RelB forms transcriptionally inactive complexes with RelA/p65

NF-κB role on tumor proliferation, migration, invasion and immune escape

Nuclear factor kappa-B (NF-κB) is a nuclear transcription factor that plays a key factor in promoting inflammation, which can lead to the development of cancer in a long-lasting inflammatory environment. The activation of NF-κB is essential in the initial phases of tumor development and progression, occurring in both pre-malignant cells and cells in the microenvironment such as phagocytes, T cells, and B cells. In addition to stimulating angiogenesis, inhibiting apoptosis, and promoting the growth of tumor cells, NF-κB activation also causes the epithelial-mesenchymal transition, and tumor immune evasion. Therapeutic strategies that focus on immune checkpoint molecules have revolutionized cancer treatment by enabling the immune system to activate immunological responses against tumor cells. This review focused on understanding the NF-κB signaling pathway in the context of cancer.

Advances in regulation of homeostasis through chromatin modifications by airway commensals

Commensal bacteria are residents of the human airway where they interact with both colonizing pathogens and host respiratory epithelial cells of this mucosal surface. It is here that commensals exert their influence through host signaling cascades, host transcriptional responses and host immunity, all of which are rooted in chromatin remodeling and histone modifications. Recent studies show that airway commensals impact host chromatin, but compared the what is known for gut commensals, the field remains in its infancy. The mechanisms by which airway commensals regulate respiratory health and homeostasis through chromatin modifications is of increasing interest, specifically since their displacement precedes the increased potential for respiratory disease. Herein we will discuss recent advances and intriguing avenues of future work aimed at deciphering how airway commensals protect and influence respiratory health.

cFLIP in the molecular regulation of astroglia-driven neuroinflammation in experimental glaucoma

BACKGROUND

Recent experimental studies of neuroinflammation in glaucoma pointed to cFLIP as a molecular switch for cell fate decisions, mainly regulating cell type-specific caspase-8 functions in cell death and inflammation. This study aimed to determine the importance of cFLIP for regulating astroglia-driven neuroinflammation in experimental glaucoma by analyzing the outcomes of astroglia-targeted transgenic deletion of cFLIP or cFLIPL.

METHODS

Glaucoma was modeled by anterior chamber microbead injections to induce ocular hypertension in mouse lines with or without conditional deletion of cFLIP or cFLIPL in astroglia. Morphological analysis of astroglia responses assessed quantitative parameters in retinal whole mounts immunolabeled for GFAP and inflammatory molecules or assayed for TUNEL. The molecular analysis included 36-plexed immunoassays of the retina and optic nerve cytokines and chemokines, NanoString-based profiling of inflammation-related gene expression, and Western blot analysis of selected proteins in freshly isolated samples of astroglia.

RESULTS

Immunoassays and immunolabeling of retina and optic nerve tissues presented reduced production of various proinflammatory cytokines, including TNFα, in GFAP/cFLIP and GFAP/cFLIPL relative to controls at 12 weeks of ocular hypertension with no detectable alteration in TUNEL. Besides presenting a similar trend of the proinflammatory versus anti-inflammatory molecules displayed by immunoassays, NanoString-based molecular profiling detected downregulated NF-κB/RelA and upregulated RelB expression of astroglia in ocular hypertensive samples of GFAP/cFLIP compared to ocular hypertensive controls. Analysis of protein expression also revealed decreased phospho-RelA and increased phospho-RelB in parallel with an increase in caspase-8 cleavage products.

CONCLUSIONS

A prominent response limiting neuroinflammation in ocular hypertensive eyes with cFLIP-deletion in astroglia values the role of cFLIP in the molecular regulation of glia-driven neuroinflammation during glaucomatous neurodegeneration. The molecular responses accompanying the lessening of neurodegenerative inflammation also seem to maintain astroglia survival despite increased caspase-8 cleavage with cFLIP deletion. A transcriptional autoregulatory response, dampening RelA but boosting RelB for selective expression of NF-κB target genes, might reinforce cell survival in cFLIP-deleted astroglia.

Anabolic Steroids Activate the NF-κB Pathway in Porcine Ovarian Putative Stem Cells Independently of the ZIP-9 Receptor

Boldenone (Bdn) and nandrolone (Ndn) are anabolic androgenic steroids (AASs) that, as our previous studies have shown, may increase the risk of neoplastic transformation of porcine ovarian putative stem cells (poPSCs). The NF-κB pathway may be important in the processes of carcinogenesis and tumour progression. Therefore, in this work, we decided to test the hypothesis of whether Bdn and Ndn can activate the NF-κB pathway by acting through the membrane androgen receptor ZIP-9. For this purpose, the expression profiles of both genes involved in the NF-κB pathway and the gene coding for the ZIP-9 receptor were checked. The expression and localization of proteins of this pathway in poPSCs were also examined. Additionally, the expression of the ZIP-9 receptor and the concentration of the NF-κB1 and 2 protein complex were determined. Activation of the NF-κB pathway was primarily confirmed by an increase in the relative abundances of phosphorylated forms of RelA protein and IκBα inhibitor. Reduced quantitative profiles pinpointed not only for genes representing this pathway but also for unphosphorylated proteins, and, simultaneously, decreased concentration of the NF-κB1 and 2 complex may indicate post-activation silencing by negative feedback. However, the remarkably and sustainably diminished expression levels noticed for the SLC39A9 gene and ZIP-9 protein suggest that this receptor does not play an important role in the regulation of the NF-κB pathway.

An EZH2-NF-κB regulatory axis drives expression of pro-oncogenic gene signatures in triple negative breast cancer

The histone methyltransferase EZH2 has been studied most extensively in the context of PRC2-dependent gene repression. Accumulating evidence indicates non-canonical functions for EZH2 in cancer contexts including promoting paradoxical gene expression through interactions with transcription factors, including NF-κB in triple negative breast cancer (TNBC). We profile EZH2 and NF-κB factor co-localization and positive gene regulation genome-wide, and define a subset of NF-κB targets and genes associated with oncogenic functions in TNBC that is enriched in patient datasets. We demonstrate interaction between EZH2 and RelA requiring the recently identified transactivation domain (TAD) which mediates EZH2 recruitment to, and activation of certain NF-κB-dependent genes, and supports downstream migration and stemness phenotypes in TNBC cells. Interestingly, EZH2-NF-κB positive regulation of genes and stemness does not require PRC2. This study provides new insight into pro-oncogenic regulatory functions for EZH2 in breast cancer through PRC2-independent, and NF-κB-dependent regulatory mechanisms.

The Recent Research Progress of NF-κB Signaling on the Proliferation, Migration, Invasion, Immune Escape and Drug Resistance of Glioblastoma

Glioblastoma multiforme (GBM) is the most common and invasive primary central nervous system tumor in humans, accounting for approximately 45-50% of all primary brain tumors. How to conduct early diagnosis, targeted intervention, and prognostic evaluation of GBM, in order to improve the survival rate of glioblastoma patients, has always been an urgent clinical problem to be solved. Therefore, a deeper understanding of the molecular mechanisms underlying the occurrence and development of GBM is also needed. Like many other cancers, NF-κB signaling plays a crucial role in tumor growth and therapeutic resistance in GBM. However, the molecular mechanism underlying the high activity of NF-κB in GBM remains to be elucidated. This review aims to identify and summarize the NF-κB signaling involved in the recent pathogenesis of GBM, as well as basic therapy for GBM via NF-κB signaling.

Iron metabolism and ferroptosis in diabetic bone loss: from mechanism to therapy

Osteoporosis, one of the most serious and common complications of diabetes, has affected the quality of life of a large number of people in recent years. Although there are many studies on the mechanism of diabetic osteoporosis, the information is still limited and there is no consensus. Recently, researchers have proven that osteoporosis induced by diabetes mellitus may be connected to an abnormal iron metabolism and ferroptosis inside cells under high glucose situations. However, there are no comprehensive reviews reported. Understanding these mechanisms has important implications for the development and treatment of diabetic osteoporosis. Therefore, this review elaborates on the changes in bones under high glucose conditions, the consequences of an elevated glucose microenvironment on the associated cells, the impact of high glucose conditions on the iron metabolism of the associated cells, and the signaling pathways of the cells that may contribute to diabetic bone loss in the presence of an abnormal iron metabolism. Lastly, we also elucidate and discuss the therapeutic targets of diabetic bone loss with relevant medications which provides some inspiration for its cure.

