Foxp3 induces IL-4 gene silencing by affecting nuclear translocation of NFκB and chromatin structure

Widely Targeted Lipidomics and Transcriptomics Analysis Revealed Changes of Lipid Metabolism in Spleen Dendritic Cells in Shrimp Allergy

Shrimp allergy (SA) is pathological type 2 inflammatory immune responses against harmless shrimp protein allergen, which is caused by complex interactions between dendritic cells (DCs) and other immune cells. Lipid metabolism in different DCs states are significantly changed. However, the lipid metabolism of spleen DCs in SA remain ambiguous. In this study, we established a BALB/c mouse shrimp protein extract-induced allergy model to determine the lipid profile of spleen DCs in SA, and the molecular mechanism between lipid metabolism and immune inflammation was preliminarily studied. Spleen DCs were sorted by fluorescence-activated cell sorting, and then widely targeted lipidomics and transcriptomics analysis were performed. Principal component analysis presented the lipidome alterations in SA. The transcriptomic data showed that Prkcg was involved in lipid metabolism, immune system, and inflammatory signaling pathway. In the correlation analysis, the results suggested that Prkcg was positively correlated with triacylglycerol (Pearson correlation coefficient = 0.917, p = 0.01). The lipidomics and transcriptomics integrated pathway analysis indicated the activated metabolic conversion from triacylglycerol to 1,2-diacyl-sn-glycerol and the transmission of lipid metabolism to immune inflammation (from triacylglycerol and ceramide to Prkcg) in SA spleen DCs, and cellular experiments in vitro showed that glyceryl trioleate and C16 ceramide treatment induced immune function alteration in DCs.

Evaluation of the Function of Probiotics, Emphasizing the Role of their Binding to the Intestinal Epithelium in the Stability and their Effects on the Immune System

Due to the importance of using cost-effective methods for therapeutic purposes, the function of probiotics as safe microorganisms and the study of their relevant functional mechanisms have recently been in the spotlight. Finding the mechanisms of attachment and stability and their beneficial effects on the immune system can be useful in identifying and increasing the therapeutic effects of probiotics. In this review, the functional mechanisms of probiotics were comprehensively investigated. Relevant articles were searched in scientific sources, documents, and databases, including PubMed, NCBI, Bactibace, OptiBac, and Bagel4. The most important functional mechanisms of probiotics and their effects on strengthening the epithelial barrier, competitive inhibition of pathogenic microorganisms, production of antimicrobials, binding and interaction with the host, and regulatory effects on the immune system were discussed.

In this regard, the attachment of probiotics to the epithelium is very important because the prerequisite for their proper functioning is to establish a proper connection to the epithelium. Therefore, more attention should be paid to the binding effect of probiotics, including sortase A, a significant factor involved in the expression of sortase-dependent proteins (SDP), on their surface as mediators of intestinal epithelial cell binding. In general, by investigating the functional mechanisms of probiotics, it was concluded that the mechanism by which probiotics regulate the immune system and adhesion capacity can directly and indirectly have preventive and therapeutic effects on a wide range of diseases. However, further study of these mechanisms requires extensive research on various aspects.

Notch and NF-κB: Coach and Players of Regulatory T-Cell Response in Cancer

The Notch signaling pathway plays multiple roles in driving T-cell fate decisions, proliferation, and aberrant growth. NF-κB is a cell-context key player interconnected with Notch signaling either in physiological or in pathological conditions. This review focuses on how the multilayered crosstalk between different Notches and NF-κB subunits may converge on Foxp3 gene regulation and orchestrate CD4⁺ regulatory T (Treg) cell function, particularly in a tumor microenvironment. Notably, Treg cells may play a pivotal role in the inhibition of antitumor immune responses, possibly promoting tumor growth. A future challenge is represented by further dissection of both Notch and NF-κB pathways and consequences of their intersection in tumor-associated Treg biology. This may shed light on the molecular mechanisms regulating Treg cell expansion and migration to peripheral lymphoid organs thought to facilitate tumor development and still to be explored. In so doing, new opportunities for combined and/or more selective therapeutic approaches to improve anticancer immunity may be found.

