FOXO1 regulates dendritic cell activity through ICAM-1 and CCR7

Functional Polymorphisms Regulate FOXO1 Transcript Expression and Contribute to the Risk and Symptom Severity of HDM-Induced Allergic Rhinitis

INTRODUCTION

FOXO1 plays an important role in regulating immune processes that contribute to allergic inflammation; however, genetic variants influencing FOXO1 expression in AR pathogenesis remains unclear. This study aimed to investigate the functional effect of FOXO1 single nucleotide polymorphisms (SNPs) on AR development by performing genetic association and functional analysis studies.

METHODS

This study belongs to a part of an ongoing Singapore/Malaysia cross-sectional genetics and epidemiological study (SMCSGES). We assessed the associations of FOXO1 transcript expression levels in peripheral blood mononuclear cells (PBMC) with AR phenotype, total nasal symptom score (TNSS), and SNP genotype in a sub-cohort of n = 658 individuals from the SMCSGES population. Associations of FOXO1 SNPs with AR were assessed in a cohort of n = 5,072 individuals from the SMCSGES population. In vitro promoter luciferase assay was used to evaluate the effect of AR-associated SNPs on FOXO1 promoter activity.

RESULTS

FOXO1 transcript expression in PBMC was significantly associated with the risk of AR (p < 0.05) and TNSS among AR patients (p < 0.0001). We identified a significant association between tag-SNPs rs9549246 and FOXO1 transcript expression in PBMC from the SMCSGES sub-cohort and the multiethnic eQTLGen consortium (false discovery rate-adjusted p < 0.05). The minor allele "A" of tag-SNP rs9549246 was significantly associated with a higher risk of AR (p = 0.04422, odds ratio = 1.21, 95% confidence interval = 1.01-1.45) in the SMCSGES genotyping cohort (n = 5,072). In vitro luciferase assay showed the minor allele "A" of rs35594717 (tagged by rs9549246) was significantly associated with a higher FOXO1 promoter activity (p < 0.05).

CONCLUSION

FOXO1 transcript expression in PBMC has a strong association with the risk and symptom severity of AR. Genetic variants tagged by rs9549246 were shown to affect the expression of FOXO1 and contribute to the development of AR in the SMCSGES population.

An update on periodontal inflammation and bone loss

Periodontal disease is a chronic inflammatory condition that affects the supporting structures of the teeth, including the periodontal ligament and alveolar bone. Periodontal disease is due to an immune response that stimulates gingivitis and periodontitis, and its systemic consequences. This immune response is triggered by bacteria and may be modulated by environmental conditions such as smoking or systemic disease. Recent advances in single cell RNA-seq (scRNA-seq) and in vivo animal studies have provided new insight into the immune response triggered by bacteria that causes periodontitis and gingivitis. Dysbiosis, which constitutes a change in the bacterial composition of the microbiome, is a key factor in the initiation and progression of periodontitis. The host immune response to dysbiosis involves the activation of various cell types, including keratinocytes, stromal cells, neutrophils, monocytes/macrophages, dendritic cells and several lymphocyte subsets, which release pro-inflammatory cytokines and chemokines. Periodontal disease has been implicated in contributing to the pathogenesis of several systemic conditions, including diabetes, rheumatoid arthritis, cardiovascular disease and Alzheimer's disease. Understanding the complex interplay between the oral microbiome and the host immune response is critical for the development of new therapeutic strategies for the prevention and treatment of periodontitis and its systemic consequences.

Oxidative Stress and FOXO-1 Relationship in Stage III Periodontitis

OBJECTIVES

8-Hydroxideoxyguanosine (8-OHdG) is a marker of oxidative stress, and Forkhead Box-O1 (FOXO1) is a transcription factor and signaling integrator in cell and tissue homeostasis. This study aims to determine FOXO1 and 8-OHdG levels in serum and saliva samples of periodontitis patients and to evaluate their relationship with clinical periodontal parameters.

MATERIALS AND METHODS

Twenty healthy individuals, twenty generalized Stage III Grade B periodontitis patients, and nineteen generalized Stage III Grade C periodontitis patients were included in the study. Clinical periodontal parameters (plaque index (PI), probing depth (PD), bleeding on probing (BOP), and clinical attachment level (CAL)) were recorded. Salivary and serum 8-OHdG and FOX-O1 levels were analyzed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Clinical periodontal parameters showed a statistically significant increase in periodontitis groups compared to the control group (p < 0.05). 8-OHdG salivary levels were significantly higher in both periodontitis groups compared to the control group. The salivary FOXO1 levels were significantly lower in both periodontitis groups compared to the control group. Salivary FOXO1 level had a low-grade negative correlation with BOP and salivary 8-OHdG level.

CONCLUSIONS

While reactive oxygen species increase in periodontal inflammation, low expression of FOXO1, an important transcription factor for antioxidant enzymes, supports that this molecule plays a vital role in tissue destruction, and FOXO1 can be seen as a potential immune modulator.

CLINICAL RELEVANCE

The role of FOXO1 in supporting antioxidant defense may suggest that FOXO1 is a candidate target for periodontitis treatment.

Human Amniotic MSC Response in LPS-Stimulated Ascites from Patients with Cirrhosis: FOXO1 Gene and Th17 Activation in Enhanced Antibacterial Activation

Spontaneous bacterial peritonitis (SBP) is a severe complication in patients with decompensated liver cirrhosis and is commonly treated with broad spectrum antibiotics. However, the rise of antibiotic resistance requires alternative therapeutic strategies. As recently shown, human amnion-derived mesenchymal stem cells (hA-MSCs) are able, in vitro, to promote bacterial clearance and modulate the immune and inflammatory response in SBP. Our results highlight the upregulation of FOXO1, CXCL5, CXCL6, CCL20, and MAPK13 in hA-MSCs as well as the promotion of bacterial clearance, prompting a shift in the immune response toward a Th17 lymphocyte phenotype after 72 h treatment. In this study, we used an in vitro SBP model and employed omics techniques (next-generation sequencing) to investigate the mechanisms by which hA-MSCs modify the crosstalk between immune cells in LPS-stimulated ascitic fluid. We also validated the data obtained via qRT-PCR, cytofluorimetric analysis, and Luminex assay. These findings provide further support to the hope of using hA-MSCs for the prevention and treatment of infective diseases, such as SBP, offering a viable alternative to antibiotic therapy.

