Atypical IκB proteins in immune cell differentiation and function

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.

The anti-inflammatory effects of itaconate and its derivatives in neurological disorders

Almost 16 % of the global population is affected by neurological disorders, including neurodegenerative and cerebral neuroimmune diseases, triggered by acute or chronic inflammation. Neuroinflammation is recognized as a common pathogenic mechanism in a wide array of neurological conditions including Alzheimer's disease, Parkinson's disease, postoperative cognitive dysfunction, stroke, traumatic brain injury, and multiple sclerosis. Inflammatory process in the central nervous system (CNS) can lead to neuronal damage and neuronal apoptosis, consequently exacerbating these diseases. Itaconate, an immunomodulatory metabolite from the tricarboxylic acid cycle, suppresses neuroinflammation and modulates the CNS immune response. Emerging human studies suggest that itaconate levels in plasma and cerebrospinal fluid may serve as biomarkers associated with inflammatory responses in neurological disorders. Preclinical studies have shown that itaconate and its highly cell-permeable derivatives are promising candidates for preventing and treating neuroinflammation-related neurological disorders. The underlying mechanism may involve the regulation of immune cells in the CNS and neuroinflammation-related signaling pathways and molecules including Nrf2/KEAP1 signaling pathway, reactive oxygen species, and NLRP3 inflammasome. Here, we introduce the metabolism and function of itaconate and the synthesis and development of its derivatives. We summarize the potential impact and therapeutic potential of itaconate and its derivatives on brain immune cells and the associated signaling pathways and molecules, based on preclinical evidence via various neurological disorder models. We also discuss the challenges and potential solutions for clinical translation to promote further research on itaconate and its derivatives for neuroinflammation-related neurological disorders.

Immunostimulatory potential of extruded plant-based meat: effect of extrusion moisture level on macrophage activation

In this study, the effect of different moisture levels in extruded plant-based meat on macrophage immunostimulation, and the potential of this meat as a protein source and a solution to environmental and economic challenges associated with conventional meat was investigated. To determine the effects of the extruded plant-based meat, cell viability assay, enzyme-linked immunosorbent assay, flow cytometry, and western blotting were performed. Low-moisture (LMME) and high-moisture meat extracts (HMME) showed higher potential to activate macrophages and regulate cytokine production than raw material extract. Treatment with LMME and HMME resulted in increased expression of CD80, CD86, and MHC class I/II proteins, indicating their potential to activate macrophages. Western blotting suggested that the immune activation observed in a previous study of macrophages was because of the phosphorylation of MAPKs and NF-κB. These findings suggest that extruded plant-based meat can potentially be used as an immunostimulatory food ingredient.

Insights on the NF-κB system in polycystic ovary syndrome, attractive therapeutic targets

The nuclear factor κappa B (NF-κB) signaling plays a well-known function in inflammation and regulates a wide variety of biological processes. Low-grade chronic inflammation is gradually considered to be closely related to the pathogenesis of Polycystic ovary syndrome (PCOS). In this review, we provide an overview on the involvement of NF-κB in the progression of PCOS particularly, such as hyperandrogenemia, insulin resistance, cardiovascular diseases, and endometrial dysfunction. From a clinical perspective, progressive recognition of NF-κB pathway provides opportunities for therapeutic interventions aimed at inhibiting pathway-specific mechanisms. With the accumulation of basic experimental and clinical data, NF-κB signaling pathway was recognized as a therapeutic target. Although there have been no specific small molecule NF-κB inhibitors in PCOS, a plethora of natural and synthetic compound have emerged for the pharmacologic intervention of the pathway. The traditional herbs developed for NF-κB pathway have become increasingly popular in recent years. Abundant evidence elucidated that NF-κB inhibitors can significantly improve the symptoms of PCOS. Herein, we summarized evidence relating to how NF-κB pathway is involved in the development and progression of PCOS. Furthermore, we present an in-depth overview of NF-κB inhibitors for therapy interventions of PCOS. Taken together, the NF-κB signaling may be a futuristic treatment strategy for PCOS.

IκBζ is an essential mediator of immunity to oropharyngeal candidiasis

Fungal infections are a global threat; yet, there are no licensed vaccines to any fungal pathogens. Th17 cells mediate immunity to Candida albicans, particularly oropharyngeal candidiasis (OPC), but essential downstream mechanisms remain unclear. In the murine model of OPC, IκBζ (Nfkbiz, a non-canonical NF-κB transcription factor) was upregulated in an interleukin (IL)-17-dependent manner and was essential to prevent candidiasis. Deletion of Nfkbiz rendered mice highly susceptible to OPC. IκBζ was dispensable in hematopoietic cells and acted partially in the suprabasal oral epithelium to control OPC. One prominent IκBζ-dependent gene target was β-defensin 3 (BD3) (Defb3), an essential antimicrobial peptide. Human oral epithelial cells required IκBζ for IL-17-mediated induction of BD2 (DEFB4A, human ortholog of mouse Defb3) through binding to the DEFB4A promoter. Unexpectedly, IκBζ regulated the transcription factor Egr3, which was essential for C. albicans induction of BD2/DEFB4A. Accordingly, IκBζ and Egr3 comprise an antifungal signaling hub mediating mucosal defense against oral candidiasis.

Bcl-3 regulates T cell function through energy metabolism

BACKGROUND

Bcl-3 is a member of the IκB protein family and an essential modulator of NF-κB activity. It is well established that Bcl-3 is critical for the normal development, survival and differentiation of adaptive immune cells, especially T cells. However, the regulation of immune cell function by Bcl-3 through metabolic pathways has rarely been studied.

