the p65:p50 heterodimer. Disproportionate increase in activated p65 and subsequent transactivation of effector molecules is integral to the pathogenesis of many chronic diseases such as the rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and even neurodegenerative pathologies. Hence, the NF-κB p65 signaling pathway has been a pivotal point for intense drug discovery and development. This review begins with an overview of p65-mediated signaling followed by discussion of strategies that directly target NF-κB p65 in the context of chronic inflammation.

Nuclear factor-kappa B: Glucocorticoid-induced leucine zipper interface analogs suppress pathology in an Alzheimer's disease model

INTRODUCTION

Glucocorticoid-induced leucine zipper is a regulatory protein that sequesters activated nuclear factor-kappa B p65. Previously, we showed that rationally designed analogs of the p65-binding domain of glucocorticoid-induced leucine zipper, referred to as glucocorticoid-induced leucine zipper analogs (GAs), inhibited amyloid β-induced metabolic activity and inflammatory cytokines in mixed brain cell cultures. Here, we investigate the therapeutic efficacy of GA in an Alzheimer's disease model.

METHODS

GA and control peptides were synthesized covalently as peptide amides with the cell-penetrating agent. C57Bl/6J mice induced with lipopolysaccharide-mediated neuroinflammation (250 mg/kg i.p/day for six days) were treated on alternate days with GA-1, GA-2, or control peptides (25 mg/kg i.v). Brain tissues were assessed for gliosis, cytokines, and antiapoptotic factors.

RESULTS

The brain tissues of GA-1- and GA-2-treated mice exhibited significantly reduced gliosis, suppressed inflammatory cytokines, and elevated antiapoptotic factors.

DISCUSSION

The antineuroinflammatory effects of GA suggest potential therapeutic application for Alzheimer's disease.

Role of the NFκB-signaling pathway in cancer

Cancer is a group of cells that malignantly grow and proliferate uncontrollably. At present, treatment modes for cancer mainly comprise surgery, chemotherapy, radiotherapy, molecularly targeted therapy, gene therapy, and immunotherapy. However, the curative effects of these treatments have been limited thus far by specific characteristics of tumors. Abnormal activation of signaling pathways is involved in tumor pathogenesis and plays critical roles in growth, progression, and relapse of cancers. Targeted therapies against effectors in oncogenic signaling have improved the outcomes of cancer patients. NFκB is an important signaling pathway involved in pathogenesis and treatment of cancers. Excessive activation of the NFκB-signaling pathway has been documented in various tumor tissues, and studies on this signaling pathway for targeted cancer therapy have become a hot topic. In this review, we update current understanding of the NFκB-signaling pathway in cancer.

Prognostic value of expression of nuclear factor kappa-B/p65 in non-GCB DLBCL patients

Purpose

We estimated the expression of nuclear factor kappa B/p65 in non-germinal center B-cell-like subtype diffuse large B-cell lymphoma, to investigate its relationship to clinicopathological features, and to further evaluate its prognostic value and clarify its impact on survival.

Results

Among the 49 patients enrolled in this study, 14 (28.6%) had positive p65 expression. The negative p65 group had significantly better survival compared to the positive p65 group in terms of both the 3-year estimated OS (91.2% vs. 39.3%, p = 0.003) and PFS (75.6% vs. 26.5%, p = 0.002). In patients with 4 or more risk factors, p65 was an independent prognostic factor of OS (HR 5.99, 95%CI=1.39-25.75, p=0.016) and PFS (HR 4.01, 95%CI=1.15-14.00, p=0.029).

Materials and Methods

The expression of the NF-κB/p65 protein was deteremined by immunohistochemistry in 49 non-GCB DLBCL. Survival was assessed by the Kaplan–Meier method and Cox multivariate analysis. The median patient follow-up period was 24 months.

Conclusions

The expression of NF-κB/p65 has prognostic value in high risk non-GCB DLBCL, and it is a suitable target for the development of new therapies.