Co-expression of regulatory B-cell markers, transforming growth factor β and interleukin-10 as a prognostic factor in diffuse large B-cell lymphoma

Regulatory B cells (Bregs) suppress antitumor immunity by producing anti-inflammatory cytokines such as transforming growth factor β (TGF-β) and interleukin-10 (IL-10) and promoting tumor growth. It is unknown whether diffuse large B-cell lymphoma (DLBCL), a common subtype of B-cell malignancy, exhibits characteristics similar to those of Bregs. This study aimed to clarify the features of DLBCLs carrying Breg markers. In 123 DLBCL cases, we evaluated TGF-β and IL-10 expression in tumor biopsy samples using immunohistochemical staining and retrospectively analyzed their clinicopathological characteristics. Fifteen cases (12.2 %) classified as Breg-type DLBCL were positive for both TGF-β and IL-10. Breg-type DLBCL is mainly classified as having activated B cell-like cells of origin. Breg-type DLBCL cases showed significantly worse progression-free survival and overall survival (OS) than other DLBCL cases (P = 0.0016 and P = 0.042, respectively). In multivariate analysis, Breg-type DLBCL significantly affected OS (hazard ratio, 3.13; 95 % confidence interval 1.15-8.55; P = 0.025). Gene expression analysis showed that the expression of follicular dendritic cell-associated genes (FCER2, PIK3CD, FOXO1) was downregulated in Breg-type DLBCLs compared to other DLBCLs. These results suggest that the double expression of Breg markers, TGF-β and IL-10, in tumor cells indicates a poor prognosis in DLBCL patients. Further studies evaluating genomic abnormalities could confirm the characteristics of Breg-type DLBCL.

GM-CSF receptor/SYK/JNK/FOXO1/CD11c signaling promotes atherosclerosis

Atherosclerosis complicates chronic inflammatory diseases, such as rheumatoid arthritis and systemic lupus erythematosus, suggesting that a shared physiological pathway regulates inflammatory responses in these diseases wherein spleen tyrosine kinase (SYK) is involved. We aimed to identify a shared therapeutic target for atherosclerosis and inflammatory diseases. We used Syk-knockout atherosclerosis-prone mice to determine whether SYK is involved in atherosclerosis via the inflammatory response and elucidate the mechanism of SYK signaling. The Syk-knockout mice showed reduced atherosclerosis in vivo, and macrophages derived from this strain showed ameliorated cell migration in vitro. CD11c expression decreased on Syk-knockout monocytes and macrophages; it was upregulated by forkhead box protein O1 (FOXO1) after stimulation with granulocyte-macrophage colony-stimulating factor (GM-CSF), and c-Jun amino-terminal kinase (JNK) mediated SYK signaling to FOXO1. Furthermore, FOXO1 inhibitor treatment mitigated atherosclerosis in mice. Thus, GM-CSF receptor/SYK/JNK/FOXO1/CD11c signaling in monocytes and macrophages and FOXO1 could be therapeutic targets for atherosclerosis and inflammatory diseases.

Systemic Alterations in Type-2 Conventional Dendritic Cells Lead to Impaired Tumor Immunity in Pancreatic Cancer

Intratumoral T-cell dysfunction is a hallmark of pancreatic tumors, and efforts to improve dendritic cell (DC)-mediated T-cell activation may be critical in treating these immune therapy unresponsive tumors. Recent evidence indicates that mechanisms that induce dysfunction of type 1 conventional DCs (cDC1) in pancreatic adenocarcinomas (PDAC) are drivers of the lack of responsiveness to checkpoint immunotherapy. However, the impact of PDAC on systemic type 2 cDC2 development and function has not been well studied. Herein, we report the analysis of 3 cohorts, totaling 106 samples, of human blood and bone marrow (BM) from patients with PDAC for changes in cDCs. We found that circulating cDC2s and their progenitors were significantly decreased in the blood of patients with PDAC, and repressed numbers of cDC2s were associated with poor prognosis. Serum cytokine analyses identified IL6 as significantly elevated in patients with PDAC and negatively correlated with cDC numbers. In vitro, IL6 impaired the differentiation of cDC1s and cDC2s from BM progenitors. Single-cell RNA sequencing analysis of human cDC progenitors in the BM and blood of patients with PDAC showed an upregulation of the IL6/STAT3 pathway and a corresponding impairment of antigen processing and presentation. These results suggested that cDC2s were systemically suppressed by inflammatory cytokines, which was linked to impaired antitumor immunity.

Osteoimmunology in Periodontitis and Orthodontic Tooth Movement

PURPOSE OF REVIEW

To review the role of the immune cells and their interaction with cells found in gingiva, periodontal ligament, and bone that leads to net bone loss in periodontitis or bone remodeling in orthodontic tooth movement.

RECENT FINDINGS

Periodontal disease is one of the most common oral diseases causing inflammation in the soft and hard tissues of the periodontium and is initiated by bacteria that induce a host response. Although the innate and adaptive immune response function cooperatively to prevent bacterial dissemination, they also play a major role in gingival inflammation and destruction of the connective tissue, periodontal ligament, and alveolar bone characteristic of periodontitis. The inflammatory response is triggered by bacteria or their products that bind to pattern recognition receptors that induce transcription factor activity to stimulate cytokine and chemokine expression. Epithelial, fibroblast/stromal, and resident leukocytes play a key role in initiating the host response and contribute to periodontal disease. Single-cell RNA-seq (scRNA-seq) experiments have added new insight into the roles of various cell types in the response to bacterial challenge. This response is modified by systemic conditions such as diabetes and smoking. In contrast to periodontitis, orthodontic tooth movement (OTM) is a sterile inflammatory response induced by mechanical force. Orthodontic force application stimulates acute inflammatory responses in the periodontal ligament and alveolar bone stimulated by cytokines and chemokines that produce bone resorption on the compression side. On the tension side, orthodontic forces induce the production of osteogenic factors, stimulating new bone formation. A number of different cell types, cytokines, and signaling/pathways are involved in this complex process. Inflammatory and mechanical force-induced bone remodeling involves bone resorption and bone formation. The interaction of leukocytes with host stromal cells and osteoblastic cells plays a key role in both initiating the inflammatory events as well as inducing a cellular cascade that results in remodeling in orthodontic tooth movement or in tissue destruction in periodontitis.

Variable Intrinsic Expression of Immunoregulatory Biomarkers in Breast Cancer Cell Lines, Mammospheres, and Co-Cultures

Advances in immunotherapy have increased interest in knowing the role of the immune system in breast cancer (BC) pathogenesis. Therefore, immune checkpoints (IC) and other pathways related to immune regulation, such as JAK2 and FoXO1, have emerged as potential targets for BC treatment. However, their intrinsic gene expression in vitro has not been extensively studied in this neoplasia. Thus, we evaluated the mRNA expression of tumor-cell-intrinsic CTLA-4, PDCD1 (PD1), CD274 (PD-L1), PDCD1LG2 (PD-L2), CD276 (B7-H3), JAK2, and FoXO1 in different BC cell lines, derived mammospheres, and co-cultures with peripheral blood mononuclear cells (PBMCs) by real-time quantitative polymerase chain reaction (qRT-PCR). Our results showed that intrinsic CTLA-4, CD274 (PD-L1), and PDCD1LG2 (PD-L2) were highly expressed in triple-negative cell lines, while CD276 was predominantly overexpressed in luminal cell lines. In contrast, JAK2 and FoXO1 were under-expressed. Moreover, high levels of CTLA-4, PDCD1 (PD1), CD274 (PD-L1), PDCD1LG2 (PD-L2), and JAK2 were found after mammosphere formation. Finally, the interaction between BC cell lines and peripheral blood mononuclear cells (PBMCs) stimulates the intrinsic expression of CTLA-4, PCDC1 (PD1), CD274 (PD-L1), and PDCD1LG2 (PD-L2). In conclusion, the intrinsic expression of immunoregulatory genes seems very dynamic, depending on BC phenotype, culture conditions, and tumor-immune cell interactions.

