Elevated levels of Bcl-3 inhibits Treg development and function resulting in spontaneous colitis

Regulation and Function of the Atypical IκBs-Bcl-3, IκBNS, and IκBζ-in Lymphocytes and Autoimmunity

Signaling pathways involving NF-κB transcription factors have essential roles in inflammation, immunity, cell proliferation, differentiation, and survival. Classical IκB proteins, such as IκBα and IκBβ, bind to NF-κB via ankyrin repeats to sequester NF-κB in the cytoplasm and thus suppress NF-κB activity. Unlike these constitutively expressed classical IκBs, the expression of the atypical IκBs Bcl-3, IκBNS, and IκBζ is induced in immune cells after recognition of antigens, pathogen-associated molecular patterns (PAMPs) or cytokines, upon which they localize to the nucleus and form complexes with transcription factors and regulators on the DNA. Atypical, nuclear IκBs have been proposed to modulate NF-κB activity in a context-dependent manner as they can either inhibit or increase gene expression of a subset of NF-κB target genes. This complexity may be related to the molecular function of atypical IκBs, which bind to different transcription factor complexes and form a bridge to different cofactors or epigenetic modifiers. Recent research has identified novel target genes of atypical IκBs that include chemokines, cytokines, and master regulators of lymphocyte differentiation, underscoring prominent roles in adaptive immune and autoimmune responses. Here, we summarize our current understanding of atypical IκBs in lymphocytes with a focus on their emerging role in autoimmunity.

The NF-κB signaling network in the life of T cells

NF-κB is a crucial transcription factor in lymphocyte signaling. It is activated by environmental cues that drive lymphocyte differentiation to combat infections and cancer. As a key player in inflammation, NF-κB also significantly impacts autoimmunity and transplant rejection, making it an important therapeutic target. While the signaling molecules regulating this pathway are well-studied, the effect of changes in NF-κB signaling levels on T lymphocyte differentiation, fate, and function is not fully understood. Advances in computational biology and new NF-κB-inducible animal models are beginning to clarify these questions. In this review, we highlight recent findings related to T cells, focusing on how environmental cues affecting NF-κB signaling levels determine T cell fate and function.

Lag3 and PD-1 pathways preferentially regulate NFAT-dependent TCR signalling programmes during early CD4+ T cell activation

Introduction

Lag3 and PD-1 are immune checkpoints that regulate T cell responses and are current immunotherapy targets. Yet how they function to control early stages of CD4+ T cell activation remains unclear.

Methods

Here, we show that the PD-1 and Lag3 pathways exhibit layered control of the early CD4+ T cell activation process, with the effects of Lag3 more pronounced in the presence of PD-1 pathway co-blockade (CB). RNA sequencing revealed that CB drove an early NFAT-dependent transcriptional profile, including promotion of ICOShi T follicular helper cell differentiation.

Results

NFAT pathway inhibition abolished CB-induced upregulation of NFAT-dependent co-receptors ICOS and OX40, whilst unaffecting the NFAT-independent gene Nr4a1. Mechanistically, Lag3 and PD-1 pathways functioned additively to regulate the duration of T cell receptor signals during CD4+ T cell re-activation. Phenotypic changes in peripheral blood CD4+ T cells in humans on anti-Lag3 and anti-PD-1 combination therapy revealed upregulation of genes encoding ICOS and OX40 on distinct CD4+ T cell subsets, highlighting the potential translational relevance of our findings.

Conclusion

Our data therefore reveal that PD-1 and Lag3 pathways converge to additively regulate TCR signal duration and may preferentially control NFAT-dependent transcriptional activity during early CD4+ T cell re-activation.

Diversity and function of regulatory T cells in health and autoimmune diseases

Regulatory T cell (Treg) play a pivotal role in immune regulation and maintaining host immune homeostasis. Treg heterogeneity, characterized by diverse gene expression profiles and functional states, is complex in both health and disease. Research reveals that Tregs are not a uniform population but exhibit diversity based on their origin, location, and functional status. This heterogeneity is crucial for understanding Treg roles in various pathological conditions. Dysfunctional Tregs are closely linked to the pathogenesis of autoimmune diseases, although the precise mechanisms remain unclear. The phenotypic and functional heterogeneity of Tregs is particularly significant in diseases such as systemic lupus erythematosus, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, type 1 diabetes, psoriasis and autoimmune liver diseases. This review explores Treg origins, classifications, and heterogeneity in these conditions, aiming to provide new perspectives and strategies for diagnosis and treatment. Understanding Treg heterogeneity and plasticity promises to reveal novel therapeutic targets and advance precision immunotherapy development.