Structural characterization of interactions between transactivation domain 1 of the p65 subunit of NF-κB and transcription regulatory factors

p65 is a member of the NF-κB family of transcriptional regulatory proteins that functions as the activating component of the p65-p50 heterodimer. Through its acidic transactivation domain (TAD), p65 has the capacity to form interactions with several different transcriptional regulatory proteins, including TFIIB, TFIIH, CREB-binding protein (CBP)/p300 and TAFII31. Like other acidic TADs, the p65 TAD contains two subdomains (p65TA1 and p65TA2) that interact with different regulatory factors depending on the target gene. Despite its role in controlling numerous NF-κB target genes, there are no high-resolution structures of p65TA1 bound to a target transcriptional regulatory factor. In this work, we characterize the interaction of p65TA1 with two factors, the Tfb1/p62 subunit of TFIIH and the KIX domain of CBP. In these complexes, p65TA1 transitions into a helical conformation that includes its characteristic ΦXXΦΦ motif (Φ = hydrophobic amino acid). Structural and functional studies demonstrate that the two binding interfaces are primarily stabilized by three hydrophobic amino acids within the ΦXXΦΦ motif and these residues are also crucial to its ability to activate transcription. Taken together, the results provide an atomic level description of how p65TA1 is able to bind different transcriptional regulatory factors needed to activate NF-κB target genes.

CCCTC-binding factor inhibits breast cancer cell proliferation and metastasis via inactivation of the nuclear factor-kappaB pathway

CCCTC-binding factor (CTCF) is an important epigenetic regulator implicated in multiple cellular processes, including growth, proliferation, differentiation, and apoptosis. Although CTCF deletion or mutation has been associated with human breast cancer, the role of CTCF in breast cancer is questionable. We investigated the biological functions of CTCF in breast cancer and the underlying mechanism. The results showed that CTCF expression in human breast cancer cells and tissues was significantly lower than that in normal breast cells and tissues. In addition, CTCF expression correlated significantly with cancer stage (P = 0.043) and pathological differentiation (P = 0.029). Furthermore, CTCF overexpression resulted in the inhibition of proliferation, migration, and invasion, while CTCF knockdown induced these processes in breast cancer cells. Transcriptome analysis and further experimental confirmation in MDA-MD-231 cells revealed that forced overexpression of CTCF might attenuate the DNA-binding ability of nuclear factor-kappaB (NF-κB) p65 subunit and inhibit activation of NF-κB and its target pro-oncogenes (tumor necrosis factor alpha-induced protein 3 [TNFAIP3]) and genes for growth-related proteins (early growth response protein 1 [EGR1] and growth arrest and DNA-damage-inducible alpha [GADD45a]). The present study provides a new insight into the tumor suppressor roles of CTCF in breast cancer development and suggests that the CTCF/NF-κB pathway is a potential target for breast cancer therapy.

Noncoding RNAs Regulating NF-κB Signaling

As transcription factors that regulate expression of a variety of genes essential for diverse physiological and pathological processes, nuclear factor kappa B (NF-κB) family molecules play important roles in the development and progression of malignant tumor, and constitutive activation of NF-κB has been evidenced in various types of tumor tissues. Underlying its pathologic role, deregulated expression and/or transactivating activity of NF-κB usually involves multiple layers of molecular mechanisms. Noncoding RNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are known to modulate expression and biological functions of regulatory proteins in a variety of cancer contexts. In this chapter, the regulatory role of miRNAs and lncRNAs in NF-κB signaling in malignant diseases will be discussed.

Role of Transcription Factors in Pulmonary Artery Smooth Muscle Cells: An Important Link to Hypoxic Pulmonary Hypertension

Hypoxia, namely a lack of oxygen in the blood, induces pulmonary vasoconstriction and vasoremodeling, which serve as essential pathologic factors leading to pulmonary hypertension (PH). The underlying molecular mechanisms are uncertain; however, pulmonary artery smooth muscle cells (PASMCs) play an essential role in hypoxia-induced pulmonary vasoconstriction, vasoremodeling, and PH. Hypoxia causes oxidative damage to DNAs, proteins, and lipids. This damage (oxidative stress) modulates the activity of ion channels and elevates the intracellular calcium concentration ([Ca²⁺]_i, Ca²⁺ signaling) of PASMCs. The oxidative stress and increased Ca²⁺ signaling mutually interact with each other, and synergistically results in a variety of cellular responses. These responses include functional and structural abnormalities of mitochondria, sarcoplasmic reticulum, and nucleus; cell contraction, proliferation, migration, and apoptosis, as well as generation of vasoactive substances, inflammatory molecules, and growth factors that mediate the development of PH. A number of studies reveal that various transcription factors (TFs) play important roles in hypoxia-induced oxidative stress, disrupted PAMSC Ca²⁺ signaling and the development and progress of PH. It is believed that in the pathogenesis of PH, hypoxia facilitates these roles by mediating the expression of multiple genes. Therefore, the identification of specific genes and their transcription factors implicated in PH is necessary for the complete understanding of the underlying molecular mechanisms. Moreover, this identification may aid in the development of novel and effective therapeutic strategies for PH.

