Enhancement of lymphocyte migration and cytokine production by ephrinB1 system in rheumatoid arthritis

Ephs in cancer progression: complexity and context-dependent nature in signaling, angiogenesis and immunity

Eph receptors constitute the largest family of receptor tyrosine kinases, comprising 14 distinct members classified into two subgroups: EphAs and EphBs.. Despite their essential functions in normal physiological processes, accumulating evidence suggests that the involvement of the Eph family in cancer is characterized by a dual and often contradictory nature. Research indicates that Eph/ephrin bidirectional signaling influences cell-cell communication, subsequently regulating cell migration, adhesion, differentiation and proliferation. The contradictory functionalities may arise from the diversity of Eph signaling pathways and the heterogeneity of different cancer microenvironment. In this review, we aim to discuss the dual role of the Eph receptors in tumor development, attempting to elucidate the paradoxical functionality through an exploration of Eph receptor signaling pathways, angiogenesis, immune responses, and more. Our objective is to provide a comprehensive understanding of the molecular mechanisms underlying tumor development. Additionally, we will explore the evolving landscape of utilizing Eph receptors as potential targets for tumor therapy and diagnostic tools.

Peripheral T-cell responses of EphB2- and EphB3-deficient mice in a model of collagen-induced arthritis

Both EphB2- and EphB3-deficient mice exhibit profound histological alterations in the thymic epithelial network but few changes in T-cell differentiation, suggesting that this organization would be sufficient to produce functional T lymphocytes. Also, other antigen-presenting cells involved in immunological education could substitute the thymic epithelium. Accordingly, we found an increased frequency of plasmacytoid dendritic cells but not of conventional dendritic cells, medullary fibroblasts or intrathymic B lymphocytes. In addition, there are no lymphoid infiltrates in the organs of mutant mice nor do they contain circulating autoantibodies. Furthermore, attempts to induce arthritic lesions after chicken type II collagen administration fail totally in EphB2-deficient mice whereas all WT and half of the immunized EphB3-/- mice develop a typical collagen-induced arthritis. Our results point out that Th17 cells, IL4-producing Th2 cells and regulatory T cells are key for the induction of disease, but mutant mice appear to have deficits in T cell activation or cell migration properties. EphB2-/- T cells show reduced in vitro proliferative responses to anti-CD3/anti-CD28 antibodies, produce low levels of anti-type II collagen antibodies, and exhibit low proportions of T follicular helper cells. On the contrary, EphB3-/- lymph node cells respond accurately to the different immune stimuli although in lower levels than WT cells but show a significantly reduced migration in in vitro transwell assays, suggesting that no sufficient type II collagen-dependent activated lymphoid cells reached the joints, resulting in reduced arthritic lesions.

EphB1 promotes the differentiation and maturation of dendritic cells in non-small cell lung cancer

EphB1 is implicated in numerous physiological and pathological processes, including nervous system diseases, cardiovascular diseases and cancers. It binds to membrane-bound ligands and drives bidirectional signaling. EphB1, along with its ligand ehrinB, plays a pivotal role in activating immune cells. However, despite its presence in dendritic cells (DCs), EphB1's involvement in the differentiation and maturation of DCs in cancers remains inadequately understood. In this study, we found compromised differentiation and maturation of DCs in EphB1-/- mice bearing lung adenocarcinoma syngeneic tumors. Our in vitro assays revealed that EphB1 phosphorylation induced DC differentiation and maturation. Cox-2, a key enzyme involved in the production of proinflammatory molecules, is implicated in DC differentiation induced by phosphorylated EphB1. Additionally, the study has identified lead compounds that specifically target EphB1 phosphorylation sites. Collectively, this research on EphB1 phosphorylation has provided valuable insights into the regulation of immune cell functionality and holds the potential for the development of innovative therapeutic strategies for a range of diseases.

Eph-Ephrin Signaling Mediates Cross-Talk Within the Bone Microenvironment

Skeletal integrity is maintained through the tightly regulated bone remodeling process that occurs continuously throughout postnatal life to replace old bone and to repair skeletal damage. This is maintained primarily through complex interactions between bone resorbing osteoclasts and bone forming osteoblasts. Other elements within the bone microenvironment, including stromal, osteogenic, hematopoietic, endothelial and neural cells, also contribute to maintaining skeletal integrity. Disruption of the dynamic interactions between these diverse cellular systems can lead to poor bone health and an increased susceptibility to skeletal diseases including osteopenia, osteoporosis, osteoarthritis, osteomalacia, and major fractures. Recent reports have implicated a direct role for the Eph tyrosine kinase receptors and their ephrin ligands during bone development, homeostasis and skeletal repair. These membrane-bound molecules mediate contact-dependent signaling through both the Eph receptors, termed forward signaling, and through the ephrin ligands, referred to as reverse signaling. This review will focus on Eph/ ephrin cross-talk as mediators of hematopoietic and stromal cell communication, and how these interactions contribute to blood/ bone marrow function and skeletal integrity during normal steady state or pathological conditions.

Ephs and Ephrins in Adult Endothelial Biology

Eph receptors and their ephrin ligands are important guidance molecules during neurological and vascular development. In recent years, it has become clear that the Eph protein family remains functional in adult physiology. A subset of Ephs and ephrins is highly expressed by endothelial cells. As endothelial cells form the first barrier between the blood and surrounding tissues, maintenance of a healthy endothelium is crucial for tissue homeostasis. This review gives an overview of the current insights of the role of ephrin ligands and receptors in endothelial function and leukocyte recruitment in the (patho)physiology of adult vascular biology.