The atypical IκB family member Bcl3 determines differentiation and fate of intestinal RORγt+ regulatory T-cell subsets

Peripherally-induced regulatory T cells (pTregs) expressing the retinoic acid receptor-related orphan-receptor gamma t (RORγt) are indispensable for intestinal immune homeostasis. Nuclear factor kappa family members regulate the differentiation of thymic Tregs and promote their survival in the periphery. However, the Treg intrinsic molecular mechanisms controlling the size of the pTregs in the intestine and associated lymphoid organs remain unclear. Here, we provide direct evidence that B-cell lymphoma 3 (Bcl3) limits the development of pTregs in a T cell-intrinsic manner. Moreover, the absence of Bcl3 allowed for the formation of an unusual intestinal Treg population co-expressing the transcription factors Helios and RORγt. The expanded RORγt+ Treg populations in the absence of Bcl3 displayed an activated phenotype and secreted high levels of the anti-inflammatory cytokines interleukin (IL)-10 and transforming growth factor beta. They were fully capable of suppressing effector T cells in a transfer colitis model despite an intrinsic bias to trans-differentiate toward T helper 17-like cells. Finally, we provide a Bcl3-dependent gene signature in pTregs including altered responsiveness to the cytokines IL-2, IL-6, and tumor necrosis factor alpha. Our results demonstrate that Bcl3 acts as a molecular switch to limit the expansion of different intestinal Treg subsets and may thus serve as a novel therapeutic target for inflammatory bowel disease by restoring intestinal immune tolerance.

Molecular characterization of m6A RNA methylation regulators with features of immune dysregulation in IgA nephropathy

The role of RNA N6-methyladenosine (m6A) modification in immunity is being elucidated. This study aimed to explore the potential association between m6A regulators and the immune microenvironment in IgA nephropathy (IgAN). The expression profiles of 24 m6A regulators in 107 IgAN patients were obtained from the Gene Expression Omnibus (GEO) database. The least absolute shrinkage and selection operator (LASSO) regression and logistic regression analysis were utilized to construct a model for distinguishing IgAN from control samples. Based on the expression levels of m6A regulators, unsupervised clustering was used to identify m6A-induced molecular clusters in IgAN. Gene set enrichment analysis (GSEA) and immunocyte infiltration among different clusters were examined. The gene modules with the highest correlation for each of the three clusters were identified by weighted gene co-expression network analysis (WGCNA). A model containing 10 m6A regulators was developed using LASSO and logistic regression analyses. Three molecular clusters were determined using consensus clustering of 24 m6A regulators. A decrease in the expression level of YTHDF2 in IgAN samples was significantly negatively correlated with an increase in resting natural killer (NK) cell infiltration and was positively correlated with the abundance of M2 macrophage infiltration. The risk scores calculated by the nomogram were significantly higher for cluster-3, and the expression levels of m6A regulators in this cluster were generally low. Immunocyte infiltration and pathway enrichment results for cluster-3 differed significantly from those for the other two clusters. Finally, the expression of YTHDF2 was significantly decreased in IgAN based on immunohistochemical staining. This study demonstrated that m6A methylation regulators play a significant role in the regulation of the immune microenvironment in IgAN. Based on m6A regulator expression patterns, IgAN can be classified into multiple subtypes, which might provide additional insights into novel therapeutic methods for IgAN.

Lupus susceptibility gene Pbx1 controls the development, stability, and function of regulatory T cells via Rtkn2 expression

The maintenance of regulatory T (Treg) cells critically prevents autoimmunity. Pre-B cell leukemia transcription factor 1 (Pbx1) variants are associated with lupus susceptibility, particularly through the expression of a dominant negative isoform Pbx1-d in CD4+ T cells. Pbx1-d overexpression impaired Treg cell homeostasis and promoted inflammatory CD4+ T cells. Here, we showed a high expression of Pbx1 in human and murine Treg cells, which is decreased in lupus patients and mice. Pbx1 deficiency or Pbx1-d overexpression reduced the number, stability, and suppressive activity of Treg cells, which increased murine responses to immunization and autoimmune induction. Mechanistically, Pbx1 deficiency altered the expression of genes implicated in cell cycle and apoptosis in Treg cells. Intriguingly, Rtkn2, a Rho-GTPase previously associated with Treg homeostasis, was directly transactivated by Pbx1. Our results suggest that the maintenance of Treg cell homeostasis and stability by Pbx1 through cell cycle progression prevent the expansion of inflammatory T cells that otherwise exacerbates lupus progression in the hosts.

