Noncanonical NF-κB signaling is limited by classical NF-κB activity

Update in the molecular mechanism and biomarkers of diabetic retinopathy

Diabetic retinopathy (DR) is a serious complication of diabetes caused by long-term hyperglycemia that leads to microvascular and neuronal damage in the retina. The molecular mechanisms of DR involve oxidative stress, inflammatory responses, neurodegenerative changes, and vascular dysfunction triggered by hyperglycemia. Oxidative stress activates multiple metabolic pathways, such as the polyol, hexosamine, and protein kinase C (PKC) pathways, resulting in the production of, which in turn promote the formation of advanced glycation end products (AGEs). These pathways exacerbate vascular endothelial damage and the release of inflammatory factors, activating inflammatory signaling pathways such as the NF-κB pathway, leading to retinal cell damage and apoptosis. Additionally, DR involves neurodegenerative changes, including the activation of glial cells, neuronal dysfunction, and cell death. Research on the multiomics molecular markers of DR has revealed complex mechanisms at the genetic, epigenetic, and transcriptional levels. Genome-wide association studies (GWASs) have identified multiple genetic loci associated with DR that are involved in metabolic and inflammatory pathways. Noncoding RNAs, such as miRNAs, circRNAs, and lncRNAs, participate in the development of DR by regulating gene expression. Proteomic, metabolomic and lipidomic analyses have revealed specific proteins, metabolites and lipid changes associated with DR, providing potential biomarkers for the early diagnosis and treatment of this disease. This review provides a comprehensive perspective for understanding the molecular network of DR and facilitates the exploration of innovative therapeutic approaches.

IL-1β stimulates a novel axis within the NFκB pathway in endothelial cells regulated by IKKα and TAK-1

In this study we examined the activation of the non-canonical NFκB signalling pathway in endothelial cells. In HUVECs, LIGHT stimulated a delayed induction of serine 866/870 p100 phosphorylation linked to p52 NFκB formation. Surprisingly, the canonical ligand, IL-1β, stimulated a rapid phosphorylation or p100 which was not associated with p52 formation. Inhibition of IKKα activity, using DN-IKKα adenovirus, IKKα siRNA or a novel first-in-class selective IKKα inhibitor, SU1261, revealed IL-1β induced p100 phosphorylation to be dependent on IKKα. In contrast, IKKβ inhibition was found to be without effect. The NIK inhibitor, CW15337, did not affect IL-1β induced p100 phosphorylation however, both p100 and pIKKα/β phosphorylation was substantially reduced by inhibition of the upstream kinase TAK-1, suggesting phosphorylation of p100 is mediated by IKKα from within the canonical NEMO/IKKβ /IKKα complex. IL-1β also stimulated a rapid increase in nuclear translocation of p52, which was not affected by NIK inhibition, suggesting a source of p52 independent of p100 processing. Inhibition of TAK-1 abolished p52 and p65 nuclear translocation in response to IL-1β. SiRNA deletion or inhibition with dominant-negative virus of IKKα activity partially reduced p52 translocation, however pharmacological inhibition of IKKα was without effect. Inhibition of IKKβ abolished both p52 and p65 translocation. Taken together these results show that IL-1β stimulates a novel IKKα -dependent axis within the non-canonical NFκB pathway in endothelial cells which is NIK-independent and regulated by TAK-1. However, this pathway is not primarily responsible for the early nuclear translocation of p52, which is dependent on IKKβ. Elucidation of both these new pathways may be significant for NFκB biology within the endothelium.

Simultaneous binding of quercetin and catechin to FOXO3 enhances IKKα transcription inhibition and suppression of oxidative stress-induced acute alcoholic liver injury in rats

INTRODUCTION

Oxidative stress is one of the major contributors to acute alcoholic liver injury (AALI), which is a common alcoholic liver disease. Quercetin and catechin are flavonoid antioxidants present in plant foods and possess chemopreventive and chemotherapeutic activities. Quercetin and catechin are often included in the same meal and ingested together. While they show cooperative actions against oxidative damage, the underlying mechanisms behind their counteracting effects against oxidative stress-induced AALI remain poorly understood.

OBJECTIVES

The aim of this study was to understand the mechanism underlying the enhanced antioxidant effect of quercetin-catechin combination to alleviate AALI in rats.

METHODS

The ethanol (EtOH)-treated rats and H2O2-treated liver cells were used to demonstrate the enhanced antioxidant effect of quercetin and catechin. Then we used RNA-sequencing to compare quercetin alone, catechin alone and quercetin-catechin combination and then identified the critical role of IKKα combining with gene silencing and overexpression techniques. Its transcription factor, FOXO3 was found through yeast one-hybrid assay, luciferase reporter assay, EMSA and ChIP assay. Finally, the interaction between quercetin, catechin and FOXO3 was verified through molecular docking, UV-Vis absorption spectroscopy, fluorescence spectroscopy, and CD spectroscopy.

RESULTS

The study demonstrated the enhanced antioxidant effect of a quercetin-catechin combination in EtOH-treated rats and in H2O2-treated liver cells. Quercetin and catechin cooperatively inhibited IKKα/p53 pathway and activated Nrf2 signaling pathway. IKKα was a critical negative regulator in their joint action. FOXO3 bound to IKKα promoter to regulate IKKα transcription. Quercetin and catechin influenced FOXO3-IKKα binding through attaching directly to FOXO3 at different sites and altering FOXO3's secondary structures.

CONCLUSION

Our study revealed the mechanism of quercetin and catechin against oxidative stress-induced AALI through jointly interacting with transcription factor. This research opens new vistas for examining the joint effect of therapeutics towards functional proteins and confirms the chemopreventive effects of multiple flavonoids via co-regulation.

LUBAC enables tumor-promoting LTβ receptor signaling by activating canonical NF-κB

Lymphotoxin β receptor (LTβR), a member of the TNF receptor superfamily (TNFR-SF), is essential for development and maturation of lymphoid organs. In addition, LTβR activation promotes carcinogenesis by inducing a proinflammatory secretome. Yet, we currently lack a detailed understanding of LTβR signaling. In this study we discovered the linear ubiquitin chain assembly complex (LUBAC) as a previously unrecognized and functionally crucial component of the native LTβR signaling complex (LTβR-SC). Mechanistically, LUBAC-generated linear ubiquitin chains enable recruitment of NEMO, OPTN and A20 to the LTβR-SC, where they act coordinately to regulate the balance between canonical and non-canonical NF-κB pathways. Thus, different from death receptor signaling, where LUBAC prevents inflammation through inhibition of cell death, in LTβR signaling LUBAC is required for inflammatory signaling by enabling canonical and interfering with non-canonical NF-κB activation. This results in a LUBAC-dependent LTβR-driven inflammatory, protumorigenic secretome. Intriguingly, in liver cancer patients with high LTβR expression, high expression of LUBAC correlates with poor prognosis, providing clinical relevance for LUBAC-mediated inflammatory LTβR signaling.

Inhibition of NF-κB signaling unveils novel strategies to overcome drug resistance in cancers

Drug resistance in cancer remains a major challenge in oncology, impeding the effectiveness of various treatment modalities. The nuclear factor-kappa B (NF-κB) signaling pathway has emerged as a critical player in the development of drug resistance in cancer cells. This comprehensive review explores the intricate relationship between NF-κB and drug resistance in cancer. We delve into the molecular mechanisms through which NF-κB activation contributes to resistance against chemotherapeutic agents, targeted therapies, and immunotherapies. Additionally, we discuss potential strategies to overcome this resistance by targeting NF-κB signaling, such as small molecule inhibitors and combination therapies. Understanding the multifaceted interactions between NF-κB and drug resistance is crucial for the development of more effective cancer treatment strategies. By dissecting the complex signaling network of NF-κB, we hope to shed light on novel therapeutic approaches that can enhance treatment outcomes, ultimately improving the prognosis for cancer patients. This review aims to provide a comprehensive overview of the current state of knowledge on NF-κB and its role in drug resistance, offering insights that may guide future research and therapeutic interventions in the fight against cancer.