NF-κB mediated regulation of tumor cell proliferation in hypoxic microenvironment

Hypoxia is caused by a cancer-promoting milieu characterized by persistent inflammation. NF-κB and HIF-1α are critical participants in this transition. Tumor development and maintenance are aided by NF-κB, while cellular proliferation and adaptability to angiogenic signals are aided by HIF-1α. Prolyl hydroxylase-2 (PHD-2) has been hypothesized to be the key oxygen-dependent regulator of HIF-1α and NF-transcriptional B's activity. Without low oxygen levels, HIF-1α is degraded by the proteasome in a process dependent on oxygen and 2-oxoglutarate. As opposed to the normal NF-κB activation route, where NF-κB is deactivated by PHD-2-mediated hydroxylation of IKK, this method actually activates NF-κB. HIF-1α is protected from degradation by proteasomes in hypoxic cells, where it then activates transcription factors involved in cellular metastasis and angiogenesis. The Pasteur phenomenon causes lactate to build up inside the hypoxic cells. As part of a process known as lactate shuttle, MCT-1 and MCT-4 cells help deliver lactate from the blood to neighboring, non-hypoxic tumour cells. Non-hypoxic tumour cells use lactate, which is converted to pyruvate, as fuel for oxidative phosphorylation. OXOPHOS cancer cells are characterized by a metabolic switch from glucose-facilitated oxidative phosphorylation to lactate-facilitated oxidative phosphorylation. Although PHD-2 was found in OXOPHOS cells. There is no clear explanation for the presence of NF-kappa B activity. The accumulation of the competitive inhibitor of 2-oxo-glutarate, pyruvate, in non-hypoxic tumour cells is well established. So, we conclude that PHD-2 is inactive in non-hypoxic tumour cells due to pyruvate-mediated competitive suppression of 2-oxo-glutarate. This results in canonical activation of NF-κB. In non-hypoxic tumour cells, 2-oxoglutarate serves as a limiting factor, rendering PHD-2 inactive. However, FIH prevents HIF-1α from engaging in its transcriptional actions. Using the existing scientific literature, we conclude in this study that NF-κB is the major regulator of tumour cell growth and proliferation via pyruvate-mediated competitive inhibition of PHD-2.

Signaling Pathways in Inflammation and Cardiovascular Diseases: An Update of Therapeutic Strategies

Inflammatory processes represent a pivotal element in the development and complications of cardiovascular diseases (CVDs). Targeting these processes can lead to the alleviation of cardiomyocyte (CM) injury and the increase of reparative mechanisms. Loss of CMs from inflammation-associated cardiac diseases often results in heart failure (HF). Evidence of the crosstalk between nuclear factor-kappa B (NF-κB), Hippo, and mechanistic/mammalian target of rapamycin (mTOR) has been reported in manifold immune responses and cardiac pathologies. Since these signaling cascades regulate a broad array of biological tasks in diverse cell types, their misregulation is responsible for the pathogenesis of many cardiac and vascular disorders, including cardiomyopathies and atherosclerosis. In response to a myriad of proinflammatory cytokines, which induce reactive oxygen species (ROS) production, several molecular mechanisms are activated within the heart to inaugurate the structural remodeling of the organ. This review provides a global landscape of intricate protein–protein interaction (PPI) networks between key constituents of NF-κB, Hippo, and mTOR signaling pathways as quintessential targetable candidates for the therapy of cardiovascular and inflammation-related diseases.

Aryl Hydrocarbon Receptor Mechanisms Affecting Chronic Kidney Disease

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix transcription factor that binds diverse endogenous and xenobiotic ligands, which regulate AHR stability, transcriptional activity, and cell signaling. AHR activity is strongly implicated throughout the course of chronic kidney disease (CKD). Many diverse organic molecules bind and activate AHR and these ligands are reported to either promote glomerular and tubular damage or protect against kidney injury. AHR crosstalk with estrogen, peroxisome proliferator-activated receptor-γ, and NF-κB pathways may contribute to the diversity of AHR responses during the various forms and stages of CKD. The roles of AHR in kidney fibrosis, metabolism and the renin angiotensin system are described to offer insight into CKD pathogenesis and therapies.

Proteomic analysis of early phosphorylated proteins in acute pancreatitis model

Background and Objective:

The exact mechanism of acute pancreatitis (AP), which is an inflammation of the pancreas, still remains unclear. In this study, we examined the protein phosphorylation changes during the early stage of AP in mice using proteomic analysis.

Methods:

AP model in mice was constructed using an intraperitoneal injection of cerulein. Blood samples and pancreas were collected at 1, 3, 6, 9h after the final injection (n=3 at each time point). Samples collected 3h after the final injection were separately mixed and named S (saline group) and C1 (cerulein group); samples collected 6h after the final injection from the cerulein group were mixed and named C2. Proteins from S, C1, and C2 were extracted, digested by trypsin, and subjected to LC-MS/MS analysis, bioinformatics analysis, and Western blotting.

Results:

A total of 549 sites (426 proteins) were upregulated, and 501 sites (367 proteins) were downregulated in C1 compared to S; while 491 phosphorylation sites (377 proteins) were upregulated and 367 sites (274 proteins) were downregulated in C2 compared to S. Motif analysis showed that proline-directed kinase and basophilic kinase had a key role during early AP. During an early AP stage, the cellular distributions of proteins slightly changed. The types of domains changed with the development of AP. Phosphorylation proteins associated with calcium signaling, especially IP3R mediated calcium release, lysosome and autophagosome pathway, pancreatic digestive activation, and secretion, were found to be involved in the development of early AP independent of NF-kB activation. Moreover, the MAPK family was found to have a greater impact at the early stage of AP. We also found differentially expressed phosphorylations of amylase and trypsinogen and increased phosphorylation of MAPK6 S189 in early AP.

Conclusion:

IP3R mediated calcium release and activation of MAPK family are key events promoting the development of early AP.

Ragweed pollen induces allergic conjunctivitis immune tolerance in mice via regulation of the NF-κB signal pathway

AIM

To investigate the feasibility and mechanism of immune tolerance in allergic conjunctivitis.

METHODS

The allergic conjunctivitis immune tolerance mice model was established by ragweed pollen (RW) and the related cytokines were detected. The mice were divided into 9 groups and the maslinic acid (MA) or PBS were given for different group after modeling. The expression levels of chemokine ligand 5 (CCL5) and P-65 in the conjunctival tissue were analyzed by immunohistochemistry, quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot. The percentage of interleukin-17 (IL-17) and CD4+CD25+ in the splenocyte supernatant was analyzed by flow cytometry. Furthermore, the serum and splenocyte supernatant concentration of total-IgE, interleukin-10 (IL-10), and IL-17 was analyzed by enzyme linked immune response (ELISA).

RESULTS

After the model was established, symptoms of conjunctivitis were alleviated, the level of P-65, CCL5, IL-17, and total-IgE was raised, while the expression of IL-10, CD4+CD25+ was decreased. This result fully demonstrated that a typical IL-17/regulatory-T-cells (Treg cells) imbalance and NF-κB activation. When the NF-κB signal pathway was suppressed, it showed that there was a further relief of conjunctivitis in mice. At the same time, the expression of total-IgE, IL-17, and CCL5 was decreased and the expression of anti-inflammatory factor (IL-10, CD4+CD25+) was increased.

CONCLUSION

In the state of immune tolerance, symptoms of conjunctivitis in mice are alleviated, the Th-17 cells of allergic conjunctivitis mice are inhibited, and Treg cells activity is enhanced.