SIRT6 mediates MRTF-A deacetylation in vascular endothelial cells to antagonize oxLDL-induced ICAM-1 transcription

Oxidized low-density lipoprotein (oxLDL), a known risk factor for atherosclerosis, activates the transcription of adhesion molecules (ICAM-1) in endothelial cells. We previously showed that myocardin-related transcription factor A (MRTF-A) mediates oxLDL-induced ICAM-1 transcription. Here we confirm that ICAM-1 transactivation paralleled dynamic alterations in MRTF-A acetylation. Since treatment with the antioxidant NAC dampened MRTF-A acetylation, MRTF-A acetylation appeared to be sensitive to cellular redox status. Of interest, silencing of SIRT6, a lysine deacetylase, restored MRTF-A acetylation despite the addition of NAC. SIRT6 directly interacted with MRTF-A to modulate MRTF-A acetylation. Deacetylation of MRTF-A by SIRT6 led to its nuclear expulsion thus dampening MRTF-A occupancy on the ICAM-1 promoter. Moreover, SIRT6 expression was downregulated with oxLDL stimulation likely owing to promoter hypermethylation in endothelial cells. DNA methyltransferase 1 (DNMT1) was recruited to the SIRT6 promoter and mediated SIRT6 repression. The ability of DNMT1 to repress SIRT6 promoter partly was dependent on ROS-sensitive serine 154 phosphorylation. In conclusion, our data unveil a novel DNMT1-SIRT6 axis that contributes to the regulation of MRTF-A acetylation and ICAM-1 transactivation in endothelial cells.

Kinsenoside attenuates liver fibro-inflammation by suppressing dendritic cells via the PI3K-AKT-FoxO1 pathway

Kinsenoside (KD) exhibits anti-inflammatory and immunosuppressive effects. Dendritic cells (DCs) are critical regulators of the pathologic inflammatory milieu in liver fibrosis (LF). Herein, we explored whether and how KD repressed development of LF via DC regulation and verified the pathway involved in the process. Given our analysis, both KD and adoptive transfer of KD-conditioned DCs conspicuously reduced hepatic histopathological damage, proinflammatory cytokine release and extracellular matrix deposition in CCl₄-induced LF mice. Of note, KD restrained the LF-driven rise in CD86, MHC-II, and CCR7 levels and, simultaneously, upregulated PD-L1 expression on DCs specifically, which blocked CD8⁺T cell activation. Additionally, KD reduced DC glycolysis, maintained DCs immature, accompanied by IL-12 decrease in DCs. Inhibiting DC function by KD disturbed the communication of DCs and HSCs with the expression or secretion of α-SMA and Col-I declined in the liver. Mechanistically, KD suppressed the phosphorylation of PI3K-AKT driven by LF or PI3K agonist, followed by enhanced nuclear transport of FoxO1 and upregulated interaction of FoxO1 with the PD-L1 promoter in DCs. PI3K inhibitor or si-IL-12 acting on DC could relieve LF, HSC activation and diminish the effect of KD. In conclusion, KD suppressed DC maturation with promoted PD-L1 expression via PI3K-AKT-FoxO1 and decreased IL-12 secretion, which blocked activation of CD8⁺T cells and HSCs, thereby alleviating liver injury and fibro-inflammation in LF.

New Insights of CCR7 Signaling in Dendritic Cell Migration and Inflammatory Diseases

CCR7, collaborated with its ligands CCL19 and CCL21, controls extensive migratory events in the immune system. CCR7-bearing dendritic cells can swarm into T-cell zones in lymph nodes, initiating the antigen presentation and T-cell response. Abnormal expression of CCR7 in dendritic cells will cause a series of inflammatory diseases due to the chaotic dendritic cell trafficking. In this review, we take an in-depth look at the structural–functional domains of CCR7 and CCR7-bearing dendritic cell trajectory to lymph nodes. Then, we summarize the regulatory network of CCR7, including transcriptional regulation, translational and posttranslational regulation, internalization, desensitization, and recycling. Furthermore, the potential strategies of targeting the CCR7 network to regulate dendritic cell migration and to deal with inflammatory diseases are integrated, which not only emphasizes the possibility of CCR7 to be a potential target of immunotherapy but also has an implication on the homing of dendritic cells to benefit inflammatory diseases.

A Pilot Single Cell Analysis of the Zebrafish Embryo Cellular Responses to Uropathogenic Escherichia coli Infection

Background: Uropathogenic Escherichia coli (UPEC) infections are common and when they disseminate can be of high morbidity. Methods: We studied the effects of UPEC infection using single cell RNA sequencing (scRNAseq) in zebrafish. Bulk RNA sequencing has historically been used to evaluate gene expression patterns, but scRNAseq allows gene expression to be evaluated at the single cell level and is optimal for evaluating heterogeneity within cell types and rare cell types. Zebrafish cohorts were injected with either saline or UPEC,and scRNAseq and canonical pathway analyses were performed. Results: Canonical pathway analysis of scRNAseq data provided key information regarding innate immune pathways in the cells determined to be thymus cells, ionocytes, macrophages/monocytes, and pronephros cells. Pathways activated in thymus cells included interleukin 6 (IL-6) signaling and production of reactive oxygen species. Fc receptor-mediated phagocytosis was a leading canonical pathway in the pronephros and macrophages. Genes that were downregulated in UPEC vs saline exposed embryos involved the cellular response to the Gram-negative endotoxin lipopolysaccharide (LPS) and included Forkhead Box O1a (Foxo1a), Tribbles Pseudokinase 3 (Trib3), Arginase 2 (Arg2) and Polo Like Kinase 3 (Plk3). Conclusions: Because 4-day post fertilization zebrafish embryos only have innate immune systems, the scRNAseq provides insights into pathways and genes that cell types utilize in the bacterial response. Based on our analysis, we have identified genes and pathways that might serve as genetic targets for treatment and further investigation in UPEC infections at the single cell level.