RESULTS

In this study, we explored the role of Bcl-3 in the metabolism and function of T cells via the mTOR pathway. We verified that the proliferation of Bcl-3-deficient Jurkat T cells was inhibited, but their activation was promoted, and Bcl-3 depletion regulated cellular energy metabolism by reducing intracellular ATP and ROS production levels and mitochondrial membrane potential. Bcl-3 also regulates cellular energy metabolism in naive CD4+ T cells. In addition, the knockout of Bcl-3 altered the expression of mTOR, Akt, and Raptor, which are metabolism-related genes, in Jurkat cells.

CONCLUSIONS

This finding indicates that Bcl-3 may mediate the energy metabolism of T cells through the mTOR pathway, thereby affecting their function. Overall, we provide novel insights into the regulatory role of Bcl-3 in T-cell energy metabolism for the prevention and treatment of immune diseases.

MAPK/MAK/MRK overlapping kinase (MOK) controls microglial inflammatory/type-I IFN responses via Brd4 and is involved in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal and incurable neurodegenerative disease affecting motor neurons and characterized by microglia-mediated neurotoxic inflammation whose underlying mechanisms remain incompletely understood. In this work, we reveal that MAPK/MAK/MRK overlapping kinase (MOK), with an unknown physiological substrate, displays an immune function by controlling inflammatory and type-I interferon (IFN) responses in microglia which are detrimental to primary motor neurons. Moreover, we uncover the epigenetic reader bromodomain-containing protein 4 (Brd4) as an effector protein regulated by MOK, by promoting Ser492-phospho-Brd4 levels. We further demonstrate that MOK regulates Brd4 functions by supporting its binding to cytokine gene promoters, therefore enabling innate immune responses. Remarkably, we show that MOK levels are increased in the ALS spinal cord, particularly in microglial cells, and that administration of a chemical MOK inhibitor to ALS model mice can modulate Ser492-phospho-Brd4 levels, suppress microglial activation, and modify the disease course, indicating a pathophysiological role of MOK kinase in ALS and neuroinflammation.

IκBNS-deficiency protects mice from fatal Listeria monocytogenes infection by blunting pro-inflammatory signature in Ly6Chigh monocytes and preventing exaggerated innate immune responses

IκB proteins regulate the inhibition and activation of NF-κB transcription factor complexes. While classical IκB proteins keep NF-κB complexes inactive in the cytoplasm, atypical IκB proteins act on activated NF-κB complexes located in the nucleus. Most of the knowledge regarding the function of IκB proteins has been collected in vitro, while far less is known regarding their impact on activation and regulation of immune responses during in vivo infections. Combining in vivo Listeria monocytogenes (Lm) infection with comparative ex vivo transcriptional profiling of the hepatic response to the pathogen we observed that in contrast to wild type mice that mounted a robust inflammatory response, IκB_NS-deficiency was generally associated with a transcriptional repression of innate immune responses. Whole tissue transcriptomics revealed a pronounced IκB_NS-dependent reduction of myeloid cell-associated transcripts in the liver together with an exceptionally high Nfkbid promoter activity uncovered in Ly6C^high inflammatory monocytes prompted us to further characterize the specific contribution of IκB_NS in the inflammatory response of monocytes to the infectious agent. Indeed, Ly6C^high monocytes primed during Lm infection in the absence of IκB_NS displayed a blunted response compared to wild type-derived Ly6C^high monocytes as evidenced by the reduced early expression of hallmark transcripts of monocyte-driven inflammation such as Il6, Nos2 and Il1β. Strikingly, altered monocyte activation in IκB_NS-deficient mice was associated with an exceptional resistance against Lm infection and protection was associated with a strong reduction in immunopathology in Lm target organs. Of note, mice lacking IκB_NS exclusively in myeloid cells failed to resist Lm infection, indicating that the observed effect was not monocyte intrinsic but monocyte extrinsic. While serum cytokine-profiling did not discover obvious differences between wild type and IκB_NS ^-/- mice for most of the analyzed mediators, IL-10 was virtually undetectable in IκB_NS-deficient mice, both in the steady state and following Lm infection. Together, we show here a crucial role for IκB_NS during Lm infection with IκB_NS-deficient mice showing an overall blunted pro-inflammatory immune response attributed to a reduced pro-inflammatory signature in Ly6C^high monocytes. Reduced immunopathology and complete protection of mice against an otherwise fatal Lm infection identified IκB_NS as molecular driver of inflammation in listeriosis.

miR-4734 conditionally suppresses ER stress-associated proinflammatory responses

Prolonged metabolic stress can lead to severe pathologies. In metabolically challenged primary fibroblasts, we assigned a novel role for the poorly characterized miR-4734 in restricting ATF4 and IRE1-mediated upregulation of a set of proinflammatory cytokines and endoplasmic reticulum stress-associated genes. Conversely, inhibition of this miRNA augmented the expression of those genes. Mechanistically, miR-4734 was found to restrict the expression of the transcriptional activator NF-kappa-B inhibitor zeta (NFKBIZ), which is required for optimal expression of the proinflammatory genes and whose mRNA is targeted directly by miR-4734. Concordantly, overexpression of NFKBIZ compromised the effects of miR-4734, underscoring the importance of this direct targeting. As the effects of miR-4734 were evident under stress but not under basal conditions, it may possess therapeutic utility towards alleviating stress-induced pathologies.