The role of regulatory B cells in immune regulation and childhood allergic asthma

BACKGROUND

As the most common chronic disease in childhood, asthma displays a major public health problem worldwide with the incidence of those affected rising. As there is currently no cure for allergic asthma, it is mandatory to get a better understanding of the underlying molecular mechanism.

MAIN BODY

By producing IgE antibodies upon allergen contact, B cells play a pivotal role in allergic asthma. Besides that, IL-10-secreting B cell subsets, namely regulatory B cells (Bregs), are reported in mice and humans to play a role in allergic asthma. In humans, several Breg subsets with distinct phenotypic and functional properties are identified among B cells at different maturational and differentiation stages that exert anti-inflammatory functions by expressing several suppressor molecules. Emerging research has focused on the role of Bregs in allergic asthma as well as their role for future diagnostic and preventive strategies.

CONCLUSION

Knowledge about the exact function of human Bregs in allergic asthma is still very limited. This review aims to summarize the current knowledge on Bregs. We discuss different human Breg subsets, several ways of Breg induction as well as the mechanisms through which they exert immunoregulatory functions, and their role in (childhood) allergic asthma.

Dietary wheat amylase trypsin inhibitors exacerbate CNS inflammation in experimental multiple sclerosis

OBJECTIVE

Wheat has become a main staple globally. We studied the effect of defined pro-inflammatory dietary proteins, wheat amylase trypsin inhibitors (ATI), activating intestinal myeloid cells via toll-like receptor 4, in experimental autoimmune encephalitis (EAE), a model of multiple sclerosis (MS).

DESIGN

EAE was induced in C57BL/6J mice on standardised dietary regimes with defined content of gluten/ATI. Mice received a gluten and ATI-free diet with defined carbohydrate and protein (casein/zein) content, supplemented with: (a) 25% of gluten and 0.75% ATI; (b) 25% gluten and 0.19% ATI or (c) 1.5% purified ATI. The effect of dietary ATI on clinical EAE severity, on intestinal, mesenteric lymph node, splenic and central nervous system (CNS) subsets of myeloid cells and lymphocytes was analysed. Activation of peripheral blood mononuclear cells from patients with MS and healthy controls was compared.

RESULTS

Dietary ATI dose-dependently caused significantly higher EAE clinical scores compared with mice on other dietary regimes, including on gluten alone. This was mediated by increased numbers and activation of pro-inflammatory intestinal, lymph node, splenic and CNS myeloid cells and of CNS-infiltrating encephalitogenic T-lymphocytes. Expectedly, ATI activated peripheral blood monocytes from both patients with MS and healthy controls.

CONCLUSIONS

Dietary wheat ATI activate murine and human myeloid cells. The amount of ATI present in an average human wheat-based diet caused mild intestinal inflammation, which was propagated to extraintestinal sites, leading to exacerbation of CNS inflammation and worsening of clinical symptoms in EAE. These results support the importance of the gut-brain axis in inflammatory CNS disease.

B-cell-derived IL-10 promotes allergic sensitization in asthma regulated by Bcl-3

Aeroallergen sensitization, mainly mediated by lung epithelium and dendritic cells (DCs), is integral to allergic asthma pathogenesis and progression. IL-10 has a dual role in immune responses, as it inhibits myeloid cell activation but promotes B-cell responses and epithelial cell proliferation. Here, we report a proinflammatory function of B-cell-derived IL-10 modulated by Bcl-3 in allergic asthma. Specifically, Bcl-3-/- mice showed elevated IL-10 levels and were found to be highly vulnerable to allergic asthma induced by house dust mites (HDMs). IL-10 had a positive correlation with the levels of the DC chemoattractant CCL-20 in HDM-sensitized mice and in patients with asthma and induced a selective increase in CCL-20 production by mouse lung epithelial cells. Blockade of IL-10 or IL-10 receptors during sensitization dampened both HDM-induced sensitization and asthma development. IL-10 levels peaked 4 h post sensitization with HDM and IL-10 was primarily produced by B cells under Bcl-3-Blimp-1-Bcl-6 regulation. Mice lacking B-cell-derived IL-10 displayed decreased lung epithelial CCL-20 production and diminished DC recruitment to the lungs upon HDM sensitization, thereby demonstrating resistance to HDM-induced asthma. Moreover, responses to HDM stimulation in Bcl-3-/- mice lacking B-cell-derived IL-10 were comparable to those in Bcl-3+/+ mice. The results revealed an unexpected role of B-cell-derived IL-10 in promoting allergic sensitization and demonstrated that Bcl-3 prevents HDM-induced asthma by inhibiting B-cell-derived IL-10 production. Thus, targeting the Bcl-3/IL-10 axis to inhibit allergic sensitization is a promising approach for treating allergic asthma. IL-10 is released rapidly from lung plasma cells under Bcl-3-Blimp-1-Bcl-6 regulation upon house dust mite exposure and amplifies lung epithelial cell (EC)-derived CCL-20 production and subsequent dendritic cell (DC) recruitment to promote allergic sensitization in asthma.