Lactobacillus plantarum HAC01 regulates gut microbiota and adipose tissue accumulation in a diet-induced obesity murine model

The functional features of Lactobacillus plantarum HAC01 (HAC01), isolated from fermented Korean kimchi, were studied with regard to the fat mass, immunometabolic biomarkers and dysbiosis in a diet-induced obesity (DIO) murine model. L. rhamnosus GG (LGG) served as reference strain and a PBS-treated group as control. The administration of L. plantarum HAC01 resulted in reduction of the mesenteric adipose depot, the conjunctive tissue closely associated with the gastrointestinal tract, where lipid oxidative gene expression was upregulated compared to the control group. Metagenome analysis of intestinal microbiota showed that both strains HAC01 and LGG influenced specific bacterial families such as the Lachnospiraceae and Ruminococcaceae rather than the phyla Firmicutes and Bacteroidetes as a whole. The relative abundance of the Lachnospiraceae (phylum Firmicutes) was significantly higher in both LAB-treated groups than in the control. Comparing the impact of the two Lactobacillus strains on microbial composition in the gut also suggests strain-specific effects. The study emphasises the need for deeper studies into functional specificity of a probiotic organism at the strain level. Alleviation of obesity-associated dysbiosis by modulation of the gut microbiota appears to be associated with "indicator" bacterial taxa such as the family Lachnospiraceae. This may provide further insight into mechanisms basic to the mode of probiotic action against obesity and associated dysbiosis.

Adenovirus-mediated Foxp3 expression in lung epithelial cells reduces airway inflammation in ovalbumin and cockroach-induced asthma model

Foxp3 is a master regulator of CD4(+)CD25(+) regulatory T-cell (Treg) function and is also a suppressor of SKP2 and HER2/ErbB2. There are an increasing number of reports describing the functions of Foxp3 in cell types other than Tregs. In this context, we evaluated the functions of Foxp3 in ovalbumin- and cockroach-induced asthma models. Foxp3-EGFP-expressing adenovirus or EGFP control adenovirus was administered intratracheally (i.t.), followed by challenge with ovalbumin (OVA) or cockroach extract to induce asthma. Th2 cytokine and immune cell profiles of bronchoalveolar lavage fluid (BALF), as well as serum IgE levels, were analyzed. Histological analyses were also conducted to demonstrate the effects of Foxp3 expression on airway remodeling, goblet cell hyperplasia and inflammatory responses in the lung. Adenoviral Foxp3 was expressed only in lung epithelial cells, and not in CD4(+) or CD8(+) cells. BALF from Foxp3 gene-delivered mice showed significantly reduced numbers of total immune cells, eosinophils, neutrophils, macrophages and lymphocytes in response to cockroach allergen or OVA. In addition, Foxp3 expression in the lung reduced the levels of Th2 cytokines and IgE in BALF and serum, respectively. Moreover, histopathological analysis also showed that Foxp3 expression substantially inhibited eosinophil infiltration into the airways, goblet cell hyperplasia and smooth muscle cell hypertrophy. Furthermore, when Tregs were depleted by diphtheria toxin in Foxp3(DTR) mice, the anti-asthmatic functions of Foxp3 were not altered in OVA-challenged asthma models. In this study, our results suggest that Foxp3 expression in lung epithelial cells, and not in Tregs, inhibited OVA- and cockroach extract-induced asthma.

