Ephrin-A1 suppresses Th2 cell activation and provides a regulatory link to lung epithelial cells

Diversity of Intercellular Communication Modes: A Cancer Biology Perspective

From the moment a cell is on the path to malignant transformation, its interaction with other cells from the microenvironment becomes altered. The flow of molecular information is at the heart of the cellular and systemic fate in tumors, and various processes participate in conveying key molecular information from or to certain cancer cells. For instance, the loss of tight junction molecules is part of the signal sent to cancer cells so that they are no longer bound to the primary tumors and are thus free to travel and metastasize. Upon the targeting of a single cell by a therapeutic drug, gap junctions are able to communicate death information to by-standing cells. The discovery of the importance of novel modes of cell-cell communication such as different types of extracellular vesicles or tunneling nanotubes is changing the way scientists look at these processes. However, are they all actively involved in different contexts at the same time or are they recruited to fulfill specific tasks? What does the multiplicity of modes mean for the overall progression of the disease? Here, we extend an open invitation to think about the overall significance of these questions, rather than engage in an elusive attempt at a systematic repertory of the mechanisms at play.

Twin study: genotype-dependent epigenetic factors affecting free thyroxine levels in the normal range

Aim: To explore the clinical application of DNA methylation affecting thyroid function, we evaluated the association of DNA methylation with free thyroxine (FT4) and TSH measurements in monozygotic twins. Materials & methods: Discordant pairs for FT4 or TSH levels were examined for the relationship between the within-pair difference of each measurement and the DNA methylation levels using epigenome-wide association studies. The contribution of polymorphisms to the methylation sensitivity was also examined. Results: We found two CpG sites significantly associated with FT4 levels, and also some CpG sites showing significant differences in their methylation levels within FT4-discordant pairs depending on the polymorphism in EPHB2. Conclusion: The FT4 level may be associated with a combination of methylation and polymorphisms in the EPHB2 gene.

Selection of functional EPHB2 genotypes from ENU mutated grass carp treated with GCRV

Background

N-ethyl-N-nitrosourea (ENU) mutagenesis is a useful method for the genetic engineering of plants, and the production of functional mutants in animal models including mice and zebrafish. Grass carp reovirus (GCRV) is a haemorrhagic disease of grass carp which has caused noteworthy losses in fingerlings over the last few years. To overcome this problem, we used ENU mutant grass carp in an attempt to identify functional resistance genes for future hereditary rearing projects in grass carp.

Results

This study used ENU-mutated grass carp to identify genetic markers associated with resistance to the haemorrhagic disease caused by GCRV. Bulked segregant analysis (BSA) was performed on two homozygous gynogenetic ENU grass carp groups who were susceptible or resistant to GCRV. This analysis identified 466,162 SNPs and 197,644 InDels within the genomes of these mixed pools with a total of 170 genes annotated in the associated region, including 49 genes with non-synonymous mutations at SNP sites and 25 genes with frame shift mutations at InDel sites. Of these 170 mutated genes, 5 randomly selected immune-related genes were shown to be more strongly expressed in the resistant group as compared to the susceptible animals. In addition, we found that one immune-related gene, EPHB2, presented with two heterozygous SNP mutations which altered the animal’s responded to GCRV disease. These SNPs were found in the intron region of EPHB2 at positions 5859 (5859^G > A) and 5968 (5968^G > A) and were significantly (p = 0.002, 0.003) associated with resistance to GCRV. These SNP sites were also shown to correlate with the GCRV-resistant phenotype in these ENU grass carp. We also evaluated the mortality of the different ENU fish genotypes in response to GCRV and the SNPs in EPHB2. The outcomes of these evaluations will be useful in future selections of GCRV-resistant genes for genetic breeding in grass carp.

Conclusion

Our results provide a proof of concept for the application of BSA-sequence analysis in detecting genes responsible for specific functional genotypes and may help to develop better methods for marker-assisted selection, especially for disease resistance in response to GCRV.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07858-x.