Regulation of autoreactive CD4 T cells by FoxO1 signaling in CNS autoimmunity

Myelin-specific CD4 T effector cells (Teffs), Th1 and Th17 cells, are encephalitogenic in experimental autoimmune encephalomyelitis (EAE), a well-defined murine model of multiple sclerosis (MS) and implicated in MS pathogenesis. Forkhead box O 1 (FoxO1) is a conserved effector molecule in PI3K/Akt signaling and critical in the differentiation of CD4 T cells into T helper subsets. However, it is unclear whether FoxO1 may be a target for redirecting CD4 T cell differentiation and benefit CNS autoimmunity. Using a selective FoxO1 inhibitor AS1842856, we show that inhibition of FoxO1 suppressed the differentiation and expansion of Th1 cells. The transdifferentiation of Th17 cells into encephalitogenic Th1-like cells was suppressed by FoxO1 inhibition upon reactivation of myelin-specific CD4 T cells from EAE mice. The transcriptional balance skewed from the Th1 transcription factor T-bet toward the Treg transcription factor Foxp3. Myelin-specific CD4 T cells treated with the FoxO1 inhibitor were less encephalitogenic in adoptive transfer EAE studies. Inhibition of FoxO1 in T cells from MS patients significantly suppressed the expansion of Th1 cells. Furthermore, FoxO1 inhibition with AS1842856 promoted the development of functional iTreg cells. The immune checkpoint programmed cell death protein-1 (PD-1)-induced Foxp3 expression in CD4 T cells was impaired by FoxO1 inhibition. These data illustrate an important role of FoxO1 signaling in CNS autoimmunity via regulating autoreactive Teff and Treg balance.

The Roles of FOXO1 in Periodontal Homeostasis and Disease

Periodontitis is an oral chronic inflammatory disease that is initiated by periodontal microbial communities and requires disruption of the homeostatic responses. The prevalence of periodontal disease increases with age; more than 70% of adults 65 years and older have periodontal disease. A pathogenic microbial community is required for initiating periodontal disease. Dysbiotic immune-inflammatory response and bone remodeling are characteristics of periodontitis. The transcription factor forkhead box protein O1 (FOXO1) is a key regulator of a number of cellular processes, including cell survival and differentiation, immune status, reactive oxygen species (ROS) scavenging, and apoptosis. Although accumulating evidence indicates that FOXO1 activity can be induced by periodontal pathogens, the roles of FOXO1 in periodontal homeostasis and disease have not been well documented. The present review summarizes how the FOXO1 signaling axis can regulate periodontal bacteria-epithelial interactions, immune-inflammatory response, bone remodeling, and wound healing.

Functional crosstalk between myeloid Foxo1-β-catenin axis and Hedgehog/Gli1 signaling in oxidative stress response

Foxo1 transcription factor is an evolutionarily conserved regulator of cell metabolism, oxidative stress, inflammation, and apoptosis. Activation of Hedgehog/Gli signaling is known to regulate cell growth, differentiation, and immune function. However, the molecular mechanisms by which interactive cell signaling networks restrain oxidative stress response and necroptosis are still poorly understood. Here, we report that myeloid-specific Foxo1 knockout (Foxo1^M-KO) mice were resistant to oxidative stress-induced hepatocellular damage with reduced macrophage/neutrophil infiltration, and proinflammatory mediators in liver ischemia/reperfusion injury (IRI). Foxo1^M-KO enhanced β-catenin-mediated Gli1/Snail activity, and reduced receptor-interacting protein kinase 3 (RIPK3) and NIMA-related kinase 7 (NEK7)/NLRP3 expression in IR-stressed livers. Disruption of Gli1 in Foxo1^M-KO livers deteriorated liver function, diminished Snail, and augmented RIPK3 and NEK7/NLRP3. Mechanistically, macrophage Foxo1 and β-catenin colocalized in the nucleus, whereby the Foxo1 competed with T-cell factor (TCF) for interaction with β-catenin under inflammatory conditions. Disruption of the Foxo1–β-catenin axis by Foxo1 deletion enhanced β-catenin/TCF binding, activated Gli1/Snail signaling, leading to inhibited RIPK3 and NEK7/NLRP3. Furthermore, macrophage Gli1 or Snail knockout activated RIPK3 and increased hepatocyte necroptosis, while macrophage RIPK3 ablation diminished NEK7/NLRP3-driven inflammatory response. Our findings underscore a novel molecular mechanism of the myeloid Foxo1–β-catenin axis in regulating Hedgehog/Gli1 function that is key in oxidative stress-induced liver inflammation and necroptosis.

Talin1 controls dendritic cell activation by regulating TLR complex assembly and signaling

Talin critically controls integrin-dependent cell migration, but its regulatory role in skin dendritic cells (DCs) during inflammatory responses has not been investigated. Here, we show that talin1 regulates not only integrin-dependent Langerhans cell (LC) migration, but also MyD88-dependent Toll-like receptor (TLR)-stimulated DC activation. Talin1-deficient LCs failed to exit the epidermis, resulting in reduced LC migration to skin-draining lymph nodes (sdLNs) and defective skin tolerance induction, while talin1-deficient dermal DCs unexpectedly accumulated in the dermis despite their actomyosin-dependent migratory capabilities. Furthermore, talin1-deficient DCs exhibited compromised chemotaxis, NFκB activation, and proinflammatory cytokine production. Mechanistically, talin1 was required for the formation of preassembled TLR complexes in DCs at steady state via direct interaction with MyD88 and PIP5K. Local production of PIP2 by PIP5K then recruited TIRAP to the preassembled complexes, which were required for TLR signalosome assembly during DC activation. Thus, talin1 regulates MyD88-dependent TLR signaling pathways in DCs through a novel mechanism with implications for antimicrobial and inflammatory immune responses.

METTL14 aggravates endothelial inflammation and atherosclerosis by increasing FOXO1 N6-methyladeosine modifications

Aims: The N6-methyladenosine (m⁶A) modification plays an important role in various biological processes, but its role in atherosclerosis remains unknown. The aim of this study was to investigate the role and mechanism of m⁶A modification in endothelial cell inflammation and its influence on atherosclerosis development.

Methods: We constructed a stable TNF-α-induced endothelial cell inflammation model and assessed the changes in the expression of m⁶A modification-related proteins to identify the major factors involved in this process. The m⁶A-modified mRNAs were identified by methylated RNA immunoprecipitation (RIP) sequencing and forkhead box O1 (FOXO1) was selected as a potential target. Through cytological experiments, we verified whether methyltransferase-like 14 (METTL14) regulates FOXO1 expression by regulating m⁶A-dependent mRNA and protein interaction. The effect of METTL14 on atherosclerosis development in vivo was verified using METTL14 knockout mice.

Results: These findings confirmed that METTL14 plays major roles in TNF-α-induced endothelial cell inflammation. During endothelial inflammation, m⁶A modification of FOXO1, an important transcription factor, was remarkably increased. Moreover, METTL14 knockdown significantly decreased TNF-α-induced FOXO1 expression. RIP assay confirmed that METTL14 directly binds to FOXO1 mRNA, increases its m⁶A modification, and enhances its translation through subsequent YTH N6-methyladenosine RNA binding protein 1 recognition. Furthermore, METTL14 was shown to interact with FOXO1 and act directly on the promoter regions of VCAM-1 and ICAM-1 to promote their transcription, thus mediating endothelial cell inflammatory response. In vivo experiments showed that METTL14 gene knockout significantly reduced the development of atherosclerotic plaques.

Conclusion: METTL14 promotes FOXO1 expression by enhancing its m⁶A modification and inducing endothelial cell inflammatory response as well as atherosclerotic plaque formation. Decreased expression of METTL14 can inhibit endothelial inflammation and atherosclerosis development. Therefore, METTL14 may serve as a potential target for the clinical treatment of atherosclerosis.