Chlorogenic Acid Alleviated AFB1-Induced Hepatotoxicity by Regulating Mitochondrial Function, Activating Nrf2/HO-1, and Inhibiting Noncanonical NF-κB Signaling Pathway

Aflatoxin B1 (AFB1), a kind of mycotoxin, imposes acute or chronic toxicity on humans and causes great public health concerns. Chlorogenic acid (CGA), a natural phenolic substance, shows a powerful antioxidant and anti-inflammatory effect. This study was conducted to investigate the effect and mechanism of CGA on alleviating cytotoxicity induced by AFB1 in L-02 cells. The results showed that CGA (160 μM) significantly recovered cell viability and cell membrane integrity in AFB1-treated (8 μM) cells. Furthermore, it was found that CGA reduced AFB1-induced oxidative injury by neutralizing reactive oxygen species (ROS) and activating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. In addition, CGA showed anti-inflammatory effects as it suppressed the expression of inflammation-related genes (IL-6, IL-8, and TNF-α) and AFB1-induced noncanonical nuclear factor kappa-B (NF-κB) activation. Moreover, CGA mitigated AFB1-induced apoptosis by maintaining the mitochondrial membrane potential (MMP) and inhibiting mRNA expressions of Caspase-3, Caspase-8, Bax, and Bax/Bcl-2. These findings revealed a possible mechanism: CGA prevents AFB1-induced cytotoxicity by maintaining mitochondrial membrane potential, activating Nrf2/HO-1, and inhibiting the noncanonical NF-κB signaling pathway, which may provide a new direction for the application of CGA.

Efficacy of Sishen Wan on dinitrobenzene sulfonic acid-induced ulcerative colitis and its effect on toll-like receptor 2/interleukin-1 receptor-associated kinase-4/nuclear factor-κB signal pathway

OBJECTIVE

To investigate the therapeutic effect of Sishen Wan (, SSW) on ulcerative colitis (UC) induced by dinitrobenzene sulfonic acid and its effect on toll-like receptor 2/interleukin-1 receptor-associated kinase-4/nuclear factor-κB (TLR2/IRAK4/NF-κB) sig-naling pathway in colonic tissue.

METHODS

In this study, 120 Sprague-Dawley rats were randomly divided into blank and model groups. The experimental UC model in rats was established by subcutaneous injection of hydrocortisone + senna gavage for 21 d + dinitrobenzene sulfonic acid (DNBS)/ ethanol solution enema. The successful model rats were randomly divided into the model group; mesalazine (0.36 g/kg) group; and high-, medium-, and low- dose SSW (24, 12, and 6 g/kg) groups. The model and blank groups were gavaged with equal volumes of distilled water once a day for 21 d. The general condition of the rats was observed, and the body mass, fecal properties, and occult blood were recorded for calculating the disease activity index (DAI) score. The colonic tissue of the rats was collected, and its general morphology and pathological form were noted for obtaining the colonic mucosal injury index (CMDI) score. Hematoxylin-eosin staining was used to view the pathological changes of the colon tissue in each group, apoptosis of the cells was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, and quantitative real-time polymerase chain reaction was used to measure the expressions of TLR2, myeloid differentiation primary response gene 88 (MyD88), IRAK4, and NF-κB p65 mRNA in the colon tissue. The expressions of TLR2, MyD88, IRAK4, and NF-κB p65 protein were detected using western blotting and immunohistochemistry assay, and the levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the colon tissue were determined using enzyme linked immunosorbent assay.

RESULTS

Compared with the blank group, the general condition of the model group was relatively poor. The DAI and CMDI scores of the model group increased significantly (< 0.01), the glands and intestinal mucosa disappeared partially, and several inflammatory cells infiltrated and gathered in the mucosal layer and base layer of the rats in the model group. Furthermore, the cell apoptosis and expression levels of TLR2, MyD88, IRAK4, and NF-κB p65 mRNA and protein in the colon tissue of rats in the model group increased significantly (< 0.01). The levels of IL-1β and TNF-α increased significantly in the colon tissue of rats in the model group (< 0.01). After treatment with SSW, compared with the model group, the general condition of the UC rats improved. Moreover, the DAI and CMDI scores of the UC rats decreased significantly (< 0.05), and the pathological changes in the colon tissue of the UC rats tended to be normal. The cell apoptosis and expression levels of TLR2, MyD88, IRAK4, and NF-κB p65 mRNA and protein in the colon tissue of the UC rats decreased gradually ( < 0.01), and the levels of IL-1β and TNF-α decreased significantly (< 0.01).

CONCLUSION

SSW can improve the general condition and alleviate the intestinal mucosal injury of UC model rats. Additionally, SSW can inhibit the TLR2/IRAK4/ NF-κB signaling pathway, but further studies are required to confirm it.

The Therapeutic Potential of Targeting NIK in B Cell Malignancies

NF-κB-inducing kinase (NIK) is a key player in non-canonical NF-κB signaling, involved in several fundamental cellular processes, and is crucial for B cell function and development. In response to certain signals and ligands, such as CD40, BAFF and lymphotoxin-β activation, NIK protein stabilization and subsequent NF-κB activation is achieved. Overexpression or overactivation of NIK is associated with several malignancies, including activating mutations in multiple myeloma (MM) and gain-of-function in MALT lymphoma as a result of post-translational modifications. Consequently, drug discovery studies are devoted to pharmacologic modulation of NIK and development of specific novel small molecule inhibitors. However, disease-specific in vitro and in vivo studies investigating NIK inhibition are as of yet lacking, and clinical trials with NIK inhibitors remain to be initiated. In order to bridge the gap between bench and bedside, this review first briefly summarizes our current knowledge on NIK activation, functional activity and stability. Secondly, we compare current inhibitors targeting NIK based on efficacy and specificity, and provide a future perspective on the therapeutic potential of NIK inhibition in B cell malignancies.

Exploring new pathways in endocrine-resistant breast cancer

The most common breast cancer (BC) subtypes are hormone-dependent, being either estrogen receptor-positive (ER⁺), progesterone receptor-positive (PR⁺), or both, and altogether comprise the luminal subtype. The mainstay of treatment for luminal BC is endocrine therapy (ET), which includes several agents that act either directly targeting ER action or suppressing estrogen production. Over the years, ET has proven efficacy in reducing mortality and improving clinical outcomes in metastatic and nonmetastatic BC. However, the development of ET resistance promotes cancer survival and progression and hinders the use of endocrine agents. Several mechanisms implicated in endocrine resistance have now been extensively studied. Based on the current clinical and pre-clinical data, the present article briefly reviews the well-established pathways of ET resistance and continues by focusing on the three most recently uncovered pathways, which may mediate resistance to ET, namely receptor activator of nuclear factor kappa B ligand (RANKL)/receptor activator of nuclear factor kappa B (RANK), nuclear factor kappa B (NFκB), and Notch. It additionally overviews the evidence underlying the approval of combined therapies to overcome ET resistance in BC, while highlighting the relevance of future studies focusing on putative mediators of ET resistance to uncover new therapeutic options for the disease.

Novel T Follicular Helper-like T-Cell Lymphoma Therapies: From Preclinical Evaluation to Clinical Reality

Simple Summary

This work reviews the multiple efforts that have been and are being invested by researchers as well as clinicians to improve the treatment of a specific T-cell lymphoma called follicular helper peripheral T-cell lymphoma. Still, though treatments for B-cell lymphomas have improved, this particular T-cell lymphoma has little to no new therapeutic options that show marked improvements in the survival of the patients compared to treatment with chemotherapy. We report here the evaluation of targeted new therapies for this T-cell lymphoma in new preclinical models for this cancer or in clinical trials with the objective to offer better (combination) treatment options.