Bcl-3 regulates the function of Th17 cells through raptor mediated glycolysis metabolism

Bcl-3 is an atypical IκB family member that regulates transcription in the nucleus by binding to the p50/p52 homologous dimer subunit. Although various studies illustrate the important role of Bcl-3 in physiological function, its role in metabolism is still unclear. We found that Bcl-3 has a metabolic regulatory effect on autoimmunity. Bcl-3-depleted mice are unable to develop experimental autoimmune encephalomyelitis. The disease resistance was linked to an increase in lactate levels in Th17 cells, and lactate could alleviate EAE development in WT mice. Bcl-3 deficient mice had more differentiated Th17 cells and an increased extracellular acidification rate in these cells. Concurrently, their ultimate respiration rate and respiratory reserve capacity were significantly lower than wild-type mice. However, adding GNE-140 (LADH inhibitor) to Bcl-3-deficient Th17 cells could reverse the phenomenon, and lactate supplementation could increase the glycolysis metabolism of Th17 cells in WT mice. Mechanically, Bcl-3 could interact with Raptor through ANK and RNC domains. Therefore, Bcl-3 regulates Th17 pathogenicity by promoting Raptor mediated energy metabolism, revealing a novel regulation of adaptive immunity.

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.

NF-κB in control of regulatory T cell development, identity, and function

Regulatory T cells (Treg cells) act as a major rheostat regulating the strength of immune responses, enabling tolerance of harmless foreign antigens, and preventing the development of pathogenic immune responses in various disease settings such as cancer and autoimmunity. Treg cells are present in all lymphoid and non-lymphoid tissues, and the latter often fulfill important tasks required for the physiology of their host organ. The activation of NF-κB transcription factors is a central pathway for the reprogramming of gene expression in response to inflammatory but also homeostatic cues. Genetic mouse models have revealed essential functions for NF-κB transcription factors in modulating Treg development and function, with some of these mechanistic insights confirmed by recent studies analyzing Treg cells from patients harboring point mutations in the genes encoding NF-κB proteins. Molecular insights into the NF-κB pathway in Treg cells hold substantial promise for novel therapeutic strategies to manipulate dysfunctional or inadequate cell numbers of immunosuppressive Treg cells in autoimmunity or cancer. Here, we provide an overview of the manifold roles that NF-κB factors exert in Treg cells.

High-Dimensional DNA Methylation Mediates the Effect of Smoking on Crohn's Disease

Epigenome-wide mediation analysis aims to identify high-dimensional DNA methylation at cytosine-phosphate-guanine (CpG) sites that mediate the causal effect of linking smoking with Crohn's disease (CD) outcome. Studies have shown that smoking has significant detrimental effects on the course of CD. So we assessed whether DNA methylation mediates the association between smoking and CD. Among 103 CD cases and 174 controls, we estimated whether the effects of smoking on CD are mediated through DNA methylation CpG sites, which we referred to as causal mediation effect. Based on the causal diagram, we first implemented sure independence screening (SIS) to reduce the pool of potential mediator CpGs from a very large to a moderate number; then, we implemented variable selection with de-sparsifying the LASSO regression. Finally, we carried out a comprehensive mediation analysis and conducted sensitivity analysis, which was adjusted for potential confounders of age, sex, and blood cell type proportions to estimate the mediation effects. Smoking was significantly associated with CD under odds ratio (OR) of 2.319 (95% CI: 1.603, 3.485, p < 0.001) after adjustment for confounders. Ninety-nine mediator CpGs were selected from SIS, and then, seven candidate CpGs were obtained by de-sparsifying the LASSO regression. Four of these CpGs showed statistical significance, and the average causal mediation effects (ACME) were attenuated from 0.066 to 0.126. Notably, three significant mediator CpGs had absolute sensitivity parameters of 0.40, indicating that these mediation effects were robust even when the assumptions were slightly violated. Genes (BCL3 and FKBP5) harboring these four CpGs were related to CD. These findings suggest that changes in methylation are involved in the mechanism by which smoking increases risk of CD.

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.