RelB and Neuroinflammation

Neuroinflammation within the central nervous system involves multiple cell types that coordinate their responses by secreting and responding to a plethora of inflammatory mediators. These factors activate multiple signaling cascades to orchestrate initial inflammatory response and subsequent resolution. Activation of NF-κB pathways in several cell types is critical during neuroinflammation. In contrast to the well-studied role of p65 NF-κB during neuroinflammation, the mechanisms of RelB activation in specific cell types and its roles during neuroinflammatory response are less understood. In this review, we summarize the mechanisms of RelB activation in specific cell types of the CNS and the specialized effects this transcription factor exerts during neuroinflammation.

MALT1 as a promising target to treat lymphoma and other diseases related to MALT1 anomalies

Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a key adaptor protein that regulates the NF-κB pathway, in which MALT1 functions as a scaffold protein and protease to trigger downstream signals. The abnormal expression of MALT1 is closely associated with lymphomagenesis and other diseases, including solid tumors and autoimmune diseases. MALT1 is the only protease in the underlying pathogenesis of these diseases, and its proteolytic activity can be pharmacologically regulated. Therefore, MALT1 is a potential and promising target for anti-lymphoma and other MALT1-related disease treatments. Currently, the development of MALT1 inhibitors is still in its early stages. This review presents an overview of MALT1, particularly its X-ray structures and biological functions, and elaborates on the pathogenesis of diseases associated with its dysregulation. We then summarize previously reported MALT1 inhibitors, focusing on their molecular structure, biological activity, structure-activity relationship, and limitations. Finally, we propose future research directions to accelerate the discovery of novel MALT1 inhibitors with clinical applications. Overall, this review provides a comprehensive and systematic overview of MALT1-related research advances and serves as a theoretical basis for drug discovery and research.

NF-κB2 and RELB offer prognostic information in colorectal cancer and NFKB2 rs7897947 represents a genetic risk factor for disease development

The Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) family of transcription factors plays an important role in immune responses and cancer development and progression. We have focused on NF-κB2 and RELB of the alternative pathway of NF-κB, which remains largely underexplored in colorectal cancer (CRC). We found that NF-κB2 and RELB protein levels were upregulated in tumour and surrounding stromal tissue compared to distant non-neoplastic tissue (NN) and associated stroma (p<0.001 in all associations). Moreover, low RELB protein expression was associated with decreased overall survival (p = 0.032). Lower RELB gene expression levels were observed in tumour compared to NN tissue (p = 0.003) and were associated with shorter time to progression (TTP) (p = 0.025). NF-κB2 gene expression levels were similar in tumour and NN tissue, but higher tumour levels were prognostic for improved survival (p = 0.038) and TTP (p<0.001). We also assessed the significance of two NF-κB2 genetic polymorphisms, rs12769316 and rs7897947. Both polymorphisms were associated with lymph node infiltration (p = 0.045 and p = 0.009, respectively). In addition, rs12769316 AA homozygotes relapsed less often compared to G allele carriers (p = 0.029). Moreover, rs7897947 allele frequencies differed significantly between CRC patients and healthy controls (p<0.001) and the minor allele (G) was associated with reduced risk for developing CRC (p<0.001, OR: 0.527, 95% CI: 0.387-0.717). In conclusion, the alternative NF-κB pathway appears deregulated in CRC. Moreover, NF-κB2 and RELB expression levels seem to be significant for the clinical outcome of CRC patients and rs7897947 appears to be a risk factor for CRC development.

Toll like Receptor signalling by Prevotella histicola activates alternative NF-κB signalling in Cystic Fibrosis bronchial epithelial cells compared to P. aeruginosa

Cystic Fibrosis (CF), caused by mutations affecting the CFTR gene, is characterised by viscid secretions in multiple organ systems. CF airways contain thick mucus, creating a gradient of hypoxia, which promotes the establishment of polymicrobial infection. Such inflammation predisposes to further infection, a self-perpetuating cycle in mediated by NF-κB. Anaerobic Gram-negative Prevotella spp. are found in sputum from healthy volunteers and CF patients and in CF lungs correlate with reduced levels of inflammation. Prevotella histicola (P. histicola) can suppress murine lung inflammation, however, no studies have examined the role of P. histicola in modulating infection and inflammation in the CF airways. We investigated innate immune signalling and NF-kB activation in CF epithelial cells CFBE41o- in response to clinical stains of P. histicola and Pseudomonas aeruginosa (P. aeruginosa). Toll-Like Receptor (TLR) expressing HEK-293 cells and siRNA assays for TLRs and IKKα were used to confirm signalling pathways. We show that P. histicola infection activated the alternative NF-kB signalling pathway in CF bronchial epithelial cells inducing HIF-1α protein. TLR5 signalling was responsible for the induction of the alternative NF-kB pathway through phosphorylation of IKKα. The induction of transcription factor HIF-1α was inversely associated with the induction of the alternative NF-kB pathway and knockdown of IKKα partially restored canonical NF-kB activation in response to P. histicola. This study demonstrates that different bacterial species in the respiratory microbiome can contribute differently to inflammation, either by activating inflammatory cascades (P. aeruginosa) or by muting the inflammatory response by modulating similar or related pathways (P. histicola). Further work is required to assess the complex interactions of the lung microbiome in response to mixed bacterial infections and their effects in people with CF.

A Cellular Stress Response Induced by the CRISPR-dCas9 Activation System Is Not Heritable Through Cell Divisions

The CRISPR-Cas9 system can be modified to perform "epigenetic editing" by utilizing the catalytically inactive (dead) Cas9 (dCas9) to recruit regulatory proteins to specific genomic locations. In prior studies, epigenetic editing with multimers of the transactivator VP16 and guide RNAs (gRNAs) was found to cause adverse cellular responses. These side effects may confound studies inducing new cellular properties, especially if the cellular responses are maintained through cell divisions-an epigenetic regulatory property. Here, we show how distinct components of this CRISPR-dCas9 activation system, particularly dCas9 with untargeted gRNAs, upregulate genes associated with transcriptional stress, defense response, and regulation of cell death. Our results highlight a previously undetected acute stress response to CRISPR-dCas9 components in human cells, which is transient and not maintained through cell divisions.

NF-κB c-Rel Dictates the Inflammatory Threshold by Acting as a Transcriptional Repressor

NF-κB/Rel family of transcription factors plays a central role in initiation and resolution of inflammatory responses. Here, we identified a function of the NF-κB subunit c-Rel as a transcriptional repressor of inflammatory genes. Genetic deletion of c-Rel substantially potentiates the expression of several TNF-α-induced RelA-dependent mediators of inflammation. v-Rel, the viral homologue of c-Rel, but not RelB, also possesses this repressive function. Mechanistically, we found that c-Rel selectively binds to the co-repressor HDAC1 and competitively binds to the DNA mediating HDAC1 recruitment to the promoters of inflammatory genes. A specific point mutation at tyrosine25 in c-Rel's DNA-binding domain, for which a missense single nucleotide variation (Y25H) exists in humans, completely abrogated its ability to bind DNA and repress TNF-α-induced, RelA-mediated transcription. Our findings reveal that the transactivator NF-κB subunit c-Rel also plays a role as a transcriptional repressor in the maintenance of inflammatory homeostasis.

Mechanisms of lymphatic system-specific viral replication and its potential role in autoimmune disease

Viral infections can be fatal because of the direct cytopathic effects of the virus or the induction of a strong, uncontrolled inflammatory response. Virus and host intrinsic characteristics strongly modulate the outcome of viral infections. Recently we determined the circumstances under which enhanced replication of virus within the lymphoid tissue is beneficial for the outcome of a disease. This enforced viral replication promotes anti-viral immune activation and, counterintuitively, accelerates virus control. In this review we summarize the mechanisms that contribute to enforced viral replication. Antigen-presenting cells and CD169⁺ macrophages exhibit enforced viral replication after infection with the model viruses lymphocytic choriomeningitis virus (LCMV) and vesicular stomatitis virus (VSV). Ubiquitin-specific peptidase 18 (Usp18), an endogenous type I interferon blocker in CD169⁺ macrophages, has been identified as a proviral gene, as are B cell activating factor (BAFF) and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Lymphotoxins (LT) strongly enhance viral replication in the spleen and lymph nodes. All these factors modulate splenic architecture and thereby promote the development of CD169⁺ macrophages. Tumor necrosis factor alpha (TNF-α) and nuclear factor kappa-light-chain-enhancer of activated B cell signaling (NF-κB) have been found to promote the survival of infected CD169⁺ macrophages, thereby similarly promoting enforced viral replication. Association of autoimmune disease with infections is evident from (1) autoimmune phenomena described during a chronic virus infection; (2) onset of autoimmune disease simultaneous to viral infections; and (3) experimental evidence. Involvement of virus infection during onset of type I diabetes is strongly evident. Epstein-Bar virus (EBV) infection was discussed to be involved in the pathogenesis of systemic lupus erythematosus. In conclusion, several mechanisms promote viral replication in secondary lymphatic organs. Identifying such factors in humans is a challenge for future studies.

