IKK-1 and IKK-2: cytokine-activated IkappaB kinases essential for NF-kappaB activation

Targeting TNF and TNF Receptor Pathway in HIV-1 Infection: from Immune Activation to Viral Reservoirs

Several cellular functions such as apoptosis, cellular proliferation, inflammation, and immune regulation involve the tumor necrosis factor-α (TNF)/TNF receptor (TNFR) pathway. Human immunodeficiency virus 1 (HIV-1) interacts with the TNF/TNFR pathway. The activation of the TNF/TNFR pathway impacts HIV-1 replication, and the TNF/TNFR pathway is the target of HIV-1 proteins. A hallmark of HIV-1 infection is immune activation and inflammation with increased levels of TNF in the plasma and the tissues. Therefore, the control of the TNF/TNFR pathway by new therapeutic approaches could participate in the control of immune activation and impact both viral replication and viral persistence. In this review, we will describe the intricate interplay between HIV-1 proteins and TNF/TNFR signaling and how TNF/TNFR activation modulates HIV-1 replication and discuss new therapeutic approaches, especially anti-TNF therapy, that could control this pathway and ultimately favor the clearance of infected cells to cure HIV-infected patients.

BAP31 is involved in T cell activation through TCR signal pathways

BAP31 is a ubiquitously expressed endoplasmic reticulum (ER) membrane protein. The functions of BAP31 in the immune system have not been investigated due to the lack of animal models. Therefore we created a BAP31 conditional knockdown mouse by performing a knockdown of BAP31 in the thymus. In doing so, we demonstrate that the maturation of T cells is normal but the number of T cells is less in the thymus of the knockout mouse. In addition, the spleen and lymph nodes of peripheral immune organs contained a lesser proportion of the mature T cells in the thymus specific BAP31 knockout mice. The BAP31 knockout T cells decreased the proliferation activated by TCR signal pathways. Further studies clarified that BAP31 affects the phosphorylation levels of both Zap70/Lck/Lat of the upstream members and Akt/GSK/Jnk/Erk of the downstream members of TCR signal pathways. Furthermore, BAP31 can regulate the expression of some markers such as CD3/TCRα/TCRβ and some cytokines like IL-2/IFN-γ/IL-6/TNF-α which are important for T cell activation. Taken together, these results demonstrate that BAP31 may play an important role in T cell activation by regulating TCR signaling.

Herpes Simplex Virus 1 UL24 Abrogates the DNA Sensing Signal Pathway by Inhibiting NF-κB Activation

Cyclic GMP-AMP synthase (cGAS) is a newly identified DNA sensor that recognizes foreign DNA, including the genome of herpes simplex virus 1 (HSV-1). Upon binding of viral DNA, cGAS produces cyclic GMP-AMP, which interacts with and activates stimulator of interferon genes (STING) to trigger the transcription of antiviral genes such as type I interferons (IFNs), and the production of inflammatory cytokines. HSV-1 UL24 is widely conserved among members of the herpesviruses family and is essential for efficient viral replication. In this study, we found that ectopically expressed UL24 could inhibit cGAS-STING-mediated promoter activation of IFN-β and interleukin-6 (IL-6), and UL24 also inhibited interferon-stimulatory DNA-mediated IFN-β and IL-6 production during HSV-1 infection. Furthermore, UL24 selectively blocked nuclear factor κB (NF-κB) but not IFN-regulatory factor 3 promoter activation. Coimmunoprecipitation analysis demonstrated that UL24 bound to the endogenous NF-κB subunits p65 and p50 in HSV-1-infected cells, and UL24 was also found to bind the Rel homology domains (RHDs) of these subunits. Furthermore, UL24 reduced the tumor necrosis factor alpha (TNF-α)-mediated nuclear translocation of p65 and p50. Finally, mutational analysis revealed that the region spanning amino acids (aa) 74 to 134 of UL24 [UL24(74-134)] is responsible for inhibiting cGAS-STING-mediated NF-κB promoter activity. For the first time, UL24 was shown to play an important role in immune evasion during HSV-1 infection.IMPORTANCE NF-κB is a critical component of the innate immune response and is strongly induced downstream of most pattern recognition receptors (PRRs), leading to the production of IFN-β as well as a number of inflammatory chemokines and interleukins. To establish persistent infection, viruses have evolved various mechanisms to counteract the host NF-κB pathway. In the present study, for the first time, HSV-1 UL24 was demonstrated to inhibit the activation of NF-κB in the DNA sensing signal pathway via binding to the RHDs of the NF-κB subunits p65 and p50 and abolishing their nuclear translocation.

Dietary alpha-linolenic acid/linoleic acid ratios modulate immune response, physical barrier and related signaling molecules mRNA expression in the gills of juvenile grass carp (Ctenopharyngodon idella)

This study was conducted to explore the possible effects of dietary ALA/LNA ratios on the gill immunity, tight junction and antioxidant capacity, and the related signaling factor mRNA levels of juvenile grass carp (Ctenopharyngodon idella). Fish were fed diets with different ALA/LNA ratios (0.01, 0.34, 0.68, 1.03, 1.41, 1.76 and 2.15) for 60 days. The present results showed that ALA/LNA ratio of 1.03 significantly enhanced lysozyme and acid phosphatase activities, complement 3 contents, promoted mRNA levels of antimicrobial peptides (Hepcidin and liver expression antimicrobial peptide-2), anti-inflammatory cytokines (interleukin 10 and transforming growth factor β1) and inhibitor protein κBα, whereas suppressed pro-inflammatory cytokines (interleukin 1β, interleukin 8, tumor necrosis factor a and interferon γ2), and signal molecules (IκB kinase β, IκB kines γ and nuclear factor κB p65) mRNA levels in the gill, indicating that optimal dietary ALA/LNA ratio improve gill immunity of juvenile fish. Besides, ALA/LNA ratio of 1.03 increased mRNA levels of the barrier functional proteins (occludin, zonula occludens-1, claudin-b, -c and -3), and reduced the pore-formation proteins (claudin-15a) and myosin light-chain kinase mRNA abundance in the gill of juvenile grass carp, indicating optimum ALA/LNA ratio strengthen gill tight junction of juvenile fish. Additionally, ALA/LNA ratio of 1.03 increased glutathione contents, copper/zinc superoxide dismutase, glutathione peroxidase, glutathione S-transferase and glutathione reductase activities and mRNA abundance, and nuclear factor erythoid 2-related factor 2 mRNA levels in the gill of fish, suggesting that optimal ALA/LNA ratio ameliorate gill antioxidant status of juvenile fish. Interestingly, dietary ALA/LNA ratios had no effect on IκB kinase α and catalase activities in fish gills. Collectively, optimal dietary ALA/LNA ratio could improve gill immunity and strengthen physical barrier of juvenile fish. Based on the quadratic regression analysis of complement 3 content in the gill, optimal dietary ALA/LNA ratio for maximum growth of juvenile grass carp was estimated to be 1.12.

ZNF395 Is an Activator of a Subset of IFN-Stimulated Genes

Activation of the interferon (IFN) pathway in response to infection with pathogens results in the induction of IFN-stimulated genes (ISGs) including proinflammatory cytokines, which mount the proper antiviral immune response. However, aberrant expression of these genes is pathogenic to the host. In addition to IFN-induced transcription factors non-IFN-regulated factors contribute to the transcriptional control of ISGs. Here, we show by genome wide expression analysis, siRNA-mediated suppression and Doxycycline-induced overexpression that the cellular transcription factor ZNF395 activates a subset of ISGs including the chemokines CXCL10 and CXCL11 in keratinocytes. We found that ZNF395 acts independently of IFN but enhances the IFN-induced expression of CXCL10 and CXCL11. Luciferase reporter assays revealed a requirement of intact NFκB-binding sites for ZNF395 to stimulate the CXCL10 promoter. The transcriptional activation of CXCL10 and CXCL11 by ZNF395 was abolished after inhibition of IKK by BMS-345541, which increased the stability of ZNF395. ZNF395 encodes at least two motifs that mediate the enhanced degradation of ZNF395 in response to IKK activation. Thus, IKK is required for ZNF395-mediated activation of transcription and enhances its turn-over to keep the activity of ZNF395 low. Our results support a previously unrecognized role of ZNF395 in the innate immune response and inflammation.