IκBNS expression in B cells is dispensable for IgG responses to T cell-dependent antigens

Mice lacking the atypical inhibitory kappa B (IκB) protein, IκBNS, a regulator of the NF-κB pathway encoded by the nfkbid gene, display impaired antibody responses to both T cell-independent (TI) and T cell-dependent (TD) antigens. To better understand the basis of these defects, we crossed mice carrying floxed nfkbid alleles with mice expressing Cre under the transcriptional control of the Cd79a gene to create mice that lacked IκBNS expression only in B cells. Analyses of these conditional knock-out mice revealed intact CD4+ and CD8+ T cell populations, including preserved frequencies of FoxP3+ regulatory T cells, which are known to be reduced in IκBNS knock-out mice. Like IκBNS knock-out mice, mice with conditional IκBNS ablation in B cells displayed defective IgM responses to TI antigens and a severe reduction in peritoneal B-1a cells. However, in contrast to mice lacking IκBNS altogether, the conditional IκBNS knock-out mice responded well to TD antigens compared to the control mice, with potent IgG responses following immunization with the viral antigen, rSFV-βGal or the widely used hapten-protein model antigen, NP-CGG. Furthermore, B cell intrinsic IκBNS expression was dispensable for germinal center (GC) formation and T follicular helper cell responses to NP-CGG immunization. The results presented here suggest that the defect in antibody responses to TD antigens observed in IκBNS knock-out mice results from a B cell extrinsic defect.

Emerging role of IκBζ in inflammation: Emphasis on psoriasis

Psoriasis is a chronic inflammatory disorder affecting skin and joints that results from immunological dysfunction such as enhanced IL-23 induced Th-17 differentiation. IkappaB-Zeta (IκBζ) is an atypical transcriptional factor of the IκB protein family since, contrary to the other family members, it positively regulates NF-κB pathway by being exclusively localized into the nucleus. IκBζ deficiency reduces visible manifestations of experimental psoriasis by diminishing expression of psoriasis-associated genes. It is thus tempting to consider IκBζ as a potential therapeutic target for psoriasis as well as for other IL23/IL17-mediated inflammatory diseases. In this review, we will discuss the regulation of expression of NFKBIZ and its protein IκBζ, its downstream targets, its involvement in pathogenesis of multiple disorders with emphasis on psoriasis and evidences supporting that inhibition of IκBζ may be a promising alternative to current therapeutic managements of psoriasis.

Nfkbid Overexpression in Nonobese Diabetic Mice Elicits Complete Type 1 Diabetes Resistance in Part Associated with Enhanced Thymic Deletion of Pathogenic CD8 T Cells and Increased Numbers and Activity of Regulatory T Cells

Type 1 diabetes (T1D) in both humans and NOD mice is caused by T cell-mediated autoimmune destruction of pancreatic β cells. Increased frequency or activity of autoreactive T cells and failures of regulatory T cells (Tregs) to control these pathogenic effectors have both been implicated in T1D etiology. Due to the expression of MHC class I molecules on β cells, CD8 T cells represent the ultimate effector population mediating T1D. Developing autoreactive CD8 T cells normally undergo extensive thymic negative selection, but this process is impaired in NOD mice and also likely T1D patients. Previous studies identified an allelic variant of Nfkbid, a NF-κB signal modulator, as a gene strongly contributing to defective thymic deletion of autoreactive CD8 T cells in NOD mice. These previous studies found ablation of Nfkbid in NOD mice using the clustered regularly interspaced short palindromic repeats system resulted in greater thymic deletion of pathogenic CD8 AI4 and NY8.3 TCR transgenic T cells but an unexpected acceleration of T1D onset. This acceleration was associated with reductions in the frequency of peripheral Tregs. In this article, we report transgenic overexpression of Nfkbid in NOD mice also paradoxically results in enhanced thymic deletion of autoreactive CD8 AI4 T cells. However, transgenic elevation of Nfkbid expression also increased the frequency and functional capacity of peripheral Tregs, in part contributing to the induction of complete T1D resistance. Thus, future identification of a pharmaceutical means to enhance Nfkbid expression might ultimately provide an effective T1D intervention approach.

IκBζ regulates the development of nonalcoholic fatty liver disease through the attenuation of hepatic steatosis in mice

IκBζ is a transcriptional regulator that augments inflammatory responses from the Toll-like receptor or interleukin signaling. These innate immune responses contribute to the progression of nonalcoholic fatty liver disease (NAFLD); however, the role of IκBζ in the pathogenesis of NAFLD remains elusive. We investigated whether IκBζ was involved in the progression of NAFLD in mice. We generated hepatocyte-specific IκBζ-deficient mice (Alb-Cre; Nfkbiz^fl/fl) by crossing Nfkbiz^fl/fl mice with Alb-Cre transgenic mice. NAFLD was induced by feeding the mice a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). CDAHFD-induced IκBζ expression in the liver was observed in Nfkbiz^fl/fl mice, but not in Alb-Cre; Nfkbiz^fl/fl mice. Contrary to our initial expectation, IκBζ deletion in hepatocytes accelerated the progression of NAFLD after CDAHFD treatment. Although the increased expression of inflammatory cytokines and apoptosis-related proteins by CDAHFD remained unchanged between Nfkbiz^fl/fl and Alb-Cre; Nfkbiz^fl/fl mice, early-stage steatosis of the liver was significantly augmented in Alb-Cre; Nfkbiz^fl/fl mice. Overexpression of IκBζ in hepatocytes via the adeno-associated virus vector attenuated liver steatosis caused by the CDAHFD in wild-type C57BL/6 mice. This preventive effect of IκBζ overexpression on steatosis was not observed without transcriptional activity. Microarray analysis revealed a correlation between IκBζ expression and the changes of factors related to triglyceride biosynthesis and lipoprotein uptake. Our data suggest that hepatic IκBζ attenuates the progression of NAFLD possibly through the regulation of the factors related to triglyceride metabolism.