Pulmonary neutrophilia caused by absence of the NF-κB member RelB is dampened by exposure to cigarette smoke

Inflammation is a response to injury and infection. Although protective under physiological conditions, excessive and persistent inflammation is linked to numerous diseases. As the lungs are continuously exposed to the external environment, the respiratory system is particularly liable to damage from inflammation. RelB is a member of the non-canonical NF-κB pathway that may control lung inflammation caused by cigarette smoke (CS), a leading cause of morbidity and mortality worldwide. Our lab has previously shown that RelB protects against CS-induced inflammation in vitro, leading us to hypothesize that RelB would protect against acute CS-induced pulmonary inflammation in vivo. We exposed wild-type (Relb+/+) and RelB-deficient mice (Relb-/-) mice to room air or to CS and found that CS exposure caused a sustained decrease in pulmonary granulocytes in Relb-/- mice that was predominated by a decrease in neutrophils. Pulmonary inflammation caused by other irritants, including chlorine, ovalbumin (OVA; to mimic features of asthma) and lipopolysaccharide (LPS) was not controlled by RelB. Differential cytokine analysis suggests that alterations in chemotactic cytokines do not fully account for the CS-specific decrease in neutrophils in Relb-/- mice. Flow cytometric analysis of the bronchoalveolar lavage and bone marrow cells also reveal that it is unlikely that the sustained decrease is caused by excessive cell death or decreased hematopoiesis from the bone marrow. Overall, our results indicate that RelB regulates acute CS-induced pulmonary inflammation. Understanding how RelB regulates CS-induced inflammation may potentiate the discovery of new therapeutic strategies for many of the inflammatory diseases caused by CS.

A detrimental role of RelB in mature oligodendrocytes during experimental acute encephalomyelitis

Background

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS). It is firmly established that overactivation of the p65 (RelA) nuclear factor kappa B (NF-κB) transcription factor upregulates expression of inflammatory mediators in both immune and non-immune resident CNS cells and promotes inflammation during MS. In contrast to p65, NF-κB family member RelB regulates immune cell development and can limit inflammation. Although RelB expression is induced during inflammation in the CNS, its role in MS remains unknown.

Methods

To examine the role of RelB in non-immune CNS cells, we generated mice with RelB specifically deleted in astrocytes (RelB^ΔAST), oligodendrocytes (RelB^ΔOLIGO), or neural progenitor-derived cells (RelB^ΔNP). We used experimental autoimmune encephalomyelitis (EAE), an accepted mouse model of MS, to assess the effect of RelB deletion on disease outcomes and performed analysis on the histological, cellular, and molecular level.

Results

Despite being a negative regulator of inflammation, conditional knockout of RelB in non-immune resident CNS cells surprisingly decreased the severity of EAE. This protective effect was recapitulated by conditional deletion of RelB in oligodendrocytes but not astrocytes. Deletion of RelB in oligodendrocytes reduced disease severity, promoted survival of mature oligodendrocytes, and correlated with increased activation of p65 NF-κB.

Conclusions

These findings suggest that RelB fine tunes inflammation and cell death/survival during EAE. Importantly, our data points out the detrimental role RelB plays in controlling survival of mature oligodendrocytes, which could be explored as a viable option to treat MS in the future.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1548-7) contains supplementary material, which is available to authorized users.

NF-κB/Rel Transcription Factors in Pancreatic Cancer: Focusing on RelA, c-Rel, and RelB

Regulation of Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/Rel transcription factors (TFs) is extremely cell-type-specific owing to their ability to act disparately in the context of cellular homeostasis driven by cellular fate and the microenvironment. This is also valid for tumor cells in which every single component shows heterogenic effects. Whereas many studies highlighted a per se oncogenic function for NF-κB/Rel TFs across cancers, recent advances in the field revealed their additional tumor-suppressive nature. Specifically, pancreatic ductal adenocarcinoma (PDAC), as one of the deadliest malignant diseases, shows aberrant canonical-noncanonical NF-κB signaling activity. Although decades of work suggest a prominent oncogenic activity of NF-κB signaling in PDAC, emerging evidence points to the opposite including anti-tumor effects. Considering the dual nature of NF-κB signaling and how it is closely linked to many other cancer related signaling pathways, it is essential to dissect the roles of individual Rel TFs in pancreatic carcinogenesis and tumor persistency and progression. Here, we discuss recent knowledge highlighting the role of Rel TFs RelA, RelB, and c-Rel in PDAC development and maintenance. Next to providing rationales for therapeutically harnessing Rel TF function in PDAC, we compile strategies currently in (pre-)clinical evaluation.

RelB acts as a molecular switch driving chronic inflammation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a primary brain tumor characterized by extensive necrosis and immunosuppressive inflammation. The mechanisms by which this inflammation develops and persists in GBM remain elusive. We identified two cytokines interleukin-1β (IL-1) and oncostatin M (OSM) that strongly negatively correlate with patient survival. We found that these cytokines activate RelB/p50 complexes by a canonical NF-κB pathway, which surprisingly drives expression of proinflammatory cytokines in GBM cells, but leads to their inhibition in non-transformed astrocytes. We discovered that one allele of the gene encoding deacetylase Sirtuin 1 (SIRT1), needed for repression of cytokine genes, is deleted in 80% of GBM tumors. Furthermore, RelB specifically interacts with a transcription factor Yin Yang 1 (YY1) in GBM cells and activates GBM-specific gene expression programs. As a result, GBM cells continuously secrete proinflammatory cytokines and factors attracting/activating glioma-associated microglia/macrophages and thus, promote a feedforward inflammatory loop.

RelB controls adaptive responses of astrocytes during sterile inflammation

In response to brain injury or infections, astrocytes become reactive, undergo striking morphological and functional changes, and secrete and respond to a spectrum of inflammatory mediators. We asked whether reactive astrocytes also display adaptive responses during sterile IL-1β-induced neuroinflammation, which may limit tissue injury associated with many disorders of the central nervous system. We found that astrocytes display days-to-weeks long specific tolerance of cytokine genes, which is coordinated by NF-κB family member, RelB. However, in contrast to innate immune cells, astrocytic tolerance does not involve epigenetic silencing of the cytokine genes. Establishment of tolerance depends on persistent higher levels of RelB in tolerant astrocytes and its phosphorylation on serine 472. Mechanistically, this phosphorylation prevents efficient removal of RelB from cytokine promoters by IκBα and helps to establish tolerance. Importantly, ablation of RelB from astrocytes in mice abolishes tolerance during experimental neuroinflammation in vivo.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

NFKB1 and Cancer: Friend or Foe?

Current evidence strongly suggests that aberrant activation of the NF-κB signalling pathway is associated with carcinogenesis. A number of key cellular processes are governed by the effectors of this pathway, including immune responses and apoptosis, both crucial in the development of cancer. Therefore, it is not surprising that dysregulated and chronic NF-κB signalling can have a profound impact on cellular homeostasis. Here we discuss NFKB1 (p105/p50), one of the five subunits of NF-κB, widely implicated in carcinogenesis, in some cases driving cancer progression and in others acting as a tumour-suppressor. The complexity of the role of this subunit lies in the multiple dimeric combination possibilities as well as the different interacting co-factors, which dictate whether gene transcription is activated or repressed, in a cell and organ-specific manner. This review highlights the multiple roles of NFKB1 in the development and progression of different cancers, and the considerations to make when attempting to manipulate NF-κB as a potential cancer therapy.