Abstract

The classification of peripheral T-cell lymphomas (PTCL) is constantly changing and contains multiple subtypes. Here, we focus on Tfh-like PTCL, to which angioimmunoblastic T-cell lymphoma (AITL) belongs, according to the last WHO classification. The first-line treatment of these malignancies still relies on chemotherapy but gives very unsatisfying results for these patients. Enormous progress in the last decade in terms of understanding the implicated genetic mutations leading to signaling and epigenetic pathway deregulation in Tfh PTCL allowed the research community to propose new therapeutic approaches. These findings point towards new biomarkers and new therapies, including hypomethylating agents, such as azacytidine, and inhibitors of the TCR-hyperactivating molecules in Tfh PTCL. Additionally, metabolic interference, inhibitors of the NF-κB and PI3K-mTOR pathways and possibly novel immunotherapies, such as antibodies and chimeric antigen receptors (CAR) directed against Tfh malignant T-cell surface markers, are discussed in this review among other new treatment options.

Diversity of NF-κB signalling and inflammatory heterogeneity in Rheumatic Autoimmune Disease

Systemic Autoimmune Rheumatic Diseases, including Rheumatoid Arthritis, Systemic Lupus Erythematosus and Sjogren's syndrome, are characterised by a loss of immune tolerance and chronic inflammation. There is marked heterogeneity in clinical and molecular phenotypes in each condition, and the aetiology of these is unclear. NF-κB is an inducible transcription factor that is critical in the physiological inflammatory response, and which has been implicated in chronic inflammation. Genome-wide association studies have linked risk alleles related to the NF-κB pathway to the pathogenesis of multiple Systemic Autoimmune Rheumatic Diseases. This review describes how cell- and pathway-specific NF-κB activation contribute to the spectrum of clinical phenotypes and molecular pathotypes in rheumatic disease. Potential clinical applications are explored, including therapeutic interventions and utilisation of NF-κB as a biomarker of disease subtypes and treatment response.

Regulation of Bcl-XL by non-canonical NF-κB in the context of CD40-induced drug resistance in CLL

In chronic lymphocytic leukemia (CLL), the lymph node (LN) microenvironment delivers critical survival signals by inducing the expression of anti-apoptotic Bcl-2 members Bcl-XL, Bfl-1, and Mcl-1, resulting in apoptosis blockade. We determined previously that resistance against various drugs, among which is the clinically applied BH3 mimetic venetoclax, is dominated by upregulation of the anti-apoptotic regulator Bcl-XL. Direct clinical targeting of Bcl-XL by, e.g., Navitoclax is however not desirable due to induction of thrombocytopenia. Since the actual regulation of Bcl-XL in CLL in the context of the LN microenvironment is not well elucidated, we investigated various candidate LN signals to drive Bcl-XL expression. We found a dominance for NF-κB signaling upon CD40 stimulation, which results in activation of both the canonical and non-canonical NF-κB signaling pathways. We demonstrate that expression of Bcl-XL is first induced by the canonical NF-κB pathway, and subsequently boosted and continued via non-canonical NF-κB signaling through stabilization of NIK. NF-κB subunits p65 and p52 can both bind to the Bcl-XL promoter and activate transcription upon CD40 stimulation. Moreover, canonical NF-κB signaling was correlated with Bfl-1 expression, whereas Mcl-1 in contrast, was not transcriptionally regulated by NF-κB. Finally, we applied a novel compound targeting NIK to selectively inhibit the non-canonical NF-κB pathway and showed that venetoclax-resistant CLL cells were sensitized to venetoclax. In conclusion, protective signals from the CLL microenvironment can be tipped towards apoptosis sensitivity by interfering with non-canonical NF-κB signaling.

Aldose reductase deficiency inhibits LPS-induced M1 response in macrophages by activating autophagy

Macrophage M1 polarization mediates inflammatory responses and tissue damage. Recently, aldose reductase (AR) has been shown to play a critical role in M1 polarization in macrophages. However, the underlying mechanisms are unknown. Here, we demonstrated, for the first time, that AR deficiency repressed the induction of inducible nitric oxide synthase in lipopolysaccharide (LPS)-stimulated macrophages via activation of autophagy. This suppression was related to a defect in the inhibitor of nuclear factor κB (NF-κB) kinase (IKK) complex in the classical NF-κB pathway. However, the mRNA levels of IKKβ and IKKγ were not reduced in LPS-treated AR knockout (KO) macrophages, indicating that their proteins were downregulated at the post-transcriptional level. We discovered that LPS stimuli induced the recruitment of more beclin1 and increased autophagosome formation in AR-deficient macrophages. Blocking autophagy through 3-methyladenine and ammonium chloride treatment restored IKKβ and IKKγ protein levels and increased nitric oxide synthase production in LPS-stimulated AR-deficient macrophages. More assembled IKKβ and IKKγ underwent ubiquitination and recruited the autophagic adaptor p62 in LPS-induced AR KO macrophages, promoting their delivery to autophagosomes and lysosomes. Collectively, these findings suggest that AR deficiency is involved in the regulation of NF-κB signaling, and extends the role of selective autophagy in fine-tuned M1 macrophage polarization.

Molecular characterization and functional analysis of duck IKKα

IκB kinase α (IKKα) is a vital component of the IKK complex, which is involved in innate immune response, inflammation, cell death and proliferation. Although the functional characteristics of IKKα have been extensively studied in mammals and fish, the roles of IKKα in avian remain largely unknown. In this study, we cloned and characterized the duck IKKα (duIKKα) gene for the first time. DuIKKα encoded a protein of 757 amino acid residues and showed high sequence identities with the goose IKKα. The duIKKα was expressed in all tested tissues, and a relatively high expression of duIKKα mRNA was detected in liver and heart. Overexpression of duIKKα dramatically increased NF-κB activity and induced the expression of duck cytokines IFN-β, IL-1β, IL-6, IL-8 and RANTES in DEFs. Knockdown of duIKKα by small interfering RNA significantly decreased LPS-, poly(I:C)-, poly(dA:dT)-, duck enteritis virus (DEV)-, or duck Tembusu virus (DTMUV)-induced NF-κB activation. Moreover, duIKKα exhibited antiviral activity against DTMUV infection. These findings provide important insights into the roles of duIKKα in avian innate immunity.

Interdependence of Anti-Inflammatory and Antioxidant Properties of Squalene-Implication for Cardiovascular Health

Cardiovascular diseases (CVD) have been recognized as the leading cause of mortality worldwide, accounting for 31% of global mortality. Among the risk factors of CVD, hyperlipidemia has been established as the most potent risk factor. Statins, a class of drug that reduces lower-density lipoprotein cholesterol (LDL-C), are the preferred medical treatment. However, due to the development of statin-associated muscle symptoms, statins are associated with patients' discontinuation and nonadherence. Other statin-induced side effects, such as hepatotoxicity and gastrointestinal upset, all contribute to patients choosing alternative medicines. Squalene (SQ), an unsaturated hydrocarbon naturally synthesized in plants and animals, could become the alternative treatment or supplementary agent for cardiovascular health. SQ has been shown to exert cardioprotective effect via its antioxidant activity. Oxidative stress and inflammatory responses are closely related to each other, which proposes an interdependence relation between antioxidant and anti-inflammatory. Therefore, this review explores the interdependence between the antioxidant and anti-inflammatory effects of SQ implicated on cardiovascular health.

NF-κB as an Important Factor in Optimizing Poxvirus-Based Vaccines against Viral Infections

Poxviruses are large dsDNA viruses that are regarded as good candidates for vaccine vectors. Because the members of the Poxviridae family encode numerous immunomodulatory proteins in their genomes, it is necessary to carry out certain modifications in poxviral candidates for vaccine vectors to improve the vaccine. Currently, several poxvirus-based vaccines targeted at viral infections are under development. One of the important aspects of the influence of poxviruses on the immune system is that they encode a large array of inhibitors of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which is the key element of both innate and adaptive immunity. Importantly, the NF-κB transcription factor induces the mechanisms associated with adaptive immunological memory involving the activation of effector and memory T cells upon vaccination. Since poxviruses encode various NF-κB inhibitor proteins, before the use of poxviral vaccine vectors, modifications that influence NF-κB activation and consequently affect the immunogenicity of the vaccine should be carried out. This review focuses on NF-κB as an essential factor in the optimization of poxviral vaccines against viral infections.