Novel biomarkers of a peripheral blood interferon signature associated with drug-naïve early arthritis patients distinguish persistent from self-limiting disease course

We profiled gene expression signatures to distinguish rheumatoid arthritis (RA) from non-inflammatory arthralgia (NIA), self-limiting arthritis (SLA), and undifferentiated arthritis (UA) as compared to healthy controls as novel potential biomarkers for therapeutic responsiveness. Global gene expression profiles of PBMCs from 43 drug-naïve patients presenting with joint symptoms were evaluated and differentially expressed genes identified by comparative analysis with 24 healthy volunteers. Patients were assessed at presentation with follow up at 6 and 12 months. Gene ontology and network pathway analysis were performed using DAVID Bioinformatics Resources v6.7. Gene expression profiles were also determined after disease-modifying anti-rheumatic drug (DMARD) treatment in the inflammatory arthritis groups (i.e. RA and UA) and confirmed by qRT-PCR. Receiver operating characteristic (ROC) curves analysis and Area Under the Curve (AUC) estimation were performed to assess the diagnostic value of candidate gene expression signatures. A type I interferon (IFN) gene signature distinguished DMARD-naïve patients who will subsequently develop persistent inflammatory arthritis (i.e. RA and UA) from those with NIA. In patients with RA, the IFN signature is characterised by up-regulation of SIGLEC1 (p = 0.00597) and MS4A4A (p = 0.00000904). We also identified, EPHB2 (p = 0.000542) and PDZK1IP1 (p = 0.0206) with RA-specific gene expression profiles and elevated expression of the ST6GALNAC1 (p = 0.0023) gene in UA. ROC and AUC risk score analysis suggested that MSA4A (AUC: 0.894, 0.644, 0.720), PDZK1IP1 (AUC: 0.785, 0.806, 0.977), and EPHB2 (AUC: 0.794, 0.723, 0.620) at 0, 6, and 12 months follow-up can accurately discriminate patients with RA from healthy controls and may have practical value for RA diagnosis. In patients with early inflammatory arthritis, ST6GALNAC1 is a potential biomarker for UA as compared with healthy controls whereas EPHB2, MS4A4A, and particularly PDZK1IP1 may discriminate RA patients. SIGLEC1 may also be a useful marker of disease activity in UA.

EPH receptor B2 stimulates human monocyte adhesion and migration independently of its EphrinB ligands

The molecular basis of atherosclerosis is not fully understood and mice studies have shown that Ephrins and EPH receptors play a role in the atherosclerotic process. We set out to assess the role for monocytic EPHB2 and its Ephrin ligands in human atherosclerosis and show a role for EPHB2 in monocyte functions independently of its EphrinB ligands. Immunohistochemical staining of human aortic sections at different stages of atherosclerosis showed that EPHB2 and its ligand EphrinB are expressed in atherosclerotic plaques and that expression proportionally increases with plaque severity. Functionally, stimulation with EPHB2 did not affect endothelial barrier function, nor did stimulation with EphrinB1 or EphrinB2 affect monocyte‐endothelial interactions. In contrast, reduced expression of EPHB2 in monocytes resulted in decreased monocyte adhesion to endothelial cells and a decrease in monocyte transmigration, mediated by an altered morphology and a decreased ability to phosphorylate FAK. Our results suggest that EPHB2 expression in monocytes results in monocyte accumulation by virtue of an increase of transendothelial migration, which can subsequently contribute to atherosclerotic plaque progression.

Emerging Roles for Eph Receptors and Ephrin Ligands in Immunity

Eph receptors are the largest family of receptor tyrosine kinases and mediate a myriad of essential processes in humans from embryonic development to adult tissue homeostasis through interactions with membrane-bound ephrin ligands. The ubiquitous expression of Eph receptors and ephrin ligands among the cellular players of the immune system underscores the importance of these molecules in orchestrating an optimal immune response. This review provides an overview of the various roles of Eph receptors and ephrin ligands in immune cell development, activation, and migration. We also discuss the role of Eph receptors in disease pathogenesis as well as the implications of Eph receptors as future immunotherapy targets. Given the diverse and critical roles of Eph receptors and ephrin ligands throughout the immune system during both resting and activated states, this review aims to highlight the critical yet underappreciated roles of this family of signaling molecules in the immune system.

MALAT1-Driven Inhibition of Wnt Signal Impedes Proliferation and Inflammation in Fibroblast-Like Synoviocytes Through CTNNB1 Promoter Methylation in Rheumatoid Arthritis

Fibroblast-like synoviocytes (FLSs) participate in the pathogenesis of rheumatoid arthritis (RA). Emerging evidence has highlighted the role of long non-coding RNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) and its potential involvement in RA. In this study, we test the hypothesis that the MALAT1 might inhibit proliferation and inflammatory response of FLSs in RA. The expression of MALAT1 was examined in synovial tissues from patients with RA. The effect of MALAT1 on cultured FLSs was analyzed by introducing overexpressed MALAT1 or short hairpin RNA (shRNA) against MALAT1. To validate whether methylation of CTNNB1 promoter was affected by MALAT1 alternation, we assessed the recruitment of DNA methyltransferases to CTNNB1 promoter. In cultured FLSs with shRNA-mediated CTNNB1 knockdown or activated Wnt signaling, we found the interaction between CTNNB1 and Wnt signaling. MALAT1 expression was reduced in synovial tissues of RA. MALAT1 could bind to CTNNB1 promoter region and recruit methyltransferase to promote CTNNB1 promoter methylation, thereby inhibiting CTNNB1. Notably, MALAT1 could suppress the transcription and expression of CTNNB1, thereby modulating the Wnt signaling pathway. Silenced MALAT1 stimulated the nucleation of β-catenin and the secretion of inflammatory cytokines including interleukin-6, interleukin-10, and tumor necrosis factor-α. Additionally, shRNA-mediated MALAT1 silencing elevated proliferation and suppressed apoptosis of FLSs accompanied. These findings provide evidence for the inhibitory effect of MALAT1 on proliferation and inflammation of FLSs by promoting CTNNB1 promoter methylation and inhibiting the Wnt signaling pathway. Therefore, this study provides a candidate therapeutic target for RA.

Chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating expression of ephrin-B1

Advanced solid tumors are exposed to hypoxic conditions over longer periods of time as they grow. Tumor hypoxia is a major factor that induces malignant progression, but most previous studies on tumor hypoxia were performed under short-term hypoxia for up to 72 hours and few studies have focused on tumor response to chronic hypoxic conditions. Here we show a molecular mechanism by which chronic hypoxia promotes invasive behavior in prostate cancer cells. We found that an epithelial-mesenchymal transition (EMT)-driving transcription factor, slug, is specifically upregulated under chronic hypoxia and promotes tumor cell migration and invasion. Unexpectedly, processes associated with EMT, such as loss of E-cadherin, are not observed under chronic hypoxia. Instead, expression of ephrin-B1, a ligand of Eph-related receptor tyrosine kinases, is markedly induced by slug through E-box motifs and promotes cell migration and invasion. Furthermore, slug and ephrin-B1 are highly coexpressed in chronic hypoxic cells of human prostate adenocarcinoma tissues after androgen deprivation, which is known to cause tumor hypoxia. Taken together, these results indicate that chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating the expression of ephrin-B1. In addition, ephrin-B1 may be a novel therapeutic target in combination with androgen deprivation therapy for aggressive prostate cancer.