Foxo3a tempers excessive glutaminolysis in activated T cells to prevent fatal gut inflammation in the murine IL-10-/- model of colitis

Mutations in susceptibility alleles correlate with gut-inflammatory diseases, such as Crohn's disease; however, this does not often impact the disease progression indicating the existence of compensatory genes. We show that a reduction in Foxo3a expression in IL-10-deficient mice results in a spontaneous and aggressive Crohn's- like disease with 100% penetrance, which is rescued by deletion of myeloid cells, T cells and inhibition of mTORC1. In Foxo3a^-/- IL-10^-/- mice, there is poor cell death of myeloid cells in the gut, leading to increased accumulation of myeloid and T cells in the gut. Myeloid cells express high levels of inflammatory cytokines, and regulatory T cells are dysfunctional despite increased abundance. Foxo3a signaling represses the transcription of glutaminase (GLS/GLS2) to prevent over-consumption of glutamine by activated T cells and its conversion to glutamate that contributes to the TCA cycle and mTORC1 activation. Finally, we show that Foxo3a restricts the abundance of colitogenic microbiota in IL-10-deficient mice. Thus, by suppressing glutaminolysis in activated T cells Foxo3a mediates a critical checkpoint that prevents the development of fulminant gut inflammatory disease.

Mesenchymal stem cells enhance Treg immunosuppressive function at the fetal-maternal interface

Well-regulated maternal-fetal immune tolerance is a prerequisite for normal pregnancy. Hyperactivated immune cells and overwhelming inflammatory responses trigger adverse gestation outcome, such as recurrent spontaneous abortion (RSA). Local exacerbation of immunomodulatory cells in maternal decidua is a critical event, tightly linked with fetus acceptance. Owning to the notable immunoregulatory potentials, mesenchymal stromal cells (MSCs) and regulatory T cells (Tregs) have been separately reported as promising therapeutic approaches for refractory RSA attributable to certain immune disorders. However, the cross-talk between MSCs and Tregs at the fetal-maternal interface remains poorly understood. Here we revealed, for the first time, that umbilical MSCs could induce expansion of decidual Foxp3⁺CD4⁺ T cells with upregulated production of IL-10 and TGF-β. Meanwhile, MSCs reinforced the immune suppressive functions of decidual Tregs (dTregs). More important, MSCs-instructed dTregs gained enhanced capacity to suppress Th1 and Th17 related inflammatory responses. In vivo data demonstrated that adoptive transfer of MSCs obviously promoted accumulation of Foxp3⁺ dTregs in lipopolysaccharide (LPS)-induced mice abortion model and spontaneous abortion model (DBA/2-mated female CBA/J mice). Furthermore, MSCs treatment effectively ameliorated absorption rate in both models. This study may offer a new insight for the application of MSCs and Tregs in clinical recurrent miscarriage.

Bcl-3 suppresses differentiation of RORγt+ regulatory T cells

Regulatory T cells (Tregs) exert inhibitory function under various physiological conditions and adopt diverse characteristics following environmental cues. Multiple subsets of Tregs expressing master transcription factors of helper T cells such as RORγt, T-bet, Gata3 and PPARγ have been characterized, but the molecular mechanism governing the differentiation of these subsets remains largely unknown. Here we report that the atypical IκB protein family member Bcl-3 suppresses RORγt+ Treg accumulation. The suppressive effect of Bcl-3 was particularly evident in the mouse immune tolerance model of anti-CD3 therapy. Using conditional knockout mice, we illustrate that loss of Bcl-3 specifically in Tregs was sufficient to boost RORγt+ Treg formation and resistance of mice to dextran sulfate sodium-induced colitis. We further demonstrate the suppressive effect of Bcl-3 on RORγt+ Treg differentiation in vitro. Our results reveal a novel role of nuclear factor-kappa B signaling pathways in Treg subset differentiation that may have clinical implications in immunotherapy.

The role of B-Cell Lymphoma-3 (BCL-3) in enabling the hallmarks of cancer: implications for the treatment of colorectal carcinogenesis

With its identification as a proto-oncogene in chronic lymphocytic leukaemia and central role in regulating NF-κB signalling, it is perhaps not surprising that there have been an increasing number of studies in recent years investigating the role of BCL-3 (B-Cell Chronic Lymphocytic Leukaemia/Lymphoma-3) in a wide range of human cancers. Importantly, this work has begun to shed light on our mechanistic understanding of the function of BCL-3 in tumour promotion and progression. Here, we summarize the current understanding of BCL-3 function in relation to the characteristics or traits associated with tumourigenesis, termed ‘Hallmarks of Cancer’. With the focus on colorectal cancer, a major cause of cancer related mortality in the UK, we describe the evidence that potentially explains why increased BCL-3 expression is associated with poor prognosis in colorectal cancer. As well as promoting tumour cell proliferation, survival, invasion and metastasis, a key emerging function of this proto-oncogene is the regulation of the tumour response to inflammation. We suggest that BCL-3 represents an exciting new route for targeting the Hallmarks of Cancer; in particular by limiting the impact of the enabling hallmarks of tumour promoting inflammation and cell plasticity. As BCL-3 has been reported to promote the stem-like potential of cancer cells, we suggest that targeting BCL-3 could increase the tumour response to conventional treatment, reduce the chance of relapse and hence improve the prognosis for cancer patients.