Targeting NF-κB-Inducing Kinase (NIK) in Immunity, Inflammation, and Cancer

NF-κB-inducing kinase (NIK), the essential upstream kinase, which regulates activation of the noncanonical NF-κB pathway, has important roles in regulating immunity and inflammation. In addition, NIK is vital for maintaining cellular health through its control of fundamental cellular processes, including differentiation, growth, and cell survival. As such aberrant expression or regulation of NIK is associated with several disease states. For example, loss of NIK leads to severe immune defects, while the overexpression of NIK is observed in inflammatory diseases, metabolic disorders, and the development and progression of cancer. This review discusses recent studies investigating the therapeutic potential of NIK inhibitors in various diseases.

LIGHT aggravates sepsis-associated acute kidney injury via TLR4-MyD88-NF-κB pathway

Sepsis‐associated acute kidney injury (SA‐AKI) is a common clinical critical care syndrome. It has received increasing attention due to its high morbidity and mortality; however, its pathophysiological mechanisms remain elusive. LIGHT, the 14th member of the tumour necrosis factor (TNF) superfamily and a bidirectional immunoregulatory molecule that regulates inflammation, plays a pivotal role in disease pathogenesis. In this study, mice with an intraperitoneal injection of LPS and HK‐2 cells challenged with LPS were employed as a model of SA‐AKI in vivo and in vitro, respectively. LIGHT deficiency notably attenuated kidney injury in pathological damage and renal function and markedly mitigated the inflammatory reaction by decreasing inflammatory mediator production and inflammatory cell infiltration in vivo. The TLR4‐Myd88‐NF‐κB signalling pathway in the kidney of LIGHT knockout mice was dramatically down‐regulated compared to the controls. Recombinant human LIGHT aggravated LPS‐treated HK‐2 cell injury by up‐regulating the expression of the TLR4‐Myd88‐NF‐κB signalling pathway and inflammation levels. TAK 242 (a selective TLR4 inhibitor) reduced this trend to some extent. In addition, blocking LIGHT with soluble receptor fusion proteins HVEM‐Fc or LTβR‐Fc in mice attenuated renal dysfunction and pathological damage in SA‐AKI. Our findings indicate that LIGHT aggravates inflammation and promotes kidney damage in LPS‐induced SA‐AKI via the TLR4‐Myd88‐NF‐κB signalling pathway, which provide potential strategies for the treatment of SA‐AKI.

RelB sustains endocrine resistant malignancy: an insight of noncanonical NF-κB pathway into breast Cancer progression

BACKGROUND

The activation of the NF-κB pathway plays a crucial role in the progression of breast cancer (BCa) and also involved in endocrine therapy resistance. On the contrary to the canonical NF-κB pathway, the effect of the noncanonical NF-κB pathway in BCa progression remains elusive.

METHODS

BCa tumor tissues and the corresponding cell lines were examined to determine the correlation between RelB and the aggressiveness of BCa. RelB was manipulated in BCa cells to examine whether RelB promotes cell proliferation and motility by quantitation of apoptosis, cell cycle, migration, and invasion. RNA-Seq was performed to identify the critical RelB-regulated genes involved in BCa metastasis. Particularly, RelB-regulated MMP1 transcription was verified using luciferase reporter and ChIP assay. Subsequently, the effect of RelB on BCa progression was further validated using BCa mice xenograft models.

RESULTS

RelB uniquely expresses at a high level in aggressive BCa tissues, particularly in triple-negative breast cancer (TNBC). RelB promotes BCa cell proliferation through increasing G1/S transition and/or decreasing apoptosis by upregulation of Cyclin D1 and Bcl-2. Additionally, RelB enhances cell mobility by activating EMT. Importantly, RelB upregulates bone metastatic protein MMP1 expression through binding to an NF-κB enhancer element located at the 5'-flanking region. Accordingly, in vivo functional validation confirmed that RelB deficiency impairs tumor growth in nude mice and inhibits lung metastasis in SCID mice. Video abstract.

The potential function of IKKα in gastric precancerous lesion via mediating Maspin

OBJECTIVE

To know the potential role of IKKα (an NF-κB noncanonical pathway) in gastric precancerous lesion via mediating Maspin.

METHODS

Gastric cancer, precancerous lesion and control tissues (chronic non-atrophic gastritis) were collected for determining the expression of IKKα and Maspin by immunohistochemistry. Thereafter, gastric precancerous models were established and divided into the Control group, Model group and Model + shIKKα group. All rats were subjected to observe the pathological changes and ultramicro structure of the gastric mucosa by HE staining or electron microscope, and to measure the serum levels of inflammatory cytokines by ELISA, the expression of apoptosis-related proteins by immunohistochemistry, as well as the expression of IKKα and Maspin by quantitative real-time PCR and Western blotting.

RESULTS

Precancerous lesion and gastric cancer tissues manifested significant upregulation of IKKα positive expression, concomitant with downregulation of the positive expression of Maspin, and these changes were more evident in the gastric cancer tissues. In comparison with the Control group, rats in the Model group had significant increases in serum levels of TNF-α, IL-1β, IL-6 and COX-2, with up-regulations of Bcl-2, CyclinD1, IKKα and p-IKKα, and down-regulations of Bax, Caspase-3 and Maspin. shIKKα treatment attenuate inflammation and apoptosis in gastric precancerous lesion (GPL) rat, with the downregulation of IKKα and p-IKKα, and upregulation of Maspin.

CONCLUSION

Inhibiting IKKα, via upregulating Maspin, can mitigate the inflammation and promote cell apoptosis in precancerous rats, thereby delaying the development of the precancerous lesions.

Endocrinotherapy resistance of prostate and breast cancer: Importance of the NF‑κB pathway (Review)

Prostate cancer (PCa) and breast cancer (BCa) are two common sex hormone‑related cancer types with high rates of morbidity, and are leading causes of cancer death globally in men and women, respectively. The biological function of androgen or estrogen is a key factor for PCa or BCa tumorigenesis, respectively. Nevertheless, after hormone deprivation therapy, the majority of patients ultimately develop hormone‑independent malignancies that are resistant to endocrinotherapy. It is widely recognized, therefore, that understanding of the mechanisms underlying the process from hormone dependence towards hormone independence is critical to discover molecular targets for the control of advanced PCa and BCa. This review aimed to dissect the important mechanisms involved in the therapeutic resistance of PCa and BCa. It was concluded that activation of the NF‑κB pathway is an important common mechanism for metastasis and therapeutic resistance of the two types of cancer; in particular, the RelB‑activated noncanonical NF‑κB pathway appears to be able to lengthen and strengthen NF‑κB activity, which has been a focus of recent investigations.