The tumour microenvironment of the upper and lower gastrointestinal tract differentially influences dendritic cell maturation

Background

Only 10–30% of oesophageal and rectal adenocarcinoma patients treated with neoadjuvant chemoradiotherapy have a complete pathological response. Inflammatory and angiogenic mediators in the tumour microenvironment (TME) may enable evasion of anti-tumour immune responses.

Methods

The TME influence on infiltrating dendritic cells (DCs) was modelled by treating immature monocyte-derived DCs with Tumour Conditioned Media (TCM) from distinct gastrointestinal sites, prior to LPS-induced maturation.

Results

Cell line conditioned media from gastrointestinal cell lines inhibited LPS-induced DC markers and TNF-α secretion. TCM generated from human tumour biopsies from oesophageal, rectal and colonic adenocarcinoma induced different effects on LPS-induced DC markers - CD54, CD80, HLA-DR, CD86 and CD83 were enhanced by oesophageal cancer; CD80, CD86 and CD83 were enhanced by rectal cancer, whereas CD54, HLA-DR, CD86, CD83 and PD-L1 were inhibited by colonic cancer. Notably, TCM from all GI cancer types inhibited TNF-α secretion. Additionally, TCM from irradiated biopsies inhibited DC markers. Profiling the TCM showed that IL-2 levels positively correlated with maturation marker CD54, while Ang-2 and bFGF levels negatively correlated with CD54.

Conclusion

This study identifies that there are differences in DC maturational capacity induced by the TME of distinct gastrointestinal cancers. This could potentially have implications for anti-tumour immunity and response to radiotherapy.

FOXO3 Transcription Factor Regulates IL-10 Expression in Mycobacteria-Infected Macrophages, Tuning Their Polarization and the Subsequent Adaptive Immune Response

Alveolar Macrophages play a key role in the development of a robust adaptive immune response against the agent of Tuberculosis (TB), Mycobacterium tuberculosis (M.tb). However, macrophage response is often hampered by the production of IL-10, a potent suppressor of the host immune response. The secretion of IL-10 correlates with TB pathogenesis and persistence in host tissues. Concordantly, inhibition of IL-10 signaling, during BCG vaccination, confers higher protection against M.tb through a sustained Th1 and Th17 responses. Therefore, uncovering host effectors, underlying mycobacteria-induced expression of IL-10, may be beneficial toward the development of IL-10-blocking tools to be used either as adjuvants in preventive vaccination or as adjunct during standard treatment of TB. Here, we investigated the role of FOXO3 transcription factor in mycobacteria-induced secretion of IL-10. We observed that PI3K/Akt/FOXO3 axis regulates IL-10 expression in human macrophages. Knocking down of FOXO3 expression resulted in an increase of IL-10 production in BCG-infected macrophages. The gene reporter assay further confirmed the transcriptional regulation of IL-10 by FOXO3. In silico analysis identified four Forkhead binding motifs on the human IL-10 promoter, from which the typical FOXO3 one at position -203 was the major target as assessed by mutagenesis and CHIP binding assays. Further, we also observed a decrease in gene expression levels of the M1 typical markers (i.e., CD80 and CD86) in SiFOXO3-transfected macrophages while activation of FOXO3 led to the increase in the expression of CD86, MHCI, and MHCII. Finally, co-culture of human lymphocytes with siFOXO3-transfected macrophages, loaded with mycobacterial antigens, showed decreased expression of Th1/Th17 specific markers and a simultaneous increase in expression of IL-4 and IL-10. Taken together, we report for the first time that FOXO3 modulates IL-10 secretion in mycobacteria-infected macrophage, driving their polarization and the subsequent adaptive immune response. This work proposes FOXO3 as a potential target for the development of host-directed strategies for better treatment or prevention of TB.

Mucosal Immunity and the FOXO1 Transcription Factors

FOXO1 transcription factors affect a number of cell types that are important in the host response. Cell types whose functions are modulated by FOXO1 include keratinocytes in the skin and mucosal dermis, neutrophils and macrophages, dendritic cells, Tregs and B-cells. FOXO1 is activated by bacterial or cytokine stimulation. Its translocation to the nucleus and binding to promoter regions of genes that have FOXO response elements is stimulated by the MAP kinase pathway and inhibited by the PI3 kinase/AKT pathway. Downstream gene targets of FOXO1 include pro-inflammatory signaling molecules (TLR2, TLR4, IL-1β, and TNF-α), wound healing factors (TGF-β, VEGF, and CTGF) adhesion molecules (integrins-β1, -β3, -β6, α_vβ₃, CD11b, CD18, and ICAM-1), chemokine receptors (CCR7 and CXCR2), B cell regulators (APRIL and BLYS), T-regulatory modulators (Foxp3 and CTLA-4), antioxidants (GPX-2 and cytoglobin), and DNA repair enzymes (GADD45α). Each of the above cell types are found in oral mucosa and modulated by bacteria or an inflammatory microenvironment. FOXO1 contributes to the regulation of these cells, which collectively maintain and repair the epithelial barrier, formation and activation of Tregs that are needed to resolve inflammation, mobilization, infiltration, and activation of anti-bacterial defenses in neutrophils, and the homing of dendritic cells to lymph nodes to induce T-cell and B-cell responses. The goal of the manuscript is to review how the transcription factor, FOXO1, contributes to the activation and regulation of key leukocytes needed to maintain homeostasis and respond to bacterial challenge in oral mucosal tissues. Examples are given with an emphasis on lineage specific deletion of Foxo1 to explore the impact of FOXO1 on cell behavior, inflammation and susceptibility to infection.

Differential Control of iNKT Cell Effector Lineage Differentiation by the Forkhead Box Protein O1 (Foxo1) Transcription Factor

The invariant NKT (iNKT) cells recognize glycolipid antigens presented by the non-classical MHC like molecule CD1d. They represent an innate T-cell lineage with the ability to rapidly produce a variety of cytokines in response to agonist stimulation to bridge innate and adaptive immunity. In thymus, most iNKT cells complete their maturation and differentiate to multiple effector lineages such as iNKT-1, iNKT-2, and iNKT-17 cells that possess the capability to produce IFNγ, IL-4, and IL-17A, respectively, and play distinct roles in immune responses and diseases. Mechanisms that control iNKT lineage fate decisions are still not well understood. Evidence has revealed critical roles of Foxo1 of the forkhead box O1 subfamily of transcription factors in the immune system. However, its role in iNKT cells has been unknown. In this report, we demonstrate that deletion of Foxo1 causes severe decreases of iNKT cell total numbers due to impairment of late but not early iNKT cell development. Deficiency of Foxo1 results in decreases of iNKT-1 but increases of iNKT-17 cells. Our data reveal that Foxo1 controls iNKT effector lineage fate decision by promoting iNKT-1 but suppressing iNKT-17 lineages.