Novel Nuclear Factor-KappaB Targeting Peptide Suppresses β-Amyloid Induced Inflammatory and Apoptotic Responses in Neuronal Cells

In the central nervous system (CNS), activation of the transcription factor nuclear factor-kappa B (NF-κβ) is associated with both neuronal survival and increased vulnerability to apoptosis. The mechanisms underlying these dichotomous effects are attributed to the composition of NF-κΒ dimers. In Alzheimer’s disease (AD), β-amyloid (Aβ) and other aggregates upregulate activation of p65:p50 dimers in CNS cells and enhance transactivation of pathological mediators that cause neuroinflammation and neurodegeneration. Hence selective targeting of activated p65 is an attractive therapeutic strategy for AD. Here we report the design, structural and functional characterization of peptide analogs of a p65 interacting protein, the glucocorticoid induced leucine zipper (GILZ). By virtue of binding the transactivation domain of p65 exposed after release from the inhibitory IκΒ proteins in activated cells, the GILZ analogs can act as highly selective inhibitors of activated p65 with minimal potential for off-target effects.

A RelA(p65) Thr505 phospho-site mutation reveals an important mechanism regulating NF-κB-dependent liver regeneration and cancer

Post-translational modifications of nuclear factor (NF)-κB subunits provide a mechanism to differentially regulate their activity in response to the many stimuli that induce this pathway. However, the physiological significance of these modifications is largely unknown, and it remains unclear if these have a critical role in the normal and pathological functions of NF-κB in vivo. Among these, phosphorylation of the RelA(p65) Thr505 residue has been described as an important regulator of NF-κB activity in cell lines, but its physiological significance was not known. Therefore, to learn more about the role of this pathway in vivo, we generated a knockin mouse with a RelA T505A mutation. Unlike RelA knockout mice, the RelA T505A mice develop normally but exhibit aberrant hepatocyte proliferation following liver partial hepatectomy or damage resulting from carbon tetrachloride (CCl4) treatment. Consistent with these effects, RelA T505A mice exhibit earlier onset of cancer in the N-nitrosodiethylamine model of hepatocellular carcinoma. These data reveal a critical pathway controlling NF-κB function in the liver that acts to suppress the tumour-promoting activities of RelA.

Ctenopharyngodon idella NF-κB subunit p65 modulates the transcription of IκBα in CIK cells

NF-κB is an important transcription factor for regulating the multiple inflammatory and immune related gene transcription. It can bind with the nuclear factor κB site within the promoter of target genes to regulate their transcriptions. p65, the all-important subunit of NF-κB, is ubiquitously expressed in cells. In the present study, we cloned and identified the p65 subunit from grass carp (Ctenopharyngodon idella) (named Cip65) by homologous cloning and RACE technique. The full length of Cip65 cDNA is 2481 bp along with 9 bp 5' UTR, 639 bp 3' UTR and the largest open reading frame (1833 bp) encoding a polypeptide of 610 amino acids with a well conserved Rel-homology domain (RHD) in N-terminal and a putative transcription activation domain (TAD) in C-terminal. Cip65 gathers with other teleost p65 proteins to form a fish-specific clade clearly distinct from those of mammalian and amphibian counterparts on the phylogenetic tree. In CIK (C. idellus kidney) cells, the expression of Cip65 was significantly up-regulated under the stimulation with Poly I:C. As one member of the NF-κB inhibitor protein (IκB) family, IκBα can dominate the activity of NF-κB by interacting with it. To study the molecular mechanisms of negative feedback loop of NF-κB signaling in fish, we cloned grass carp IκBα (CiIκBα) promoter sequence. CiIκBα promoter is 414 bp in length containing two RelA binding sites and a putative atypical TATA-box. Meanwhile, Cip65 and its mutant proteins including C-terminus deletion mutant of Cip65 (Cip65-ΔC) and N-terminus deletion mutant of Cip65 (Cip65-ΔN) were expressed in Escherichia coli BL21 and purified by affinity chromatography with the Ni-NTA His-Bind resin. In vitro, Cip65 rather than Cip65-ΔC and Cip65-ΔN showed high affinity with CiIκBα promoter sequence by gel mobility shift assays. In vivo, the cotransfection of pcDNA3.1-Cip65 (or pcDNA3.1-Cip65-ΔC, pcDNA3.1-Cip65-ΔN respectively) with pGL3-CiIκBα and pRL-TK renilla luciferase plasmid into CIK cells showed that pcDNA3.1-Cip65 rather than pcDNA3.1-Cip65-ΔC and pcDNA3.1-Cip65-ΔN, can increase the luciferase activity. Taken together, these results suggested that Cip65 can regulate the expression of CiIκBα and works as a negative feedback loop in NF-κB pathway.