Condensed tannins decreased the growth performance and impaired intestinal immune function in on-growing grass carp (Ctenopharyngodon idella)

The present study investigated the effects of condensed tannins (CT) on intestinal immune function in on-growing grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp were fed six diets containing different levels of CT (0, 10·00, 20·00, 30·00, 40·00 and 50·00 g/kg diet) for 70 d and then challenged with Aeromonas hydrophila for 14 d. The results showed that, compared with the control group, dietary CT (1) induced intestinal histopathological lesions and aggravated enteritis; (2) decreased lysozyme and acid phosphatase activities, complement 3 (C3), C4 and IgM contents and down-regulated the Hepcidin, liver-expressed antimicrobial peptide (LEAP)-2A, LEAP-2B, Mucin2 and β-defensin-1 mRNA levels in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI) (P < 0·05); (3) down-regulated the mRNA levels of anti-inflammatory cytokines transforming growth factor (TGF)-β1, TGF-β2 (not in MI and DI), IL-4/13A (not IL-4/13B), IL-10 and IL-11 partly correlated with target of rapamycin (TOR) signalling; and (4) up-regulated the mRNA levels of pro-inflammatory cytokines interferon-γ2, IL-1β, IL-6, IL-8 (not in PI), IL-12p35, IL-12p40, IL-15 and IL-17D partly related to NF-κB signalling in the intestine of on-growing grass carp. Overall, the results indicated that CT could impair the intestinal immune function, and its potential regulation mechanisms were partly associated with the TOR and NF-κB signalling pathways. Finally, based on the percentage weight gain and enteritis morbidity, the maximum allowable levels of CT for on-growing grass carp (232·22-890·11 g) were estimated to be 18·6 and 17·4 g/kg diet, respectively.

NF-κB-Mediated Neuroinflammation in Parkinson's Disease and Potential Therapeutic Effect of Polyphenols

Different animal and human studies from last two decades in the case of Parkinson's disease (PD) have concentrated on oxidative stress due to increased inflammation and cytokine-dependent neurotoxicity leading to induction of dopaminergic (DA) degeneration pathway in the nigrostriatal region. Chronic inflammation, the principle hallmark of PD, forms the basis of neurodegeneration. Aging in association with activation of glia due to neuronal injury, perhaps because of immune alterations and genetic predispositions, leads to deregulation of inflammatory pathways premising the onset of PD. A family of inducible transcription factors, nuclear factor-κB (NF-κB), is found to show expression in various cells and tissues, such as microglia, neurons, and astrocytes which play an important role in activation and regulation of inflammatory intermediates during inflammation. Both canonical and non-canonical NF-κB pathways are involved in the regulation of the stimulated cells. During the prodromal/asymptomatic stage of age-associated neurodegenerative diseases (i.e., PD and AD), chronic neuroinflammation may act silently as the driver of neuronal dysfunction. Though research has provided an insight over age-related neurodegeneration in PD, elaborative role of NF-κB in neuroinflammation is yet to be completely understood and thus requires more investigation. Polyphenols, a group of naturally occurring compound in medicinal plants, have gained attention because of their anti-oxidative and anti-neuroinflammatory properties in neurodegenerative diseases. In this aspect, this review highlights the role of NF-κB and the possible therapeutic roles of polyphenols in NF-κB-mediated neuroinflammation in PD.

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.

T-lymphocyte-specific knockout of IKK-2 or NEMO induces Th17 cells in an experimental nephrotoxic nephritis mouse model

Experimental nephrotoxic serum nephritis (NTN) is a model for T-cell-mediated human rapid progressive glomerulonephritis. T-cell receptor stimulation involves intracellular signaling events that ultimately lead to the activation of transcription factors, such as NF-κB. We explored the involvement of the NF-κB components IKK-2 and NEMO in NTN, by using cell-specific knockouts of IKK-2 and NEMO in CD4⁺ T lymphocytes. Our results demonstrate that although the course of disease was not grossly altered in CD4xIKK2^Δ and CD4xNEMO^Δ animals, renal regulatory T cells were significantly reduced and T helper (T_h)1 and T_h17 cells significantly increased in both knockout mouse groups. The expression of the renal cytokines and chemokines IL-1β, CCL-2, and CCL-20 was also significantly altered in both knockout mice. Lymphocyte transcriptome analysis confirmed the increased expression of T_h17-related cytokines in spleen CD4⁺ T cells. Moreover, our array data demonstrate an interrupted canonical NF-κB pathway and an increased expression of noncanonical NF-κB pathway-related genes in nephritic CD4xNEMO^Δ mice, highlighting different downstream effects of deletion of IKK-2 or NEMO in T lymphocytes. We propose that better understanding of the role of IKK-2 and NEMO in nephritis is essential for the clinical application of kinase inhibitors in patients with glomerulonephritis.-Guo, L., Huang, J., Chen, M., Piotrowski, E., Song, N., Zahner, G., Paust, H.-J., Alawi, M., Geffers, R., Thaiss, F. T-lymphocyte-specific knockout of IKK-2 or NEMO induces T_h17 cells in an experimental nephrotoxic nephritis mouse model.

Intranuclear delivery of synthetic nuclear factor-kappa B p65 reduces inflammasomes after surgery

Patients undergoing surgery can suffer from various complications, including post-operative bleeding, local or systematic infection, and neurologic disorders. Major surgery can initiate innate immune responses and trigger overproduction of inflammatory mediators, which can contribute to organ dysfunction. Inflammasomes are innate immune complexes, which are connected to the pathogenesis of various diseases, including atherosclerosis, hemorrhagic brain injury, and Alzheimer's disease. In the present study, we hypothesized that nucleotide-binding oligomerization domain-containing-like receptor protein (NLRP) inflammasomes may have a role in the pathological effects of surgery. Therefore, we designed a protein inhibitor of nuclear factor kappa B (NF-κB) p65 transcripts, called nt-p65-TMD (nuclear transducible (nt) transcription modulated domain (TMD) of RelA (p65)), that can penetrate the nucleus, and evaluated its therapeutic efficacy for dampening surgery-induced inflammasome activation. It was found that the nt-p65-TMD significantly reduced the NLRP1 inflammasome complex components (NLRP1, ASC, and Caspase-1) and interleukin (IL)-1β and IL-18 productions in the spleen after surgery. In the spleen, specific cell population and selective mediators were altered after surgery with/without nt-p65-TMD treatment. Also, we found that treatment of nt-p65-TMD decreased cell death in the spleen after surgery. Therefore, nt-p65-TMD is a potential novel strategy for reducing surgery-induced NLRP1 inflammasome and complications.

NFκB Promotes Ovarian Tumorigenesis via Classical Pathways That Support Proliferative Cancer Cells and Alternative Pathways That Support ALDH+ Cancer Stem-like Cells

Understanding the mechanisms supporting tumor-initiating cells (TIC) is vital to combat advanced-stage recurrent cancers. Here, we show that in advanced ovarian cancers NFκB signaling via the RelB transcription factor supports TIC populations by directly regulating the cancer stem-like associated enzyme aldehyde dehydrogenase (ALDH). Loss of RelB significantly inhibited spheroid formation, ALDH expression and activity, chemoresistance, and tumorigenesis in subcutaneous and intrabursal mouse xenograft models of human ovarian cancer. RelB also affected expression of the ALDH gene ALDH1A2 Interestingly, classical NFκB signaling through the RelA transcription factor was equally important for tumorigenesis in the intrabursal model, but had no effect on ALDH. In this case, classical signaling via RelA was essential for proliferating cells, whereas the alternative signaling pathway was not. Our results show how NFκB sustains diverse cancer phenotypes via distinct classical and alternative signaling pathways, with implications for improved understanding of disease recurrence and therapeutic response. Cancer Res; 77(24); 6927-40. ©2017 AACR.

Molecular and functional characterization of pigeon (Columba livia) tumor necrosis factor receptor-associated factor 3

Tumor necrosis factor receptor-associated factor 3 (TRAF3) plays a key antiviral role by promoting type I interferon production. We cloned the pigeon TRAF3 gene (PiTRAF3) according to its predicted mRNA sequence to investigate its function. The 1704-bp full-length open reading frame encodes a 567-amino acid protein. One Ring finger, two TRAF-type Zinc fingers, one Coiled coil, and one MATH domain were inferred. RT-PCR showed that PiTRAF3 was expressed in all tissues, with relatively weak expression in the heart and liver. In HEK293T cells, over-expression of wild-type, △Ring, △Zinc finger, and △Coiled coil PiTRAF3, but not a △MATH form, significantly increased IFN-β promoter activity. Zinc finger and Coiled coil domains were essential for NF-κB activation. In chicken HD11 cells, PiTRAF3 increased IFN-β promoter activity and four domains were all contributing. R848 stimulation of pigeon peripheral blood mononuclear cells and splenocytes significantly increased expression of PiTRAF3 and the inflammatory cytokine genes CCL5, IL-8, and IL-10. These data demonstrate TRAF3's innate immune function and improve understanding of its involvement in poultry antiviral defense.