Bcl-3: A Double-Edged Sword in Immune Cells and Inflammation

The NF-κB transcription factor family controls the transcription of many genes and regulates a number of pivotal biological processes. Its activity is regulated by the IκB family of proteins. Bcl-3 is an atypical member of the IκB protein family that regulates the activity of nuclear factor NF-κB. It can promote or inhibit the expression of NF-κB target genes according to the received cell type and stimulation, impacting various cell functions, such as proliferation and differentiation, induction of apoptosis and immune response. Bcl-3 is also regarded as an environment-dependent cell response regulator that has dual roles in the development of B cells and the differentiation, survival and proliferation of Th cells. Moreover, it also showed a contradictory role in inflammation. At present, in addition to the work aimed at studying the molecular mechanism of Bcl-3, an increasing number of studies have focused on the effects of Bcl-3 on inflammation, immunity and malignant tumors in vivo. In this review, we focus on the latest progress of Bcl-3 in the regulation of the NF-κB pathway and its extensive physiological role in inflammation and immune cells, which may help to provide new ideas and targets for the early diagnosis or targeted treatment of various inflammatory diseases, immunodeficiency diseases and malignant tumors.

Cytokine Networks in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic systemic inflammation causing progressive joint damage that can lead to lifelong disability. The pathogenesis of RA involves a complex network of various cytokines and cells that trigger synovial cell proliferation and cause damage to both cartilage and bone. Involvement of the cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 is central to the pathogenesis of RA, but recent research has revealed that other cytokines such as IL-7, IL-17, IL-21, IL-23, granulocyte macrophage colony-stimulating factor (GM-CSF), IL-1β, IL-18, IL-33, and IL-2 also play a role. Clarification of RA pathology has led to the development of therapeutic agents such as biological disease-modifying anti-rheumatic drugs (DMARDs) and Janus kinase (JAK) inhibitors, and further details of the immunological background to RA are emerging. This review covers existing knowledge regarding the roles of cytokines, related immune cells and the immune system in RA, manipulation of which may offer the potential for even safer and more effective treatments in the future.

RTEC-intrinsic IL-17-driven inflammatory circuit amplifies antibody-induced glomerulonephritis and is constrained by Regnase-1

Antibody-mediated glomerulonephritis (AGN) is a clinical manifestation of many autoimmune kidney diseases for which few effective treatments exist. Chronic inflammatory circuits in renal glomerular and tubular cells lead to tissue damage in AGN. These cells are targeted by the cytokine IL-17, which has recently been shown to be a central driver of the pathogenesis of AGN. However, surprisingly little is known about the regulation of pathogenic IL-17 signaling in the kidney. Here, using a well-characterized mouse model of AGN, we show that IL-17 signaling in renal tubular epithelial cells (RTECs) is necessary for AGN development. We also show that Regnase-1, an RNA binding protein with endoribonuclease activity, is a negative regulator of IL-17 signaling in RTECs. Accordingly, mice with a selective Regnase-1 deficiency in RTECs exhibited exacerbated kidney dysfunction in AGN. Mechanistically, Regnase-1 inhibits IL-17-driven expression of the transcription factor IκBξ and, consequently, its downstream gene targets, including Il6 and Lcn2. Moreover, deletion of Regnase-1 in human RTECs reduced inflammatory gene expression in a IκBξ-dependent manner. Overall, these data identify an IL-17-driven inflammatory circuit in RTECs during AGN that is constrained by Regnase-1.

Regulation of the Nfkbiz Gene and Its Protein Product IkBζ in Animal Models of Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition that arises from a poorly regulated inflammatory response to pathogenic organisms. Current treatments are limited to antibiotics, fluid resuscitation, and other supportive therapies. New targets for monitoring disease progression and therapeutic interventions are therefore critically needed. We previously reported that lipocalin-2 (Lcn2), a bacteriostatic mediator with potent proapoptotic activities, was robustly induced in sepsis. Other studies showed that Lcn2 was a predictor of mortality in septic patients. However, how Lcn2 is regulated during sepsis is poorly understood. We evaluated how IkBζ, an inducer of Lcn2, was regulated in sepsis using both the cecal ligation and puncture (CLP) and endotoxemia (lipopolysaccharide [LPS]) animal models. We show that Nfkbiz, the gene encoding IkBζ, was rapidly stimulated but, unlike Lcn2, whose expression persists during sepsis, mRNA levels of Nfkbiz decline to near basal levels several hours after its induction. In contrast, we observed that IkBζ expression remained highly elevated in septic animals following CLP but not LPS, indicating the occurrence of a CLP-specific mechanism that extends IkBζ half-life. By using an inhibitor of IkBζ, we determined that the expression of Lcn2 was largely controlled by IkBζ. Altogether, these data indicate that the high IkBζ expression in tissues likely contributes to the elevated expression of Lcn2 in sepsis. Since IkBζ is also capable of promoting or repressing other inflammatory genes, it might exert a central role in sepsis.