Paradoxes of the EphB1 receptor in malignant brain tumors

Eph receptors are a subfamily of receptor tyrosine kinases. Eph receptor-mediated forward and ephrin ligand-mediated reverse signalings are termed bidirectional signaling. Increasing evidence shows that Eph/ephrin signaling regulates cell migration, adhesion, morphological changes, differentiation, proliferation and survival through cell–cell communication. Some recent studies have started to implicate Eph/ephrin signaling in tumorigenesis, metastasis, and angiogenesis. Previous studies have shown that EphB1 receptor and its ephrin ligands are expressed in the central nervous system. EphB1/ephrin signaling plays an important role in the regulation of synapse formation and maturation, migration of neural progenitors, establishment of tissue patterns, and the development of immune organs. Besides, various recent studies have detected the abnormal expression of EphB1 receptor in different brain tumors. However, the underlying molecular mechanisms of EphB1/ephrins signaling in the development of these tumors are not fully understood. This review focuses on EphB1 that has both tumor-suppressing and -promoting roles in some brain tumors. Understanding the intracellular mechanisms of EphB1 in tumorigenesis and metastasis of brain tumors might provide a foundation for the development of EphB1-targeted therapies.

Netrin-1 Augments Chemokinesis in CD4+ T Cells In Vitro and Elicits a Proinflammatory Response In Vivo

Netrin-1 is a neuronal guidance cue that regulates cellular activation, migration, and cytoskeleton rearrangement in multiple cell types. It is a chemotropic protein that is expressed within tissues and elicits both attractive and repulsive migratory responses. Netrin-1 has recently been found to modulate the immune response via the inhibition of neutrophil and macrophage migration. However, the ability of Netrin-1 to interact with lymphocytes and its in-depth effects on leukocyte migration are poorly understood. In this study, we profiled the mRNA and protein expression of known Netrin-1 receptors on human CD4(+) T cells. Neogenin, uncoordinated-5 (UNC5)A, and UNC5B were expressed at low levels in unstimulated cells, but they increased following mitogen-dependent activation. By immunofluorescence, we observed a cytoplasmic staining pattern of neogenin and UNC5A/B that also increased following activation. Using a novel microfluidic assay, we found that Netrin-1 stimulated bidirectional migration and enhanced the size of migratory subpopulations of mitogen-activated CD4(+) T cells, but it had no demonstrable effects on the migration of purified CD4(+)CD25(+)CD127(dim) T regulatory cells. Furthermore, using a short hairpin RNA knockdown approach, we observed that the promigratory effects of Netrin-1 on T effectors is dependent on its interactions with neogenin. In the humanized SCID mouse, local injection of Netrin-1 into skin enhanced inflammation and the number of neogenin-expressing CD3(+) T cell infiltrates. Neogenin was also observed on CD3(+) T cell infiltrates within human cardiac allograft biopsies with evidence of rejection. Collectively, our findings demonstrate that Netrin-1/neogenin interactions augment CD4(+) T cell chemokinesis and promote cellular infiltration in association with acute inflammation in vivo.

Bidirectional ephrin signaling in bone

The interaction between ephrin ligands (efn) and their receptors (Eph) is capable of inducing forward signaling, from ligand to receptor, as well as reverse signaling, from receptor to ligand. The ephrins are widely expressed in many tissues, where they mediate cell migration and adherence, properties that make the efn-Eph signaling critically important in establishing and maintaining tissue boundaries. The efn-Eph system has also received considerable attention in skeletal tissues, as ligand and receptor combinations are predicted to mediate interactions between the different types of cells that regulate bone development and homeostasis. This review summarizes our current understanding of efn-Eph signaling with a particular focus on the expression and functions of ephrins and their receptors in bone.

Eph/ephrin-B-mediated cell-to-cell interactions govern MTS20(+) thymic epithelial cell development

Thymus development is a complex process in which cell-to-cell interactions between thymocytes and thymic epithelial cells (TECs) are essential to allow a proper maturation of both thymic cell components. Although signals that control thymocyte development are well known, mechanisms governing TEC maturation are poorly understood, especially those that regulate the maturation of immature TEC populations during early fetal thymus development. In this study, we show that EphB2-deficient, EphB2LacZ and EphB3-deficient fetal thymuses present a lower number of cells and delayed maturation of DN cell subsets compared to WT values. Moreover, deficits in the production of chemokines, known to be involved in the lymphoid seeding into the thymus, contribute in decreased proportions of intrathymic T cell progenitors (PIRA/B(+)) in the mutant thymuses from early stages of development. These features correlate with increased proportions of MTS20(+) cells but fewer MTS20(-) cells from E13.5 onward in the deficient thymuses, suggesting a delayed development of the first epithelial cells. In addition, in vitro the lack of thymocytes or the blockade of Eph/ephrin-B-mediated cell-to-cell interactions between either thymocytes-TECs or TECs-TECs in E13.5 fetal thymic lobes coursed with increased proportions of MTS20(+) TECs. This confirms, for the first time, that the presence of CD45(+) cells, corresponding at these stages to DN1 and DN2 cells, and Eph/ephrin-B-mediated heterotypic or homotypic cell interactions between thymocytes and TECs, or between TECs and themselves, contribute to the early maturation of MTS20(+) TECs.