Structural Basis for the Activation of IKK1/α

Distinct signaling pathways activate the NF-κB family of transcription factors. The canonical NF-κB-signaling pathway is mediated by IκB kinase 2/β (IKK2/β), while the non-canonical pathway depends on IKK1/α. The structural and biochemical bases for distinct signaling by these otherwise highly similar IKKs are unclear. We report single-particle cryoelectron microscopy (cryo-EM) and X-ray crystal structures of human IKK1 in dimeric (∼150 kDa) and hexameric (∼450 kDa) forms. The hexamer, which is the representative form in the crystal but comprises only ∼2% of the particles in solution by cryo-EM, is a trimer of IKK1 dimers. While IKK1 hexamers are not detectable in cells, the surface that supports hexamer formation is critical for IKK1-dependent cellular processing of p100 to p52, the hallmark of non-canonical NF-κB signaling. Comparison of this surface to that in IKK2 indicates significant divergence, and it suggests a fundamental role for this surface in signaling by these kinases through distinct pathways.

Dietary vitamin C deficiency depressed the gill physical barriers and immune barriers referring to Nrf2, apoptosis, MLCK, NF-κB and TOR signaling in grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare

This study explored the effects of vitamin C on the physical barriers and immune barriers, and relative mRNA levels of signaling molecules in the gill of grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare. The results indicated that compared with optimal vitamin C supplementation, vitamin C deficiency (2.9 mg/kg diet) (1) increased reactive oxygen species, malondialdehyde and protein carbonyl (PC) contents (P < 0.05), decreased the copper/zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities and mRNA levels (P < 0.05), and glutathione and vitamin C contents (P < 0.05), down-regulated NF-E2-related factor 2 mRNA level (P < 0.05), and up-regulated Kelch-like ECH-associating protein (Keap) 1a (rather than Keap1b) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency induced oxidative injury in fish gill; (2) up-regulated caspase-3, -7, -8, -9, Fas ligand, B-cell lymphoma protein 2 associated X protein, apoptotic protease activating factor-1 mRNA levels (P < 0.05), and down-regulated inhibitor of apoptosis protein and B-cell lymphoma-2 (rather than myeloid cell leukemia-1) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated cell apoptosis in fish gill; (3) up-regulated pore-forming TJs Claudin-12, 15a, -15b, and related signaling molecules myosin light chain kinase, p38 mitogen-activated protein kinase (rather than c-Jun N-terminal kinases) mRNA levels (P < 0.05), and down-regulated barrier-forming TJs Occludin, zonula occludens (ZO) 1, ZO-2, Claudin-c, -3c, -7a, -7b mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency disrupted tight junctional complexes in fish gill; (4) decreased lysozyme and acid phosphatase (ACP) activities, and complement 3 (C3), C4 and IgM contents (P < 0.05), down-regulated the mRNA levels of antimicrobial peptides liver expressed antimicrobial peptide (LEAP) 2A, LEAP-2B, Hepcidin, β-defensin mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency decrease fish gill immune function; (5) down-regulated the mRNA levels of anti-inflammatory cytokines-related factors interleukin 10 (IL-10), IL-11, transforming growth factor (TGF) β1, TGF-β2, inhibitor of κBa and eIF4E-binding protein 1 (4E-BP1) (rather than 4E-BP2) (P < 0.05), and up-regulated pro-inflammatory cytokines-related factors interferon γ2, IL-1β, IL-6, IL-8, IL-12 P35, IL-12 P40, nuclear factor κB (NF-κB) p65 (rather than NF-κB p52), IκB kinases (IKK) (only IKKα and IKKγ), target of rapamycin and ribosomal protein S6 kinase 1 mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated fish gill inflammation. In conclusion, vitamin C deficiency disrupted physical barriers and immune barriers, and regulated relative mRNA levels of signaling molecules in fish gill. The vitamin C requirement for against gill rot morbidity of grass carp (264-1031 g) was estimated to be 156.0 mg/kg diet. In addition, based on the gill biochemical indices (antioxidant indices MDA, PC and vitamin C contents, and immune indices LA and ACP activity) the vitamin C requirements for grass carp (264-1031 g) were estimated to be 116.8, 156.6, 110.8, 57.8 and 134.9 mg/kg diet, respectively.

The NF-κB subunit RelB controls p100 processing by competing with the kinases NIK and IKK1 for binding to p100

The heterodimer formed by the nuclear factor κB (NF-κB) subunits p52 and RelB is the product of noncanonical signaling in which the key event is the proteolytic processing of p100 to generate p52. The kinases NF-κB-inducing kinase (NIK) and inhibitor of κB kinase 1 (IKK1; also known as IKKα) are activated during noncanonical signaling and play essential roles in p100 processing. In resting cells, RelB remains associated with unprocessed p100 as a transcriptionally inert p100:RelB complex, which is part of a larger assembly with other NF-κB factors known as the "kappaBsome." We investigated how these two different RelB-containing complexes with opposing effects on target gene transcription are formed. We found that RelB controls the extent of both p100 processing and kappaBsome formation during noncanonical signaling. Within an apparently "transitional" complex that contains RelB, NIK, IKK1, and p100, RelB and the NIK:IKK1 complex competed with each other for binding to a region of p100. A fraction of p100 in the transitional complex was refractory to processing, which resulted in the formation of the kappaBsome. However, another fraction of p100 protein underwent NIK:IKK1-mediated phosphorylation and processing while remaining bound to RelB, thus forming the p52:RelB heterodimer. Our results suggest that changes in the relative concentrations of RelB, NIK:IKK1, and p100 during noncanonical signaling modulate this transitional complex and are critical for maintaining the fine balance between the processing and protection of p100.

Lymphocyte-specific deletion of IKK2 or NEMO mediates an increase in intrarenal Th17 cells and accelerates renal damage in an ischemia-reperfusion injury mouse model

Acute kidney injury (AKI) is associated with poor patient outcome and a global burden for end-stage renal disease. Ischemia-reperfusion injury (IRI) is one of the major causes of AKI, and experimental work has revealed many details of the inflammatory response in the kidney, such as activation of the NF-κB pathway. Here, we investigated whether deletion of the NF-κB kinases IKK2 or NEMO in lymphocytes or systemic inhibition of IKK2 would cause different kidney inflammatory responses after IRI induction. Serum creatinine, blood urea nitrogen (BUN) level, and renal tubular injury score were significantly increased in CD4^creIKK2^f/f (CD4xIKK2^Δ) and CD4^creNEMO^f/f (CD4xNEMO^Δ) mice compared with CD4cre mice after IRI induction. The frequency of Th17 cells infiltrating the kidneys of CD4xIKK2^Δ or CD4xNEMO^Δ mice was also significantly increased at all time points. CCL20, an important chemokine in Th17 cell recruitment, was significantly increased at early time points after the induction of IRI. IL-1β, TNF-α, and CCL2 were also significantly increased in different patterns. A specific IKK2 inhibitor, KINK-1, reduced BUN and serum creatinine compared with nontreated mice after IRI induction, but the frequency of kidney Th17 cells was also significantly increased. In conclusion, although systemic IKK2 inhibition improved kidney function, lymphocyte-specific deletion of IKK2 or NEMO aggravated kidney injury after IRI, and, in both conditions, the percentage of Th17 cells was increased. Our findings demonstrate the critical role of the NF-κB pathway in Th17 activation, which advises caution when using systemic IKK2 inhibitors in patients with kidney injury, since they might impair the T cell response and aggravate renal disease.