Modulation of Estrogen Response Element-Driven Gene Expressions and Cellular Proliferation with Polar Directions by Designer Transcription Regulators

Estrogen receptor α (ERα), as a ligand-dependent transcription factor, mediates 17β-estradiol (E2) effects. ERα is a modular protein containing a DNA binding domain (DBD) and transcription activation domains (AD) located at the amino- and carboxyl-termini. The interaction of the E2-activated ERα dimer with estrogen response elements (EREs) of genes constitutes the initial step in the ERE-dependent signaling pathway necessary for alterations of cellular features. We previously constructed monomeric transcription activators, or monotransactivators, assembled from an engineered ERE-binding module (EBM) using the ERα-DBD and constitutively active ADs from other transcription factors. Monotransactivators modulated cell proliferation by activating and repressing ERE-driven gene expressions that simulate responses observed with E2-ERα. We reasoned here that integration of potent heterologous repression domains (RDs) into EBM could generate monotransrepressors that alter ERE-bearing gene expressions and cellular proliferation in directions opposite to those observed with E2-ERα or monotransactivators. Consistent with this, monotransrepressors suppressed reporter gene expressions that emulate the ERE-dependent signaling pathway. Moreover, a model monotransrepressor regulated DNA synthesis, cell cycle progression and proliferation of recombinant adenovirus infected ER-negative cells through decreasing as well as increasing gene expressions with polar directions compared with E2-ERα or monotransactivator. Our results indicate that an ‘activator’ or a ‘repressor’ possesses both transcription activating/enhancing and repressing/decreasing abilities within a chromatin context. Offering a protein engineering platform to alter signal pathway-specific gene expressions and cell growth, our approach could also be used for the development of tools for epigenetic modifications and for clinical interventions wherein multigenic de-regulations are an issue.

Scutellarein Reduces Inflammatory Responses by Inhibiting Src Kinase Activity

Flavonoids are plant pigments that have been demonstrated to exert various pharmacological effects including anti-cancer, anti-diabetic, anti-atherosclerotic, anti-bacterial, and anti-inflammatory activities. However, the molecular mechanisms in terms of exact target proteins of flavonoids are not fully elucidated yet. In this study, we aimed to evaluate the anti-inflammatory mechanism of scutellarein (SCT), a flavonoid isolated from Erigeron breviscapus, Clerodendrum phlomidis and Oroxylum indicum Vent that have been traditionally used to treat various inflammatory diseases in China and Brazil. For this purpose, a nitric oxide (NO) assay, polymerase chain reaction (PCR), nuclear fractionation, immunoblot analysis, a kinase assay, and an overexpression strategy were employed. Scutellarein significantly inhibited NO production in a dose-dependent manner and reduced the mRNA expression levels of inducible NO synthase (iNOS) and tumor necrosis factor (TNF)-α in lipopolysaccharide (LPS)-activated RAW264.7 cells. In addition, SCT also dampened nuclear factor (NF)-κB-driven expression of a luciferase reporter gene upon transfection of a TIR-domain-containing adapter-inducing interferon-β (TRIF) construct into Human embryonic kidney 293 (HEK 293) cells; similarly, NF-κ B nuclear translocation was inhibited by SCT. Moreover, the phosphorylation levels of various upstream signaling enzymes involved in NF-κB activation were decreased by SCT treatment in LPS-treated RAW264.7 cells. Finally, SCT strongly inhibited Src kinase activity and also inhibited the autophosphorylation of overexpressed Src. Therefore, our data suggest that SCT can block the inflammatory response by directly inhibiting Src kinase activity linked to NF-κB activation.

Cloning and characterization of the proximal promoter region of rainbow trout (Oncorhynchus mykiss) interleukin-6 gene

Interleukin-6 (IL6) is a pleiotropic cytokine with important immunoregulatory functions. Its expression is inducible in immune cells and tissues of several fish species. We also found that IL6 mRNA abundance was significantly increased in spleen, liver, and gill of rainbow trout after experimental infection with Aeromonas salmonicida. Genomic DNA sequences of IL6 orthologs from three salmonid species revealed a conserved exon/intron structure and a high overall nucleotide identity of >88%. To uncover key mechanisms regulating IL6 expression in salmonid fish, we amplified a fragment of the proximal IL6 promoter from rainbow trout and identified in-silico conserved binding sites for NF-κB and CEBP. The activity of this IL6 promoter fragment was analyzed in the established human embryonic kidney line HEK-293. Luciferase- and GFP-based reporter systems revealed that the proximal IL6 promoter is activated by Escherichia coli. Essentially, both reporter systems proved that NF-κB p50, but not NF-κB p65 or CEBP, activates the IL6 promoter fragment. Truncation of this fragment caused a significant decrease in IL6 promoter activation. This characterization of the proximal promoter of the IL6-encoding gene provides basic knowledge about the IL6 gene expression in rainbow trout.