Herpes Simplex Virus 1 Ubiquitin-Specific Protease UL36 Abrogates NF-κB Activation in DNA Sensing Signal Pathway

The DNA sensing pathway triggers innate immune responses against DNA virus infection, and NF-κB signaling plays a critical role in establishing innate immunity. We report here that the herpes simplex virus 1 (HSV-1) ubiquitin-specific protease (UL36USP), which is a deubiquitinase (DUB), antagonizes NF-κB activation, depending on its DUB activity. In this study, ectopically expressed UL36USP blocked promoter activation of beta interferon (IFN-β) and NF-κB induced by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). UL36USP restricted NF-κB activation mediated by overexpression of STING, TANK-binding kinase 1, IκB kinase α (IKKα), and IKKβ, but not p65. UL36USP was also shown to inhibit IFN-stimulatory DNA-induced IFN-β and NF-κB activation under conditions of HSV-1 infection. Furthermore, UL36USP was demonstrated to deubiquitinate IκBα and restrict its degradation and, finally, abrogate NF-κB activation. More importantly, the recombinant HSV-1 lacking UL36USP DUB activity, denoted as C40A mutant HSV-1, failed to cleave polyubiquitin chains on IκBα. For the first time, UL36USP was shown to dampen NF-κB activation in the DNA sensing signal pathway to evade host antiviral innate immunity.IMPORTANCE It has been reported that double-stranded-DNA-mediated NF-κB activation is critical for host antiviral responses. Viruses have established various strategies to evade the innate immune system. The N terminus of the HSV-1 UL36 gene-encoded protein contains the DUB domain and is conserved across all herpesviruses. This study demonstrates that UL36USP abrogates NF-κB activation by cleaving polyubiquitin chains from IκBα and therefore restricts proteasome-dependent degradation of IκBα and that DUB activity is indispensable for this process. This study expands our understanding of the mechanisms utilized by HSV-1 to evade the host antiviral innate immune defense induced by NF-κB signaling.

Sensitization of melanoma cells to alkylating agent-induced DNA damage and cell death via orchestrating oxidative stress and IKKβ inhibition

Nitrosourea represents one of the most active classes of chemotherapeutic alkylating agents for metastatic melanoma. Treatment with nitrosoureas caused severe systemic side effects which hamper its clinical use. Here, we provide pharmacological evidence that reactive oxygen species (ROS) induction and IKKβ inhibition cooperatively enhance nitrosourea-induced cytotoxicity in melanoma cells. We identified SC-514 as a ROS-inducing IKKβ inhibitor which enhanced the function of nitrosoureas. Elevated ROS level results in increased DNA crosslink efficiency triggered by nitrosoureas and IKKβ inhibition enhances DNA damage signals and sensitizes nitrosourea-induced cell death. Using xenograft mouse model, we confirm that ROS-inducing IKKβ inhibitor cooperates with nitrosourea to reduce tumor size and malignancy in vivo. Taken together, our results illustrate a new direction in nitrosourea treatment, and reveal that the combination of ROS-inducing IKKβ inhibitors with nitrosoureas can be potentially exploited for melanoma therapy.

The NR4A subfamily of nuclear receptors: potential new therapeutic targets for the treatment of inflammatory diseases

INTRODUCTION

Prolonged inflammatory response contributes to the pathogenesis of chronic disease-related disturbances. Among nuclear receptors (NRs), the orphan NR4A subfamily, which includes Nur77 (NR4A1), Nurr1 (NR4A2) and NOR1 (NR4A3), has recently emerged as a therapeutic target for the treatment of inflammation. Areas covered: This review focuses on the capacity of NR4A receptors to counter-regulate the development of the inflammatory response, with a special focus on the molecular transrepression mechanisms. Expert opinion: Recent studies have highlighted the role of NR4A receptors as significant regulators of the inflammatory response. NR4A receptors are rapidly induced by inflammatory stimuli, thus suggesting that they are required for the initiation of inflammation. Nevertheless, NR4A anti-inflammatory properties indicate that this acute regulation could be a protective reaction aimed at resolving inflammation in the later stages. Therefore, NR4A receptors are involved in a negative feedback mechanism to maintain the inflammatory balance. However, the underlying mechanisms are not entirely clear. Only a small number of NR4A-target genes have been identified, and the transcriptional repression mechanisms are only beginning to emerge. Despite further research is needed to fully understand the role of NR4A receptors in inflammation, these NRs should be considered as targets for new therapeutic approaches to inflammatory diseases.

Targeting IKK and NF-κB for Therapy

In addition to regulating immune responses, the NF-κB family of transcription factors also promotes cellular proliferation and survival. NF-κB and its activating kinase, IKK, have become appealing therapeutic targets because of their critical roles in the progression of many diseases including chronic inflammation and cancer. Here, we discuss the conditions that lead to pathway activation, the effects of constitutive activation, and some of the strategies used to inhibit NF-κB signaling.

Selinexor, a Selective Inhibitor of Nuclear Export (SINE) compound, acts through NF-κB deactivation and combines with proteasome inhibitors to synergistically induce tumor cell death

The nuclear export protein, exportin-1 (XPO1/CRM1), is overexpressed in many cancers and correlates with poor prognosis. Selinexor, a first-in-class Selective Inhibitor of Nuclear Export (SINE) compound, binds covalently to XPO1 and blocks its function. Treatment of cancer cells with selinexor results in nuclear retention of major tumor suppressor proteins and cell cycle regulators, leading to growth arrest and apoptosis. Recently, we described the selection of SINE compound resistant cells and reported elevated expression of inflammation-related genes in these cells. Here, we demonstrated that NF-κB transcriptional activity is up-regulated in cells that are naturally resistant or have acquired resistance to SINE compounds. Resistance to SINE compounds was created by knockdown of the cellular NF-κB inhibitor, IκB-α. Combination treatment of selinexor with proteasome inhibitors decreased NF-κB activity, sensitized SINE compound resistant cells and showed synergistic cytotoxicity in vitro and in vivo. Furthermore, we showed that selinexor inhibited NF-κB activity by blocking phosphorylation of the IκB-α and the NF-κB p65 subunits, protecting IκB-α from proteasome degradation and trapping IκB-α in the nucleus to suppress NF-κB activity. Therefore, combination treatment of selinexor with a proteasome inhibitor may be beneficial to patients with resistance to either single-agent.

X-linked inhibitor of apoptosis-associated factor 1 regulates TNF receptor 1 complex stability

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is a cytokine-regulated, tumor necrosis factor (TNF) receptor-associated factor (TRAF) domain-containing protein that has a poorly defined cellular function. Here, we show that ectopically expressed XAF1 inhibits TNF-ɑ-induced NF-κB activation, whereas shRNA silencing of endogenous XAF1 augments it. Our data suggest that XAF1 may inhibit TNF-ɑ-induced NF-κB activation by disrupting the assembly of the TRADD/TRAF2/RIP1 complex (complex I) downstream of TNF receptor activation. XAF1 interacts with TRAF2 and inhibits TRAF2-dependent NF-κB activation, in part, by blocking TRAF2 polyubiquitination. Our findings also indicate that although XAF1 does not directly inhibit RIP1-dependent NF-κB activation, it binds RIP1 and disrupts RIP1/TRADD association. Our data suggest that XAF1 acts as a feedback regulator of the TNF receptor signaling pathway to suppress NF-κB activation.

Co-activator candidate interactions for orphan nuclear receptor NR2E1

Background

NR2E1 (Tlx) is an orphan nuclear receptor that regulates the maintenance and self-renewal of neural stem cells, and promotes tumourigenesis. Nr2e1-null mice exhibit reduced cortical and limbic structures and pronounced retinal dystrophy. NR2E1 functions mainly as a repressor of gene transcription in association with the co-repressors atrophin-1, LSD1, HDAC and BCL11A. Recent evidence suggests that NR2E1 also acts as an activator of gene transcription. However, co-activator complexes that interact with NR2E1 have not yet been identified. In order to find potential novel co-regulators for NR2E1, we used a microarray assay for real-time analysis of co-regulator–nuclear receptor interaction (MARCoNI) that contains peptides representing interaction motifs from potential co-regulatory proteins, including known co-activator nuclear receptor box sequences (LxxLL motif).

Results

We found that NR2E1 binds strongly to an atrophin-1 peptide (Atro box) used as positive control and to 19 other peptides that constitute candidate NR2E1 partners. Two of these proteins, p300 and androgen receptor (AR), were further validated by reciprocal pull-down assays. The specificity of NR2E1 binding to peptides in the array was evaluated using two single amino acid variants, R274G and R276Q, which disrupted the majority of the binding interactions observed with wild-type NR2E1. The decreased binding affinity of these variants to co-regulators was further validated by pull-down assays using atrophin1 as bait. Despite the high conservation of arginine 274 in vertebrates, its reduced interactions with co-regulators were not significant in vivo as determined by retinal phenotype analysis in single-copy Nr2e1-null mice carrying the variant R274G.