Negative role of TAK1 in marginal zone B-cell development incidental to NF-κB noncanonical pathway activation

The transcription factor nuclear factor-κB (NF-κB) signaling pathway is crucial in B-cell physiology. One key molecule regulating this pathway is the serine/threonine kinase TAK1 (MAP3K7). TAK1 is responsible for positive feedback mechanisms in B-cell receptor signaling that serve as an NF-κB activation threshold. This study aimed to better understand the correlation between TAK1-mediated signaling and B-cell development and humoral immune responses. Here we showed that a B-cell conditional deletion of TAK1 using mb1-cre resulted in a dramatic elimination of the humoral immune response, consistent with the absence of the B-1 B-cell subset. When monitoring the self-reactive B-cell system (the immunoglobulin hen egg lysozyme/soluble hen egg lysozyme double-transgenic mouse model), we found that TAK1-deficient B cells exhibited an enhanced susceptibility to cell death that might explain the disappearance of the B1 subset. In contrast, these mice gained numerous marginal zone (MZ) B cells. We consequently examined the basal and B-cell receptor-induced activity of NF-κB2 that is reported to regulate MZ B-cell development, and demonstrated that the activity of NF-κB2 increased in TAK1-deficient B cells. Thus, our results present a novel in vivo function, the negative role of TAK1 in MZ B-cell development that is likely associated with NF-κB2 activation.

Noncanonical NF-κB Signaling in Health and Disease

Noncanonical NF-κB signaling differs from canonical NF-κB signaling by being activated through different cell surface receptors, cytoplasmic adaptors, and NF-κB dimers. Under normal physiological conditions, this noncanonical pathway has been implicated in diverse biological processes, including lymphoid organogenesis, B cell maturation, osteoclast differentiation, and various functions of other immune cells. Recently, dysfunction of this pathway has also been causally associated with numerous immune-mediated pathologies and human malignancies. Here, we summarize the core elements as well as the recently identified novel regulators of the noncanonical NF-κB signaling pathway. The involvement of this pathway in different pathologies and the potential therapeutic options that are currently envisaged are also discussed.

The non-canonical NF-κB pathway is induced by cytokines in pancreatic beta cells and contributes to cell death and proinflammatory responses in vitro

AIMS/HYPOTHESIS

Activation of the transcription factor nuclear factor (NF)-κB by proinflammatory cytokines plays an important role in beta cell demise in type 1 diabetes. Two main signalling pathways are known to activate NF-κB, namely the canonical and the non-canonical pathways. Up to now, studies on the role of NF-κB activation in beta cells have focused on the canonical pathway. The aim of this study was to investigate whether cytokines activate the non-canonical pathway in beta cells, how this pathway is regulated and the consequences of its activation on beta cell fate.

METHODS

NF-κB signalling was analysed by immunoblotting, promoter reporter assays and real-time RT-PCR, after knockdown or overexpression of key genes/proteins. INS-1E cells, FACS-purified rat beta cells and the human beta cell line EndoC-βH1 exposed to cytokines were used as models.

RESULTS

IL-1β plus IFN-γ induced stabilisation of NF-κB-inducing kinase and increased the expression and cleavage of p100 protein, culminating in the nuclear translocation of p52, the hallmark of the non-canonical signalling. This activation relied on different crosstalks between the canonical and non-canonical pathways, some of which were beta cell specific. Importantly, cytokine-mediated activation of the non-canonical pathway controlled the expression of 'late' NF-κB-dependent genes, regulating both pro-apoptotic and inflammatory responses, which are implicated in beta cell loss in early type 1 diabetes.

CONCLUSIONS/INTERPRETATION

The atypical activation of the non-canonical NF-κB pathway by proinflammatory cytokines constitutes a novel 'feed-forward' mechanism that contributes to the particularly pro-apoptotic effect of NF-κB in beta cells.

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.

Synergy between CD40 and MyD88 Does Not Influence Host Survival to Salmonella Infection

Previous studies using purified toll-like receptor (TLR) ligands plus agonistic anti-CD40 antibodies showed that TLRs and CD40 can act synergistically on dendritic cells (DCs) to optimize T cell activation and Th1 differentiation. However, a synergistic effect of TLRs and CD40 during bacterial infection is not known. Here, we show that mice lacking the TLR adaptor MyD88 alone, or lacking both MyD88 and CD40 [double knockout (DKO) mice], are compromised in survival to Salmonella infection but have intact recruitment of neutrophils and inflammatory monocytes as well as unaltered abundance of DC subsets and DC activation in infected tissues. In contrast to infected wildtype and CD40(-/-) mice, both MyD88(-/-) mice and DKO mice lack detectable serum IFN-γ and have elevated IL-10. A synergistic effect of TLRs and CD40 was revealed in co-culture experiments where OT-II T cell proliferation was compromised when DKO DCs were pulsed with OVA protein and OVA323-339 peptide, but not with heat-killed Salmonella expressing OVA (HKSOVA), relative to MyD88(-/-) DCs. By contrast, MyD88(-/-) or DKO DCs pulsed with any of the antigens had a similar ability to induce IFN-γ that was lower than WT or CD40(-/-) DCs. DKO DCs pulsed with HKSOVA, but not with OVA or OVA323-339, had increased IL-10 relative to MyD88(-/-) DCs. Finally, HKSOVA-pulsed MyD88(-/-) and DKO DCs had similar and low induction of NFκB-dependent and -independent genes upon co-culture with OT-II cells. Overall, our data revealed that synergistic effects of CD40 and MyD88 do not influence host survival to Salmonella infection or serum levels of IFN-γ or IL-10. However, synergistic effects of MyD88 and CD40 may be apparent on some (IL-10 production) but not all (OT-II proliferation and IFN-γ production) DC functions and depend on the complexity of the antigen. Indeed, synergistic effects observed using purified ligands and well-defined antigens may not necessarily apply when complex antigens, such as live bacteria, challenge the immune system.

The contribution of NF-κB signalling to immune regulation and tolerance

BACKGROUND

Immune regulation is necessary to control inflammatory responses and to prevent autoimmune diseases. Therefore, mechanisms of central and peripheral tolerance have evolved to ensure that T cells recognize antigens as self- or non-self-antigens. The thymus is crucially important for central tolerance induction to self-antigens via negative selection of T cells. However, if T cells escape negative selection in the thymus and enter the periphery, peripheral mechanisms are active to warrant immune tolerance. Secondary lymphoid organs, as well as tolerogenic dendritic cells and regulatory T cells, play an important role in peripheral tolerance. In chronic inflammatory diseases, tertiary lymphoid organs are sometimes formed that may also be involved in the induction of peripheral tolerance. This review discusses the main processes that are involved in immune regulation and tolerance, and focuses on the contribution of NF-κB signalling to these processes.

MATERIAL AND METHODS

This narrative review is based on peer-reviewed publications listed on PubMed up to December 2014. The focus of our literature search was on studies investigating the role of (non)canonical NF-κB signalling in central and peripheral mechanisms of tolerance. Only studies published in English language were considered.

RESULTS

This review discusses the immune phenotype of mutant mice with defective (non)canonical NF-κB signalling, corroborated with human data, and emphasizes the contribution of the noncanonical NF-κB pathway to immune regulation and tolerance induction.

CONCLUSIONS

Noncanonical NF-κB signalling has an important immunoregulatory role in the immune system and contributes to both central and peripheral mechanisms of tolerance.

Relationship between expression of NIBP and noncanonical NF-κB signaling: Clinical significance in colon carcinoma

AIM: To investigate the expression of NIK, IKKβ binding protein (NIBP), phosphorylated p100 (p-p100), p52, CD44, Vimentin and E-cadherin in colon carcinoma and to explore their clinical significance.

METHODS: Immunohistochemistry was used to detect the expression of NIBP, p-p100, p52, CD44, E-cadherin and Vimentin in 114 paraffin-embedded colon carcinoma tissues, 20 colon adenoma tissues and 50 normal colon mucosa tissues.