Noncanonical NF-κB in Cancer

The NF-κB pathway is a critical regulator of immune responses and is often dysregulated in cancer. Two NF-κB pathways have been described to mediate these responses, the canonical and the noncanonical. While understudied compared to the canonical NF-κB pathway, noncanonical NF-κB and its components have been shown to have effects, usually protumorigenic, in many different cancer types. Here, we review noncanonical NF-κB pathways and discuss its important roles in promoting cancer. We also discuss alternative NF-κB-independent functions of some the components of noncanonical NF-κB signaling. Finally, we discuss important crosstalk between canonical and noncanonical signaling, which blurs the two pathways, indicating that understanding the full picture of NF-κB regulation is critical to deciphering how this broad pathway promotes oncogenesis.

NF-κB Activation in Lymphoid Malignancies: Genetics, Signaling, and Targeted Therapy

The NF-κB transcription factor family plays a crucial role in lymphocyte proliferation and survival. Consequently, aberrant NF-κB activation has been described in a variety of lymphoid malignancies, including diffuse large B-cell lymphoma, Hodgkin lymphoma, and adult T-cell leukemia. Several factors, such as persistent infections (e.g., with Helicobacter pylori), the pro-inflammatory microenvironment of the cancer, self-reactive immune receptors as well as genetic lesions altering the function of key signaling effectors, contribute to constitutive NF-κB activity in these malignancies. In this review, we will discuss the molecular consequences of recurrent genetic lesions affecting key regulators of NF-κB signaling. We will particularly focus on the oncogenic mechanisms by which these alterations drive deregulated NF-κB activity and thus promote the growth and survival of the malignant cells. As the concept of a targeted therapy based on the mutational status of the malignancy has been supported by several recent preclinical and clinical studies, further insight in the function of NF-κB modulators and in the molecular mechanisms governing aberrant NF-κB activation observed in lymphoid malignancies might lead to the development of additional treatment strategies and thus improve lymphoma therapy.

GSK3β modulates NF-κB activation and RelB degradation through site-specific phosphorylation of BCL10

Glycogen synthase kinase 3β (GSK3β) is a ubiquitously expressed serine/threonine kinase involved in the regulation of various cellular functions, such as energy homoeostasis, cell growth and developmental processes. More recently, GSK3β has been identified as a part of a protein complex involved in the regulation of the CARMA1-BCL10-MALT1 complex (CBM complex) formation, which is a key signalling event upon antigen receptor engagement of B and T cells, required for the activation of the NF-κB and JNK pathways. However, conflicting reports have been published regarding the role of GSK3β for the activation of the NF-κB signalling pathways. Therefore, we aimed to determine the impact of GSK3β on the NF-κB signalling induced upon T cell activation. Blocking GSK3β by either pharmacologic inhibitors (SB216763 and SB415286) or by RNAi caused a reduced proteolysis of the MALT1 targets CYLD1, BCL10 and RelB as well as diminished IκBα degradation, NF-κB DNA binding and NF-κB activity. This negative effect on NF-κB appears to be due to a diminished CBM complex formation caused by a reduced BCL10 phosphorylation. Taken together, we provide here evidence for a novel regulatory mechanism by which GSK3β affects NF-κB signalling in activated T cells.

Tumor Necrosis Factor-Mediated Survival of CD169+ Cells Promotes Immune Activation during Vesicular Stomatitis Virus Infection

Innate immune activation is essential to mount an effective antiviral response and to prime adaptive immunity. Although a crucial role of CD169⁺ cells during vesicular stomatitis virus (VSV) infections is increasingly recognized, factors regulating CD169⁺ cells during viral infections remain unclear. Here, we show that tumor necrosis factor is produced by CD11b⁺ Ly6C⁺ Ly6G⁺ cells following infection with VSV. The absence of TNF or TNF receptor 1 (TNFR1) resulted in reduced numbers of CD169⁺ cells and in reduced type I interferon (IFN-I) production during VSV infection, with a severe disease outcome. Specifically, TNF triggered RelA translocation into the nuclei of CD169⁺ cells; this translocation was inhibited when the paracaspase MALT-1 was absent. Consequently, MALT1 deficiency resulted in reduced VSV replication, defective innate immune activation, and development of severe disease. These findings indicate that TNF mediates the maintenance of CD169⁺ cells and innate and adaptive immune activation during VSV infection.IMPORTANCE Over the last decade, strategically placed CD169⁺ metallophilic macrophages in the marginal zone of the murine spleen and lymph nodes (LN) have been shown to play a very important role in host defense against viral pathogens. CD169⁺ macrophages have been shown to activate innate and adaptive immunity via "enforced virus replication," a controlled amplification of virus particles. However, the factors regulating the CD169⁺ macrophages remain to be studied. In this paper, we show that after vesicular stomatitis virus infection, phagocytes produce tumor necrosis factor (TNF), which signals via TNFR1, and promote enforced virus replication in CD169⁺ macrophages. Consequently, lack of TNF or TNFR1 resulted in defective immune activation and VSV clearance.

Oxidative stress and cellular pathways of asthma and inflammation: Therapeutic strategies and pharmacological targets

Asthma is a complex inflammatory disease characterized by airway inflammation and hyperresponsiveness. The mechanisms associated with the development and progression of asthma have been widely studied in multiple populations and animal models, and these have revealed involvement of various cell types and activation of intracellular signaling pathways that result in activation of inflammatory genes. Significant contributions of Toll-like-receptors (TLRs) and transcription factors such as NF-кB, have been reported as major contributors to inflammatory pathways. These have also recently been associated with mechanisms of oxidative biology. This is of important clinical significance as the observed inefficacy of current available treatments for severe asthma is widely attributed to oxidative stress. Therefore, targeting oxidizing molecules in conjunction with inflammatory mediators and transcription factors may present a novel therapeutic strategy for asthma. In this review, we summarize TLRs and NF-кB pathways in the context of exacerbation of asthma pathogenesis and oxidative biology, and we discuss the potential use of polyphenolic flavonoid compounds, known to target these pathways and possess antioxidant activity, as potential therapeutic agents for asthma.

Nuclear Factor-kappaB in Autoimmunity: Man and Mouse

NF-κB (nuclear factor-kappa B) is a transcription complex crucial for host defense mediated by innate and adaptive immunity, where canonical NF-κB signaling, mediated by nuclear translocation of RelA, c-Rel, and p50, is important for immune cell activation, differentiation, and survival. Non-canonical signaling mediated by nuclear translocation of p52 and RelB contributes to lymphocyte maturation and survival and is also crucial for lymphoid organogenesis. We outline NF-κB signaling and regulation, then summarize important molecular contributions of NF-κB to mechanisms of self-tolerance. We relate these mechanisms to autoimmune phenotypes described in what is now a substantial catalog of immune defects conferred by mutations in NF-κB pathways in mouse models. Finally, we describe Mendelian autoimmune syndromes arising from human NF-κB mutations, and speculate on implications for understanding sporadic autoimmune disease.

The p38-MK2/3 Module Is Critical for IL-33-Induced Signaling and Cytokine Production in Dendritic Cells

IL-33 is an IL-1 cytokine superfamily member. Binding of IL-33 to the IL-33R induces activation of the canonical NF-κB signaling and activation of MAPKs. In bone marrow-derived dendritic cells, IL-33 induces the production of IL-6, IL-13, and TNF-α. However, the signaling pathways resulting in IL-33-induced effector functions of dendritic cells are unknown. In this article, we show that the IL-33-induced cytokine production is only partly dependent on p65. Thereby, p65 mediates the production of IL-6, but not of IL-13, whereas the p38-Mapk-activated protein kinases 2/3 (MK2/3) signaling module mediates the IL-13, but not the IL-6, production. In addition, GM-CSF, which is critical for the differentiation and proliferation of bone marrow-derived dendritic cells, potentiates the p65-dependent IL-6 and the p38-MK2/3-dependent IL-13 production. Furthermore, we found that effective TNF-α production is only induced in the presence of GM-CSF and IL-33 via the p38-MK2/3 signaling module. Taken together, we found that the p38-MK2/3 signaling module is essential to mediate IL-33-induced cytokine production in dendritic cells.