Arid2-IR promotes NF-κB-mediated renal inflammation by targeting NLRC5 transcription

Increasing evidence shows that long non-coding RNAs (lncRNAs) play an important role in a variety of disorders including kidney diseases. It is well recognized that inflammation is the initial step of kidney injury and is largely mediated by nuclear factor Kappa B (NF-κB) signaling. We had previously identified lncRNA-Arid2-IR is an inflammatory lncRNA associated with NF-κB-mediated renal injury. In this study, we examined the regulatory mechanism through which Arid2-IR activates NF-κB signaling. We found that Arid2-IR was differentially expressed in response to various kidney injuries and was induced by transforming growth factor beta 1(TGF-β1). Using RNA sequencing and luciferase assays, we found that Arid2-IR regulated the activity of NF-κB signal via NLRC5-dependent mechanism. Arid2-IR masked the promoter motifs of NLRC5 to inhibit its transcription. In addition, during inflammatory response, Filamin A (Flna) was increased and functioned to trap Arid2-IR in cytoplasm, thereby preventing its nuclear translocation and inhibition of NLRC5 transcription. Thus, lncRNA Arid2-IR mediates NF-κB-driven renal inflammation via a NLRC5-dependent mechanism and targeting Arid2-IR may be a novel therapeutic strategy for inflammatory diseases in general.

The CDK4/6-EZH2 pathway is a potential therapeutic target for psoriasis

Psoriasis is a frequent, inflammatory skin disease characterized by keratinocyte hyperproliferation and a disease-related infiltration of immune cells. Here, we identified a novel proinflammatory signaling pathway driven by cyclin-dependent kinase 4 (CDK4) and CDK6 and the methyltransferase EZH2 as a valid target for psoriasis therapy. Delineation of the pathway revealed that CDK4/6 phosphorylated EZH2 in keratinocytes, thereby triggering a methylation-induced activation of STAT3. Subsequently, active STAT3 resulted in the induction of IκBζ, which is a key proinflammatory transcription factor required for cytokine synthesis in psoriasis. Pharmacological or genetic inhibition of CDK4/6 or EZH2 abrogated psoriasis-related proinflammatory gene expression by suppressing IκBζ induction in keratinocytes. Importantly, topical application of CDK4/6 or EZH2 inhibitors on the skin was sufficient to fully prevent the development of psoriasis in various mouse models by suppressing STAT3-mediated IκBζ expression. Moreover, we found a hyperactivation of the CDK4/6-EZH2 pathway in human and mouse psoriatic skin lesions. Thus, this study not only identifies a novel psoriasis-relevant proinflammatory pathway, but also proposes the repurposing of CDK4/6 or EZH2 inhibitors as a new therapeutic option for patients with psoriasis.

The potential of using itaconate as treatment for inflammation-related heart diseases

Intracellular metabolites can cause critical changes in biological functions. Itaconate is perhaps the most fascinating substance in macrophages. Lipopolysaccharide can activate aconitate decarboxylase 1 and induces the generation of itaconate from the tricarboxylic acid cycle by decarboxylation of cis-aconitate. It has been reported that itaconate has beneficial effects on inflammation and oxidation. The mechanisms involved in these effects include the suppression of succinate dehydrogenase, the activation of nuclear factor E2-related factor 2 by alkylation of Kelch-like ECH-associated protein 1, suppression of aerobic glycolysis through regulation of glyceraldehyde-3-phosphate dehydrogenase and fructose-bisphosphate aldolase A, and suppression of IκBζ translation through activating transcription factor 3 activation. All of these findings elucidated the possible therapeutic implications of itaconate in inflammation-related diseases. In this review, we highlight that itaconate is a crucial molecule of the immunomodulatory response in macrophages and can regulate between immune response and cardiovascular metabolism. Furthermore, these discoveries suggest that itaconate is a very novel therapeutic molecule for the treatment of inflammation-related heart diseases.

Substrate stiffness modulates bone marrow-derived macrophage polarization through NF-κB signaling pathway

The stiffness of the extracellular matrix (ECM) plays an important role in regulating the cellular programming. However, the mechanical characteristics of ECM affecting cell differentiation are still under investigated. Herein, we aimed to study the effect of ECM substrate stiffness on macrophage polarization. We prepared polyacrylamide hydrogels with different substrate stiffness, respectively. After the hydrogels were confirmed to have a good biocompatibility, the bone marrow-derived macrophages (BMMs) from mice were incubated on the hydrogels. With simulated by the low substrate stiffness, BMMs displayed an enhanced expression of CD86 on the cell surface and production of reactive oxygen species (ROS) in cells, and secreted more IL-1β and TNF-α in the supernatant. On the contrary, stressed by the medium stiffness, BMMs expressed more CD206, produced less ROS, and secreted more IL-4 and TGF-β. In vivo study by delivered the hydrogels subcutaneously in mice, more CD68+CD86+ cells around the hydrogels with the low substrate stiffness were observed while more CD68+CD206+ cells near by the middle stiffness hydrogels. In addition, the expressions of NIK, phosphorylated p65 (pi-p65) and phosphorylated IκB (pi-IκB) were significantly increased after stimulation with low stiffness in BMMs. Taken together, these findings demonstrated that substrate stiffness could affect macrophages polarization. Low substrate stiffness promoted BMMs to shift to classically activated macrophages (M1) and the middle one to alternatively activated macrophages (M2), through modulating ROS-initiated NF-κB pathway. Therefore, we anticipated ECM-based substrate stiffness with immune modulation would be under consideration in the clinical applications if necessary.

Post-translational Modifications of IκBα: The State of the Art

The nuclear factor-kappa B (NF-κB) signaling pathway regulates a variety of biological functions in the body, and its abnormal activation contributes to the pathogenesis of many diseases, such as cardiovascular and respiratory diseases and cancers. Therefore, to ensure physiological homeostasis of body systems, this pathway is strictly regulated by IκBα transcription, IκBα synthesis, and the IκBα-dependent nuclear transport of NF-κB. Particularly, the post-translational modifications of IκBα including phosphorylation, ubiquitination, SUMOylation, glutathionylation and hydroxylation are crucial in the abovementioned regulatory process. Because of the importance of the NF-κB pathway in maintaining body homeostasis, understanding the post-translational modifications of IκBα can not only provide deeper insights into the regulation of NF-κB pathway but also contribute to the development of new drug targets and biomarkers for the diseases.