Bcl-3 inhibits lupus-like phenotypes in BL6/lpr mice

Bcl-3 is an atypical member of the IκB family that modulates NF-κB activity in nuclei. lpr mice carry the lpr mutation in Fas, resulting in functional loss of this death receptor; they serve as models for lupus erythematosus and autoimmune lymphoproliferation syndrome (ALPS). To explore the biologic roles of Bcl-3 in this disease model, we generated BL6/lpr mice lacking Bcl-3. Unlike lpr mice on an MRL background, BL6/lpr mice present with very mild lupus- or ALPS-like phenotypes. Bcl-3 KO BL6/lpr mice, however, developed severe splenomegaly, dramatically increased numbers of double negative T cells - a hallmark of human lupus, ALPS, and MRL/lpr mice - and exhibited inflammation in multiple organs, despite low levels of autoantibodies, similar to those in BL6/lpr mice. Loss of Bcl-3 specifically in T cells exacerbated select lupus-like phenotypes, specifically organ infiltration. Mechanistically, elevated levels of Tnfα in Bcl-3 KO BL6/lpr mice may promote lupus-like phenotypes, since loss of Tnfα in these mice reversed the pathology due to loss of Bcl-3. Contrary to the inhibitory functions of Bcl-3 revealed here, this regulator has also been shown to promote inflammation in different settings. Our findings highlight the profound, yet highly context-dependent roles of Bcl-3 in the development of inflammation-associated pathology.

Histone Deacetylase 9 Activates IKK to Regulate Atherosclerotic Plaque Vulnerability

RATIONALE

Arterial inflammation manifested as atherosclerosis is the leading cause of mortality worldwide. Genome-wide association studies have identified a prominent role of HDAC (histone deacetylase)-9 in atherosclerosis and its clinical complications including stroke and myocardial infarction.

OBJECTIVE

To determine the mechanisms linking HDAC9 to these vascular pathologies and explore its therapeutic potential for atheroprotection.

METHODS AND RESULTS

We studied the effects of Hdac9 on features of plaque vulnerability using bone marrow reconstitution experiments and pharmacological targeting with a small molecule inhibitor in hyperlipidemic mice. We further used 2-photon and intravital microscopy to study endothelial activation and leukocyte-endothelial interactions. We show that hematopoietic Hdac9 deficiency reduces lesional macrophage content while increasing fibrous cap thickness thus conferring plaque stability. We demonstrate that HDAC9 binds to IKK (inhibitory kappa B kinase)-α and β, resulting in their deacetylation and subsequent activation, which drives inflammatory responses in both macrophages and endothelial cells. Pharmacological inhibition of HDAC9 with the class IIa HDAC inhibitor TMP195 attenuates lesion formation by reducing endothelial activation and leukocyte recruitment along with limiting proinflammatory responses in macrophages. Transcriptional profiling using RNA sequencing revealed that TMP195 downregulates key inflammatory pathways consistent with inhibitory effects on IKKβ. TMP195 mitigates the progression of established lesions and inhibits the infiltration of inflammatory cells. Moreover, TMP195 diminishes features of plaque vulnerability and thereby enhances plaque stability in advanced lesions. Ex vivo treatment of monocytes from patients with established atherosclerosis reduced the production of inflammatory cytokines including IL (interleukin)-1β and IL-6.

CONCLUSIONS

Our findings identify HDAC9 as a regulator of atherosclerotic plaque stability and IKK activation thus providing a mechanistic explanation for the prominence of HDAC9 as a vascular risk locus in genome-wide association studies. Its therapeutic inhibition may provide a potent lever to alleviate vascular inflammation. Graphical Abstract: A graphical abstract is available for this article.