The role of Nuclear Factor-kappa B signaling in human cervical cancer

Background The Nuclear Factor kappaB (NF-kB) family consists of transcription factors that play a complex and essential role in the regulation of immune responses and inflammation. NF-kB has recently generated considerable interest as it has been implicated in human cancer initiation, progression and resistance to treatment. In the present comprehensive review the different aspects of NF-kB signaling in the carcinogenesis of cancer of the uterine cervix are discussed. NF-kB functions as part of a network, which determines the pattern of its effects on the expression of several other genes (such as crosstalks with reactive oxygen species, p53, STAT3 and miRNAS) and thus its function. Activation of NF-kB triggered by a HPV infection is playing an important role in the innate and adaptive immune response of the host. The virus induces down regulation of NF-kB to liquidate the inhibitory activity for its replication triggered by the immune system leading a status of persistant HPV infection. During the progression to high grade intraepithelial neoplasia and cervical cancer NF-KB becomes constitutionally activated again. Mutations in NF-kB genes are rare in solid tumors but mutations of upstream signaling molecules such as RAS, EGFR, PGF, HER2 have been implicated in elevated NF-kB signaling. NF-kB can stimulate transcription of proliferation regulating genes (eg. cyclin D1 and c-myc), genes involved in metastasis, VEGF dependent angiogenesis and cell immortality by telomerase. NF-kB activation can also induce the expression of activation-induced cytodine deaminase (AID) and the APOBEC proteins, providing a mechanistic link between the NF-kB pathway and mutagenic characteristic of cervical cancer. Inhibition of NF-kB has the potential to be used to reverse resistance to radiotherapy and systemic anti-cancer medication, but currently no clinicaly active NF-kB targeting strategies are available.

Regulation of NF-κB by the p105-ABIN2-TPL2 complex and RelAp43 during rabies virus infection

At the crossroad between the NF-κB and the MAPK pathways, the ternary complex composed of p105, ABIN2 and TPL2 is essential for the host cell response to pathogens. The matrix protein (M) of field isolates of rabies virus was previously shown to disturb the signaling induced by RelAp43, a NF-κB protein close to RelA/p65. Here, we investigated how the M protein disturbs the NF-κB pathway in a RelAp43-dependant manner and the potential involvement of the ternary complex in this mechanism. Using a tandem affinity purification coupled with mass spectrometry approach, we show that RelAp43 interacts with the p105-ABIN2-TPL2 complex and we observe a strong perturbation of this complex in presence of M protein. M protein interaction with RelAp43 is associated with a wide disturbance of NF-κB signaling, involving a modulation of IκBα-, IκBβ-, and IκBε-RelAp43 interaction and a favored interaction of RelAp43 with the non-canonical pathway (RelB and p100/p52). Monitoring the interactions between host and viral proteins using protein-fragment complementation assay and bioluminescent resonance energy transfer, we further show that RelAp43 is associated to the p105-ABIN2-TPL2 complex as RelAp43-p105 interaction stabilizes the formation of a complex with ABIN2 and TPL2. Interestingly, the M protein interacts not only with RelAp43 but also with TPL2 and ABIN2. Upon interaction with this complex, M protein promotes the release of ABIN2, which ultimately favors the production of RelAp43-p50 NF-κB dimers. The use of recombinant rabies viruses further indicates that this mechanism leads to the control of IFNβ, TNF and CXCL2 expression during the infection and a high pathogenicity profile in rabies virus infected mice. All together, our results demonstrate the important role of RelAp43 and M protein in the regulation of NF-κB signaling.

Rabies virus is a recurring zoonosis responsible for about 60,000 deaths per year. A key feature of rabies virus is its stealth, allowing it to spread within the host and escape the immune response. To do so, rabies virus developed several mechanisms, including a thorough interference with cell signaling pathways. Here, we focused our attention on the molecular aspects of rabies virus escape to the NF-κB pathway through the interaction between the M protein and the NF-κB protein RelAp43. Monitoring close range interactions, we found that RelAp43 plays an important role in the stabilization of the p105-ABIN2-TPL2 complex, which is essential in the regulation of both NF-κB and MAPK pathways, and we brought a new insight on the dynamics within the host protein complex. These results were confirmed in living cells and in mice. Overall, our data suggest that rabies virus interference with the p105-ABIN2-TPL2 complex is a cornerstone of its stealth strategy to escape the immune response.

Cooperation of Rel family members in regulating Aβ1-40-mediated pro-inflammatory cytokine secretion by retinal pigment epithelial cells

Amyloid-beta (Aβ) is a hallmark component of age-related macular degeneration (AMD), which induces secretion of pro-inflammatory cytokines from retinal pigment epithelium (RPE). Previous studies have shown that p50/RelA (p65), a member of NF-κB family, is an essential pro-inflammatory transcription factor responding to Aβ_1-40 stimulation, but few focused on the other two Rel transcription factor members – RelB and c-Rel – and their role in Aβ_1-40-mediated inflammation. It was reported that RelA, RelB and c-Rel are also implicated in various NF-κB-mediated inflammatory diseases. Therefore, we infer that Aβ_1-40-mediated inflammation targets not only the classical inflammation regulator, RelA, but also RelB and c-Rel. In this study, we demonstrate that intravitreally injected Aβ_1-40 mice develop AMD-like pathologic changes, coupled with Rel protein (RelA, RelB and c-Rel) synthesis and nuclear translocation. To focus on the interaction mechanism of Rel proteins, we found that RelB and c-Rel formed a heterodimer with RelA in mice model. We also found that c-Rel silencing decreased the levels of Aβ_1-40-dependent RelA expression, indicating that RelB and c-Rel may interact with RelA as coactivator and c-Rel is required to activate the expression of RelA. Moreover, Rel protein silencing decreased the expression of distinct pro-inflammatory cytokines. Together, we demonstrate that besides RelA, RelB and c-Rel can also be activated by Aβ_1-40, all of which mediate pro-inflammatory cytokine transcription and RPE damage. Our findings imply that RPE-mediated inflammation under the stimulation of Aβ_1-40 is multi-targeted and RelA, RelB and c-Rel proteins may be the new targets of anti-inflammatory agents.

Valproic acid increases NF-κB transcriptional activation despite decreasing DNA binding ability in P19 cells, which may play a role in VPA-initiated teratogenesis

The nuclear factor-kappa B (NF-κB) family of transcription factors regulate gene expression in response to diverse stimuli. We previously demonstrated that valproic acid (VPA) exposure in utero decreases total cellular protein expression of the NF-κB subunit p65 in CD-1 mouse embryos with a neural tube defect but not in phenotypically normal littermates. This study evaluated p65 mRNA and protein expression in P19 cells and determined the impact on DNA binding ability and activity. Exposure to 5mM VPA decreased p65 mRNA and total cellular protein expression however, nuclear p65 protein expression was unchanged. VPA reduced NF-κB DNA binding and nuclear protein of the p65 DNA-binding partner, p50. NF-κB transcriptional activity was increased with VPA alone, despite decreased phosphorylation of p65 at Ser276, and when combined with tissue necrosis factor α. These results demonstrate that VPA increases NF-κB transcriptional activity despite decreasing DNA binding, which may play a role in VPA-initiated teratogenesis.

Noncanonical NF-κB mediates the Suppressive Effect of Neutrophil Elastase on IL-8/CXCL8 by Inducing NKRF in Human Airway Smooth Muscle

Neutrophil elastase (NE) suppresses IL-8/CXCL8 in human airway smooth muscle cells (hASM) while stimulating its production in respiratory epithelial cells. This differential effect is mediated by the selective induction of NKRF and dysregulation in chronic inflammatory diseases. We hypothesized that the differential activation of NF-κB subunits confer the opposite effect of NKRF on IL-8/CXCL8 in primary hASM and A549 cells stimulated with NE. The events occurring at the promoters of NKRF and IL-8/CXCL8 were observed by ChIP assays, and the functional role of RelB was confirmed by knockdown and overexpression. Although p65 was stimulated in both cell types, RelB was only activated in NE-treated hASM, as confirmed by NF-κB DNA binding ELISA, Western blotting and confocal microscopy. Knockdown of RelB abolished the induction of NKRF and converted the suppression of IL-8/CXCL8 to stimulation. The forced expression of RelB induced NKRF production in hASM and A549 cells. NE activated the NIK/IKK1/RelB non-canonical NF-κB pathway in hASM but not in A549. The nuclear-translocated RelB was recruited to the NKRF promoter around the putative κB site, accompanied by p52 and RNA polymerase II. In conclusion, NFRF is a novel RelB-response gene, and NE is a stimulator of the non-canonical RelB/NF-κB pathway in hASM.