A Short Overview of Changes in Inflammatory Cytokines and Oxidative Stress in Response to Physical Activity and Antioxidant Supplementation

Excessive release of inflammatory cytokines and oxidative stress (OS) are triggering factors in the onset of chronic diseases. One of the factors that can ensure health in humans is regular physical activity. This type of activity can enhance immune function and dramatically prevent the spread of the cytokine response and OS. However, if physical activity is done intensely at irregular intervals, it is not only unhealthy but can also lead to muscle damage, OS, and inflammation. In this review, the response of cytokines and OS to exercise is described. In addition, it is focused predominantly on the role of reactive oxygen and nitrogen species (RONS) generated from muscle metabolism and damage during exercise and on the modulatory effects of antioxidant supplements. Furthermore, the influence of factors such as age, sex, and type of exercise protocol (volume, duration, and intensity of training) is analyzed. The effect of antioxidant supplements on improving OS and inflammatory cytokines is somewhat ambiguous. More research is needed to understand this issue, considering in greater detail factors such as level of training, health status, age, sex, disease, and type of exercise protocol.

Itaconate: A Metabolite Regulates Inflammation Response and Oxidative Stress

Metabolic products can lead to crucial biological function alterations. Itaconate is probably the best example of how a metabolic process can be diverted to generate an immunomodulator effect in macrophages. Through inflammatory stimuli, such as lipopolysaccharide, the immune response gene 1 is activated and promotes the production of itaconate from the tricarboxylic acid cycle by decarboxylating cis-aconitate. Itaconate has been reported to have multiple immunoregulatory and antioxidative effects. In addition, reports have described its antibacterial and protumor effects. The involved mechanism in these effects includes the activation of nuclear factor E2-related factor 2 by alkylation of Kelch-like ECH-associated protein 1, inhibition of aerobic glycolysis by targeting glyceraldehyde-3-phosphate dehydrogenase and fructose-bisphosphate aldolase A, inhibition of succinate dehydrogenase, and blockade of IκBζ translation. All of these discoveries elucidated the transformation of the pro- into anti-inflammatory status in macrophages, which is crucial in innate immunity and set the ground for the emerging therapeutic implications of itaconate. In this review, we point out that itaconate is a novel and pivotal metabolic determinant of the immunoregulatory response in macrophages and highlight studies that have improved our understanding of the connection between the immune response and metabolism. In addition, we shed light on the therapeutic potential of itaconate and its derivatives to treat inflammatory diseases.

Induction of IκBζ Augments Cytokine and Chemokine Production by IL-33 in Mast Cells

IκBζ (encoded by the Nfkbiz) is a member of the nuclear IκB family, which is involved in the expression of secondary response genes based on signals from TLR or IL-1R. ST2L, an IL-33R, is a member of the IL-1R family and abundantly expressed in tissue-resident immune cells, such as mast cells and innate lymphoid cells; however, its downstream signaling pathway remains unelucidated. In this study, we examined the role of IκBζ in ST2L-mediated cytokine and chemokine production in mast cells. Murine bone marrow cells were differentiated ex vivo into bone marrow-derived mast cells (BMMCs). The treatment of BMMCs with IL-33 transiently induced robust IκBζ expression. Of the 40 cytokines and chemokines examined using a cytokine and chemokine array, the concentrations of IL-6, IL-13, CCL2, CCL3, and TNF-α in the supernatant were augmented by IL-33. The deletion of IκBζ in BMMCs resulted in a significant reduction of the production of these mediators and the expression of their mRNA. NF-κB p50 but not p65 translocated to the nucleus by IL-33 and was not affected by the deletion of IκBζ. However, induction of IκBζ and the resultant cytokine and chemokine productions were significantly inhibited by pretreatment with an NF-κB inhibitor. The deletion of IκBζ did not affect the phosphorylation of ERK, p38 MAPK, or JNK by IL-33, and the treatment with inhibitors of these mitogen-activated kinases failed to abolish the expression of Nfkbiz Our findings suggest that IκBζ augments IL-33-dependent cytokine and chemokine production in BMMCs through the action of NF-κB.

Threonine Phosphorylation of IκBζ Mediates Inhibition of Selective Proinflammatory Target Genes

Transcription factors of the NF-κB family play a crucial role for immune responses by activating the expression of chemokines, cytokines, and antimicrobial peptides involved in pathogen clearance. IκBζ, an atypical nuclear IκB protein and selective coactivator of particular NF-κB target genes, has recently been identified as an essential regulator for skin immunity. This study discovered that IκBζ is strongly induced in keratinocytes that sense the fungal glucan zymosan A. Additionally, IκBζ is essential for the optimal expression of proinflammatory genes, such as IL6, CXCL5, IL1B, or S100A9. Moreover, this study found that IκBζ was not solely regulated on the transcriptional level but also by phosphorylation events. This study identified several IκBζ phosphorylation sites, including a conserved cluster of threonine residues located in the N-terminus of the protein, which can be phosphorylated by MAPKs. Surprisingly, IκBζ phosphorylation at this threonine cluster promoted the recruitment of histone deacetylase 1 to specific target gene promoters and, thus, negatively controlled transcription. Taken together, this study proposes a model of how an antifungal response translates to the expression of proinflammatory cytokines and highlights an additional layer of complexity in the regulation of the NF-κB responses in keratinocytes.