Conclusions

We showed that MARCoNI is a specific assay to test interactions of NR2E1 with candidate co-regulators. In this way, we unveiled 19 potential co-regulator partners for NR2E1, including eight co-activators. All the candidates here identified need to be further validated using in vitro and in vivo models. This assay was sensitive to point mutations in NR2E1 ligand binding domain making it useful to identify mutations and/or small molecules that alter binding of NR2E1 to protein partners.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3173-5) contains supplementary material, which is available to authorized users.

IRF5 and IRF5 Disease-Risk Variants Increase Glycolysis and Human M1 Macrophage Polarization by Regulating Proximal Signaling and Akt2 Activation

Interferon regulatory factor 5 (IRF5) regulates inflammatory M1 macrophage polarization, and disease-associated IRF5 genetic variants regulate pattern-recognition-receptor (PRR)-induced cytokines. PRR-stimulated macrophages and M1 macrophages exhibit enhanced glycolysis, a central mediator of inflammation. We find that IRF5 is needed for PRR-enhanced glycolysis in human macrophages and in mice in vivo. Upon stimulation of the PRR nucleotide binding oligomerization domain containing 2 (NOD2) in human macrophages, IRF5 binds RIP2, IRAK1, and TRAF6. IRF5, in turn, is required for optimal Akt2 activation, which increases expression of glycolytic pathway genes and HIF1A as well as pro-inflammatory cytokines and M1 polarization. Furthermore, pro-inflammatory cytokines and glycolytic pathways co-regulate each other. Rs2004640/rs2280714 TT/TT IRF5 disease-risk-carrier cells demonstrate increased IRF5 expression and increased PRR-induced Akt2 activation, glycolysis, pro-inflammatory cytokines, and M1 polarization relative to GG/CC carrier macrophages. Our findings identify that IRF5 disease-associated polymorphisms regulate diverse immunological and metabolic outcomes and provide further insight into mechanisms contributing to the increasingly recognized important role for glycolysis in inflammation.

TAK1 and IKK2, novel mediators of SCF-induced signaling and potential targets for c-Kit-driven diseases

NF-κB activation depends on the IKK complex consisting of the catalytically active IKK1 and 2 subunits and the scaffold protein NEMO. Hitherto, IKK2 activation has always been associated with IκBα degradation, NF-κB activation, and cytokine production. In contrast, we found that in SCF-stimulated primary bone marrow-derived mast cells (BMMCs), IKK2 is alternatively activated. Mechanistically, activated TAK1 mediates the association between c-Kit and IKK2 and therefore facilitates the Lyn-dependent IKK2 activation which suffices to mediate mitogenic signaling but, surprisingly, does not result in NF-κB activation. Moreover, the c-Kit-mediated and Lyn-dependent IKK2 activation is targeted by MyD88-dependent pathways leading to enhanced IKK2 activation and therefore to potentiated effector functions. In neoplastic cells, expressing constitutively active c-Kit mutants, activated TAK1 and IKKs do also not induce NF-κB activation but mediate uncontrolled proliferation, resistance to apoptosis and enables IL-33 to mediate c-Kit-dependent signaling. Together, we identified the formation of the c-Kit-Lyn-TAK1 signalosome which mediates IKK2 activation. Unexpectedly, this IKK activation is uncoupled from the NF-κB-machinery but is critical to modulate functional cell responses in primary-, and mediates uncontrolled proliferation and survival of tumor-mast cells. Therefore, targeting TAK1 and IKKs might be a novel approach to treat c-Kit-driven diseases.

Cis- and Trans-gnetin H from Paeonia suffruticosa suppress inhibitor kappa B kinase phosphorylation in LPS-stimulated human THP-1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

The inflammatory response is an important mechanism in host defense; however, overstimulation and chronic inflammation are involved in many important human diseases. Currently, tumor necrosis factor-alpha blockers such as infliximab and adalimumab along with methotrexate are used in cases of severe and chronic disease. However, there are severe side effects and limitations associated with these treatments. Cis- and trans-gnetin H are compounds isolated from the seeds of Paeonia suffruticosa, a medicinal plant used in traditional Chinese medicine for the treatment of many conditions, including inflammatory diseases. In this study, we investigated possible anti-inflammatory mechanisms of cis- and trans-gnetin H against LPS-stimulated human THP-1 cells.

MATERIAL AND METHODS

PMA-differentiated THP-1 cells were pretreated with increasing concentrations of cis- and trans-gnetin H with or without LPS. Following treatment, cytotoxicity and the TNF-α, IL-1β, and IL-8 response were measured. We also characterized the nuclear translocation of NF-κB subunit p65 (RelA) by immunofluorescence and then investigated NF-κB activation by measuring the phosphorylation of NF-κB mediators, IKK-β, IκB α, and p65 by western blotting.

RESULTS

We found that cis- and trans-gnetin H significantly inhibited the cytokine response in a concentration-dependent manner without affecting cell viability. Cis- and trans-gnetin H effectively inhibited nuclear translocation of p65 and phosphorylation of IKK-β, IκB α, and p65. While both compounds showed promising anti-inflammatory effects, trans-gnetin H was determined to be more effective in suppressing cytokine responses.

CONCLUSION

We demonstrated that cis- and trans-gnetin H suppress cytokine response in LPS-stimulated THP-1 cells by preventing activation of key signaling molecules, IKK-β, IκB α, and p65, involved in the NF-κB pathway and suggest the use of cis- and trans-gnetin H in potential therapies for conditions and diseases associated with chronic inflammation.

Hypoxia attenuates the proinflammatory response in colon cancer cells by regulating IκB

Two main features common to all solid tumors are tissue hypoxia and inflammation, both of which cause tumor progression, metastasis, therapy resistance and increased mortality. Chronic inflammation is associated with increased cancer risk, as demonstrated for inflammatory bowel disease patients developing colon cancer. However, the interplay between hypoxia and inflammation on the molecular level remains to be elucidated. We found that MC-38 mouse colon cancer cells contain functional hypoxic (HIF-1α) and inflammatory (p65/RelA) signaling pathways. In contrast to cells of the myeloid lineage, HIF-1α levels remained unaffected in MC-38 cells treated with LPS, and hypoxia failed to induce NF-κB. A similar regulation of canonical HIF and NF-κB target genes confirmed these results. RNA deep sequencing of HIF-1α and p65/RelA knock-down cells revealed that a surprisingly large fraction of HIF target genes required p65/RelA for hypoxic regulation and a number of p65/RelA target genes required HIF-1α for proinflammatory regulation, respectively. Hypoxia attenuated the inflammatory response to LPS by inhibiting nuclear translocation of p65/RelA independently of HIF-1α, which was associated with enhanced IκBα levels and decreased IKKβ phosphorylation. These data demonstrate that the interaction between hypoxic and inflammatory signaling pathways needs to be considered when designing cancer therapies targeting HIF or NF-κB.

Human Bocavirus NS1 and NS1-70 Proteins Inhibit TNF-α-Mediated Activation of NF-κB by targeting p65

Human bocavirus (HBoV), a parvovirus, is a single-stranded DNA etiologic agent causing lower respiratory tract infections in young children worldwide. Nuclear factor kappa B (NF-κB) transcription factors play crucial roles in clearance of invading viruses through activation of many physiological processes. Previous investigation showed that HBoV infection could significantly upregulate the level of TNF-α which is a strong NF-κB stimulator. Here we investigated whether HBoV proteins modulate TNF-α–mediated activation of the NF-κB signaling pathway. We showed that HBoV NS1 and NS1-70 proteins blocked NF-κB activation in response to TNF-α. Overexpression of TNF receptor-associated factor 2 (TRAF2)-, IκB kinase alpha (IKKα)-, IκB kinase beta (IKKβ)-, constitutively active mutant of IKKβ (IKKβ SS/EE)-, or p65-induced NF-κB activation was inhibited by NS1 and NS1-70. Furthermore, NS1 and NS1-70 didn’t interfere with TNF-α-mediated IκBα phosphorylation and degradation, nor p65 nuclear translocation. Coimmunoprecipitation assays confirmed the interaction of both NS1 and NS1-70 with p65. Of note, NS1 but not NS1-70 inhibited TNF-α-mediated p65 phosphorylation at ser536. Our findings together indicate that HBoV NS1 and NS1-70 inhibit NF-κB activation. This is the first time that HBoV has been shown to inhibit NF-κB activation, revealing a potential immune-evasion mechanism that is likely important for HBoV pathogenesis.