Forkhead transcription factor FOXO3a mediates interferon-γ-induced MHC II transcription in macrophages

Macrophages are professional antigen-presenting cells relying on the expression of class II major histocompatibility complex (MHC II) genes. Interferon-γ (IFN-γ) activates MHC II transcription via the assembly of an enhanceosome centred on class II trans-activator (CIITA). In the present study, we investigated the role of the forkhead transcription factor FOXO3a in IFN- γ-induced MHC II transcription in macrophages. Knockdown of FOXO3a, but not FOXO1 or FOXO4, diminished IFN-γ-induced MHC II expression in RAW cells. On the contrary, over-expression of FOXO3a, but neither FOXO1 nor FOXO4, enhanced CIITA-mediated trans-activation of the MHC II promoter. IFN-γ treatment promoted the recruitment of FOXO3a to the MHC II promoter. Co-immunoprecipitation and RE-ChIP assays showed that FOXO3a was a component of the MHC II enhanceosome forming interactions with CIITA, RFX5, RFXB and RFXAP. FOXO3a contributed to MHC II transcription by altering histone modifications surrounding the MHC II promoter. Of interest, FOXO3a was recruited to the type IV CIITA promoter and directly activated CIITA transcription by interacting with signal transducer of activation and transcription 1 in response to IFN-γ stimulation. In conclusion, our data unveil a novel role for FOXO3a in the regulation of MHC II transcription in macrophages.

CD16+ monocytes give rise to CD103+RALDH2+TCF4+ dendritic cells with unique transcriptional and immunological features

Classical CD16^- vs intermediate/nonclassical CD16⁺ monocytes differ in their homing potential and biological functions, but whether they differentiate into dendritic cells (DCs) with distinct contributions to immunity against bacterial/viral pathogens remains poorly investigated. Here, we employed a systems biology approach to identify clinically relevant differences between CD16⁺ and CD16^- monocyte-derived DCs (MDDCs). Although both CD16⁺ and CD16^- MDDCs acquire classical immature/mature DC markers in vitro, genome-wide transcriptional profiling revealed unique molecular signatures for CD16⁺ MDDCs, including adhesion molecules (ITGAE/CD103), transcription factors (TCF7L2/TCF4), and enzymes (ALDH1A2/RALDH2), whereas CD16^- MDDCs exhibit a CDH1/E-cadherin⁺ phenotype. Of note, lipopolysaccharides (LPS) upregulated distinct transcripts in CD16⁺ (eg, CCL8, SIGLEC1, MIR4439, SCIN, interleukin [IL]-7R, PLTP, tumor necrosis factor [TNF]) and CD16^- MDDCs (eg, MMP10, MMP1, TGM2, IL-1A, TNFRSF11A, lysosomal-associated membrane protein 1, MMP8). Also, unique sets of HIV-modulated genes were identified in the 2 subsets. Further gene set enrichment analysis identified canonical pathways that pointed to "inflammation" as the major feature of CD16⁺ MDDCs at immature stage and on LPS/HIV exposure. Finally, functional validations and meta-analysis comparing the transcriptome of monocyte and MDDC subsets revealed that CD16⁺ vs CD16^- monocytes preserved their superior ability to produce TNF-α and CCL22, as well as other sets of transcripts (eg, TCF4), during differentiation into DC. These results provide evidence that monocyte subsets are transcriptionally imprinted/programmed with specific differentiation fates, with intermediate/nonclassical CD16⁺ monocytes being precursors for pro-inflammatory CD103⁺RALDH2⁺TCF4⁺ DCs that may play key roles in mucosal immunity homeostasis/pathogenesis. Thus, alterations in the CD16⁺ /CD16^- monocyte ratios during pathological conditions may dramatically influence the quality of MDDC-mediated immunity.

PU.1 plays a pivotal role in dendritic cell migration from the periphery to secondary lymphoid organs via regulating CCR7 expression

C-C chemokine receptor type 7 (CCR7) is essential for migration of dendritic cells (DCs) to draining lymph nodes. PU.1/Spi1 is a transcription factor playing a critical role in the gene regulation of DCs. PU.1 knockdown decreased the expression of CCR7 in bone marrow-derived DCs and subsequently attenuated migration in vitro and in vivo. Reporter assays, EMSA, and chromatin immunoprecipitation assays revealed that PU.1 binds to the most proximal Ets motif of the Ccr7 promoter, which is involved in transcriptional activation. The CCR7 expression level, which was higher in the programmed cell death 1 ligand 2 (PD-L2)⁺ population than in the PD-L2^- population and was markedly suppressed by TGF-β treatment, coincided with the binding level of PU.1 to the Ccr7 promoter. The PU.1 binding level in CCR7^high mesenteric lymph nodes DCs was higher than in other DC subtypes. The involvement of PU.1 in the expression of the CCR7 gene was also observed in human DCs. We conclude that PU.1 plays a pivotal role in DC migration by transactivating the CCR7 gene via the Ets motif in the promoter in both humans and mice.-Yashiro, T., Takeuchi, H., Nakamura, S., Tanabe, A., Hara, M., Uchida, K., Okumura, K., Kasakura, K., Nishiyama, C. PU.1 plays a pivotal role in dendritic cell migration from the periphery to secondary lymphoid organs via regulating CCR7 expression.

The Role of Forkhead Box 1 (FOXO1) in the Immune System: Dendritic Cells, T Cells, B Cells, and Hematopoietic Stem Cells

Forkhead box-O (FOXO) transcription factors have a fundamental role in the development and differentiation of immune cells. FOXO1 and FOXO3 are FOXO members that are structurally similar and bind to the same conserved consensus DNA sequences to induce transcription. FOXO1 has been studied in detail in the activation of dendritic cells (DCs), where it plays an important role through the regulation of target genes such as ICAM-1, CCR7, and the integrin αvβ3. FOXO1 is activated by bacteria challenge in DCs and promotes DC bacterial phagocytosis, migration, homing to lymph nodes, DC stimulation of CD4+ T cells and resting B cells, and antibody production. Deletion of FOXO1 in DCs enhances susceptibility to bacteria-induced periodontal disease. FOXO1 and FOXO3 maintain naive T cell quiescence and survival. FOXO1 and FOXO3 enhance the formation of regulatory T cells and inhibit the formation of T-helper 1 (Th1) and Th17 cells. FOXO1 promotes differentiation, proliferation, survival, immunoglobulin gene rearrangement, and class switching in B cells, but FOXO3 has little effect. Both FOXO1 and FOXO3 are important in the maintenance of hematopoietic stem cells by protecting them from oxidative stress. This review examines FOXO1/FOXO3 in the adaptive immune response, key target genes, and FOXO inhibition by the phosphoinositide 3-kinase/AKT pathway.

Targeting PIM Kinase with PD1 Inhibition Improves Immunotherapeutic Antitumor T-cell Response

PURPOSE

Adoptive T-cell therapy (ACT) of cancer, which involves the infusion of ex vivo-engineered tumor epitope reactive autologous T cells into the tumor-bearing host, is a potential treatment modality for cancer. However, the durable antitumor response following ACT is hampered either by loss of effector function or survival of the antitumor T cells. Therefore, strategies to improve the persistence and sustain the effector function of the antitumor T cells are of immense importance. Given the role of metabolism in determining the therapeutic efficacy of T cells, we hypothesize that inhibition of PIM kinases, a family of serine/threonine kinase that promote cell-cycle transition, cell growth, and regulate mTORC1 activity, can improve the potency of T cells in controlling tumor.