Membrane-mediated regulation of vascular identity

Vascular diseases span diverse pathology, but frequently arise from aberrant signaling attributed to specific membrane-associated molecules, particularly the Eph-ephrin family. Originally recognized as markers of embryonic vessel identity, Eph receptors and their membrane-associated ligands, ephrins, are now known to have a range of vital functions in vascular physiology. Interactions of Ephs with ephrins at cell-to-cell interfaces promote a variety of cellular responses such as repulsion, adhesion, attraction, and migration, and frequently occur during organ development, including vessel formation. Elaborate coordination of Eph- and ephrin-related signaling among different cell populations is required for proper formation of the embryonic vessel network. There is growing evidence supporting the idea that Eph and ephrin proteins also have postnatal interactions with a number of other membrane-associated signal transduction pathways, coordinating translation of environmental signals into cells. This article provides an overview of membrane-bound signaling mechanisms that define vascular identity in both the embryo and the adult, focusing on Eph- and ephrin-related signaling. We also discuss the role and clinical significance of this signaling system in normal organ development, neoplasms, and vascular pathologies.

EphB4 Expressing Stromal Cells Exhibit an Enhanced Capacity for Hematopoietic Stem Cell Maintenance

The tyrosine kinase receptor, EphB4, mediates cross-talk between stromal and hematopoietic populations during bone remodeling, fracture repair and arthritis, through its interactions with the ligand, ephrin-B2. This study demonstrated that transgenic EphB4 mice (EphB4 Tg), over-expressing EphB4 under the control of collagen type-1 promoter, exhibited higher frequencies of osteogenic cells and hematopoietic stem/progenitor cells (HSC), correlating with a higher frequency of long-term culture-initiating cells (LTC-IC), compared with wild type (WT) mice. EphB4 Tg stromal feeder layers displayed a greater capacity to support LTC-IC in vitro, where blocking EphB4/ephrin-B2 interactions decreased LTC-IC output. Similarly, short hairpin RNA-mediated EphB4 knockdown in human bone marrow stromal cells reduced their ability to support high ephrin-B2 expressing CD34(+) HSC in LTC-IC cultures. Notably, irradiated EphB4 Tg mouse recipients displayed enhanced bone marrow reconstitution capacity and enhanced homing efficiency of transplanted donor hematopoietic stem/progenitor cells relative to WT controls. Studies examining the expression of hematopoietic supportive factors produced by stromal cells indicated that CXCL12, Angiopoietin-1, IL-6, FLT-3 ligand, and osteopontin expression were more highly expressed in EphB4 Tg stromal cells compared with WT controls. These findings indicate that EphB4 facilitates stromal-mediated support of hematopoiesis, and constitute a novel component of the HSC niche.

Epigenome analysis reveals TBX5 as a novel transcription factor involved in the activation of rheumatoid arthritis synovial fibroblasts

In this study, we analyzed the methylation status of human promoters in rheumatoid arthritis synovial fibroblasts (RASF). Differentially methylated genes between RASF and osteoarthritis synovial fibroblasts (OASF) were identified by methylated DNA immunoprecipitation and hybridization to human promoter tiling arrays. The methylation status was confirmed by pyrosequencing. Gene and protein expression of differentially methylated genes was evaluated with real-time PCR, Western blot, and immunohistochemistry. Chromatin immunoprecipitation was used to measure the gene promoter-associated acetylation and methylation of histones. Transcription factor-specific targets were identified with microarray and luciferase assays. We found that the transcription factor T-box transcription factor 5 (TBX5) was less methylated in rheumatoid arthritis (RA) synovium and RASF than in osteoarthritis (OA) samples. Demethylation of the TBX5 promoter in RASF and RA synovium was accompanied by higher TBX5 expression than in OASF and OA synovium. In RA synovium, TBX5 expression was primarily localized to the synovial lining. In addition, the TBX5 locus was enriched in activating chromatin marks, such as histone 4 lysine 4 trimethylation and histone acetylation, in RASF. In our functional studies, we observed that 790 genes were differentially expressed by 2-6-fold after overexpression of TBX5 in OASF. Bioinformatic analysis of these genes revealed that the chemokines IL-8, CXCL12, and CCL20 were common targets of TBX5 in OASF. Taken together, our data show that TBX5 is a novel inducer of important chemokines in RASF. Thus, we conclude that RASF contribute to the inflammatory processes operating in the pathogenesis of RA via epigenetic control of TBX5.

Eph receptors: new players in Alzheimer's disease pathogenesis

Alzheimer's disease (AD) is devastating and leads to permanent losses of memory and other cognitive functions. Although recent genetic evidences strongly argue for a causative role of Aβ in AD onset and progression (Jonsson et al., 2012), its role in AD etiology remains a matter of debate. However, even if not the sole culprit or pathological trigger, genetic and anatomical evidences in conjunction with numerous pharmacological studies, suggest that Aβ peptides, at least contribute to the disease. How Aβ contributes to memory loss remains largely unknown. Soluble Aβ species referred to as Aβ oligomers have been shown to be neurotoxic and induce network failure and cognitive deficits in animal models of the disease. In recent years, several proteins were described as potential Aβ oligomers receptors, amongst which are the receptor tyrosine kinases of Eph family. These receptors together with their natural ligands referred to as ephrins have been involved in a plethora of physiological and pathological processes, including embryonic neurogenesis, learning and memory, diabetes, cancers and anxiety. Here we review recent discoveries on Eph receptors-mediated protection against Aβ oligomers neurotoxicity as well as their potential as therapeutic targets in AD pathogenesis.

Genome-wide DNA methylation profiling in rheumatoid arthritis identifies disease-associated methylation changes that are distinct to individual T- and B-lymphocyte populations

Changes to the DNA methylome have been described in patients with rheumatoid arthritis (RA). In previous work, we reported genome-wide methylation differences in T-lymphocyte and B-lymphocyte populations from healthy individuals. Now, using HumanMethylation450 BeadChips to interrogate genome-wide DNA methylation, we have determined disease-associated methylation changes in blood-derived T- and B-lymphocyte populations from 12 female patients with seropositive established RA, relative to 12 matched healthy individuals. Array data were analyzed using NIMBL software and bisulfite pyrosequencing was used to validate array candidates. Genome-wide DNA methylation, determined by analysis of LINE-1 sequences, revealed higher methylation in B-lymphocytes compared with T-lymphocytes (P ≤ 0.01), which is consistent with our findings in healthy individuals. Moreover, loci-specific methylation differences that distinguished T-lymphocytes from B-lymphocytes in healthy individuals were also apparent in RA patients. However, disease-associated methylation differences were also identified in RA. In these cases, we identified 509 and 252 CpGs in RA-derived T- and B-lymphocytes, respectively, that showed significant changes in methylation compared with their cognate healthy counterparts. Moreover, this included a restricted set of 32 CpGs in T-lymphocytes and 20 CpGs in B-lymphocytes (representing 15 and 10 genes, respectively, and including two, MGMT and CCS, that were common to both cell types) that displayed more substantial changes in methylation. These changes, apparent as hyper- or hypo-methylation, were independently confirmed by pyrosequencing analysis. Validation by pyrosequencing also revealed additional sites in some candidate genes that also displayed altered methylation in RA. In this first study of genome-wide DNA methylation in individual T- and B-lymphocyte populations in RA patients, we report disease-associated methylation changes that are distinct to each cell type and which support a role for discrete epigenetic regulation in this disease.