Syk/Src-targeted anti-inflammatory activity of Codariocalyx motorius ethanolic extract

ETHNOPHARMACOLOGICAL RELEVANCE

Codariocalyx motorius (Houtt.) H. Ohashi (Fabaceae) is one of several ethnopharmacologically valuable South Asian species prescribed as an herbal medicine for various inflammatory diseases. Due to the lack of systematic studies on this plant, we aimed to explore the inhibitory activity of Codariocalyx motorius toward inflammatory responses using its ethanolic extract (Cm-EE).

MATERIALS AND METHODS

Lipopolysaccharide (LPS)-treated macrophages and a HCl/EtOH-induced gastritis model were used for evaluation of the anti-inflammatory activity of Cm-EE. HPLC and spectroscopic analysis were employed to identify potential active components. Mechanistic approaches to determine target enzymes included kinase assays, reporter gene assays, and overexpression of target enzymes.

RESULTS

Cm-EE strongly suppressed nitric oxide (NO) and prostaglandin E2 (PGE2) release. Cm-EE-mediated inhibition was observed at the transcriptional level in the form of suppression of NF-κB (p65) translocation and activation. This extract also lowered the levels of phosphorylation of Src and Syk, their kinase activity, and their formation of signalling complexes by binding to the downstream enzyme p85/PI3K. In accord with these findings, the phosphorylation of p85 induced by overexpression of Src or Syk was also diminished by Cm-EE. Orally administered Cm-EE clearly inhibited gastritic ulcer formation and the phosphorylation of IκBα and Src in HCl/EtOH-treated stomachs of mice. By phytochemical analysis, luteolin and its glycoside, apigenin-7-O-glucuronide, and scutellarein-6-O-glucuronide were identified as major components of Cm-EE. Among these, it was found that luteolin was able to strongly suppress NO and PGE2 production under the same conditions.

CONCLUSION

Syk/Src-targeted inhibition of NF-κB by Cm-EE could be a major anti-inflammatory mechanism contributing to its ethno pharmacological role as an anti-inflammatory herbal medicine.

Regulation of the NF-κB-Mediated Transcription of Inflammatory Genes

The NF-κB family of transcription factors plays a central role in the inducible expression of inflammatory genes during the immune response, and the proper regulation of these genes is a critical factor in the maintenance of immune homeostasis. The chromatin environment at stimulus-responsive NF-κB sites is a major determinant in transcription factor binding, and dynamic alteration of the chromatin state to facilitate transcription factor binding is a key regulatory mechanism. NF-κB is in turn able to influence the chromatin state through a variety of mechanisms, including the recruitment of chromatin modifying co-activator complexes such as p300, the competitive eviction of negative chromatin modifications, and the recruitment of components of the general transcriptional machinery. Frequently, the selective interaction with these co-activators is dependent on specific post-translational modification of NF-κB subunits. Finally, the mechanisms of inducible NF-κB activity in different immune cell types seem to be largely conserved. The diversity of cell-specific NF-κB-mediated transcriptional programs is established at the chromatin level during cell differentiation by lineage-defining transcription factors. These factors generate and maintain a cell-specific chromatin landscape that is accessible to NF-κB, thus restricting the inducible transcriptional response to a cell-appropriate output.

NF-κB: emerging roles in hippocampal development and function

The nuclear factor kappa-B family of transcription factors have been extensively studied in the immune system where they function to orchestrate the molecular response to immune challenge. However in recent years, members of this family have also been shown to play physiological roles in the development and function of the nervous system. The two best studied members of the nuclear factor kappa-B family are the p65 and the p50 proteins. In this review, we outline recent developments regarding the functions of these proteins in regulating hippocampal neurogenesis, neuronal growth and learning and memory and discuss the implications of their dysregulation during the development of the nervous system.