Ephrin-A1 and the sheddase ADAM12 are upregulated in COVID-19

More than 3.5 million people have died globally from COVID-19, yet an effective therapy is not available. It is, therefore, important to understand the signaling pathways that mediate disease progression in order to identify new molecular targets for therapeutic development. Here, we report that the blood serum levels of ephrin-A1 and the sheddase ADAM12 were significantly elevated in COVID-19 patients treated at SUNY Downstate Hospital of Brooklyn, New York. Both ephrin-A1 and ADAM12 are known to be involved in inflammation and regulate endothelial cell permeability, thus providing a gateway to lung injury. The clinical outcome correlated with the ephrin-A1 and ADAM12 serum levels during the first week of hospitalization. In contrast, the serum levels of TNFα were elevated in only a small subset of the patients, and these same patients also had highly elevated levels of the sheddase ADAM17. These data indicate that ephrin-A1-mediated inflammatory signaling may contribute to COVID-19 disease progression more so than TNFα-mediated inflammatory signaling. They also support the notion that, in COVID-19 inflammation, ADAM12 sheds ephrin-A1, while ADAM17 sheds TNFα. Furthermore, the results suggest that elevated serum levels and activity of cytokines, such as TNFα, and other secreted inflammatory molecules, such as ephrin-A1, are not simply due to overexpression, but also to upregulation of sheddases that release them into the blood circulation. Our results identify ephrin-A1, ADAM12, and other molecules in the ephrin-A1 signaling pathway as potential pharmacological targets for treating COVID-19 inflammation.

Transcriptional and proteomic insights into the host response in fatal COVID-19 cases

Coronavirus disease 2019 (COVID-19), the global pandemic caused by SARS-CoV-2, has resulted thus far in greater than 933,000 deaths worldwide; yet disease pathogenesis remains unclear. Clinical and immunological features of patients with COVID-19 have highlighted a potential role for changes in immune activity in regulating disease severity. However, little is known about the responses in human lung tissue, the primary site of infection. Here we show that pathways related to neutrophil activation and pulmonary fibrosis are among the major up-regulated transcriptional signatures in lung tissue obtained from patients who died of COVID-19 in Wuhan, China. Strikingly, the viral burden was low in all samples, which suggests that the patient deaths may be related to the host response rather than an active fulminant infection. Examination of the colonic transcriptome of these patients suggested that SARS-CoV-2 impacted host responses even at a site with no obvious pathogenesis. Further proteomics analysis validated our transcriptome findings and identified several key proteins, such as the SARS-CoV-2 entry-associated protease cathepsins B and L and the inflammatory response modulator S100A8/A9, that are highly expressed in fatal cases, revealing potential drug targets for COVID-19.

Ephrin-Eph signaling usage by a variety of viruses

Ephrin-Eph signaling is a receptor tyrosine kinase signaling pathway involved in a variety of cellular mechanisms, of which many are related to the adhesion or migration of cells. Both the Eph receptor and ephrin ligand are abundantly present on a wide variety of cell types, and strongly evolutionary conserved. This review provides an overview of how 18 genetically diverse viruses utilize the Eph receptor (Eph), ephrin ligand (ephrin) or ephrin-Eph signaling to their advantage in their viral life cycle. Both Ephs and ephrins have been shown to serve as entry receptors for a variety of viruses, via both membrane fusion and endocytosis. Ephs and ephrins are also involved in viral transmission by vectors, associated with viral replication or persistence and lastly to neurological damage caused by viral infection. Although therapeutic opportunities targeting Ephs or ephrins do not seem feasible yet, the current research does propose two models for the viral usage of ephrin-Eph signaling. Firstly, the viral entry model, in which membrane molecules are used for viral entry, leading to cells being used for replication or as a transporter. Secondly, the advantageous expression ephrin-Eph signaling model, where viruses adapt the expression of Ephs or ephrins to change cell-cell interaction to their advantage. These models can guide future research questions on the usage of Ephs or ephrins by viruses and therapeutic opportunities.