Gene Expression and Antiviral Activity of Interleukin-35 in Response to Influenza A Virus Infection

Interleukin-35 (IL-35) is a newly described member of the IL-12 family. It has been reported to inhibit inflammation and autoimmune inflammatory disease and can increase apoptotic sensitivity. Little is known about the role of IL-35 during viral infection. Herein, high levels of IL-35 were found in peripheral blood mononuclear cells and throat swabs from patients with seasonal influenza A virus (IAV) relative to healthy individuals. IAV infection of human lung epithelial and primary cells increased levels of IL-35 mRNA and protein. Further studies demonstrated that IAV-induced IL-35 transcription is regulated by NF-κB. IL-35 expression was significantly suppressed by selective inhibitors of cyclooxygenase-2 (COX-2) and inducible nitric-oxide synthase, indicating their involvement in IL-35 expression. Interestingly, IL-35 production may have suppressed IAV RNA replication and viral protein synthesis via induction of type I and III interferons (IFN), leading to activation of downstream IFN effectors, including double-stranded RNA-dependent protein kinase, 2',5'-oligoadenylate synthetase, and myxovirus resistance protein. IL-35 exhibited extensive antiviral activity against the hepatitis B virus, enterovirus 71, and vesicular stomatitis virus. Our results demonstrate that IL-35 is a novel IAV-inducible cytokine, and its production elicits antiviral activity.

Prodrugs Bioactivated to Quinones Target NF-κB and Multiple Protein Networks: Identification of the Quinonome

Electrophilic reactive intermediates resulting from drug metabolism have been associated with toxicity and off-target effects and in some drug discovery programs trigger NO-GO decisions. Many botanicals and dietary supplements are replete with such reactive electrophiles, notably Michael acceptors, which have been demonstrated to elicit chemopreventive mechanisms; and Michael acceptors are gaining regulatory approval as contemporary cancer therapeutics. Identifying protein targets of these electrophiles is central to understanding potential therapeutic benefit and toxicity risk. NO-donating NSAID prodrugs (NO-NSAIDs) have been the focus of extensive clinical and preclinical studies in inflammation and cancer chemoprevention and therapy: a subset exemplified by pNO-ASA, induces chemopreventive mechanisms following bioactivation to an electrophilic quinone methide (QM) Michael acceptor. Having previously shown that these NO-independent, QM-donors activated Nrf2 via covalent modification of Keap-1, we demonstrate that components of canonical NF-κB signaling are also targets, leading to the inhibition of NF-κB signaling. Combining bio-orthogonal probes of QM-donor ASA prodrugs with mass spectrometric proteomics and pathway analysis, we proceeded to characterize the quinonome: the protein cellular targets of QM-modification by pNO-ASA and its ASA pro-drug congeners. Further comparison was made using a biorthogonal probe of the "bare-bones", Michael acceptor, and clinical anti-inflammatory agent, dimethyl fumarate, which we have shown to inhibit NF-κB signaling. Identified quinonome pathways include post-translational protein folding, cell-death regulation, protein transport, and glycolysis; and identified proteins included multiple heat shock elements, the latter functionally confirmed by demonstrating activation of heat shock response.

The Ubiquitination of NF-κB Subunits in the Control of Transcription

Nuclear factor (NF)-κB has evolved as a latent, inducible family of transcription factors fundamental in the control of the inflammatory response. The transcription of hundreds of genes involved in inflammation and immune homeostasis require NF-κB, necessitating the need for its strict control. The inducible ubiquitination and proteasomal degradation of the cytoplasmic inhibitor of κB (IκB) proteins promotes the nuclear translocation and transcriptional activity of NF-κB. More recently, an additional role for ubiquitination in the regulation of NF-κB activity has been identified. In this case, the ubiquitination and degradation of the NF-κB subunits themselves plays a critical role in the termination of NF-κB activity and the associated transcriptional response. While there is still much to discover, a number of NF-κB ubiquitin ligases and deubiquitinases have now been identified which coordinate to regulate the NF-κB transcriptional response. This review will focus the regulation of NF-κB subunits by ubiquitination, the key regulatory components and their impact on NF-κB directed transcription.

Epidermal growth factor (EGF) triggers the malignancy of hemangioma cells via activation of NF-κB signals

Hemangioma (HA) is tumor formed by hyper-proliferation of vascular endothelial cells. However, the role and mechanisms of epidermal growth factor (EGF) on the progression of HA are not well illustrated. Our present study revealed that EGF can significantly promote the in vitro proliferation and motility of HA cells, which was confirmed by the up regulation of Bcl-2, proliferating cell nuclear antigen (PCNA), and metalloproteinase-2 (MMP-2) and MMP-9. The pharmacological inhibition of NF-κB, while not ERK1/2 or PI3K/Akt, attenuated EGF induced cell proliferation and expression of MMP-2 and MMP-9. EGF treatment also increased the phosphorylation, nuclear translocation and transcriptional activities of NF-κB in HA cells. These data suggested that NF-κB plays an essential role in EGF induced malignancy of HA cells. Furthermore, EGF treatment also increased the phosphorylation of IκB and IKKα, while not IKKβ or IKKγ. The knockdown of IKKα reversed EGF induced activation of NF-κB. EGF treatment also decreased the phosphorylation of GSK-3β and increased its activities in both HDEC and CRL-2586 EOMA cells. LiCl, a potent GSK-3β inhibitor, can obviously reverse EGF induced up regulation of p65 phosphorylation. Collectively, our study revealed that EGF can trigger the malignancy of HA cells via induction of proliferation and invasion. The activation of NF-κB through IKKα/IκBα and GSK-3β signal is essential for this process. It suggested that EGF/NF-κB signal may represent a novel therapeutic target for the treatment of human HA.

The effect of an IκB-kinase-β(IKKβ) inhibitor on tobacco smoke-induced pulmonary inflammation

PURPOSE OF THE STUDY

Inactivation of NF-κB with IKKβ knockout mice reduces tobacco smoke-induced pulmonary inflammation. In this study, we investigated whether the IKKβ inhibitor PS-1145 could attenuate the pulmonary inflammation induced by tobacco smoke.

MATERIALS AND METHODS

We divided 30 mice into three groups: a control group, a smoking group, and a PS-1145 group. Mice from the smoking and PS-1145 groups were exposed for 2 weeks to tobacco smoke. PS-1145 was injected intraperitoneally before every tobacco smoke exposure. After 2 weeks, bronchoalveolar lavage (BAL) was performed for cell counting and measuring of inflammatory chemokines. We analyzed the correlation between NF-κB and NF-κB-regulated chemokines in BAL fluid and measured the neutrophils and macrophages by immunostaining in lung tissues.

RESULTS

The PS-1145 group showed a significant reduction in the number of total cells, neutrophils, and macrophages, as well as the KC and MCP-1 level, in the BAL fluid compared to the smoking group. There was no significant difference in the level of MIP-1α. The level of NF-κB in BAL fluid was significantly positively correlated with KC and MCP-1 levels, but not with MIP-1α level. The PS-1145 group also showed a significant fewer neutrophils and macrophages in the lung tissue.

CONCLUSIONS

We conclude that the IKKβ inhibitor PS-1145 suppressed the NF-κB signaling pathway and reduced the recruitment of inflammatory cells and chemokines in pulmonary inflammation induced by tobacco smoke. IKKβ inhibition offers a potential therapeutic target for tobacco smoke-induced pulmonary inflammation.

TNF-α Modulation of Intestinal Tight Junction Permeability Is Mediated by NIK/IKK-α Axis Activation of the Canonical NF-κB Pathway

Tumor necrosis factor (TNF)-α, a key mediator of intestinal inflammation, causes an increase in intestinal epithelial tight junction (TJ) permeability by activating myosin light chain kinase (MLCK; official name MYLK3) gene. However, the precise signaling cascades that mediate the TNF-α-induced activation of MLCK gene and increase in TJ permeability remain unclear. Our aims were to delineate the upstream signaling mechanisms that regulate the TNF-α modulation of intestinal TJ barrier function with the use of in vitro and in vivo intestinal epithelial model systems. TNF-α caused a rapid activation of both canonical and noncanonical NF-κB pathway. NF-κB-inducing kinase (NIK) and mitogen-activated protein kinase kinase-1 (MEKK-1) were activated in response to TNF-α. NIK mediated the TNF-α activation of inhibitory κB kinase (IKK)-α, and MEKK1 mediated the activation of IKK complex, including IKK-β. NIK/IKK-α axis regulated the activation of both NF-κB p50/p65 and RelB/p52 pathways. Surprisingly, the siRNA induced knockdown of NIK, but not MEKK-1, prevented the TNF-α activation of both NF-κB p50/p65 and RelB/p52 and the increase in intestinal TJ permeability. Moreover, NIK/IKK-α/NF-κB p50/p65 axis mediated the TNF-α-induced MLCK gene activation and the subsequent MLCK increase in intestinal TJ permeability. In conclusion, our data show that NIK/IKK-α/regulates the activation of NF-κB p50/p65 and plays an integral role in the TNF-α-induced activation of MLCK gene and increase in intestinal TJ permeability.