Disease-modifying effects of orally bioavailable NF-B inhibitors in dystrophin-deficient muscle

Duchenne muscular dystrophy (DMD) is a devastating muscle disease characterized by progressive muscle deterioration and replacement with an aberrant fatty, fibrous matrix. Chronic upregulation of nuclear factor κB (NF-κB) is implicated as a driver of the dystrophic pathogenesis. Herein, 2 members of a novel class of NF-κB inhibitors, edasalonexent (formerly CAT-1004) and CAT-1041, were evaluated in both mdx mouse and golden retriever muscular dystrophy (GRMD) dog models of DMD. These orally bioavailable compounds consist of a polyunsaturated fatty acid conjugated to salicylic acid and potently suppress the pathogenic NF-κB subunit p65/RelA in vitro. In vivo, CAT-1041 effectively improved the phenotype of mdx mice undergoing voluntary wheel running, in terms of activity, muscle mass and function, damage, inflammation, fibrosis, and cardiac pathology. We identified significant increases in dysferlin as a possible contributor to the protective effect of CAT-1041 to sarcolemmal damage. Furthermore, CAT-1041 improved the more severe GRMD phenotype in a canine case study, where muscle mass and diaphragm function were maintained in a treated GRMD dog. These results demonstrate that NF-κB modulation by edasalonexent and CAT-1041 is effective in ameliorating the dystrophic process and these compounds are candidates for new treatments for DMD patients.

NF-κB Pathways in the Pathogenesis of Multiple Sclerosis and the Therapeutic Implications

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways are involved in cell immune responses, apoptosis and infections. In multiple sclerosis (MS), NF-κB pathways are changed, leading to increased levels of NF-κB activation in cells. This may indicate a key role for NF-κB in MS pathogenesis. NF-κB signaling is complex, with many elements involved in its activation and regulation. Interestingly, current MS treatments are found to be directly or indirectly linked to NF-κB pathways and act to adjust the innate and adaptive immune system in patients. In this review, we will first focus on the intricacies of NF-κB signaling, including the activating pathways and regulatory elements. Next, we will theorize about the role of NF-κB in MS pathogenesis, based on current research findings, and discuss some of the associated therapeutic implications. Lastly, we will review four new MS treatments which interrupt NF-κB pathways—fingolimod, teriflunomide, dimethyl fumarate (DMF) and laquinimod (LAQ)—and explain their mechanisms, and the possible strategy for MS treatments in the future.

Regulation of inflammatory responses by neuregulin-1 in brain ischemia and microglial cells in vitro involves the NF-kappa B pathway

Background

We previously demonstrated that neuregulin-1 (NRG-1) was neuroprotective in rats following ischemic stroke. Neuroprotection by NRG-1 was associated with the suppression of pro-inflammatory gene expression in brain tissues. Over-activation of brain microglia can induce pro-inflammatory gene expression by activation of transcriptional regulators following stroke. Here, we examined how NRG-1 transcriptionally regulates inflammatory gene expression by computational bioinformatics and in vitro using microglial cells.

Methods

To identify transcriptional regulators involved in ischemia-induced inflammatory gene expression, rats were sacrificed 24 h after middle cerebral artery occlusion (MCAO) and NRG-1 treatment. Gene expression profiles of brain tissues following ischemia and NRG-1 treatment were examined by microarray technology. The Conserved Transcription Factor-Binding Site Finder (CONFAC) bioinformatics software package was used to predict transcription factors associated with inflammatory genes induced following stroke and suppressed by NRG-1 treatment. NF-kappa B (NF-kB) was identified as a potential transcriptional regulator of NRG-1-suppressed genes following ischemia. The involvement of specific NF-kB subunits in NRG-1-mediated inflammatory responses was examined using N9 microglial cells pre-treated with NRG-1 (100 ng/ml) followed by lipopolysaccharide (LPS; 10 μg/ml) stimulation. The effects of NRG-1 on cytokine production were investigated using Luminex technology. The levels of the p65, p52, and RelB subunits of NF-kB and IkB-α were determined by western blot analysis and ELISA. Phosphorylation of IkB-α was investigated by ELISA.

Results

CONFAC identified 12 statistically over-represented transcription factor-binding sites (TFBS) in our dataset, including NF-kBP65. Using N9 microglial cells, we observed that NRG-1 significantly inhibited LPS-induced TNFα and IL-6 release. LPS increased the phosphorylation and degradation of IkB-α which was blocked by NRG-1. NRG-1 also prevented the nuclear translocation of the NF-kB p65 subunit following LPS administration. However, NRG-1 increased production of the neuroprotective cytokine granulocyte colony-stimulating factor (G-CSF) and the nuclear translocation of the NF-kB p52 subunit, which is associated with the induction of anti-apoptotic and suppression of pro-inflammatory gene expression.

Conclusions

Neuroprotective and anti-inflammatory effects of NRG-1 are associated with the differential regulation of NF-kB signaling pathways in microglia. Taken together, these findings suggest that NRG-1 may be a potential therapeutic treatment for treating stroke and other neuroinflammatory disorders.

Nuclear Factor κB Activity is Increased in Peripheral Blood Mononuclear Cells of Children Affected by Atopic and Non-Atopic Eczema

Atopic and non-atopic eczema is an inflammatory cutaneous disease which is common in childhood and is associated with a dysregulation of the immune system. Many genes encoding immune receptors, cytokines, chemokines, chemokine receptors, and adhesion molecules involved in the development of the disease are under the control of transcription factors belonging to the nuclear factor (NF)-κB family. To investigate the role of NF-κB in the development of eczema, 20 children, affected by relapsing chronic eczema, were enrolled in this study. Eleven of the 20 children showed IgE immunoreactivity and had a positive prick test. The DNA binding activity of NF-κB in nuclear extracts of the patients' peripheral blood mononuclear cells (PBMC) was examined by electrophoretic mobility shift assay. We found that basal NF-κB-DNA binding activity in PBMC was significantly higher in the eczema patient group in comparison with the same parameter in the healthy age-matched control group. Moreover, we observed a significant correlation between NF-κB-DNA binding activity and patients' clinical score (SCORAD). Based on these observations we speculate that NF-κB can play an important role in the immunopathogenesis of eczema and therefore could be considered as a potential therapeutic target.

Post-translational control of NF-κB signaling by ubiquitination

The transcription factor nuclear factor-kappa B (NF-κB) controls a number of essential cellular functions, including the immune response, cell proliferation, and apoptosis. NF-κB signaling must be engaged temporally and spatially and well orchestrated to prevent aberrant activation because loss of normal regulation of NF-κB is a major contributor to a variety of pathological diseases, including inflammatory diseases, autoimmune diseases, and cancers. Thus, understanding the molecular mechanisms controlling NF-κB activation is an important part of treatment of these relevant diseases. Although NF-κB transcriptional activity is largely regulated by nuclear translocation, post-translational modification of NF-κB signaling components, including phosphorylation, ubiquitination, acetylation, and methylation, has emerged as an important mechanism affecting activity. Many proteins have been shown to ubiquitinate and regulate NF-κB activation at the receptor signaling complex in response to a variety of ligands, such as tumor necrosis factor, interleukin-1, and Toll-like receptor ligands. In this review, we discuss our current knowledge of ubiquitination patterns and their functional role in NF-κB regulation.