Host deficiency in ephrin-A1 inhibits breast cancer metastasis

Background: The conventional dogma of treating cancer by focusing on the elimination of tumor cells has been recently refined to include consideration of the tumor microenvironment, which includes host stromal cells. Ephrin-A1, a cell surface protein involved in adhesion and migration, has been shown to be tumor suppressive in the context of the cancer cell. However, its role in the host has not been fully investigated. Here, we examine how ephrin-A1 host deficiency affects cancer growth and metastasis in a murine model of breast cancer.

Methods: 4T1 cells were orthotopically implanted into the mammary fat pads or injected into the tail veins of ephrin-A1 wild-type ( Efna1^+/+), heterozygous ( Efna1^+/-), or knockout ( Efna1^-/-) mice. Tumor growth, lung metastasis, and tumor recurrence after surgical resection were measured. Flow cytometry and immunohistochemistry (IHC) were used to analyze various cell populations in primary tumors and tumor-bearing lungs.

Results: While primary tumor growth did not differ between Efna1^+/+, Efna1^+/-, and Efna1^-/- mice, lung metastasis and primary tumor recurrence were significantly decreased in knockout mice. Efna1^-/- mice had reduced lung colonization of 4T1 cells compared to Efna1^+/+ littermate controls as early as 24 hours after tail vein injection. Furthermore, established lung lesions in Efna1^-/- mice had reduced proliferation compared to those in Efna1^+/+ controls.

Conclusions: Our studies demonstrate that host deficiency of ephrin-A1 does not impact primary tumor growth but does affect metastasis by providing a less favorable metastatic niche for cancer cell colonization and growth. Elucidating the mechanisms by which host ephrin-A1 impacts cancer relapse and metastasis may shed new light on novel therapeutic strategies.

Host deficiency in ephrin-A1 inhibits breast cancer metastasis

Background: The conventional dogma of treating cancer by focusing on the elimination of tumor cells has been recently refined to include consideration of the tumor microenvironment, which includes host stromal cells. Ephrin-A1, a cell surface protein involved in adhesion and migration, has been shown to be tumor suppressive in the context of the cancer cell. However, its role in the host has not been fully investigated. Here, we examine how ephrin-A1 host deficiency affects cancer growth and metastasis in a murine model of breast cancer. Methods: 4T1 cells were orthotopically implanted into the mammary fat pads or injected into the tail veins of ephrin-A1 wild-type ( Efna1 ^+/+), heterozygous ( Efna1 ^+/-), or knockout ( Efna1 ^-/-) mice. Tumor growth, lung metastasis, and tumor recurrence after surgical resection were measured. Flow cytometry and immunohistochemistry (IHC) were used to analyze various cell populations in primary tumors and tumor-bearing lungs. Results: While primary tumor growth did not differ between Efna1 ^+/+, Efna1 ^+/-, and Efna1 ^-/- mice, lung metastasis and primary tumor recurrence were significantly decreased in knockout mice. Efna1 ^-/- mice had reduced lung colonization of 4T1 cells compared to Efna1 ^+/+ littermate controls as early as 24 hours after tail vein injection. Furthermore, established lung lesions in Efna1 ^-/- mice had reduced proliferation compared to those in Efna1 ^+/+ controls. Conclusions: Our studies demonstrate that host deficiency of ephrin-A1 does not impact primary tumor growth but does affect metastasis by providing a less favorable metastatic niche for cancer cell colonization and growth. Elucidating the mechanisms by which host ephrin-A1 impacts cancer relapse and metastasis may shed new light on novel therapeutic strategies.

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.

Inhibition of EphB4-Ephrin-B2 Signaling Reprograms the Tumor Immune Microenvironment in Head and Neck Cancers