Activation of G-Protein-Coupled Estrogen Receptor Inhibits the Migration of Human Nonsmall Cell Lung Cancer Cells via IKK-β/NF-κB Signals

Estrogen signals have been suggested to modulate the progression and metastasis of nonsmall cell lung cancer (NSCLC), which is one of the leading causes of cancer deaths worldwide. While there are limited data concerning the roles and effects of G-protein-coupled estrogen receptor (GPER) on the progression of NSCLC, our present study reveals that the expression of GPER in NSCLC cells is obviously greater than that in lung fibroblast cell line MRC-5. Activation of GPER via its specific agonist G-1 decreases the in vitro motility of A549 and H358 cells and the expression of matrix metalloproteinase 2 (MMP-2) and MMP-9. Further, G-1 treatment can rapidly decrease the phosphorylation, nuclear translocation, and promoter activities of NF-κB in NSCLC cells. BAY 11-7082, the inhibitor of NF-κB, also inhibits the expression of MMP-2/9, while overexpression of p65 significantly attenuates G-1-induced downregulation of MMP-2/9. It suggests that inhibition of NF-κB mediates G-1-induced MMP-2/9 downregulation. G-1 treatment significantly down regulates the phosphorylation of IκB kinase β (IKK-β) and IκBα, while not IKK-α, in both 549 and H358 cells. ACHP, the specific inhibitor of IKK-β, can reinforce G-1-induced MMP-2/9 downregulation and invasion suppression of A549 cells. Collectively, our results suggest that activation of GPER can inhibit the migration of human NSCLC cells via suppression of IKK-β/NF-κB signals. These findings will help to better understand the roles and mechanisms of GPER as a potential therapy target for NSCLC patients.

Latanoprost-induced Cytokine and Chemokine Release From Human Tenon's Capsule Fibroblasts: Role of MAPK and NF-κB Signaling Pathways

PURPOSE

Long-term topical antiglaucoma therapy is considered a significant risk factor for failure of trabeculectomy. We investigated the effects of antiglaucoma drugs on proinflammatory cytokine and chemokine release from cultured human Tenon's capsule fibroblasts (HTFs) as well as the signaling pathways that underlie such effects.

MATERIALS AND METHODS

Release of the proinflammatory cytokine interleukin (IL)-6 and the chemokines IL-8 and monocyte chemotactic protein (MCP)-1 was measured with enzyme-linked immunosorbent assays. The phosphorylation (activation) of mitogen-activated protein kinases (MAPKs) as well as the phosphorylation and degradation of the nuclear factor-κB (NF-κB) inhibitor IκB-α were assessed by immunoblot analysis.

RESULTS

Latanoprost stimulated the release of IL-6, IL-8, and MCP-1 from HTFs in a concentration-dependent and time-dependent manner, whereas timolol maleate and pilocarpine had no such effects. Latanoprost also activated the MAPKs extracellular signal-regulated kinase, p38, and c-Jun NH2-terminal kinase as well as induced the phosphorylation and degradation of IκB-α in these cells. The latanoprost-induced release of IL-6, IL-8, and MCP-1 was attenuated by inhibitors of MAPK (PD98059, SB203580, or JNK inhibitor II) or NF-κB (IκB kinase 2 inhibitor) signaling pathways.

CONCLUSIONS

Latanoprost induced proinflammatory cytokine and chemokine release from HTFs in a manner dependent on MAPK and NF-κB signaling. These effects of latanoprost might influence bleb scarring after filtration surgery.

Phospholipase Cϵ Activates Nuclear Factor-κB Signaling by Causing Cytoplasmic Localization of Ribosomal S6 Kinase and Facilitating Its Phosphorylation of Inhibitor κB in Colon Epithelial Cells

Phospholipase Cϵ (PLCϵ), an effector of Ras and Rap small GTPases, plays a crucial role in inflammation by augmenting proinflammatory cytokine expression. This proinflammatory function of PLCϵ is implicated in its facilitative role in tumor promotion and progression during skin and colorectal carcinogenesis, although their direct link remains to be established. Moreover, the molecular mechanism underlying these functions of PLCϵ remains unknown except that PKD works downstream of PLCϵ. Here we show by employing the colitis-induced colorectal carcinogenesis model, where Apc(Min) (/+) mice are administered with dextran sulfate sodium, that PLCϵ knock-out alleviates the colitis and suppresses the following tumorigenesis concomitant with marked attenuation of proinflammatory cytokine expression. In human colon epithelial Caco2 cells, TNF-α induces sustained expression of proinflammatory molecules and sustained activation of nuclear factor-κB (NF-κB) and PKD, the late phases of which are suppressed by not only siRNA-mediated PLCϵ knockdown but also treatment with a lysophosphatidic acid (LPA) receptor antagonist. Also, LPA stimulation induces these events in an early time course, suggesting that LPA mediates TNF-α signaling in an autocrine manner. Moreover, PLCϵ knockdown results in inhibition of phosphorylation of IκB by ribosomal S6 kinase (RSK) but not by IκB kinases. Subcellular fractionation suggests that enhanced phosphorylation of a scaffolding protein, PEA15 (phosphoprotein enriched in astrocytes 15), downstream of the PLCϵ-PKD axis causes sustained cytoplasmic localization of phosphorylated RSK, thereby facilitating IκB phosphorylation in the cytoplasm. These results suggest the crucial role of the TNF-α-LPA-LPA receptor-PLCϵ-PKD-PEA15-RSK-IκB-NF-κB pathway in facilitating inflammation and inflammation-associated carcinogenesis in the colon.

Epithelial IL-18 Equilibrium Controls Barrier Function in Colitis

The intestinal mucosal barrier controlling the resident microbiome is dependent on a protective mucus layer generated by goblet cells, impairment of which is a hallmark of the inflammatory bowel disease, ulcerative colitis. Here, we show that IL-18 is critical in driving the pathologic breakdown of barrier integrity in a model of colitis. Deletion of Il18 or its receptor Il18r1 in intestinal epithelial cells (Δ/EC) conferred protection from colitis and mucosal damage in mice. In contrast, deletion of the IL-18 negative regulator Il18bp resulted in severe colitis associated with loss of mature goblet cells. Colitis and goblet cell loss were rescued in Il18bp(-/-);Il18r(Δ/EC) mice, demonstrating that colitis severity is controlled at the level of IL-18 signaling in intestinal epithelial cells. IL-18 inhibited goblet cell maturation by regulating the transcriptional program instructing goblet cell development. These results inform on the mechanism of goblet cell dysfunction that underlies the pathology of ulcerative colitis.

Inhibitory effect of baicalin on allergic response in ovalbumin-induced allergic rhinitis guinea pigs and lipopolysaccharide-stimulated human mast cells

OBJECTIVE

Baicalin, a flavonoid compound purified from the dry roots of Scutellaria baicalensis Georgi, has generally been used for the treatment of various allergic diseases. However, there is little information about the anti-inflammatory effects of baicalin for allergic rhinitis. This study aims to investigate the anti-allergic effect of baicalin on allergic response in ovalbumin (OVA)-induced allergic rhinitis guinea pigs and lipopolysaccharide (LPS)-stimulated human mast cells.

METHODS

Using in vivo models, we evaluated the effect of baicalin on allergic rhinitis symptoms via recording the number of nasal rubs and sneezes. The levels of histamine, OVA-specific immunoglobulin E(IgE), eosinophil cationic protein (ECP) and inflammatory cytokines were measured using enzyme-linked immunosorbent assay (ELISA). The histological changes of nasal mucosa were observed by light microscope after HE staining. In vitro, the release of histamine and β-hexosaminidase of compound 48/80-induced human mast cells were measured by ELISA and PNP-NAG colorimetry, respectively. The productions of inflammatory cytokines of LPS-stimulated human mast cells were determined using ELISA. Western blot was used to test the protein expression of JAK2, p-JAK2, STAT5, p-STAT5, IKKβ, p-IKKβ, IκBα, p-IκBα and NF-κB (p65) of LPS-stimulated human mast cells.