Therapeutic perspectives of Eph-ephrin system modulation

Eph receptors are the largest class of kinase receptors and, together with their ligands ephrins, they have a primary role in embryogenesis. Their expression has been found deregulated in several cancer tissues and, in many cases, abnormal levels of these proteins have been correlated to a poor prognosis. Recently, the Eph-ephrin system was found to be deregulated in other pathological processes, involving the nervous and cardiovascular systems. The increasing body of evidence supports the Eph-ephrin system as a target not only for the treatment of solid tumors, but also to face other critical diseases such as amyotrophic lateral sclerosis and diabetes driving current efforts toward the development of pharmacological tools potentially able to treat these pathologies.

EphB and Ephrin-B interactions mediate human mesenchymal stem cell suppression of activated T-cells

Mesenchymal stromal/stem cells (MSC) express the contact-dependent erythropoietin-producing hepatocellular (Eph) receptor tyrosine kinase family and their cognate ephrin ligands, which are known to regulate thymocyte maturation and selection, T-cell transendothelial migration, activation, co-stimulation, and proliferation. However, the contribution of Eph/ephrin molecules in mediating human MSC suppression of activated T-cells remains to be determined. In the present study, we showed that EphB2 and ephrin-B2 are expressed by ex vivo expanded MSC, while the corresponding ligands, ephrin-B1 and EphB4, respectively, are highly expressed by T-cells. Initial studies demonstrated that EphB2-Fc and ephrin-B2-Fc molecules suppressed T-cell proliferation in allogeneic mixed lymphocyte reaction (MLR) assays compared with human IgG-treated controls. While the addition of a third-party MSC population demonstrated dramatic suppression of T-cell proliferation responses in the MLR, blocking the function of EphB2 or EphB4 receptors using inhibitor binding peptides significantly increased T-cell proliferation. Consistent with these observations, shRNA EphB2 or ephrin-B2 knockdown expression in MSC reduced their ability to inhibit T-cell proliferation. Importantly, the expression of immunosuppressive factors, indoleamine 2, 3-dioxygenase, transforming growth factor-β1, and inducible nitric oxide synthase expressed by MSC, was up-regulated after stimulation with EphB4 and ephrin-B1 in the presence of interferon (IFN)-γ, compared with untreated controls. Conversely, key factors involved in T-cell activation and proliferation, such as interleukin (IL)-2, IFN-γ, tumor necrosis factor-α, and IL-17, were down-regulated by T-cells treated with EphB2 or ephrin-B2 compared with untreated controls. Studies utilizing signaling inhibitors revealed that inhibition of T-cell proliferation is partly mediated through EphB2-induced ephrin-B1 reverse signaling or ephrin-B2-mediated EphB4 forward signaling by activating Src, PI3Kinase, Abl, and JNK kinase pathways, activated by tyrosine phosphorylation. Taken together, these observations suggest that EphB/ephrin-B interactions play an important role in mediating human MSC inhibition of activated T cells.

Epigenome-wide profiling identifies significant differences in DNA methylation between matched-pairs of T- and B-lymphocytes from healthy individuals

Multiple reports now describe changes to the DNA methylome in rheumatoid arthritis and in many cases have analyzed methylation in mixed cell populations from whole blood. However, these approaches may preclude the identification of cell type-specific methylation, which may subsequently bias identification of disease-specific changes. To address this possibility, we conducted genome-wide DNA methylation profiling using HumanMethylation450 BeadChips to identify differences within matched pairs of T-lymphocytes and B-lymphocytes isolated from the peripheral blood of 10 healthy females. Array data were processed and differential methylation identified using NIMBL software. Validation of array data was performed by bisulfite pyrosequencing. Genome-wide DNA methylation was initially determined by analysis of LINE-1 sequences and was higher in B-lymphocytes than matched T-lymphocytes (69.8% vs. 65.2%, P ≤ 0.01). Pairwise analysis identified 679 CpGs, representing 250 genes, which were differentially methylated between T-lymphocytes and B-lymphocytes. The majority of sites (76.6%) were hypermethylated in B-lymphocytes. Pyrosequencing of selected candidates confirmed the array data in all cases. Hierarchical clustering revealed perfect segregation of samples into two distinct clusters based on cell type. Differentially methylated genes showed enrichment for biological functions/pathways associated with leukocytes and T-lymphocytes. Our work for the first time shows that T-lymphocytes and B-lymphocytes possess intrinsic differences in DNA methylation within a restricted set of functionally related genes. These data provide a foundation for investigating DNA methylation in diseases in which these cell types play important and distinct roles.

Blood cytokine, chemokine and gene expression in cholestasis patients with intractable pruritis treated with a molecular adsorbent recirculating system: a case series

BACKGROUND

The molecular adsorbent recirculating system (MARS) is an albumin-dialysis modality that has been investigated predominantly in patients with acute and acute-on-chronic liver failure.

OBJECTIVES

To report the clinical efficacy and safety of MARS therapy for intractable pruritus in cholestasis patients with stable chronic liver disease, characterizing the impact of MARS on cytokine levels and on the transcriptome in the blood compartment.

METHODS

MARS therapy was performed on three patients with cholestatic liver disease using 8 h runs for two consecutive days. The expression levels of 65 cytokines⁄chemokines and 24,000 genes were profiled by Luminex (Luminex Corporation, USA) and microarray, respectively.