Transcriptional control by NF-κB: elongation in focus

The NF-κB family of transcription factors governs the cellular reaction to a variety of extracellular signals. Following stimulation, NF-κB activates genes involved in inflammation, cell survival, cell cycle, immune cell homeostasis and more. This review focuses on studies of the past decade that uncover the transcription elongation process as a key regulatory stage in the activation pathway of NF-κB. Of interest are studies that point to the elongation phase as central to the selectivity of target gene activation by NF-κB. Particularly, the cascade leading to phosphorylation and acetylation of the NF-κB subunit p65 on serine 276 and lysine 310, respectively, was shown to mediate the recruitment of Brd4 and P-TEFb to many pro-inflammatory target genes, which in turn facilitate elongation and mRNA processing. On the other hand, some anti-inflammatory genes are refractory to this pathway and are dependent on the elongation factor DSIF for efficient elongation and mRNA processing. While these studies have advanced our knowledge of NF-κB transcriptional activity, they have also raised unresolved issues regarding the specific genomic and physiological contexts by which NF-κB utilizes different mechanisms for activation.

Overexpression of p65 attenuates celecoxib-induced cell death in MDA-MB-231 human breast cancer cell line

BACKGROUND

Celecoxib is a selective cyclooxygenase (COX)-2 inhibitor that has been reported to reduce the risk of breast cancer. In our previous study, celecoxib induced apoptosis and caused cell cycle arrest at the G0/G1 phase in the breast cancer cell line MDA-MB-231, and its effects were mediated by downregulation of NF-κB signaling. The NF-κB p65/RelA subunit may play a role in cell death through the activation of anti-apoptotic target genes including the inhibitor of apoptosis (IAP) and Bcl-2 families, and inhibition of protein kinase B/Akt. The aim of the present study was to investigate p65 as the potential target of celecoxib treatment and determine whether p65 overexpression can override the inhibitory effect of celecoxib on NF-κB activity and affect cell survival.

METHODS

The effects of p65 overexpression on celecoxib-inhibited NF-κB transcriptional activity were examined by western blotting, electrophoretic mobility shift assay (EMSA) and luciferase reporter gene assay. Cell viability and cell death were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay, and the levels of cleaved poly(ADP-ribose) polymerase (PARP) and caspase. Anti-apoptotic NF-κB target genes and cell cycle regulators were examined by western blotting to screen for the expression of target genes under direct regulation by p65.

RESULTS

Overexpression of p65 increased NF-κB transcriptional activity and interfered with celecoxib-mediated apoptosis as assessed by MTT assay and caspase-3, caspase-9, and PARP expressions. Exogenously overexpressed p65 upregulated NF-κB-responsive genes, including anti-apoptotic genes such as survivin and XIAP, and the cell cycle regulatory gene cyclin D1. However, p65 overexpression did not affect celecoxib-induced p-Akt inactivation, suggesting that celecoxib might have separate molecular mechanisms for regulating Akt signaling independently of its inhibition of NF-κB transcriptional activity.

CONCLUSIONS

p65 is a pivotal anti-apoptotic factor that can reverse celecoxib-induced growth inhibition in MDA-MB-231 cells.

Cyclin-dependent kinase 6 phosphorylates NF-κB P65 at serine 536 and contributes to the regulation of inflammatory gene expression

Nuclear factor kappa-B (NF-κB) activates multiple genes with overlapping roles in cell proliferation, inflammation and cancer. Using an unbiased approach we identified human CDK6 as a novel kinase phosphorylating NF-κB p65 at serine 536. Purified and reconstituted CDK6/cyclin complexes phosphorylated p65 in vitro and in transfected cells. The physiological role of CDK6 for basal as well as cytokine-induced p65 phosphorylation or NF-κB activation was revealed upon RNAi-mediated suppression of CDK6. Inhibition of CDK6 catalytic activity by PD332991 suppressed activation of NF-κB and TNF-induced gene expression. In complex with a constitutively active viral cyclin CDK6 stimulated NF-κB p65-mediated transcription in a target gene specific manner and this effect was partially dependent on its ability to phosphorylate p65 at serine 536. Tumor formation in thymi and spleens of v-cyclin transgenic mice correlated with increased levels of p65 Ser536 phosphorylation, increased expression of CDK6 and upregulaton of the NF-κB target cyclin D3. These results suggest that aberrant CDK6 expression or activation that is frequently observed in human tumors can contribute through NF-κB to chronic inflammation and neoplasia.