NF-κB in acute pancreatitis: Mechanisms and therapeutic potential

The incidence of acute pancreatitis (AP) is increasing globally and mortality could be high among patients with organ failure and infected necrosis. The predominant factors responsible for the morbidity and mortality of AP are systemic inflammatory response syndrome and multiorgan dysfunction. Even though preclinical studies have shown antisecretory agents (somatostatin), antioxidants (S-adenosyl methionine [SAM], selenium), protease inhibitors, platelet activating factor inhibitor (Lexipafant), and anti-inflammatory immunomodulators (eg. prostaglandin E, indomethacin) to benefit AP in terms of reducing the severity and/or mortality, most of these agents have shown heterogeneous results in clinical studies. Several years of experimental studies have implicated nuclear factor-kappa B (NF-κB) activation as an early and central event in the progression of inflammation in AP. In this manuscript, we review the literature on the role of NF-κB in the pathogenesis of AP, its early intraacinar activation, and how it results in progression of the disease. We also discuss why anti-protease, antisecretory, and anti-inflammatory agents are unlikely to be effective in clinical acute pancreatitis. NF-κB, being a central molecule that links the initial acinar injury to systemic inflammation and perpetuate the inflammation, we propose that more studies be focussed towards targeted inhibition of NF-κB activity. Direct NF-κB inhibition strategies have already been attempted in patients with various cancers. So far, peroxisome proliferator activator receptor gamma (PPAR-γ) ligand, pyrrolidine dithiocarbamate (PDTC), proteasome inhibitor and calpain I inhibitor have been shown to have direct inhibitory effects on NF-κB activation in experimental AP.

The paracaspase MALT1: biological function and potential for therapeutic inhibition

The paracaspase MALT1 has a central role in the activation of lymphocytes and other immune cells including myeloid cells, mast cells and NK cells. MALT1 activity is required not only for the immune response, but also for the development of natural Treg cells that keep the immune response in check. Exaggerated MALT1 activity has been associated with the development of lymphoid malignancies, and recently developed MALT1 inhibitors show promising anti-tumor effects in xenograft models of diffuse large B cell lymphoma. In this review, we provide an overview of the present understanding of MALT1's function, and discuss possibilities for its therapeutic targeting based on recently developed inhibitors and animal models.

Natural Agents Used in Chemoprevention of Aerodigestive and GI Cancers

Aerodigestive cancers are on an increasing level in both occurrence and mortality. A major cause in many of these cancers is disruption of the inflammatory pathway, leading to increased cell proliferation, and epigenetic silencing of normal regulatory genes. Here we review the research on several natural products: silibinin, silymarin, quercetin, neem & nimbolide, gingerol, epigallatecatechin-3- gallate, curcumin, genistein and resveratrol conducted on aerodigestive cancers. These types of cancers are primarily those from oral cavity, esophagus/windpipe, stomach, small and large intestine, colon/rectum and bile/pancreas tissues. We report on the utilization in vivo and in vitro systems to research these dose effects on the inflammatory and epigenetic pathway components within the aerodigestive cancer. To follow up on the basic research we will discuss remaining research questions and future directions involving these natural products as putative stand alone or in combination with clinical agents.

NF-κB Has a Direct Role in Inhibiting Bmp- and Wnt-Induced Matrix Protein Expression

The host response to pathogens through nuclear factor κB (NF-κB) is an essential defense mechanism for eukaryotic organisms. NF-κB-mediated host responses inhibit bone and other connective tissue synthesis and are thought to affect the transcription of matrix proteins through multiple indirect pathways. We demonstrate that inhibiting NF-κB in osteoblasts increases osteocalcin expression in vivo in mice with periodontal disease. Mutating NF-κB binding sites on osteocalcin (OC) or bone sialoprotein (Bsp) promoters rescues the negative impact of NF-κB on their transcription and that NF-κB can inhibit Wnt- and Bmp-induced OC and Bsp transcription, even when protein synthesis is inhibited, indicating a direct effect of NF-κB. This inhibition depends on p65-p50 NF-κB heterodimer formation and deacetylation by HDAC1 but is not affected by the noncanonical NF-κB pathway. Moreover, NF-κB reduces Runx2 and β-catenin binding to OC/Bsp promoters independently of their nuclear localization. Thus, inflammatory signals stimulate the direct interaction of NF-κB with response elements to inhibit binding of β-catenin and Runx2 binding to nearby consensus sites and reduce expression of matrix proteins. This direct mechanism provides a new explanation for the rapid decrease in new bone formation after inflammation-related NF-κB activation.

A multi-targeted approach to suppress tumor-promoting inflammation

Cancers harbor significant genetic heterogeneity and patterns of relapse following many therapies are due to evolved resistance to treatment. While efforts have been made to combine targeted therapies, significant levels of toxicity have stymied efforts to effectively treat cancer with multi-drug combinations using currently approved therapeutics. We discuss the relationship between tumor-promoting inflammation and cancer as part of a larger effort to develop a broad-spectrum therapeutic approach aimed at a wide range of targets to address this heterogeneity. Specifically, macrophage migration inhibitory factor, cyclooxygenase-2, transcription factor nuclear factor-κB, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase B, and CXC chemokines are reviewed as important antiinflammatory targets while curcumin, resveratrol, epigallocatechin gallate, genistein, lycopene, and anthocyanins are reviewed as low-cost, low toxicity means by which these targets might all be reached simultaneously. Future translational work will need to assess the resulting synergies of rationally designed antiinflammatory mixtures (employing low-toxicity constituents), and then combine this with similar approaches targeting the most important pathways across the range of cancer hallmark phenotypes.

TNF Induction of NF-κB RelB Enhances RANKL-Induced Osteoclastogenesis by Promoting Inflammatory Macrophage Differentiation but also Limits It through Suppression of NFATc1 Expression

TNF induces bone loss in common bone diseases by promoting osteoclast formation directly and indirectly, but it also limits osteoclast formation by inducing expression of NF-κB p100. Osteoclast precursors (OCPs) are derived from M1 (inflammatory) and M2 (resident) macrophages. However, it is not known if TNF stimulates or limits osteoclast formation through regulation of M1 or M2 differentiation or if RelB, a partner of p100, is involved. To investigate these questions, we treated bone marrow cells (BMCs) with M-CSF alone or in combination with TNF to enrich for OCPs, which we called M-OCPs and T-OCPs, respectively. We found that TNF switched CD11b⁺F4/80⁺ M-OCPs from Ly6C^-Gr1^- M2 to Ly6C⁺Gr1^-CD11c⁺ and Ly6C^-Gr1^-CD11c⁺ M1 cells. RANKL induced osteoclast formation from both Ly6C⁺Gr1^- and Ly6C^-Gr1^- T-OCPs, but only from Ly6C⁺Gr1^- M-OCPs, which formed significantly fewer osteoclasts than T-OCPs. Importantly, Ly6C⁺Gr1^- cells from both M- and T-OCPs have increased expression of the M1 marker genes, iNOS, TNF, IL-1β and TGFβ1, compared to Ly6C^-Gr1^- cells, and Ly6C^-Gr1^- cells from T-OCPs also have increased expression of iNOS and TGFβ1 compared to cells from M-OCPs. Both RANKL and TNF increased RelB mRNA expression. TNF significantly increased RelB protein levels, but RANKL did not because it also induced RelB proteasomal degradation. TNF inhibited RANKL-induced NFATc1 mRNA expression and osteoclast formation from M-OCPs, but not from T-OCPs, and it did not induce Ly6C⁺Gr1^-CD11c⁺ or Ly6C^-Gr1^-CD11c⁺ M1 macrophages from RelB-/- BMCs. Furthermore, overexpression of RelB in M-OCPs reduced RANKL-induced osteoclast formation and NFATc1 mRNA expression, but it increased TNF-induced OC formation without affecting NFATc1 levels. Thus, TNF induction of RelB directly mediates terminal osteoclast differentiation independent of NFATc1 and limits RANKL-induced osteoclastogenesis by inhibiting NFATc1 activation. However, the dominant role of TNF is to expand the OCP pool by switching the differentiation of M-CSF-induced M2 to M1 macrophages with enhanced osteoclast forming potential. Strategies to degrade RelB could prevent TNF-induced M2/M1 switching and reduce osteoclast formation.