Immunophenotyping of Human Regulatory T Cells

Regulatory T cells, also known as Tregs, play a pivotal role in maintaining homeostasis of the immune system and self-tolerance. Tregs express CD3, CD4, CD25, and FOXP3 but lack CD127. CD4 and CD3 identify helper T lymphocytes, of which Tregs are a subset. CD25 is IL-2Rα, an essential activation marker that is expressed in high levels on Tregs. FOXP3 is the canonical transcription factor, important in the development, maintenance, and identification of Tregs. CD127 is IL-7 receptor, expressed inversely with suppression, and is therefore downregulated on Tregs. Flow cytometry is a powerful tool that is capable of simultaneously measuring Tregs along with several markers associated with subpopulations of Tregs, activation, maturation, proliferation, and surrogates of functional suppression. This chapter describes a multicolor flow cytometry-based approach to measure human Tregs, including details for surface staining, fixation/permeabilization, intracellular/intranuclear staining, acquisition of samples on a flow cytometer, plus analysis and interpretation of resulting FCS files.

Missense mutation in PRKCQ is associated with Crohn's disease

OBJECTIVE

Recent genome-wide association studies have demonstrated that rs2236379 in PRKCQ is a novel significant locus for Crohn's disease (CD). However, the association has not been replicated in any populations. We therefore aimed to investigate the prevalence of the PRKCQ rs2236379 variant in the Chinese Han population and evaluate whether the genetic variant of PRKCQ confers susceptibility to CD and is associated with its clinical characteristics.

METHODS

A total of 283 patients with CD and 381 healthy controls were enrolled. Genomic DNA was extracted from their whole blood samples and polymerase chain reaction-restriction fragment length polymorphism was used for genotyping. The association between PRKCQ polymorphisms and susceptibility to CD, and between genotypes and clinical phenotypes was analyzed.

RESULTS

A higher frequency of the T allele was discovered in CD patients than in healthy controls (P = 0.027). A significant difference in the distribution of the TT and CT/CC genotypes was observed between CD patients and controls (P = 0.024). The TT genotype showed a significant association with susceptibility to CD (odds ratio 1.647, 95% confidence interval: 1.088-2.574, P = 0.019). Patients with CD with the rs2236379 TT mutant risk genotype were most likely to exhibit perianal disease (P = 0.044).

CONCLUSIONS

Our research revealed an association between the PRKCQ rs2236379 (C>T) and CD. The TT homozygous mutation increased the risk of developing CD and may contribute to perianal disease.

Alternative Splice Forms of CYLD Mediate Ubiquitination of SMAD7 to Prevent TGFB Signaling and Promote Colitis

BACKGROUND & AIMS

The CYLD lysine 63 deubiquitinase gene (CYLD) encodes tumor suppressor protein that is mutated in familial cylindromatosus, and variants have been associated with Crohn disease (CD). Splice forms of CYLD that lack exons 7 and 8 regulate transcription factors and functions of immune cells. We examined the expression of splice forms of CYLD in colon tissues from patients with CD and their effects in mice.

METHODS

We performed immunohistochemical analyses of colon tissues from patients with untreated CD and patients without inflammatory bowel diseases (controls). We obtained mice that expressed splice forms of CYLD (sCYLD mice) without or with SMAD7 (sCYLD/SMAD7 mice) from transgenes and CYLD-knockout mice (with or without transgenic expression of SMAD7) and performed endoscopic analyses. Colitis was induced in Rag1^-/- mice by transfer of CD4⁺ CD62L⁺ T cells from C57/Bl6 or transgenic mice. T cells were isolated from mice and analyzed by flow cytometry and quantitative real-time polymerase chain reaction and intestinal tissues were analyzed by histology and immunohistochemistry. CYLD forms were expressed in mouse embryonic fibroblasts, primary T cells, and HEK293T cells, which were analyzed by immunoblot, mobility shift, and immunoprecipitation assays.

RESULTS

The colonic lamina propria from patients with CD was infiltrated by T cells and had higher levels of sCYLD (but not full-length CYLD) and SMAD7 than tissues from controls. Incubation of mouse embryonic fibroblasts and T cells with transforming growth factor β increased their production of sCYLD and decreased full-length CYLD. Transgenic expression of sCYLD and SMAD7 in T cells prevented the differentiation of regulatory T cells and T-helper type 17 cells and increased the differentiation of T-helper type 1 cells. The same effects were observed in colon tissues from sCYLD/SMAD7 mice but not in those from CYLD-knockout SMAD7 mice. The sCYLD mice had significant increases in the numbers of T-helper type 1 cells and CD44^high CD62L^low memory-effector CD4⁺ T cells in the spleen and mesenteric lymph nodes compared with wild-type mice; sCYLD/SMAD7 mice had even larger increases. The sCYLD/SMAD7 mice spontaneously developed severe colitis, with infiltration of the colon by dendritic cells, neutrophils, macrophages, and CD4⁺ T cells and increased levels of Ifng, Il6, Il12a, Il23a, and Tnf mRNAs. Co-transfer of regulatory T cells from wild-type, but not from sCYLD/SMAD7, mice prevented the induction of colitis in Rag1^-/- mice by CD4⁺ T cells. We found increased levels of poly-ubiquitinated SMAD7 in sCYLD CD4⁺ T cells. CYLD formed a nuclear complex with SMAD3, whereas sCYLD recruited SMAD7 to the nucleus, which inhibited the expression of genes regulated by SMAD3 and SMAD4. We found that sCYLD mediated lysine 63-linked ubiquitination of SMAD7. The sCYLD-SMAD7 complex inhibited transforming growth factor β signaling in CD4⁺ T cells.