EXPERIMENTAL DESIGN

The role of PIM kinases in T cells was studied either by genetic ablation (PIM1^-/-PIM2^-/-PIM3^-/-) or its pharmacologic inhibition (pan-PIM kinase inhibitor, PimKi). Murine melanoma B16 was established subcutaneously and treated by transferring tumor epitope gp100-reactive T cells along with treatment regimen that involved inhibiting PIM kinases, anti-PD1 or both.

RESULTS

With inhibition of PIM kinases, T cells had significant reduction in their uptake of glucose, and upregulated expression of memory-associated genes that inversely correlate with glycolysis. In addition, the expression of CD38, which negatively regulates the metabolic fitness of the T cells, was also reduced in PimKi-treated cells. Importantly, the efficacy of antitumor T-cell therapy was markedly improved by inhibiting PIM kinases in tumor-bearing mice receiving ACT, and further enhanced by adding anti-PD1 antibody to this combination.

CONCLUSIONS

This study highlights the potential therapeutic significance of combinatorial strategies where ACT and inhibition of signaling kinase with checkpoint blockade could improve tumor control.

Effect of miR-182 on hepatic fibrosis induced by Schistosomiasis japonica by targeting FOXO1 through PI3K/AKT signaling pathway

The study aimed to investigate the impact of miR-182 and FOXO1 on S. japonica-induced hepatic fibrosis. Microarray analysis was performed to screen out differential expressed miRNAs and mRNAs. Rat hepatic fibrosis model and human hepatocellular cell line LX-2 were used to study the effect of miR-182 and FOXO1. qRT-PCR and Western blot were used to detect the expression of miR-182, FOXO1 or other fibrosis markers. The targeting relationship between FOXO1 and miR-182 was verified by luciferase reporter assay. Immunohistochemistry or immunofluorescence staining was conducted to detect FOXO1 or α-SMA in rat hepatic tissues. Cell viability and apoptosis were detected by MTT assay and flow cytometry. The expression of PI3K/AKT pathway-related proteins was detected by Western blot. miR-182 was highly expressed in liver fibrosis samples, and FOXO1 expression was negatively correlated with miR-182 expression. After transfection of miR-182, FOXO1 expression was down-regulated, with the results of LX-2 cells proliferation inhibition and apoptosis induction, as well as the aggravation of rat hepatic fibrosis. The expression of p-AKT/AKT and p-S6/S6 was increased, meaning that the PI3K/AKT signal pathway was activated. The results were reversed when treated with Wortmannin (PI3K inhibitor). After transfection of miR-182 inhibitor, FOXO1 expression was up-regulated, LX-2 cell proliferation was inhibited, and apoptosis rate was increased. High-expressed miR-182 and low-expressed FOXO1 promoted proliferation and inhibiting apoptosis on liver fibrosis cells, stimulating the development of S. japonica-induced hepatic fibrosis through feeding back to PI3K/AKT signaling pathway.

The invariant natural killer T cell-mediated chemokine X-C motif chemokine ligand 1-X-C motif chemokine receptor 1 axis promotes allergic airway hyperresponsiveness by recruiting CD103+ dendritic cells

BACKGROUND

The chemokine X-C motif chemokine ligand 1 (XCL1)-X-C motif chemokine receptor 1 (XCR1) axis has been reported to play a role in immune homeostasis and inflammation. However, it is not known whether this axis has a critical function in patients with allergic asthma.

OBJECTIVE

In the present study we explored whether the invariant natural killer T (iNKT) cell-mediated XCL1-XCR1 axis regulated allergic asthma.

METHODS

Ovalbumin (OVA)- or house dust mite-induced asthma was developed in XCL1 or XCR1 knockout (KO) mice.

RESULTS

XCL1 or XCR1 KO mice showed attenuation in airway hyperresponsiveness (AHR), numbers of CD103⁺ dendritic cells (DCs), and T_H2 responses in the lungs compared with wild-type (WT) mice during OVA- or house dust mite-induced asthma. These effects were reversed by intratracheal administration of recombinant XCL1 or adoptive transfer of CD103⁺ DCs but not CD11b⁺ DCs into XCL1 KO mice. Moreover, iNKT cells highly expressed XCL1 both in vitro and in vivo. On intranasal α-galactosyl ceramide challenge, CD103⁺ DC numbers in the lungs were increased in WT but not XCL1 KO mice. Furthermore, adoptive transfer of WT iNKT cells increased AHR, CD103⁺ DC recruitment, and T_H2 responses in the lungs of CD1d KO mice during OVA-induced asthma, whereas adoptive transfer of XCL1-deficient iNKT cells did not. In human patients, percentages and XCL1 production capacity of iNKT cells from PBMCs were greater in patients with asthma than in healthy control subjects.

CONCLUSION

These data demonstrate that the iNKT cell-mediated XCL1-XCR1 axis promotes AHR by recruiting CD103⁺ DCs into the lung in patients with allergic asthma.

FOXOs in cancer immunity: Knowns and unknowns

In the tumor microenvironment (TME), cancer cells, stromal cells, and immune cells, along with their extracellular factors, have profound effects on either promoting or repressing anti-cancer immunity. Accumulating evidence has shown the paradoxical intrinsic role of the Forkhead box O (FOXO) family of transcription factors in cancer, which can act as a tumor repressor while also maintaining cancer stem cells. FOXOs also regulate cancer immunity. FOXOs promote antitumor activity through negatively regulating the expression of immunosuppressive proteins, such as programmed death 1 ligand 1 (PD-L1), and vascular endothelial growth factor (VEGF) in tumor cells or stromal cells, which can shape an immunotolerant state in the TME. FOXOs also intrinsically control the anti-tumor immune response as well as the homeostasis and development of immune cells, including T cells, B cells, natural killer (NK) cells, macrophages, and dendritic cells. As a cancer repressor, reviving the activity of Foxo1 forces tumor-infiltrating activated regulatory T (T_reg) cells to egress from tumor tissues. As a promoter of cancer development, Foxo3 and Foxo1 negatively regulate cytotoxicity of both CD8⁺ T cells and NK cells against tumor cells. In this review, we focus on the complex role of FOXOs in regulating cancer immunity due to the various roles that they play in cancer cells, stromal cells, and immune cells. We also speculate on some possible additional roles of FOXOs in cancer immunity based on findings regarding FOXOs in non-cancer settings, such as infectious disease.