RESULTS

The oral administration of baicalin at doses of 50 and 200 mg/kg improved allergic rhinitis symptoms and the histological changes of nasal mucosa and decreased the serum levels of histamine, ECP, interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF)-α and OVA-specific IgE in OVA-induced allergic rhinitis guinea pigs. In vitro, baicalin suppressed the release of histamine and β-hexosaminidase in compound 48/80-induced human mast cells. In addition, baicalin also inhibited the productions of inflammatory cytokines such as IL-1β, IL-6, IL-8 and TNF-α and suppressed the phosphorylation of JAK2, STAT5, IKKβ, IκBα and the nuclear translocation of NF-κB (p65) subunit in LPS-stimulated human mast cells.

CONCLUSIONS

These results suggest that baicalin can effectively prevent allergic response in OVA-induced allergic rhinitis guinea pigs and inhibit inflammatory response via blocking JAK2-STAT5 and NF-κB signaling pathways in LPS-stimulated human mast cells. Considered together,the results show that baicalin may be a useful drug in the treatment of allergic rhinitis.

Inflammatory MAPK and NF-κB signaling pathways differentiated hepatitis potential of two agglomerated titanium dioxide particles

TiO2 nanoparticles (TiO2NPs) consumption and deposit in liver have possible implications for hepatitis risks. Specific signal dysregulation at early inflammatory responses needs to be characterized in TiO2NP-induced hepatopathy. MAPK and NF-κB signaling pathways are known to participate in inflammation and respond sensitively to chemical agents, making them preferable biomarkers for hepatitis. In the present study, dynamic activation of MAPK and NF-κB pathways were explored by immunoblotting and NF-κB luciferase reporter assay depending on characterization of TiO2NP agglomeration in human HepG2 cells. Inflammatory and cytotoxic potential of TiO2NPs were determined by qRT-PCR and WST-1 assay. AFM and TEM analyses uncovered ultrastructure damages underlying hepatotoxicity of TiO2NPs. Rod-like rutile agglomerated smaller and induced more pronounced cytotoxicity and immunogenicity than anatase. Correspondingly, though both rutile and anatase significantly activated p38, ERK1/2 and NF-κB pathways, rutile accelerated the maximum phosphorylation of ERK1/2 and elevated the potency of IκBα phosphorylation to its bell curve shape in comparison with a lower and sigmoid type of IκBα phosphorylation for anatase. Furthermore, cell elasticity indicated by Young's modulus and adhesion force increased accompanied with mitochondria damage, contributing to signal dysregulation and hepatotoxicity. The results suggested that differential activation of MAPK and NF-κB pathways could be early predictors for distinct hepatitis risks of two agglomerated TiO2NPs.

Regulation of signal transduction by spatial parameters: a case in NF-κB oscillation

NF-κB is a transcription factor regulating expression of more than 500 genes, and its dysfunction leads to the autoimmune and inflammatory diseases. In malignant cancer cells, NF-κB is constitutively activated. Thus the elucidation of mechanisms for NF-κB regulation is important for the establishment of therapeutic treatment caused by incorrect NF-κB responses. Cytoplasmic NF-κB translocates to the nucleus by the application of extracellular stimuli such as cytokines. Nuclear NF-κB is known to oscillate with the cycle of 1.5-4.5 h, and it is thought that the oscillation pattern regulates the expression profiles of genes. In this review, first we briefly describe regulation mechanisms of NF-κB. Next, published computational simulations on the oscillation of NF-κB are summarised. There are at least 60 reports on the computational simulation and analysis of NF-κB oscillation. Third, the importance of a 'space' for the regulation of oscillation pattern of NF-κB is discussed, showing altered oscillation pattern by the change in spatial parameters such as diffusion coefficient, nuclear to cytoplasmic volume ratio (N/C ratio), and transport through nuclear membrane. Finally, simulations in a true intracellular space (TiCS), which is an intracellular 3D space reconstructed in a computer with organelles such as nucleus and mitochondria are discussed.

V-PYRRO/NO downregulates mRNA expression levels of leukotriene C4 synthase during hepatic ischemia reperfusion injury in rats via inhibition of the nuclear factor-κB activation pathway

The aim of the present study was to explore the mechanism underlying the effects of a selective liver nitric oxide (NO) donor, O²-vinyl1-(pyrrolidin-1-yl)-diazen-1-ium-1,2-diolate (V-PYRRO/NO), on the gene expression of leukotriene C4 synthase (LTC4S) during hepatic ischemia/reperfusion (I/R). Adult male Sprague-Dawley rats were divided into 3 groups: Sham (control), I/R and V-PYRRO/NO + I/R groups. The liver was subjected to 1 h of partial hepatic ischemia followed by 5 h of reperfusion, saline or V-PYRRO/NO (1.06 µmol/kg/h) administered intravenously. The mRNA expression levels of LTC4S in rat liver tissue were examined by the reverse transcription-polymerase chain reaction method, the protein expression levels of nuclear factor-κB (NF-κB) p65, p50 and IκBα in liver cell lysates and nuclear extracts were detected by western blot analysis. Hepatic mRNA expression of LTC4S was lower in V-PYRRO/NO + I/R group compared to the I/R group. In addition, the protein expression levels of NF-κB p65 and p50 in the nucleus extract were lower in the V-PYRRO/NO + I/R group when compared with the I/R group. However, the IκBα protein in the 3 groups was not changed. Immunohistochemistry staining revealed that the I/R liver exhibited strong cytoplasmic and nuclear staining for NF-κB p65; however, the V-PYRRO/NO + I/R group liver presented slight cytoplasmic and nuclear staining. In conclusion, V-PYRRO/NO may downregulate LTC4S mRNA expression by inhibiting NF-κB activation independent of IκBα during hepatic I/R injury.

Possible Involvement of the Inhibition of NF-κB Factor in Anti-Inflammatory Actions That Melatonin Exerts on Mast Cells

Melatonin is a molecule endogenously produced in a wide variety of immune cells, including mast cells (RBL-2H3). It exhibits immunomodulatory, anti-inflammatory and anti-apoptotic properties. The physiologic mechanisms underlying these activities of melatonin have not been clarified in mast cells. This work is designed to determine the anti-inflammatory effect and mechanism of action of melatonin on activated mast cells. RBL-2H3 were pre-treated with exogenous melatonin (MELx) at physiological (100nM) and pharmacological (1 mM) doses for 30 min, washed and activated with PMACI (phorbol 12-myristate 13-acetate plus calcium ionophore A23187) for 2 h and 12 h. The data shows that pre-treatment of MELx in stimulated mast cells, significantly reduced the levels of endogenous melatonin production (MELn), TNF-α and IL-6. These effects are directly related with the MELx concentration used. MELx also inhibited IKK/NF-κB signal transduction pathway in stimulated mast cells. These results indicate a molecular basis for the ability of melatonin to prevent inflammation and for the treatment of allergic inflammatory diseases through the down-regulation of mast cell activation. J. Cell. Biochem. 117: 1926-1933, 2016. © 2016 Wiley Periodicals, Inc.

ESCRT proteins restrict constitutive NF-κB signaling by trafficking cytokine receptors

Because signaling mediated by the transcription factor nuclear factor κB (NF-κB) is initiated by ligands and receptors that can undergo internalization, we investigated how endocytic trafficking regulated this key physiological pathway. We depleted all of the ESCRT (endosomal sorting complexes required for transport) subunits, which mediate receptor trafficking and degradation, and found that the components Tsg101, Vps28, UBAP1, and CHMP4B were essential to restrict constitutive NF-κB signaling in human embryonic kidney 293 cells. In the absence of exogenous cytokines, depletion of these proteins led to the activation of both canonical and noncanonical NF-κB signaling, as well as the induction of NF-κB-dependent transcriptional responses in cultured human cells, zebrafish embryos, and fat bodies in flies. These effects depended on cytokine receptors, such as the lymphotoxin β receptor (LTβR) and tumor necrosis factor receptor 1 (TNFR1). Upon depletion of ESCRT subunits, both receptors became concentrated on and signaled from endosomes. Endosomal accumulation of LTβR induced its ligand-independent oligomerization and signaling through the adaptors TNFR-associated factor 2 (TRAF2) and TRAF3. These data suggest that ESCRTs constitutively control the distribution of cytokine receptors in their ligand-free state to restrict their signaling, which may represent a general mechanism to prevent spurious activation of NF-κB.