RESULTS: The positive expression of NIBP, p-p100, p52, CD44 and Vimentin in colon cancer tissues with metastasis was much higher than that in colon cancer tissues without metastasis, colon adenoma tissues and normal colon mucosa tissues, while the expression of E-cadherin showed a reverse trend (P < 0.05). The expression of NIBP, p-p100, p52, CD44, Vimentin and E-cadherin in colon cancer tissues was related with depth of invasion, TNM stage, lymph node metastasis and distant metastasis (P < 0.05). There were significant correlations between the expression of p-p100 and p52 or NIBP, and between the expression of CD44 and p52, E-cadherin, or Vimentin.

CONCLUSION: NIBP may regulate the epithelial-mesenchymal transition process by activating the noncanonical nuclear factor-κB (NF-κB) signal pathway and thus play an important role in the development, invasion and metastasis of colon cancer.

Non-canonical NF-κB signaling in rheumatoid arthritis: Dr Jekyll and Mr Hyde?

The nuclear factor-κB (NF-κB) family of transcription factors is essential for the expression of pro-inflammatory cytokines, but can also induce regulatory pathways. NF-κB can be activated via two distinct pathways: the classical or canonical pathway, and the alternative or non-canonical pathway. It is well established that the canonical NF-κB pathway is essential both in acute inflammatory responses and in chronic inflammatory diseases, including rheumatoid arthritis (RA). Although less extensively studied, the non-canonical NF-κB pathway is not only central in lymphoid organ development and adaptive immune responses, but is also thought to play an important role in the pathogenesis of RA. Importantly, this pathway appears to have cell type-specific functions and, since many different cell types are involved in the pathogenesis of RA, it is difficult to predict the net overall contribution of the non-canonical NF-κB pathway to synovial inflammation. In this review, we describe the current understanding of non-canonical NF-κB signaling in various important cell types in the context of RA and consider the relevance to the pathogenesis of the disease. In addition, we discuss current drugs targeting this pathway, as well as future therapeutic prospects.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) promotes glioma cell invasion through induction of NF-κB-inducing kinase (NIK) and noncanonical NF-κB signaling

BACKGROUND

High-grade gliomas are one of the most invasive and therapy-resistant cancers. We have recently shown that noncanonical NF-κB/RelB signaling is a potent driver of tumorigenesis and invasion in the aggressive, mesenchymal subtype of glioma. However, the relevant signals that induce activation of noncanonical NF-κB signaling in glioma and its function relative to the canonical NF-κB pathway remain elusive.

METHODS

The ability of tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) to regulate NF-κB signaling and promote tumor progression was investigated in both established and primary high-grade glioma tumor lines using a three-dimensional (3-D) collagen invasion assay. The roles of specific NF-κB proteins in regulating glioma cell invasion and expression of Matrix Metalloproteinase 9 (MMP9) in response to TWEAK were evaluated using shRNA-mediated loss-of-function studies. The ability of NF-κB-inducing kinase (NIK) to promote glioma growth in vivo was investigated using an orthotopic xenograft mouse model.

RESULTS

In glioma cells that display elevated noncanonical NF-κB signaling, loss of RelB attenuates invasion without affecting RelA expression or phosphorylation and RelB is sufficient to promote invasion in the absence of RelA. The cytokine TWEAK preferentially activates the noncanonical NF-κB pathway through induction of p100 processing to p52 and nuclear accumulation of both RelB and p52 without activating the canonical NF-κB pathway. Moreover, TWEAK, but not TNFα, significantly increases NIK mRNA levels. TWEAK also promotes noncanonical NFκB-dependent MMP9 expression and glioma cell invasion. Finally, expression of NIK is sufficient to increase gliomagenesis in vivo.

CONCLUSIONS

Our data establish a key role for NIK and noncanonical NF-κB in mediating TWEAK-induced, MMP-dependent glioma cell invasion. The findings also demonstrate that TWEAK induces noncanonical NF-κB signaling and signal-specific regulation of NIK mRNA expression. Together, these studies reveal the important role of noncanonical NF-κB signaling in regulating glioma invasiveness and highlight the therapeutic potential of targeting activation of NIK in this deadly disease.

Defective lymphoid organogenesis underlies the immune deficiency caused by a heterozygous S32I mutation in IκBα

Mooster et al. created a knock-in mouse harboring a mutation (S32I) in IκBα that has been identified in a patient with ectodermal dysplasia with immunodeficiency. The mice are characterized by defective architectural cell function; they lack lymph nodes, Peyer’s patches, splenic marginal zones, and follicular DCs and fail to develop germinal centers. These features have not been previously recognized in patients.

Patients with ectodermal dysplasia with immunodeficiency (ED-ID) caused by mutations in the inhibitor of NF-κB α (IκBα) are susceptible to severe recurrent infections, despite normal T and B cell numbers and intact in vitro lymphocyte function. Moreover, the outcome of hematopoietic stem cell transplantation (HSCT) in these patients is poor despite good engraftment. Mice heterozygous for the IκBα S32I mutation found in patients exhibited typical features of ED-ID. Strikingly, the mice lacked lymph nodes, Peyer’s patches, splenic marginal zones, and follicular dendritic cells and failed to develop contact hypersensitivity (CHS) or form germinal centers (GCs), all features not previously recognized in patients and typical of defective noncanonical NF-κB signaling. Lymphotoxin β receptor (LTβR)–driven induction of chemokines and adhesion molecules mediated by both canonical and noncanonical NF-κB pathways was impaired, and levels of p100 were markedly diminished in the mutant. IκBα mutant→Rag2^−/−, but not WT→IκBα mutant, bone marrow chimeras formed proper lymphoid organs and developed CHS and GCs. Defective architectural cell function explains the immunodeficiency and poor outcome of HSCT in patients with IκBα deficiency and suggests that correction of this niche is critical for reconstituting their immune function.

Stable reconstitution of IKK-deficient mouse embryonic fibroblasts

Retroviral transduction is an invaluable technique in molecular biology used to express proteins encoded by nonviral genes in mammalian cells. A key feature of this technique is the ability to create cell lines that stably express the protein of interest and can be cultured long term. Here we describe a retroviral transduction procedure for mouse embryonic fibroblasts (MEFs) that uses Platinum-E cells to rapidly package high-titer, helper-free retrovirus. This technique is useful to study the role of key signaling kinases in the NF-κB signal transduction pathway.

Negative feedback regulation of NF-κB-inducing kinase is proteasome-dependent but does not require cellular inhibitors of apoptosis

Non-canonical NF-κB signaling is controlled by the precise regulation of NF-κB inducing kinase (NIK) stability. NIK is constitutively ubiquitylated by cellular inhibitor of apoptosis (cIAP) proteins 1 and 2, leading to its complete proteasomal degradation in resting cells. Following stimulation, cIAP-mediated ubiquitylation of NIK ceases and NIK is stabilized, allowing for inhibitor of κB kinase (IKK)α activation and non-canonical NF-κB signaling. Non-canonical NF-κB signaling is terminated by feedback phosphorylation of NIK by IKKα that promotes NIK degradation; however, the mechanism of active NIK protein turnover remains unknown. To address this question, we established a strategy to precisely distinguish between basal degradation of newly synthesized endogenous NIK and induced active NIK in stimulated cells. Using this approach, we found that IKKα-mediated degradation of signal-induced activated NIK occurs through the proteasome. To determine whether cIAP1 or cIAP2 play a role in active NIK turnover, we utilized a Smac mimetic (GT13072), which promotes degradation of these E3 ubiquitin ligases. As expected, GT13072 stabilized NIK in resting cells. However, loss of the cIAPs did not inhibit proteasome-dependent turnover of signal-induced NIK showing that unlike the basal regulatory mechanism, active NIK turnover is independent of cIAP1 and cIAP2. Our results therefore establish that the negative feedback control of IKKα-mediated NIK turnover occurs via a novel proteasome-dependent and cIAP-independent mechanism.