Epirubicin, Identified Using a Novel Luciferase Reporter Assay for Foxp3 Inhibitors, Inhibits Regulatory T Cell Activity

Forkhead box protein p3 (Foxp3) is crucial to the development and suppressor function of regulatory T cells (Tregs) that have a significant role in tumor-associated immune suppression. Development of small molecule inhibitors of Foxp3 function is therefore considered a promising strategy to enhance anti-tumor immunity. In this study, we developed a novel cell-based assay system in which the NF-κB luciferase reporter signal is suppressed by the co-expressed Foxp3 protein. Using this system, we screened our chemical library consisting of approximately 2,100 compounds and discovered that a cancer chemotherapeutic drug epirubicin restored the Foxp3-inhibited NF-κB activity in a concentration-dependent manner without influencing cell viability. Using immunoprecipitation assay in a Treg-like cell line Karpas-299, we found that epirubicin inhibited the interaction between Foxp3 and p65. In addition, epirubicin inhibited the suppressor function of murine Tregs and thereby improved effector T cell stimulation in vitro. Administration of low dose epirubicin into tumor-bearing mice modulated the function of immune cells at the tumor site and promoted their IFN-γ production without direct cytotoxicity. In summary, we identified the novel action of epirubicin as a Foxp3 inhibitor using a newly established luciferase-based cellular screen. Our work also demonstrated our screen system is useful in accelerating discovery of Foxp3 inhibitors.

Probiotics and lung immune responses

There is increasing interest in the potential for microbe-based therapeutic approaches to asthma and respiratory infection. However, to date, clinical trials of probiotics in the treatment of respiratory disease have met with limited success. It is becoming clear that to identify the true therapeutic potential of microbes we must move away from a purely empirical approach to clinical trials and adopt knowledge-based selection of candidate probiotics strains, dose, and means of administration. Animal models have played a key role in the identification of mechanisms underlying the immunomodulatory capacity of specific bacteria. Microbe-induced changes in dendritic cell phenotype and function appear key to orchestrating the multiple pathways, involving inter alia, T cells, natural killer cells, and alveolar macrophages, associated with the protective effect of probiotics. Moving forward, the development of knowledge-based strategies for microbe-based therapeutics in respiratory disease will be aided by greater understanding of how specific bacterial structural motifs activate unique combinations of pattern recognition receptors on dendritic cells and thus direct desired immune responses.

The nuclear factor-κB pathway is involved in matrix metalloproteinase-9 expression in RU486-induced endometrium breakdown in mice

BACKGROUND

Progesterone-withdrawal (WP)-induced endometrial breakdown occurs in both physiological and pathological processes such as menstruation and abortion. However, the underlying mechanisms are not clearly understood. As the nuclear factor-κB (NF-κB) pathway has been proposed to play a role in endometrial breakdown, we tested this hypothesis using RU486-induced mouse menstruation-like model.

METHODS

The activation of NF-κB was evaluated by immunohistochemistry, western blot and immunofluorescence. The expression of matrix metalloproteinase-9 (MMP9) was analyzed by real-time PCR and its proteins by gelatin zymography and western blot. Chromatin immunoprecipitation was used to investigate the direct binding of NF-κB to MMP9 gene promoter. Inhibitors of NF-κB were used to block its signal in vivo and in vitro to analyze the function of NF-κB in the tissue breakdown process.

RESULTS

Administration of RU486 resulted in increased phospho-IκB levels and nuclear translocation of p65 in decidual stromal cells, accompanied by the up-regulation of NF-κB inducing kinase and IκB kinase β mRNA. The NF-κB inhibitor, 'pyrrolidine dithiocarbamate' partially suppressed the RU486-induced endometrial breakdown, thus verifying the role of this pathway in vivo. MMP9 was up- and down-regulated following the NF-κB activation and inhibition, respectively. RU486 stimulated recruitment of NF-κB p65 to the MMP9 promoter and further increased its expression. Effects of NF-κB activation and inactivation on MMP9 expression were further explored in human stromal cells in vitro. A similar MMP9 expression pattern was observed in cultured human, as well as mouse, decidual stromal cells following RU486 treatment.

CONCLUSIONS

The activation of the NF-κB pathway induces downstream target genes, including MMP9 from stromal cells to facilitate tissue breakdown in mouse uterus, highlighting the likelihood that this regulatory pattern exists in the human endometrium.