Lycopene acts through inhibition of IκB kinase to suppress NF-κB signaling in human prostate and breast cancer cells

We studied the effect of the potent dietary antioxidant lycopene on multiple points along the nuclear factor kappa B (NF-κB) signaling pathway in prostate and breast cancer cells. Lycopene significantly inhibited prostate and breast cancer cell growth at physiologically relevant concentrations of ≥1.25 μM. Similar concentrations also caused a 30-40 % reduction in inhibitor of kappa B (IκB) phosphorylation in the cells, as determined by western blotting. Furthermore, the same degree of inhibition by lycopene was observed for NF-κB transcriptional activity, as determined by reporter gene assay. Concomitant with this, immunofluorescence staining of lycopene-treated cells showed a significant suppression (≥25 %) of TNF-induced NF-κB p65 subunit nuclear translocation. Further probing of lycopene's effects on upstream elements of the NF-κB pathway showed a 25 % inhibition of both activity of recombinant IκB kinase β (IKKβ) kinase in a cell-free in vitro assay, as well as activity of IKKβ immunoprecipitated from MDA-MB-231 cells treated with lycopene. In conclusion, the anticancer properties of lycopene may occur through inhibition of the NF-κB signaling pathway, beginning at the early stage of cytoplasmic IKK kinase activity, which then leads to reduced NF-κB-responsive gene regulation. Furthermore, these effects in cancer cells were observed at concentrations of lycopene that are relevant and achievable in vivo.

Dimethyl Fumarate Inhibits the Nuclear Factor κB Pathway in Breast Cancer Cells by Covalent Modification of p65 Protein

In breast tumors, activation of the nuclear factor κB (NFκB) pathway promotes survival, migration, invasion, angiogenesis, stem cell-like properties, and resistance to therapy--all phenotypes of aggressive disease where therapy options remain limited. Adding an anti-inflammatory/anti-NFκB agent to breast cancer treatment would be beneficial, but no such drug is approved as either a monotherapy or adjuvant therapy. To address this need, we examined whether dimethyl fumarate (DMF), an anti-inflammatory drug already in clinical use for multiple sclerosis, can inhibit the NFκB pathway. We found that DMF effectively blocks NFκB activity in multiple breast cancer cell lines and abrogates NFκB-dependent mammosphere formation, indicating that DMF has anti-cancer stem cell properties. In addition, DMF inhibits cell proliferation and significantly impairs xenograft tumor growth. Mechanistically, DMF prevents p65 nuclear translocation and attenuates its DNA binding activity but has no effect on upstream proteins in the NFκB pathway. Dimethyl succinate, the inactive analog of DMF that lacks the electrophilic double bond of fumarate, is unable to inhibit NFκB activity. Also, the cell-permeable thiol N-acetyl l-cysteine, reverses DMF inhibition of the NFκB pathway, supporting the notion that the electrophile, DMF, acts via covalent modification. To determine whether DMF interacts directly with p65, we synthesized and used a novel chemical probe of DMF by incorporating an alkyne functionality and found that DMF covalently modifies p65, with cysteine 38 being essential for the activity of DMF. These results establish DMF as an NFκB inhibitor with anti-tumor activity that may add therapeutic value in the treatment of aggressive breast cancers.

NF-kappaB Signaling Pathways in Neurological Inflammation: A Mini Review

The NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells) transcription factor family is a pleiotropic regulator of many cellular signaling pathways, providing a mechanism for the cells in response to a wide variety of stimuli linking to inflammation. The stimulated cells will be regulated by not only the canonical but also non-canonical NF-κB pathways. To initiate both of these pathways, IκB-degradation triggers NF-κB release and the nuclear translocated-heterodimer (or homodimer) can associate with the κB sites of promoter to regulate the gene transcriptions. NF-κB ubiquitously expresses in neurons and the constitutive NF-κB activation is associated with processing of neuronal information. NF-κB can regulate the transcription of genes such as chemokines, cytokines, proinflammatory enzymes, adhesion molecules, proinflammatory transcription factors, and other factors to modulate the neuronal survival. In neuronal insult, NF-κB constitutively active in neuron cell bodies can protect neurons against different injuries and regulate the neuronal inflammatory reactions. Besides neurons, NF-κB transcription factors are abundant in glial cells and cerebral blood vessels and the diverse functions of NF-κB also regulate the inflammatory reaction around the neuronal environment. NF-κB transcription factors are abundant in the brain and exhibit diverse functions. Several central nerve system (CNS) diseases are linked to NF-κB activated by inflammatory mediators. The RelA and c-Rel expression produce opposite effects on neuronal survival. Importantly, c-Rel expression in CNS plays a critical role in anti-apoptosis and reduces the age-related behaviors. Moreover, the different subunits of NF-κB dimer formation can modulate the neuroninflammation, neuronal protection, or neurotoxicity. The diverse functions of NF-κB depend on the subunits of the NF-κB dimer-formation which enable us to develop a therapeutic approach to neuroinflammation based on a new concept of inflammation as a strategic tool in neuronal cells. However, the detail role of NF-κB in neuroinflammation, remains to be clarified. In the present article, we provide an updated review of the current state of our knowledge about relationship between NF-κB and neuroinflammation.

Necrosis-Induced Sterile Inflammation Mediated by Interleukin-1α in Retinal Pigment Epithelial Cells

Endogenous danger signals released from necrotic cells contribute to retinal inflammation. We have now investigated the effects of necrotic cell extracts prepared from ARPE-19 human retinal pigment epithelial cells (ANCE) on the release of proinflammatory cytokines and chemokines by healthy ARPE-19 cells. ANCE were prepared by subjection of ARPE-19 cells to freeze-thaw cycles. The release of various cytokines and chemokines from ARPE-19 cells was measured with a multiplex assay system or enzyme-linked immunosorbent assays. The expression of interleukin (IL)–1α and the phosphorylation and degradation of the endogenous nuclear factor–κB (NF-κB) inhibitor IκB-α were examined by immunoblot analysis. Among the various cytokines and chemokines examined, we found that ANCE markedly stimulated the release of the proinflammatory cytokine IL-6 and the chemokines IL-8 and monocyte chemoattractant protein (MCP)–1 by ARPE-19 cells. ANCE-induced IL-6, IL-8, and MCP-1 release was inhibited by IL-1 receptor antagonist and by an IKK2 inhibitor (a blocker of NF-κB signaling) in a concentration-dependent manner, but was not affected by a pan-caspase inhibitor (Z-VAD-FMK). Recombinant IL-1α also induced the secretion of IL-6, IL-8, and MCP-1 from ARPE-19 cells, and IL-1α was detected in ANCE. Furthermore, ANCE induced the phosphorylation and degradation of IκB-α in ARPE-19 cells. Our findings thus suggest that IL-1α is an important danger signal that is released from necrotic retinal pigment epithelial cells and triggers proinflammatory cytokine and chemokine secretion from intact cells in a manner dependent on NF-κB signaling. IL-1α is therefore a potential therapeutic target for amelioration of sterile inflammation in the retina.

Inhibition of NF-κB by deoxycholic acid induces miR-21/PDCD4-dependent hepatocellular apoptosis

MicroRNAs (miRNAs/miRs) are key regulators of liver metabolism, while toxic bile acids participate in the development of several liver diseases. We previously demonstrated that deoxycholic acid (DCA), a cytotoxic bile acid implicated in the pathogenesis of non-alcoholic fatty liver disease, inhibits miR-21 expression in hepatocytes. Here, we investigated the mechanisms by which DCA modulates miR-21 and whether miR-21 contributes for DCA-induced cytotoxicity. DCA inhibited miR-21 expression in primary rat hepatocytes in a dose-dependent manner, and increased miR-21 pro-apoptotic target programmed cell death 4 (PDCD4) and apoptosis. Both miR-21 overexpression and PDCD4 silencing hampered DCA-induced cell death. Further, DCA decreased NF-κB activity, shown to represent an upstream mechanism leading to modulation of the miR-21/PDCD4 pathway. In fact, NF-κB overexpression or constitutive activation halted miR-21-dependent apoptosis by DCA while opposite results were observed upon NF-κB inhibition. In turn, DCA-induced oxidative stress resulted in caspase-2 activation and NF-κB/miR-21 inhibition, in a PIDD-dependent manner. Finally, modulation of the NF-κB/miR-21/PDCD4 pro-apoptotic pathway by DCA was also shown to occur in the rat liver in vivo. These signalling circuits may constitute appealing targets for bile acid-associated liver pathologies.