RESULTS

A quality-of-life assessment demonstrated a marked improvement during therapy, which was sustained in two of three patients. No bleeding or infectious complications were observed. Bile acid levels were markedly reduced following MARS (mean [± SD] pretreatment 478.9±112.2 µmol⁄L versus post-treatment 89.7±68.8 µmol⁄L). Concordant decreases in cytokine⁄chemokine levels were noted for interleukin (IL)-1beta, IL-2, IL-6, IL-8, IL-12 (p40), RANTES, tranforming growth factor-alpha, tumour necrosis factor-alpha and thrombopoietin following MARS. On microarray profiling, biologically relevant concordant changes among all patients were evident for 20 different genes (10 upregulated and 10 downregulated). The upregulation of several potentially immune suppressive⁄regulatory genes (eg, early growth response 3 [EGR-3], ephrin-A2 [EFNA2] and serum amyloid A1 [SAA1]), concurrent with downregulation of genes involved in innate immunity (eg, toll-like receptor 4 interactor with leucine-rich repeats [TRIL]) and inflammation (eg, ephrin receptor B1 [EPHB1]), was observed.

CONCLUSIONS

This investigative approach offers new insights into intractable pruritus and suggests future therapeutic targets. The clinical benefit of MARS in cholestasis patients with intractable pruritus may not exclusively result from filtration of pruritogens, but also from systemic changes in cytokine⁄chemokine levels and changes in gene expression of blood cells.

Evidence that the EphA2 receptor exacerbates ischemic brain injury

Ephrin (Eph) signaling within the central nervous system is known to modulate axon guidance, synaptic plasticity, and to promote long-term potentiation. We investigated the potential involvement of EphA2 receptors in ischemic stroke-induced brain inflammation in a mouse model of focal stroke. Cerebral ischemia was induced in male C57Bl6/J wild-type (WT) and EphA2-deficient (EphA2^−/−) mice by middle cerebral artery occlusion (MCAO; 60 min), followed by reperfusion (24 or 72 h). Brain infarction was measured using triphenyltetrazolium chloride staining. Neurological deficit scores and brain infarct volumes were significantly less in EphA2^−/− mice compared with WT controls. This protection by EphA2 deletion was associated with a comparative decrease in brain edema, blood-brain barrier damage, MMP-9 expression and leukocyte infiltration, and higher expression levels of the tight junction protein, zona occludens-1. Moreover, EphA2^−/− brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3 and BAX, and higher levels of the anti-apoptotic protein, Bcl-2 as compared to WT group. We confirmed that isolated WT cortical neurons express the EphA2 receptor and its ligands (ephrin-A1–A3). Furthermore, expression of all four proteins was increased in WT primary cortical neurons following 24 h of glucose deprivation, and in the brains of WT mice following stroke. Glucose deprivation induced less cell death in primary neurons from EphA2^−/− compared with WT mice. In conclusion, our data provide the first evidence that the EphA2 receptor directly contributes to blood-brain barrier damage and neuronal death following ischemic stroke.

Eph/Ephrin signaling in injury and inflammation

The Eph/ephrin receptor-ligand system plays an important role in embryogenesis and adult life, principally by influencing cell behavior through signaling pathways, resulting in modification of the cell cytoskeleton and cell adhesion. There are 10 EphA receptors, and six EphB receptors, distinguished on sequence difference and binding preferences, that interact with the six glycosylphosphatidylinositol-linked ephrin-A ligands and the three transmembrane ephrin-B ligands, respectively. The Eph/ephrin proteins, originally described as developmental regulators that are expressed at low levels postembryonically, are re-expressed after injury to the optic nerve, spinal cord, and brain in fish, amphibians, rodents, and humans. In rodent spinal cord injury, the up-regulation of EphA4 prevents recovery by inhibiting axons from crossing the injury site. Eph/ephrin proteins may be partly responsible for the phenotypic changes to the vascular endothelium in inflammation, which allows fluid and inflammatory cells to pass from the vascular space into the interstitial tissues. Specifically, EphA2/ephrin-A1 signaling in the lung may be responsible for pulmonary inflammation in acute lung injury. A role in T-cell maturation and chronic inflammation (heart failure, inflammatory bowel disease, and rheumatoid arthritis) is also reported. Although there remains much to learn about Eph/ephrin signaling in human disease, and specifically in injury and inflammation, this area of research raises the exciting prospect that novel therapies will be developed that precisely target these pathways.

PI3K contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs

There is accumulating evidence to implicate the importance of EphBs receptors and ephrinBs ligands were involved in modulation of spinal nociceptive information. However, the downstream mechanisms that control this process are not well understood. In the present study, we investigated whether phosphatidylinositol 3-kinase (PI3K), as the downstream effectors, participates in modulation of spinal nociceptive information related to ephrinBs/EphBs. Intrathecal injection of ephrinB1-Fc produced a dose- and time-dependent thermal and mechanical hyperalgesia, accompanied by the increase of spinal PI3K-p110γ, phosphorylation of AKT (p-AKT) and c-Fos expression. Pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented activation of spinal AKT induced by ephrinB1-Fc. Inhibition of spinal PI3K signaling dose-dependently prevented and reversed pain behaviors and spinal c-Fos protein expression induced by intrathecal injection of ephrinB1-Fc. Inhibition of EphBs receptors by intrathecal injection of EphB1-Fc reduced formalin-induced inflammation and chronic constrictive injury-induced neuropathic pain behaviors accompanied by decreased expression of spinal PI3K,p-AKT and c-Fos protein. Furthermore, pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented ephrinB1-Fc-induced ERK activation in spinal. These data demonstrated that PI3K and PI3K crosstalk to ERK signaling contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs.

Developing T-cell migration: role of semaphorins and ephrins

Cell migration is a crucial event for normal T-cell development, and various ligand/receptor pairs have been implicated. Most of them, including chemokines and extracellular matrix proteins, have attractant properties on thymocytes. We discuss herein two further groups of ligand/receptor pairs, semaphorins/neuropilins and ephs/ephrins, which are constitutively expressed by thymocytes and thymic microenvironmental cells. Evidence shows that the corresponding interactions are relevant for developing T-cell migration, including the entry of bone marrow progenitor cells, migration of CD4/CD8-defined thymocyte subpopulations triggered by chemokines and/or extracellular matrix proteins, and thymocyte export. Conceptually, the data summarized here show that thymocyte migration results from a complex network of molecular interactions, which generate not only attraction, but also repulsion of migrating T-cell precursors.