Identifying targets present in the tumor microenvironment that contribute to immune evasion has become an important area of research. In this study, we identified EphB4-ephrin-B2 signaling as a regulator of both innate and adaptive components of the immune system. EphB4 belongs to receptor tyrosine kinase family that interacts with ephrin-B2 ligand at sites of cell-cell contact, resulting in bidirectional signaling. We found that EphB4-ephrin-B2 inhibition alone or in combination with radiation (RT) reduced intratumoral regulatory T cells (Tregs) and increased activation of both CD8⁺ and CD4⁺Foxp3^- T cells compared with the control group in an orthotopic head and neck squamous cell carcinoma (HNSCC) model. We also compared the effect of EphB4-ephrin-B2 inhibition combined with RT with combined anti-PDL1 and RT and observed similar tumor growth suppression, particularly at early time-points. A patient-derived xenograft model showed reduction of tumor-associated M2 macrophages and favored polarization towards an antitumoral M1 phenotype following EphB4-ephrin-B2 inhibition with RT. In vitro, EphB4 signaling inhibition decreased Ki67-expressing Tregs and Treg activation compared with the control group. Overall, our study is the first to implicate the role of EphB4-ephrin-B2 in tumor immune response. Moreover, our findings suggest that EphB4-ephrin-B2 inhibition combined with RT represents a potential alternative for patients with HNSCC and could be particularly beneficial for patients who are ineligible to receive or cannot tolerate anti-PDL1 therapy. SIGNIFICANCE: These findings present EphB4-ephrin-B2 inhibition as an alternative to anti-PDL1 therapeutics that can be used in combination with radiation to induce an effective antitumor immune response in patients with HNSCC.

G908R NOD2 variant in a family with sarcoidosis

Background

Sarcoidosis is a systemic disease characterized by the formation of immune granulomas in various organs, mainly the lungs and the lymphatic system. Exaggerated granulomatous reaction might be triggered in response to unidentified antigens in individuals with genetic susceptibility. The present study aimed to determine the genetic variants implicated in a familial case of sarcoidosis.

Methods

Sarcoidosis presentation and history, NOD2 profile, NF-κB and cytokine production in blood monocytes/macrophages were evaluated in individuals from a family with late appearance of sarcoidosis.

Results

In the present study, we report a case of familial sarcoidosis with typical thoracic sarcoidosis and carrying the NOD2 2722G > C variant. This variant is associated with the presence of three additional SNPs for the IL17RA, KALRN and EPHA2 genes, which discriminate patients expressing the disease from others. Despite a decrease in NF-κB activity, IL-8 and TNF-A mRNA levels were increased at baseline and in stimulated conditions.

Conclusions

Combination of polymorphisms in the NOD2, IL17RA, EPHA2 and KALRN genes could play a significant role in the development of sarcoidosis by maintaining a chronic pro-inflammatory status in macrophages.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0748-5) contains supplementary material, which is available to authorized users.

Regulation of endothelial migration and proliferation by ephrin-A1

Endothelial migration and proliferation are fundamental processes in angiogenesis and wound healing of injured or inflamed vessels. The present study aimed to investigate the regulation of the Eph/ephrin-system during endothelial proliferation and the impact of the ligand ephrin-A1 on proliferation and migration of human umbilical venous (HUVEC) and arterial endothelial cells (HUAEC). Endothelial cells that underwent contact inhibition showed a massive induction of ephrin-A1. In contrast, an injury to a confluent endothelial layer, associated with induction of migration and proliferation, showed reduced ephrin-A1 levels. In addition, reducing ephrin-A1 expression by siRNA led to increased proliferation, whereas the overexpression of ephrin-A1 led to decreased proliferative activity. Due to the fact that wound healing is a combination of proliferation and migration, migration was investigated in detail. First, classical wound-healing assays showed increased wound closure in both ephrin-A1 silenced and overexpressing cells. Live-cell imaging enlightened the underlying differences. Silencing of ephrin-A1 led to a faster but more disorientated migration. In contrast, ephrin-A1 overexpression did not influence velocity of the cells, but the migration was more directed in comparison to the controls. Additional analysis of EphA2-silenced cells showed similar results in terms of proliferation and migration compared to ephrin-A1 silenced cells. Detailed analysis of EphA2 phosphorylation on ligand-dependent phospho-site (Y588) and autonomous activation site (S897) revealed a distinct phosphorylation pattern. Furthermore, the endothelial cells ceased to migrate when they came in contact with an ephrin-A1 coated surface. Using a baculoviral-mediated expression system, ephrin-A1 silencing and overexpression was shown to modulate the formation of focal adhesions. This implicates that ephrin-A1 is involved in changes of the actin cytoskeleton which explains the alterations in migratory actions, at least in part. In conclusion, ephrin-A1 expression is regulated by cellular density and is itself a critical determinant of endothelial proliferation. According to current knowledge, ephrin-A1 seems to be remarkably involved in elementary processes of endothelial migration like cellular polarization, migratory direction and speed. These data support the notion that ephrin-A1 plays a pivotal role in basal mechanisms of re-endothelialization.