Mixed effects of suberoylanilide hydroxamic acid (SAHA) on the host transcriptome and proteome and their implications for HIV reactivation from latency

Suberoylanilide hydroxamic acid (SAHA) has been assessed in clinical trials as part of a "shock and kill" strategy to cure HIV-infected patients. While it was effective at inducing expression of HIV RNA ("shock"), treatment with SAHA did not result in a reduction of reservoir size ("kill"). We therefore utilized a combined analysis of effects of SAHA on the host transcriptome and proteome to dissect its mechanisms of action that may explain its limited success in "shock and kill" strategies. CD4+ T cells from HIV seronegative donors were treated with 1μM SAHA or its solvent dimethyl sulfoxide (DMSO) for 24h. Protein expression and post-translational modifications were measured with iTRAQ proteomics using ultra high-precision two-dimensional liquid chromatography-tandem mass spectrometry. Gene expression was assessed by Illumina microarrays. Using limma package in the R computing environment, we identified 185 proteins, 18 phosphorylated forms, 4 acetylated forms and 2982 genes, whose expression was modulated by SAHA. A protein interaction network integrating these 4 data types identified the HIV transcriptional repressor HMGA1 to be upregulated by SAHA at the transcript, protein and acetylated protein levels. Further functional category assessment of proteins and genes modulated by SAHA identified gene ontology terms related to NFκB signaling, protein folding and autophagy, which are all relevant to HIV reactivation. In summary, SAHA modulated numerous host cell transcripts, proteins and post-translational modifications of proteins, which would be expected to have very mixed effects on the induction of HIV-specific transcription and protein function. Proteome profiling highlighted a number of potential counter-regulatory effects of SAHA with respect to viral induction, which transcriptome profiling alone would not have identified. These observations could lead to a more informed selection and design of other HDACi with a more refined targeting profile, and prioritization of latency reversing agents of other classes to be used in combination with SAHA to achieve more potent induction of HIV expression.

The ubiquitin ligase HERC3 attenuates NF-κB-dependent transcription independently of its enzymatic activity by delivering the RelA subunit for degradation

Activation of NF-κB-dependent transcription represents an important hallmark of inflammation. While the acute inflammatory response is per se beneficial, it can become deleterious if its spatial and temporal profile is not tightly controlled. Classically, NF-κB activity is limited by cytoplasmic retention of the NF-κB dimer through binding to inhibitory IκB proteins. However, increasing evidence suggests that NF-κB activity can also be efficiently contained by direct ubiquitination of NF-κB subunits. Here, we identify the HECT-domain ubiquitin ligase HERC3 as novel negative regulator of NF-κB activity. We find that HERC3 restricts NF-κB nuclear import and DNA binding without affecting IκBα degradation. Instead HERC3 indirectly binds to the NF-κB RelA subunit after liberation from IκBα inhibitor leading to its ubiquitination and protein destabilization. Remarkably, the regulation of RelA activity by HERC3 is independent of its inherent ubiquitin ligase activity. Rather, we show that HERC3 and RelA are part of a multi-protein complex containing the proteasome as well as the ubiquitin-like protein ubiquilin-1 (UBQLN1). We present evidence that HERC3 and UBQLN1 provide a link between NF-κB RelA and the 26S proteasome, thereby facilitating RelA protein degradation. Our findings establish HERC3 as novel candidate regulating the inflammatory response initiated by NF-κB.

The IκB kinase inhibitor ACHP strongly attenuates TGFβ1-induced myofibroblast formation and collagen synthesis

Excessive accumulation of a collagen‐rich extracellular matrix (ECM) by myofibroblasts is a characteristic feature of fibrosis, a pathological state leading to serious organ dysfunction. Transforming growth factor beta1 (TGFβ1) is a strong inducer of myofibroblast formation and subsequent collagen production. Currently, there are no remedies for the treatment of fibrosis. Activation of the nuclear factor kappa B (NF‐κB) pathway by phosphorylating IκB with the enzyme IκB kinase (IKK) plays a major role in the induction of fibrosis. ACHP {2‐Amino‐6‐[2‐(cyclopropylmethoxy)‐6‐hydroxyphenyl]‐4‐(4‐piperidinyl)‐3 pyridinecarbonitrile}, a selective inhibitor of IKK, prohibits the activation of the NF‐κB pathway. It is not known whether ACHP has potential anti‐fibrotic properties. Using adult human dermal and lung fibroblasts we have investigated whether ACHP has the ability to inhibit the TGFβ1‐induced transition of fibroblasts into myofibroblasts and its excessive synthesis of ECM. The presence of ACHP strongly suppressed the induction of the myofibroblast markers alpha‐smooth muscle actin (αSMA) and SM22α, as well as the deposition of the ECM components collagen type I and fibronectin. Furthermore, post‐treatment with ACHP partly reversed the expression of αSMA and collagen type I production. Finally, ACHP suppressed the expression of the three collagen‐modifying enzymes lysyl hydroxylase (PLOD1,PLOD2 and PLOD3) in dermal fibroblasts, but did not do so in lung fibroblasts. We conclude that the IKK inhibitor ACHP has potent antifibrotic properties, and that the NF‐κB pathway plays an important role in myofibroblast biology.

Transcriptional Regulation of the Astrocytic Excitatory Amino Acid Transporter 1 (EAAT1) via NF-κB and Yin Yang 1 (YY1)

Astrocytic glutamate transporter excitatory amino acid transporter (EAAT) 1, also known as glutamate aspartate transporter (GLAST) in rodents, is one of two glial glutamate transporters that are responsible for removing excess glutamate from synaptic clefts to prevent excitotoxic neuronal death. Despite its important role in neurophysiological functions, the molecular mechanisms of EAAT1 regulation at the transcriptional level remain to be established. Here, we report that NF-κB is a main positive transcription factor for EAAT1, supported by the following: 1) EAAT1 contains two consensus sites for NF-κB, 2) mutation of NF-κB binding sites decreased EAAT1 promoter activity, and 3) activation of NF-κB increased, whereas inhibition of NF-κB decreased EAAT1 promoter activity and mRNA/protein levels. EGF increased EAAT1 mRNA/protein levels and glutamate uptake via NF-κB. The transcription factor yin yang 1 (YY1) plays a role as a critical negative regulator of EAAT1, supported by the following: 1) the EAAT1 promoter contains multiple consensus sites for YY1, 2) overexpression of YY1 decreased EAAT1 promoter activity and mRNA/protein levels, and 3) knockdown of YY1 increased EAAT1 promoter activity and mRNA/protein levels. Manganese decreased EAAT1 expression via YY1. Epigenetic modifiers histone deacetylases (HDACs) served as co-repressors of YY1 to further decrease EAAT1 promoter activity, whereas inhibition of HDACs reversed manganese-induced decrease of EAAT1 expression. Taken together, our findings suggest that NF-κB is a critical positive regulator of EAAT1, mediating the stimulatory effects of EGF, whereas YY1 is a negative regulator of EAAT1 with HDACs as co-repressors, mediating the inhibitory effects of manganese on EAAT1 regulation.

MTMR3 risk allele enhances innate receptor-induced signaling and cytokines by decreasing autophagy and increasing caspase-1 activation

Inflammatory bowel disease (IBD) is characterized by dysregulated host:microbial interactions and cytokine production. Host pattern recognition receptors (PRRs) are critical in regulating these interactions. Multiple genetic loci are associated with IBD, but altered functions for most, including in the rs713875 MTMR3/HORMAD2/LIF/OSM region, are unknown. We identified a previously undefined role for myotubularin-related protein 3 (MTMR3) in amplifying PRR-induced cytokine secretion in human macrophages and defined MTMR3-initiated mechanisms contributing to this amplification. MTMR3 decreased PRR-induced phosphatidylinositol 3-phosphate (PtdIns3P) and autophagy levels, thereby increasing PRR-induced caspase-1 activation, autocrine IL-1β secretion, NFκB signaling, and, ultimately, overall cytokine secretion. This MTMR3-mediated regulation required the N-terminal pleckstrin homology-GRAM domain and Cys413 within the phosphatase domain of MTMR3. In MTMR3-deficient macrophages, reducing the enhanced autophagy or restoring NFκB signaling rescued PRR-induced cytokines. Macrophages from rs713875 CC IBD risk carriers demonstrated increased MTMR3 expression and, in turn, decreased PRR-induced PtdIns3P and autophagy and increased PRR-induced caspase-1 activation, signaling, and cytokine secretion. Thus, the rs713875 IBD risk polymorphism increases MTMR3 expression, which modulates PRR-induced outcomes, ultimately leading to enhanced PRR-induced cytokines.