The function of dendritic cells in modulating the host response

Dendritic cells (DCs) are antigen-presenting cells that capture, process, and present antigens to lymphocytes to initiate and regulate the adaptive immune response. DCs detect bacteria in skin and mucosa and migrate into regional lymph nodes, where they stimulate antigen-specific T and B lymphocyte activation and proliferation. DCs direct CD4 T cells to differentiate to T-cell subsets such as T helper cells types 1, 2, and 17, and regulatory T cells. The periodontium is chronically exposed to oral bacteria that stimulate an inflammatory response to induce gingivitis or periodontitis. DCs play both protective and destructive roles through activation of the acquired immune response and are also reported to be a source of osteoclast precursors that promote bone resorption. FOXO1, a member of the forkhead box O family of transcription factors, plays a significant role in the activation of DCs. The function of DCs in periodontal inflammation has been investigated in a mouse model by lineage-specific deletion of FOXO1 in these cells. Deletion of FOXO1 reduces DC protective function and enhances susceptibility to periodontitis. The kinase Akt, phosphorylates FOXO1 to inhibit FOXO activity. Hence the Akt-FOXO1 axis may play a key role in regulating DCs to have a significant impact on periodontal disease.

FOXO1 Regulates Bacteria-Induced Neutrophil Activity

Neutrophils play an essential role in the innate immune response to microbial infection and are particularly important in clearing bacterial infection. We investigated the role of the transcription factor FOXO1 in the response of neutrophils to bacterial challenge with Porphyromonas gingivalis in vivo and in vitro. In these experiments, the effect of lineage-specific FOXO1 deletion in LyzM.Cre⁺FOXO1^L/L mice was compared with matched littermate controls. FOXO1 deletion negatively affected several critical aspects of neutrophil function in vivo including mobilization of neutrophils from the bone marrow (BM) to the vasculature, recruitment of neutrophils to sites of bacterial inoculation, and clearance of bacteria. In vitro FOXO1 regulated neutrophil chemotaxis and bacterial killing. Moreover, bacteria-induced expression of CXCR2 and CD11b, which are essential for several aspects of neutrophil function, was dependent on FOXO1 in vivo and in vitro. Furthermore, FOXO1 directly interacted with the promoter regions of CXCR2 and CD11b. Bacteria-induced nuclear localization of FOXO1 was dependent upon toll-like receptor (TLR) 2 and/or TLR4 and was significantly reduced by inhibitors of reactive oxygen species (ROS and nitric oxide synthase) and deacetylases (Sirt1 and histone deacetylases). These studies show for the first time that FOXO1 activation by bacterial challenge is needed to mobilize neutrophils to transit from the BM to peripheral tissues in response to infection as well as for bacterial clearance in vivo. Moreover, FOXO1 regulates neutrophil function that facilitates chemotaxis, phagocytosis, and bacterial killing.

Absence of miR-182 Augments Cardiac Allograft Survival

BACKGROUND

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate the posttranscriptional expression of target genes and are important regulators in immune responses. Previous studies demonstrated that the miRNA, miR-182 was significantly increased during allograft rejection. Further, the transcription factor Forkhead box (FOX) protein 1, (FOXO1) was shown to be a target of miR-182. The aim of this study is to further examine the role of miR-182 in alloimmune responses.

METHODS

Transplantation of BALB/c cardiac allografts was performed in C57BL/6, miR-182, B6.129S-H2 (MHC II and CD4 T cell-deficient) and B6.129S2-Tap1 (MHC I and CD8 T cell-deficient) mice, with or without CTLA-4Ig administration. T cell phenotype, FOXO1 protein levels and graft infiltrating lymphocytes were determined in C57BL/6 or miR-182 mice by flow cytometric analysis, Western blot, and immunohistochemistry, respectively.

RESULTS

We now show that T cells, mainly CD4 are the main cellular source of miR-182 during allograft rejection. In the absence of miR-182, CTLA-4Ig treatment significantly increased allograft survival (31.5 days C57BL/6 vs 60 days miR-182; P < 0.01). Further, CTLA4-Ig treatment inhibits miR-182 expression, increases FOXO1 levels, and reduces the percentage of CD4CD44 T cells after transplantation. Fewer T cells infiltrate the cardiac allografts, and memory T cells are significantly decreased in allograft recipients deficient in miR-182 with CTLA4-Ig treatment (P < 0.01).

CONCLUSIONS

Our findings suggest that miR-182 contributes to the T-cell responses to alloantigen especially under costimulation blockade. Therapeutics that target specific miRNAs may prove beneficial in transplantation.

The transcription factor NR4A3 controls CD103+ dendritic cell migration

The transcription factor NR4A3 (also known as NOR-1) is a member of the Nr4a family of nuclear receptors and is expressed in myeloid and lymphoid cells. Here, we have shown that Nr4a3 is essential for the migration of CD103+ dendritic cells (DCs) to lymph nodes (LNs). Nr4a3-deficient mice had very few CD103+ migratory DCs (mDCs) present in LNs, and mixed-chimera studies revealed that this migratory defect was cell intrinsic. We further found that CD103+ DCs from Nr4a3-deficient mice displayed a marked loss of surface expression of the chemokine CCR7. This defect in CCR7 expression was confined to CD103+ DCs, as CCR7 expression on T lymphocytes was unaffected. Moreover, CCR7 was not induced on CD103+ DCs from Nr4a3-deficient mice in response to either administration of the TLR7 agonist R848 or infection with Citrobacter rodentium in vivo. The transcription factor FOXO1 has been shown to regulate CCR7 expression. We found that FOXO1 protein was reduced in Nr4a3-deficient DCs through an AKT-dependent mechanism. Further, we found a requirement for NR4A3 in the maintenance of homeostatic mitochondrial function in CD103+ DCs, although this is likely independent of the NR4A3/FOXO1/CCR7 axis in the regulation of DC migration. Thus, NR4A3 plays an important role in the regulation of CD103+ mDCs by regulating CCR7-dependent cell migration.

Effect of Aging on Periodontal Inflammation, Microbial Colonization, and Disease Susceptibility

Periodontitis is a chronic inflammatory disease induced by a biofilm that forms on the tooth surface. Increased periodontal disease is associated with aging. We investigated the effect of aging on challenge by oral pathogens, examining the host response, colonization, and osteoclast numbers in aged versus young mice. We also compared the results with mice with lineage-specific deletion of the transcription factor FOXO1, which reduces dendritic cell (DC) function. Periodontitis was induced by oral inoculation of Porphyromonas gingivalis and Fusobacterium nucleatum in young (4 to 5 mo) and aged (14 to 15 mo) mice. Aged mice as well as mice with reduced DC function had decreased numbers of DCs in lymph nodes, indicative of a diminished host response. In vitro studies suggest that reduced DC numbers in lymph nodes of aged mice may involve the effect of advanced glycation end products on DC migration. Surprisingly, aged mice but not mice with genetically altered DC function had greater production of antibody to P. gingivalis, greater IL-12 expression, and more plasma cells in lymph nodes following oral inoculation as compared with young mice. The greater adaptive immune response in aged versus young mice was linked to enhanced levels of P. gingivalis and reduced bacterial diversity. Thus, reduced bacterial diversity in aged mice may contribute to increased P. gingivalis colonization following inoculation and increased periodontal disease susceptibility, reflected by higher TNF levels and osteoclast numbers in the periodontium of aged versus young mice.