Multiple modes of chromatin remodeling by Forkhead box proteins

Forkhead box (FOX) proteins represent a large family of transcriptional regulators unified by their DNA binding domain (DBD) known as a 'forkhead' or 'winged helix' domain. Over 40 FOX genes have been identified in the mammalian genome. FOX proteins share significant sequence similarities in the DBD which allow them to bind to a consensus DNA response element. However, their modes of action are quite diverse as they regulate gene expression by acting as pioneer factors, transcription factors, or both. This review focuses on the mechanisms of chromatin remodeling with an emphasis on three sub-classes-FOXA, FOXO, and FOXP members. FOXA proteins serve as pioneer factors to open up local chromatin structure and thereby increase accessibility of chromatin to factors regulating transcription. FOXP proteins, in contrast, function as classic transcription factors to recruit a variety of chromatin modifying enzymes to regulate gene expression. FOXO proteins represent a hybrid subclass having dual roles as pioneering factors and transcription factors. A subset of FOX proteins interacts with condensed mitotic chromatin and may function as 'bookmarking' agents to maintain transcriptional competence at specific genomic sites. The overall diversity in chromatin remodeling function by FOX proteins is related to unique structural motifs present within the DBD flanking regions that govern selective interactions with core histones and/or chromatin coregulatory proteins. This article is part of a Special Issue entitled: Chromatin in time and space.

Forkhead transcription factors: key players in health and disease

Forkhead box (FOX) proteins constitute an evolutionarily conserved family of transcription factors with a central role not only during development, but also in the adult organism. Thus, the misregulation and/or mutation of FOX genes often induce human genetic diseases, promote cancer or deregulate ageing. Indeed, germinal FOX gene mutations cause diseases ranging from infertility to language and/or speech disorders and immunological defects. Moreover, because of their central role in signalling pathways and in the regulation of homeostasis, somatic misregulation and/or mutation of FOX genes are associated with cancer. FOX proteins have undergone diversification in terms of their sequence, regulation and function. In addition to dedicated roles, evidence suggests that Forkhead factors have retained some functional redundancy. Thus, combinations of slightly defective alleles might induce disease phenotypes in humans, acting as quantitative trait loci. Uncovering such variants would be a big step towards understanding the functional interdependencies of different FOX members and their implications in complex pathologies.

Mechanisms of tolerance and allergic sensitization in the airways and the lungs

The respiratory mucosa is constantly exposed to non-infectious substances that have the potential of triggering inflammation. While many particles are excluded, soluble molecules can reach the epithelium surface, where they can be uptaken by dendritic cells and stimulate an adaptive immune response. Most mucosal responses result in tolerance to subsequent antigen encounters, which is mediated by Foxp3(+) regulatory T cells. Genetic and environmental factors, added to the ability of certain allergens to induce innate responses, can predispose to allergic sensitization. In this review we discuss recent advances in the understanding of the mechanisms of tolerance and allergic sensitization to airborne allergens.

Foxp3 is a novel repressor of microglia activation

Forkhead transcription factor 3 (Foxp3) is critical for generating CD4(+)CD25(+) regulatory T cells. However, its role in microglia has not been identified. Here, we show that Foxp3 is expressed in microglia and is upregulated upon activation. In Foxp3 mutant mice (Foxp3(sf)), microglia release higher levels of inflammatory cytokines and mediators such as NO, MCP-1, CXCL10, and ROS upon liposaccharide treatment than the wild type, while TNF-alpha and IL-1 beta were not significantly different between wild and mutant microglial cells. In addition, Foxp3 silencing enhances inflammatory responses, suggesting that the major role of Foxp3 in microglia is that of a repressor of activation. Similarly, Foxp3 overexpression reduces inflammatory responses in microglia. We also demonstrate that Foxp3 interacts directly with NF-kappaB and modulates its transcriptional activities. These findings point to the importance of Foxp3 in NF-kappaB mediated inflammatory responses in microglia.