Keratinocyte-derived IκBζ drives psoriasis and associated systemic inflammation

The transcriptional activator IκBζ is a key regulator of psoriasis, but which cells mediate its pathogenic effect remains unknown. Here we found that IκBζ expression in keratinocytes triggers not only skin lesions but also systemic inflammation in mouse psoriasis models. Specific depletion of IκBζ in keratinocytes was sufficient to suppress the induction of imiquimod- or IL-36–mediated psoriasis. Moreover, IκBζ ablation in keratinocytes prevented the onset of psoriatic lesions and systemic inflammation in keratinocyte-specific IL-17A–transgenic mice. Mechanistically, this psoriasis protection was mediated by IκBζ deficiency in keratinocytes abrogating the induction of specific proinflammatory target genes, including Cxcl5, Cxcl2, Csf2, and Csf3, in response to IL-17A or IL-36. These IκBζ-dependent genes trigger the generation and recruitment of neutrophils and monocytes that are needed for skin inflammation. Consequently, our data uncover a surprisingly pivotal role of keratinocytes and keratinocyte-derived IκBζ as key mediators of psoriasis and psoriasis-related systemic inflammation.

Deletion of IκBζ in keratinocytes is sufficient to abrogate psoriasis induction in mouse models due to changes in transcription of keratinocyte-derived chemo- and cytokines.

A translational silencing function of MCPIP1/Regnase-1 specified by the target site context

The expression of proteins during inflammatory and immune reactions is coordinated by post-transcriptional mechanisms. A particularly strong suppression of protein expression is exerted by a conserved translational silencing element (TSE) identified in the 3′ UTR of NFKBIZ mRNA, which is among the targets of the RNA-binding proteins Roquin-1/2 and MCPIP1/Regnase-1. We present evidence that in the context of the TSE MCPIP1, so far known for its endonuclease activity toward mRNAs specified by distinct stem–loop (SL) structures, also suppresses translation. Overexpression of MCPIP1 silenced translation in a TSE-dependent manner and reduced ribosome occupancy of the mRNA. Correspondingly, MCPIP1 depletion alleviated silencing and increased polysomal association of the mRNA. Translationally silenced NFKBIZ or reporter mRNAs were mostly capped, polyadenylated and ribosome associated. Furthermore, MCPIP1 silenced also cap-independent, CrPV-IRES-dependent translation. This suggests that MCPIP1 suppresses a post-initiation step. The TSE is predicted to form five SL structures. SL4 and 5 resemble target structures reported for MCPIP1 and together were sufficient for MCPIP1 binding and mRNA destabilization. Translational silencing, however, required SL1–3 in addition. Thus the NFKBIZ TSE functions as an RNA element in which sequences adjacent to the site of interaction with MCPIP1 and dispensable for accelerated mRNA degradation extend the functional repertoire of MCPIP1 to translational silencing.

TACI expression and plasma cell differentiation are impaired in the absence of functional IκBNS

Impaired classical NF‐κB pathway signaling causes reduced antibody responses to T‐independent (TI) antigens. We investigated the potential reasons for defective TI responses in mice lacking the atypical inhibitory kappa B (IκB) protein of the NF‐κB pathway, IκBNS. Analyses of the plasma cell compartment in vitro and in vivo after challenge with lipopolysaccharide (LPS) showed significant decreases in the frequencies of plasma cells in the absence of IκBNS. In vitro activation of B cells via the B cell receptor or via Toll‐like receptor 4 revealed that early activation events were unaffected in IκBNS‐deficient B cells, while proliferation was reduced compared to in similarly stimulated wildtype (wt) B cells. IκBNS‐deficient B cells also displayed impaired upregulation of the transmembrane activator and calcium modulator cyclophilin ligand interactor (TACI), which is essential for TI responses, and decreased sensitivity to TACI ligands upon stimulation. Furthermore, IκBNS‐deficient B cells, in contrast to wt B cells, displayed altered expression of IRF4, Blimp‐1 and Pax5 upon LPS‐induced differentiation, indicating impaired transcriptional regulation of plasma cell generation.

Roquin targets mRNAs in a 3'-UTR-specific manner by different modes of regulation

The RNA-binding proteins Roquin-1 and Roquin-2 redundantly control gene expression and cell-fate decisions. Here, we show that Roquin not only interacts with stem–loop structures, but also with a linear sequence element present in about half of its targets. Comprehensive analysis of a minimal response element of the Nfkbid 3′-UTR shows that six stem–loop structures cooperate to exert robust and profound post-transcriptional regulation. Only binding of multiple Roquin proteins to several stem–loops exerts full repression, which redundantly involved deadenylation and decapping, but also translational inhibition. Globally, most Roquin targets are regulated by mRNA decay, whereas a small subset, including the Nfat5 mRNA, with more binding sites in their 3′-UTRs, are also subject to translational inhibition. These findings provide insights into how the robustness and magnitude of Roquin-mediated regulation is encoded in complex cis-elements.

Roquin targets are known to contain two types of sequence-structure motifs, the constitutive and the alternative decay elements (CDE and ADE). Here, the authors describe a linear Roquin binding element (LBE) also involved in target recognition, and show that Roquin binding affects the translation of a subset of targeted mRNAs.