Expression of the Receptor Tyrosine Kinase EphB2 on Dendritic Cells Is Modulated by Toll-Like Receptor Ligation but Is Not Required for T Cell Activation

The Eph receptor tyrosine kinases interact with their ephrin ligands on adjacent cells to facilitate contact-dependent cell communication. Ephrin B ligands are expressed on T cells and have been suggested to act as co-stimulatory molecules during T cell activation. There are no detailed reports of the expression and modulation of EphB receptors on dendritic cells, the main antigen presenting cells that interact with T cells. Here we show that mouse splenic dendritic cells (DC) and bone-marrow derived DCs (BMDC) express EphB2, a member of the EphB family. EphB2 expression is modulated by ligation of TLR4 and TLR9 and also by interaction with ephrin B ligands. Co-localization of EphB2 with MHC-II is also consistent with a potential role in T cell activation. However, BMDCs derived from EphB2 deficient mice were able to present antigen in the context of MHC-II and produce T cell activating cytokines to the same extent as intact DCs. Collectively our data suggest that EphB2 may contribute to DC responses, but that EphB2 is not required for T cell activation. This result may have arisen because DCs express other members of the EphB receptor family, EphB3, EphB4 and EphB6, all of which can interact with ephrin B ligands, or because EphB2 may be playing a role in another aspect of DC biology such as migration.

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.

Ephrin-Eph signaling as a potential therapeutic target for the treatment of myocardial infarction

Although numerous strategies have been developed to reduce the initial ischemic insult and cellular injury that occurs during myocardial infarction (MI), few have progressed into the clinical arena. The epidemiologic and economic impact of MI necessitates the development of innovative therapies to rapidly and effectively reduce the initial injury and subsequent cardiac dysfunction. The Eph receptors and their cognate ligands, the ephrins, are the largest family of receptor tyrosine kinases, and their signaling has been shown to play a diverse role in various cellular processes. The recent advances in the study of ephrin-Eph signaling have shown promising progress in many fields of medicine. They have been implicated in the pathophysiology of various cancers and in the regulation of inflammation and apoptosis. Recent studies have shown that manipulation of ephrin-Eph cell signaling can favorably influence cardiomyocyte viability and ultimately preserve cardiac function post-MI. In this article, we explore the hypothesis that manipulation of ephrin-Eph signaling may potentially be a novel therapeutic target in the treatment of MI through alteration of the cellular processes that govern injury and wound healing.

Efnb1 and Efnb2 proteins regulate thymocyte development, peripheral T cell differentiation, and antiviral immune responses and are essential for interleukin-6 (IL-6) signaling

Erythropoietin-producing hepatocellular kinases (Eph kinases) constitute the largest family of cell membrane receptor tyrosine kinases, and their ligand ephrins are also cell surface molecules. Because of promiscuous interaction between Ephs and ephrins, there is considerable redundancy in this system, reflecting the essential roles of these molecules in the biological system through evolution. In this study, both Efnb1 and Efnb2 were null-mutated in the T cell compartment of mice through loxP-mediated gene deletion. Mice with this double conditional mutation (double KO mice) showed reduced thymus and spleen size and cellularity. There was a significant decrease in the DN4, double positive, and single positive thymocyte subpopulations and mature CD4 and CD8 cells in the periphery. dKO thymocytes and peripheral T cells failed to compete with their WT counterparts in irradiated recipients, and the T cells showed compromised ability of homeostatic expansion. dKO naive T cells were inferior in differentiating into Th1 and Th17 effectors in vitro. The dKO mice showed diminished immune response against LCMV infection. Mechanistic studies revealed that IL-6 signaling in dKO T cells was compromised, in terms of abated induction of STAT3 phosphorylation upon IL-6 stimulation. This defect likely contributed to the observed in vitro and in vivo phenotype in dKO mice. This study revealed novel roles of Efnb1 and Efnb2 in T cell development and function.