The coactivator role of histone deacetylase 3 in IL-1-signaling involves deacetylation of p65 NF-κB

Histone deacetylase (HDAC) 3, as a cofactor in co-repressor complexes containing silencing mediator for retinoid or thyroid-hormone receptors (SMRT) and nuclear receptor co-repressor (N-CoR), has been shown to repress gene transcription in a variety of contexts. Here, we reveal a novel role for HDAC3 as a positive regulator of IL-1-induced gene expression. Various experimental approaches involving RNAi-mediated knockdown, conditional gene deletion or small molecule inhibitors indicate a positive role of HDAC3 for transcription of the majority of IL-1-induced human or murine genes. This effect was independent from the gene regulatory effects mediated by the broad-spectrum HDAC inhibitor trichostatin A (TSA) and thus suggests IL-1-specific functions for HDAC3. The stimulatory function of HDAC3 for inflammatory gene expression involves a mechanism that uses binding to NF-κB p65 and its deacetylation at various lysines. NF-κB p65-deficient cells stably reconstituted to express acetylation mimicking forms of p65 (p65 K/Q) had largely lost their potential to stimulate IL-1-triggered gene expression, implying that the co-activating property of HDAC3 involves the removal of inhibitory NF-κB p65 acetylations at K122, 123, 314 and 315. These data describe a novel function for HDAC3 as a co-activator in inflammatory signaling pathways and help to explain the anti-inflammatory effects frequently observed for HDAC inhibitors in (pre)clinical use.

Phosphorylation of p65(RelA) on Ser(547) by ATM represses NF-κB-dependent transcription of specific genes after genotoxic stress

The NF-κB pathway is involved in immune and inflammation responses, proliferation, differentiation and cell death or survival. It is activated by many external stimuli including genotoxic stress. DNA double-strand breaks activate NF-κB in an ATM-dependent manner. In this manuscript, a direct interaction between p65(RelA) and the N-terminal extremity of ATM is reported. We also report that only one of the five potential ATM-(S/T)Q target sites present in p65, namely Ser⁵⁴⁷, is specifically phosphorylated by ATM in vitro. A comparative transcriptomic analysis performed in HEK-293 cells expressing either wild-type HA-p65 or a non-phosphorylatable mutant HA-p65_S547A identified several differentially transcribed genes after an etoposide treatment (e.g. IL8, A20, SELE). The transcription of these genes is increased in cells expressing the mutant. Substitution of Ser⁵⁴⁷ to alanine does not affect p65 binding abilities on the κB site of the IL8 promoter but reduces p65 interaction with HDAC1. Cells expressing p65_S547A have a higher level of histone H3 acetylated on Lys⁹ at the IL8 promoter, which is in agreement with the higher gene induction observed. These results indicate that ATM regulates a sub-set of NF-κB dependent genes after a genotoxic stress by direct phosphorylation of p65.

Physical and functional interaction between the ID1 and p65 for activation of NF-κB

Inhibitor of differentiation or DNA binding-1 (ID1) is an important helix-loop-helix (HLH) transcription factor involved in diverse biological functions including cell differentiation, proliferation, apoptosis, and senescence. Recently, it was reported that ID1 can activate the NF-κB signaling pathway in a variety of cancer cells and a T cell line, but the mechanisms involved in ID1-mediated transactivation of NF-κB are not clear. In this study, we demonstrate by both in vitro pull-down assays and a cell-based in vivo two-hybrid system that ID1-mediated NF-κB activation is due to its physical interaction with p65. We have identified that the transcriptional activation domain (TAD) in p65 and the HLH domain in ID1 are vital for their interaction. Interestingly, a single site mutation (Leu76) in the HLH domain of ID1 protein drastically decreased its ability to bind with p65. Using a dual-luciferase assay, we demonstrated that the interaction between ID1 and p65 modulates activation of the NF-κB signaling pathway in vivo. In addition, we demonstrated that, by affecting the nuclear translocation of p65, ID1 is essential in regulating TNF-α-induced p65 recruitment to its downstream target, the cellular inhibitor of apoptosis protein 2 (cIAP2) promoter.

The diverse and complex roles of NF-κB subunits in cancer

It is only recently that the full importance of nuclear factor-κB (NF-κB) signalling to cancer development has been understood. Although much attention has focused on the upstream pathways leading to NF-κB activation, it is now becoming clear that the inhibitor of NF-κB kinases (IKKs), which regulate NF-κB activation, have many independent functions in tissue homeostasis and normal immune function that could compromise the clinical utility of IKK inhibitors. Therefore, if the NF-κB pathway is to be properly exploited as a target for both anticancer and anti-inflammatory drugs, it is appropriate to reconsider the complex roles of the individual NF-κB subunits.