First insight into the kinome of human regulatory T cells

Regulatory T cells (Tregs) are essential for controlling peripheral tolerance by the active suppression of various immune cells including conventional T effector cells (Teffs). Downstream of the T cell receptor (TCR), more than 500 protein kinases encoded by the human genome have to be considered in signaling cascades regulating the activation of Tregs and Teffs, respectively. Following TCR engagement, Tregs posses a number of unique attributes, such as constitutive expression of Foxp3, hyporesponsiveness and poor cytokine production. Furthermore, recent studies showed that altered regulation of protein kinases is important for Treg function. These data indicate that signaling pathways in Tregs are distinctly organized and alterations at the level of protein kinases contribute to the unique Treg phenotype. However, kinase-based signaling networks in Tregs are poorly understood and necessitate further systematic characterization. In this study, we analyzed the differential expression of kinases in Tregs and Teffs by using a kinase-selective proteome strategy. In total, we revealed quantitative information on 185 kinases expressed in the human CD4(+) T cell subsets. The majority of kinases was equally abundant in both T cell subsets, but 11 kinases were differentially expressed in Tregs. Most strikingly, Tregs showed an altered expression of cell cycle kinases including CDK6. Quantitative proteomics generates first comparative insight into the kinase complements of the CD4(+) Teff and Treg subset. Treg-specific expression pattern of 11 protein kinases substantiate the current opinion that TCR-mediated signaling cascades are altered in Tregs and further suggests that Tregs exhibit significant specificities in cell-cycle control and progression.

Regulation and misregulation of Eph/ephrin expression

The erythropoietin-producing hepatocellular (Eph) receptors form the largest family of receptor tyrosine kinases. Upon interaction of the Eph receptors with their ligands the ephrins, signaling cascades are initiated downstream of both receptor and ligand, a feature known as bidirectional signaling. The Eph receptors and ephrin ligands mediate important roles in embryonic development, particularly in establishing tissue organization by mediating cell adhesion or cell repulsion. In several adult tissues, at least one Eph/ephrin pair is found to play critical roles in tissue physiology and homeostasis. In recent years numerous members of this family have gained considerable attention since changes in their expression levels are a typical feature in cancer cells. Despite the fact that Eph/ephrin developmental expression profiles are well documented, little is known on transcriptional and post-transcriptional mechanisms that permits their highly specific, graded, complementary or overlapping expression patterns. Therefore understanding the transcriptional and post-transcriptional mechanisms regulating Eph/ephrin expression has far-reaching significance in biology. This review provides an overview of the mechanisms regulating Eph/ephrin expression. We highlight important emerging mechanisms of Eph/ephrin regulation or misregulation such as epigenetics and miRNAs.

Bone cell interactions through Eph/ephrin: bone modeling, remodeling and associated diseases

Bones cannot properly form or be maintained without cell-cell interactions through ephrin ligands and Eph receptors. Cell culture analysis and evaluation of genetic mouse models and human diseases reveal various ephrins and Eph functions in the skeletal system. Migration, attachment and spreading of mesenchymal stem cells are regulated by ephrinB ligands and EphB receptors. ephrinB1 loss-of-function is associated with craniofrontonasal syndrome (CFNS) in humans and mice. In bone remodeling, ephrinB2 is postulated to act as a “coupling stimulator.” In that case, bidirectional signaling between osteoclastic ephrinB2 and osteoblastic EphB4 suppresses osteoclastic bone resorption and enhances osteoblastic bone formation, facilitating the transition between these two states. Parathyroid hormone (PTH) induces ephrinB2 in osteoblasts and enhances osteoblastic bone formation. In contrast to ephrinB2, ephrinA2 acts as a “coupling inhibitor,” since ephrinA2 reverse signaling into osteoclasts enhances osteoclastogenesis and EphA2 forward signaling into osteoblasts suppresses osteoblastic bone formation and mineralization. Furthermore, ephrins and Ephs likely modulate pathological conditions such as osteoarthritis, rheumatoid arthritis, multiple myeloma and osteosarcoma. This review focuses on ephrin/Eph-mediated cell-cell interactions in bone biology.

Involvement of EphB/Ephrin-B signaling in axonal survival in mouse experimental glaucoma

PURPOSE

To examine the functional significance of EphB/ephrin-B upregulation in mouse experimental glaucoma.

METHODS

In a loss-of-function approach, mouse mutants lacking EphB2 (EphB2(-/-)) or EphB3 (EphB3(-/-)) protein, and mutants expressing EphB2 truncated in the C-terminus (EphB2(lacZ/lacZ)) were subjected to laser-induced ocular hypertension (LIOH), an experimental mouse model of glaucoma. The number of optic nerve axons was counted in paraphenylenediamine (PPD)-stained sections and compared between EphB mutants and wild type littermates. In a gain-of-function approach, retina/optic nerve explants obtained from LIOH-treated animals were exposed to EphB2-Fc recombinant proteins or Fc control proteins. Tissue sections through the optic nerve head (ONH) were labeled with neuron-specific anti-tubulin β-III antibody to determine axonal integrity.

RESULTS

Both EphB2 and EphB3 null mutant mice exhibited more severe axonal degeneration than wild type littermates after treatment with LIOH. Mutant mice in which the C-terminal portion of EphB2 is truncated had an intermediate phenotype. Application of EphB2-Fc recombinant protein to LIOH-treated optic nerve explants resulted in greater sparing of tubulin β-III-containing retinal ganglion cell (RGC) axons.

CONCLUSIONS

These results provide genetic evidence in mice that both EphB/ephrin-B forward and reverse signaling feed into an endogenous pathway to moderate the effects of glaucomatous insult on RGC axons. LIOH-induced axon loss is maintained in retina/optic nerve explants after removal from an ocular hypertensive environment. Exogenous application of EphB2 protein enhances RGC axon survival in explants, suggesting that modulation of Eph/ephrin signaling may be of therapeutic interest.

Inflammatory memories: is epigenetics the missing link to persistent stromal cell activation in rheumatoid arthritis?

Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction. Synovial fibroblasts are recognized as key cells in the pathogenesis of RA since they attract and activate immune cells and produce matrix degrading enzymes. Most notably synovial fibroblasts from patients with RA are stably activated and produce high levels of disease-promoting molecules without further stimulation by immune cells. Accumulating data suggest that epigenetic changes in stromal cell populations might be crucially involved in the pathology of RA and other chronic inflammatory diseases. In the current review, we discuss the mechanisms by which epigenetic changes might cause the stable activation of synovial fibroblasts in RA and how changes in the epigenome might alter immune function and inflammatory response and thereby promote the development of chronic diseases.

Eph/Ephrin-mediated interactions in the thymus

In the present study, we review available information on the relevance of Eph and ephrins in numerous processes occurring in the thymus that regulate not only T cell differentiation but also thymic epithelial cell (TEC) development and organization. Eph/ephrins are a large family of receptors and ligands involved in organogenesis and homeostasis of adult tissues. They are extensively expressed in the thymus and seem to be involved in the colonization of lymphoid progenitor cells and their migration throughout the thymic parenchyma necessary to provide an adequate topological location of developing thymocytes in the epithelial network that ensures their correct differentiation. In addition, EphB2 and EphB3 play a cell-autonomous role in regulating the transitions of double-negative to double-positive cells and of double-positive to single-positive thymocytes and the lack of these molecules or their ligands ephrin B1 and ephrin B2 induces profound alterations of the TEC maturation and in the arrangement of epithelial network. We emphasize that these results are largely reflecting the role played by this family of molecules in controlling thymocyte-TEC interactions within the thymus.

Prolactin alters the mRNA expression of osteoblast-derived osteoclastogenic factors in osteoblast-like UMR106 cells

Prolactin (PRL) is known to participate in the lactation-induced maternal bone loss, presumably by inducing the release of receptor activator of nuclear factor-κB ligand (RANKL), a potent osteoclastogenic factor from osteoblasts. Since maternal bone resorption was too massive to be solely explained by RANKL and osteoclasts did not express PRL receptors (PRLR), the involvement of some other osteoblast-derived osteoclastogenic modulators was anticipated. Herein, the authors used quantitative real-time PCR to investigate the mRNA expressions of various osteoclastogenic factors in osteoblast-like UMR106 cells directly exposed to PRL for 48 h. These cells were found to express PRLR and respond to 300 ng/ml PRL by increasing RANKL mRNA expression. This PRL concentration (comparable to plasma PRL levels in lactation) also induced the upregulation of monocyte chemoattractant protein (MCP)-1, cyclooxygenase (Cox)-2, and ephrin-B1, whereas a higher concentration (500 ng/ml) was required to upregulate tumor necrosis factor (TNF)-α and interleukin (IL)-1. However, 100-500 ng/ml PRL affected neither the cell proliferation, the cell viability nor the mRNA expressions of macrophage colony-stimulating factor, IL-6, ephrin type-B receptor 4 and ephrin-B2. In conclusion, besides RANKL overexpression, PRL upregulated the expressions of other osteoclastogenic modulators, i.e., MCP-1, Cox-2, TNF-α, IL-1, and ephrin-B1, thus, further explaining how PRL induced bone loss in lactating mothers.

Regulation of immune cell responses by semaphorins and their receptors

Semaphorins were originally identified as axon guidance factors involved in the development of the neuronal system. However, accumulating evidence indicates that several members of semaphorins, so-called 'immune semaphorins', are crucially involved in various phases of immune responses. These semaphorins regulate both immune cell interactions and immune cell trafficking during physiological and pathological immune responses. Here, we review the following two functional aspects of semaphorins and their receptors in immune responses: their functions in cell-cell interactions and their involvement in immune cell trafficking.

Receptor tyrosine kinase EphA2 mediates thrombin-induced upregulation of ICAM-1 in endothelial cells in vitro

Thrombin potently induces endothelial inflammation. One of the responses is upregulation of adhesion molecules such as ICAM-1, resulting in enhanced leukocyte attachment to the endothelium. In this report, we examine the contribution of EphA2 in thrombin-induced expression of ICAM-1 in human umbilical vein endothelial cells (HUVECs). We showed that thrombin transiently induced tyrosine- phosphorylation of EphA2 in a Src-kinase dependent manner. This transactivation was mediated through PAR-1, because a PAR-1 specific agonistic peptide also transactivated EphA2. Expression knockdown of endogenous EphA2 by siRNAs blocked ICAM-1 upregulation and leukocyte/endothelium attachment induced by thrombin. Overexpression of exogenous mouse EphA2 rescued both ICAM-1 expression and leukocyte attachment induced by thrombin in endogenous EphA2-knockdown HUVECs. Mechanistically, we showed EphA2 knockdown suppressed thrombin-induced serine 536 phosphorylation of NFkappaB, an event critical of ICAM-1 transcriptional upregulation. Collectively, our results strongly suggest EphA2 is a necessary component for thrombin-induced ICAM-1 upregulation.

Activation of peripheral ephrinBs/EphBs signaling induces hyperalgesia through a MAPKs-mediated mechanism in mice

EphBs receptors and ephrinBs ligands are present in the adult brain and peripheral tissue and play a critical role in modulating multiple aspects of physiology and pathophysiology. Ours and other studies have demonstrated that spinal ephrinBs/EphBs signaling was involved in the modulation of nociceptive information and central sensitization. However, the role of ephrinBs/EphBs signaling in peripheral sensitization is poorly understood. This study shows that intraplantar (i.pl.) injection of ephrinB1-Fc produces a dose- and time-dependent thermal and mechanical hyperalgesia and the increase of spinal Fos protein expression in mice, which can be partially prevented by pre-treatment with EphB1-Fc. EphrinB1-Fc-induced hyperalgesia is accompanied with the NMDA receptor-mediated increase of expression in peripheral and spinal phosphorylated mitogen-activated protein kinases (phospho-MAPKs) including p-p38, pERK and pJNK, and also is prevented or reversed by the inhibition of peripheral and spinal MAPKs. Furthermore, in formalin inflammation pain model, pre-inhibition of EphBs receptors by the injection of EphB1-Fc reduces pain behavior, which is accompanied by the decreased expression of peripheral p-p38, pERK and pJNK. These data provide evidence that ephrinBs may act as a prominent contributor to peripheral sensitization, and demonstrate that activation of peripheral ephrinBs/EphBs system induces hyperalgesia through a MAPKs-mediated mechanism.