CONCLUSIONS

Levels of the spliced form of CYLD are increased in colon tissues from patients with CD. sCYLD mediates ubiquitination and nuclear translocation of SMAD7 and thereby decreases transforming growth factor β signaling in T cells. This prevents immune regulatory mechanisms and leads to colitis in mice.

Alpinetin exerts anti-colitis efficacy by activating AhR, regulating miR-302/DNMT-1/CREB signals, and therefore promoting Treg differentiation

Alpinetin, a flavonoid compound extracted from the seeds of Alpinia katsumadai Hayata, has been demonstrated to exert massive biological properties. This study aimed to evaluate the effect of alpinetin on dextran sulfate sodium (DSS)-induced colitis, and elucidate the potential mechanisms. Alpinetin significantly alleviated colitis in mice, accompanied with restored Th17/Treg balance in colons. In vitro, alpinetin directly promoted Treg differentiation but exerted little effect on Th17 differentiation, and the action was in an aryl hydrocarbon receptor (AhR)-dependent manner. It acted as a potential AhR activator, evidenced by increased expression of CYP1A1, dissociation of AhR/HSP90 complexes, AhR nuclear translocation, XRE-driven luciferase reporter gene and DNA-binding activity of AhR/ARNT/XRE in T cells. Furthermore, alpinetin significantly promoted expression of miR-302 but not others, and restrained expression of DNMT-1 and methylation level of Foxp3 promoter region in CD4⁺ T cells and colons of colitis mice. However, the association of CREB and Foxp3 promoter region but not expression, nuclear translocation and DNA-binding activity of CREB was up-regulated by alpinetin in CD4⁺ T cells. The relationship of alpinetin-adjusted AhR activation, expressions of miR-302 and DNMT-1, association of CREB and Foxp3 promoter region, and Treg differentiation was confirmed by using CH223191, siAhR, miR-302 inhibitor and pcDNA3.1(+)-mDNMT-1. Finally, CH223191 abolished the amelioration of alpinetin on colitis, induction of Treg cells and regulation of miR-302/DNMT-1/CREB signals in colons of colitis mice. In conclusion, alpinetin ameliorated colitis in mice via activating AhR, regulating miR-302/DNMT-1/CREB signals, therefore promoting Treg differentiation.

Immunohistochemical assessment of Survivin and Bcl3 expression as potential biomarkers for NF-κB activation in the Barrett metaplasia-dysplasia-adenocarcinoma sequence

Non-dysplastic Barrett's oesophagus (NDBE) occurs as a consequence of an inflammatory response triggered through prolonged gastro-oesophageal reflux and it may precede the development of oesophageal adenocarcinoma. NF-κB activation as a result of the inflammatory response has been shown in NDBE, but the possible mechanism involved in the process is unknown. The aim of this study was to assess, using immunohistochemistry, Survivin and Bcl3 expression as potential biomarkers for NF-κB activation along the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. Survivin is an NF-κB-inducible anti-apoptotic protein, and Bcl3 is a negative regulator of NF-κB. There was progressive upregulation of Survivin expression along the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. Bcl3 expression was upregulated in non-dysplastic Barrett's oesophagus, low-grade, high-grade dysplasia and oesophageal adenocarcinoma when compared to squamous group. The study shows the differential expression of Bcl3 between the squamous and Barrett's stage, suggesting that Bcl3 could be a surrogate marker for early event involving constitutive NF-κB activation. In addition, the study suggests that NF-κB activation may infer resistance to apoptosis through the expression of anti-apoptotic genes such as Survivin, which showed progressive increase in expression throughout the oesophageal metaplasia-dysplasia-adenocarcinoma sequence. This ability to avoid apoptosis may underlie the persistence and malignant predisposition of Barrett's metaplasia.