Novel p65 binding glucocorticoid-induced leucine zipper peptide suppresses experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a neurological disease characterized by inflammatory demyelination in the brain and spinal cord. The immune-mediated inflammation involves well orchestrated intermolecular interactions that exhibit rapid binding kinetics. The binding interfaces of transient interactions frequently include proline residues that favor an extended conformation for molecular recognition. Linear interface peptides are excellent lead inhibitors of specific protein-protein interactions because only small segments of the interface contribute to the binding. Glucocorticoid-induced leucine zipper (GILZ), a recently identified molecule exhibits potent anti-inflammatory properties. Mechanistically, a proline-rich segment in the carboxyl terminus of GILZ physically binds the p65 subunit of nuclear factor-κB and inhibits the transactivation of inflammatory cytokines. Integrating knowledge derived from the mechanism of action of GILZ with in silico structure prediction identified an immunomodulatory peptide, the GILZ-P. Treatment with GILZ-P exhibited therapeutic efficacy in experimental autoimmune encephalomyelitis, a model for human MS.

p38 mitogen-activated protein kinase pathways in asthma and COPD

The mitogen-activated protein kinase (MAPK) family includes the p38 kinases, which consist of highly conserved proline-directed serine-threonine protein kinases that are activated in response to inflammatory signals. Of the four isoforms, p38α is the most abundant in inflammatory cells and has been the most studied through mainly the availability of small molecule inhibitors. The p38 substrates include transcription factors; other protein kinases, which in turn phosphorylate transcription factors; cytoskeletal proteins and translational components; and other enzymes. Both asthma and COPD are characterized by chronic airflow obstruction, airway and lung remodeling, and chronic inflammation. p38 is involved in the inflammatory responses induced by cigarette smoke exposure, endotoxin, and oxidative stress through activation and release of proinflammatory cytokines/chemokines, posttranslational regulation of these genes, and activation of inflammatory cell migration. Inhibition of p38 MAPK prevented allergen-induced pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness, effects that may partly result from p38 activation on eosinophil apoptosis and on airway smooth muscle cell production of cytokines/chemokines. In addition, p38 regulates the augmented contractile response induced by oxidative stress. The activation of p38 observed in epithelial cells and macrophages also may underlie corticosteroid insensitivity of severe asthma and COPD. Therefore, p38 inhibitors present a potential attractive treatment of these conditions. Second-generation p38 inhibitors have been disappointing in the treatment of rheumatoid arthritis. In two 6-week studies in patients with COPD, the results were encouraging. Side effects such as liver toxicity remain a possibility, and whether the beneficial effects of p38 inhibitors are clinically significant and sustained need to be determined.

Signal integration, crosstalk mechanisms and networks in the function of inflammatory cytokines

Infection or cell damage triggers the release of pro-inflammatory cytokines such as interleukin(IL)-1α or β and tumor necrosis factor (TNF)α which are key mediators of the host immune response. Following their identification and the elucidation of central signaling pathways, recent results show a highly complex crosstalk between various cytokines and their signaling effectors. The molecular mechanisms controlling signaling thresholds, signal integration and the function of feed-forward and feedback loops are currently revealed by combining methods from biochemistry, genetics and in silico analysis. Increasing evidence is mounted that defects in information processing circuits or their components can be causative for chronic or overshooting inflammation. As progress in biosciences has always benefitted from the use of well-studied model systems, research on inflammatory cytokines may function as a paradigm to reveal general principles of signal integration, crosstalk mechanisms and signaling networks.

Natural and synthetic α,β-unsaturated carbonyls for NF-κB inhibition

BACKGROUND

The nuclear transcription factor NF-κB has gained considerable importance due to its major involvement in inflammation and constitutive activity in malignant cells. It is induced by a variety of stimuli and controls the expression of several proteins involved in biological processes. Numerous natural products and synthesized organic molecules have been reported to inhibit NF-κB and have played an integral role in identifying implicated pathways. Prominent among them are the sesquiterpene lactones, polyphenolic enones and other α,β-unsaturated carbonyl-containing molecules, particularly α-methylene-γ-butyrolactones.

DISCUSSION

This mini-review provides an introductory overview of some of the associated pathways involving NF-κB in cancer and discusses the structures and mode of action of natural α,β-unsaturated carbonyl-containing inhibitors and their synthetic counterparts. A review of the recent methods for the synthesis of α-alkylidene-γ-butyrolactones is also provided, with the aim of arousing the interest of synthetic chemists for the design and development of novel NF-κB inhibitors.

CONCLUSIONS

Modulating damaging effects without harming the inflammatory and immune responses are crucial parameters for developing NF-κB inhibitors. Examination of novel α,β-unsaturated carbonyls and the further discovery of simple methods to prepare such molecules should lead to the identification of site-specific inhibitors.