Diversity and plasticity of Th cell types predicted from regulatory network modelling

Alternative cell differentiation pathways are believed to arise from the concerted action of signalling pathways and transcriptional regulatory networks. However, the prediction of mammalian cell differentiation from the knowledge of the presence of specific signals and transcriptional factors is still a daunting challenge. In this respect, the vertebrate hematopoietic system, with its many branching differentiation pathways and cell types, is a compelling case study. In this paper, we propose an integrated, comprehensive model of the regulatory network and signalling pathways controlling Th cell differentiation. As most available data are qualitative, we rely on a logical formalism to perform extensive dynamical analyses. To cope with the size and complexity of the resulting network, we use an original model reduction approach together with a stable state identification algorithm. To assess the effects of heterogeneous environments on Th cell differentiation, we have performed a systematic series of simulations considering various prototypic environments. Consequently, we have identified stable states corresponding to canonical Th1, Th2, Th17 and Treg subtypes, but these were found to coexist with other transient hybrid cell types that co-express combinations of Th1, Th2, Treg and Th17 markers in an environment-dependent fashion. In the process, our logical analysis highlights the nature of these cell types and their relationships with canonical Th subtypes. Finally, our logical model can be used to explore novel differentiation pathways in silico.

T lymphocytes play a key role in the regulation of the immune response in mammals. Various T-helper subtypes (Th1, Th2, Th17, Treg,…) have been identified over the years, characterised by the expression of specific transcription factors and cytokines, which have a critical influence on the selection of different immune responses, driving pro-inflammatory or allergic responses, promoting alternative antibody classes, or preventing (auto)immunity by inhibiting the activation and proliferation of other cells. To gain insight into the heterogeneity and the plasticity of late T-helper lineages, we have built an integrated model of the regulatory network and signalling pathways controlling Th cell differentiation. Relying on a logical modelling framework, we have performed a systematic series of simulations to assess the effects of heterogeneous environments on Th cell differentiation. We have identified stable states corresponding to canonical Th1, Th2, Th17 and Treg subtypes, but also to hybrid cell types co-expressing combinations of Th1, Th2, Treg and Th17 markers in an environment-dependent fashion. Our analysis highlights the nature of these cell types and their relationships with canonical Th subtypes.

Foxp3 regulates megakaryopoiesis and platelet function

OBJECTIVE

Platelets are crucial for hemostasis and are vital regulators of inflammation. Foxp3 is a key transcription factor for T regulatory cell development. Humans with IPEX (immune dysregulation, polyendocrinopathy, enteropathy, x-linked) and the scurfy (Foxp3(sf)) mouse have mutations in the Foxp3 gene that lead to a host of pathologies including autoimmunity and skin diseases. Scurfy mice and some humans with IPEX are also thrombocytopenic. The purpose of this study was to determine whether the absence of functional Foxp3 leads to defects in megakaryocytes and platelets.

METHODS AND RESULTS

We discovered that human and mouse megakaryocytes express Foxp3 mRNA and protein. Using shRNA and Foxp3(sf) mice, we demonstrated that Foxp3-deficient mouse and human megakaryocyte progenitors exhibited proliferation defects. Striking platelet abnormalities were observed in both an IPEX patient and Foxp3(sf) mice. Impaired platelet spreading and release of TGF-beta and CD40 ligand (CD40L), and abnormal levels of plasma CD40L were observed in a case of IPEX syndrome. Foxp3(sf) mice were thrombocytopenic and had increased platelet volume and altered serum levels of CD40L, TXB(2), and TGF-beta.

CONCLUSIONS

These findings provide compelling new evidence that Foxp3 is needed for proper megakaryopoiesis and plays a role in regulating platelet function including spreading and release.

Epigenetic control of FOXP3 expression: the key to a stable regulatory T-cell lineage?

Regulatory T (T(Reg)) cells constitute a unique T-cell lineage that has a crucial role in immunological tolerance. Several years ago, forkhead box P3 (FOXP3) was identified as the transcription factor that was responsible for determining the development and function of these cells. However, the underlying mechanisms that are involved in the regulation of the FOXP3 gene remain unclear and therefore preclude accurate identification and manipulation of T(Reg) cells. In this Progress article, we summarize recent advances in understanding how FOXP3 expression is controlled and highlight evidence suggesting that epigenetic regulation of the FOXP3 locus contributes to its role as a lineage-specification factor.