IκBζ is a key transcriptional regulator of IL-36-driven psoriasis-related gene expression in keratinocytes

Psoriasis is an autoinflammatory disease characterized by cytokine-driven keratinocyte proliferation and infiltration of immune cells. While IL-17A and TNFα are established targets in psoriasis therapy, IL-36 is emerging as an important cytokine in this disease. The mechanisms of IL-36–driven proinflammatory responses are largely unknown. Here we identified IκBζ, a transcriptional regulator of selective NF-κB target genes, as a crucial mediator of IL-36 action. In keratinocytes, IκBζ was required for the expression of several psoriasis-related cytokines and chemokines. Moreover, genetic deletion of IκBζ prevented IL-36–mediated dermatitis induction in mice. Since IκBζ is essential not only for IL-36 but also for IL-17 signaling, our results suggest that inhibition of IκBζ function could be a future strategy in psoriasis therapy.

Proinflammatory cytokine signaling in keratinocytes plays a crucial role in the pathogenesis of psoriasis, a skin disease characterized by hyperproliferation and abnormal differentiation of keratinocytes and infiltration of inflammatory cells. Although IL-17A and TNFα are effective therapeutic targets in psoriasis, IL-36 has recently emerged as a proinflammatory cytokine. However, little is known about IL-36 signaling and its downstream transcriptional responses. Here, we found that exposure of keratinocytes to IL-36 induced the expression of IκBζ, an atypical IκB member and a specific transcriptional regulator of selective NF-κB target genes. Induction of IκBζ by IL-36 was mediated by NF-κB and STAT3. In agreement, IL-36–mediated induction of IκBζ was found to be required for the expression of various psoriasis-related genes involved in inflammatory signaling, neutrophil chemotaxis, and leukocyte activation. Importantly, IκBζ-knockout mice were protected against IL-36–mediated dermatitis, accompanied by reduced proinflammatory gene expression, decreased immune cell infiltration, and a lack of keratinocyte hyperproliferation. Moreover, expression of IκBζ mRNA was highly up-regulated in biopsies of psoriasis patients where it coincided with IL36G levels. Thus our results uncover an important role for IκBζ in IL-36 signaling and validate IκBζ as an attractive target for psoriasis therapy.

Role of the NFκB-signaling pathway in cancer

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

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.

NF-κB and the Transcriptional Control of Inflammation

The NF-κB transcription factor was discovered 30 years ago and has since emerged as the master regulator of inflammation and immune homeostasis. It achieves this status by means of the large number of important pro- and antiinflammatory factors under its transcriptional control. NF-κB has a central role in inflammatory diseases such as rheumatoid arthritis, inflammatory bowel disease, and autoimmunity, as well as diseases comprising a significant inflammatory component such as cancer and atherosclerosis. Here, we provide an overview of the studies that form the basis of our understanding of the role of NF-κB subunits and their regulators in controlling inflammation. We also describe the emerging importance of posttranslational modifications of NF-κB in the regulation of inflammation, and highlight the future challenges faced by researchers who aim to target NF-κB transcriptional activity for therapeutic benefit in treating chronic inflammatory diseases.

Toll-like receptor 9 stimulation can induce IκBζ expression and IgM secretion in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia cells strongly depend on external stimuli for their survival. Both antigen receptor and co-stimulatory receptors, including Toll-like receptors, can modulate viability and proliferation of leukemic cells. Toll-like receptor ligands, and particularly the TLR9 ligand CpG, mediate heterogeneous responses in patients' samples reflecting the clinical course of the subjects. However, the molecular framework of the key signaling events underlying such heterogeneity is undefined. We focused our studies on a subset of chronic lymphocytic leukemia cases characterized by expression of CD38 and unmutated immunoglobulin genes, who respond to CpG with enhanced metabolic cell activity. We report that, while CpG induces NFKBIZ mRNA in all the samples analyzed, it induces the IκBζ protein in a selected group of cases, through an unanticipated post-transcriptional mechanism. Interestingly, IκBζ plays a causal role in sustaining CpG-induced cell viability and chemoresistance, and CpG stimulation can unleash immunoglobulin secretion by IκBζ-positive malignant cells. These results identify and characterize IκBζ as a marker and effector molecule of distinct key pathways in chronic lymphocytic leukemia.

Transcription Factors in the Cellular Response to Charged Particle Exposure

Charged particles, such as carbon ions, bear the promise of a more effective cancer therapy. In human spaceflight, exposure to charged particles represents an important risk factor for chronic and late effects such as cancer. Biological effects elicited by charged particle exposure depend on their characteristics, e.g., on linear energy transfer (LET). For diverse outcomes (cell death, mutation, transformation, and cell-cycle arrest), an LET dependency of the effect size was observed. These outcomes result from activation of a complex network of signaling pathways in the DNA damage response, which result in cell-protective (DNA repair and cell-cycle arrest) or cell-destructive (cell death) reactions. Triggering of these pathways converges among others in the activation of transcription factors, such as p53, nuclear factor κB (NF-κB), activated protein 1 (AP-1), nuclear erythroid-derived 2-related factor 2 (Nrf2), and cAMP responsive element binding protein (CREB). Depending on dose, radiation quality, and tissue, p53 induces apoptosis or cell-cycle arrest. In low LET radiation therapy, p53 mutations are often associated with therapy resistance, while the outcome of carbon ion therapy seems to be independent of the tumor's p53 status. NF-κB is a central transcription factor in the immune system and exhibits pro-survival effects. Both p53 and NF-κB are activated after ionizing radiation exposure in an ataxia telangiectasia mutated (ATM)-dependent manner. The NF-κB activation was shown to strongly depend on charged particles' LET, with a maximal activation in the LET range of 90-300 keV/μm. AP-1 controls proliferation, senescence, differentiation, and apoptosis. Nrf2 can induce cellular antioxidant defense systems, CREB might also be involved in survival responses. The extent of activation of these transcription factors by charged particles and their interaction in the cellular radiation response greatly influences the destiny of the irradiated and also neighboring cells in the bystander effect.