Allergic asthma: influence of genetic and environmental factors

Allergic asthma is a chronic airway inflammatory disease in which exposure to allergens causes intermittent attacks of breathlessness, airway hyper-reactivity, wheezing, and coughing. Allergic asthma has been called a "syndrome" resulting from a complex interplay between genetic and environmental factors. Worldwide, >300 million individuals are affected by this disease, and in the United States alone, it is estimated that >35 million people, mostly children, suffer from asthma. Although animal models, linkage analyses, and genome-wide association studies have identified numerous candidate genes, a solid definition of allergic asthma has not yet emerged; however, such studies have contributed to our understanding of the multiple pathways to this syndrome. In contrast with animal models, in which T-helper 2 (T(H)2) cell response is the dominant feature, in human asthma, an initial exposure to allergen results in T(H)2 cell-dependent stimulation of the immune response that mediates the production of IgE and cytokines. Re-exposure to allergen then activates mast cells, which release mediators such as histamines and leukotrienes that recruit other cells, including T(H)2 cells, which mediate the inflammatory response in the lungs. In this minireview, we discuss the current understanding of how associated genetic and environmental factors increase the complexity of allergic asthma and the challenges allergic asthma poses for the development of novel approaches to effective treatment and prevention.

EphrinA1 inhibits malignant mesothelioma tumor growth via let-7 microRNA-mediated repression of the RAS oncogene

EphrinA1 binding with receptor EphA2 suppresses malignant mesothelioma (MM) growth. The mechanisms whereby EphrinA1 attenuates the MM cell (MMC) growth are not clear. In this study, we report that the activation of MMCs with EphrinA1 leads to an induction of let-7 microRNA (miRNA) expression, repression of RAS proto-oncogene and the attenuation of MM tumor growth. The expression of miRNAs was determined by reverse transcription-quantitative polymerase chain reaction and in situ hybridization. RAS expression was determined by q-PCR, western blotting and immunofluorescence. MMC proliferation and tumor growth were determined by WST-1 and Matrigel assay, respectively. EphrinA1 activation induced several fold increases in let-7a1, let-7a3, let-7f1 and let-7f2 miRNA expression in MMCs. In contrast, EphrinA1 activation significantly downregulated H-RAS, K-RAS and N-RAS expression and inhibited MMC proliferation and tumor growth. In MMCs transfected with 2'-O-methyl antisense oligonucleotides to let-7 miRNA, EphrinA1 activation failed to inhibit the proliferative response and tumor growth. In mismatch antisense oligonucleotide-treated MMCs, the proliferation and tumor growth were comparable to untreated proliferating cells. Furthermore, the transfection of MMCs with let-7a miRNA precursor inhibited RAS expression and attenuated MMC tumor growth. Our data revealed that EphrinA1 signaling induces let-7 miRNA expression and attenuates MM tumor growth by targeting RAS proto-oncogene in MMCs.

Activation of EphA receptors on CD4+CD45RO+ memory cells stimulates migration

We have demonstrated previously that binding of ephrin-A1 to EphA receptors on human CD4(+) and CD8(+) T cells stimulates migration. Two EphA receptors have been reported in T cells: EphA1 at the protein level and EphA4 at the mRNA level. In this study, we wanted to investigate the expression profile of these receptors in T cell subpopulations and to test if expression differences would affect the potential of cells to migrate upon ephrin-A1 binding. We have generated an anti-EphA4 mAb for expression analysis. Our data show that functional EphA4 is expressed on the cell surface of CD4(+) and CD8(+) T cells. In addition, EphA4 receptor expression is induced after overnight incubation in serum-free medium, in particular, on CD4(+)CD45RO(+) T cells. Migration of CD4(+) T cells in response to ephrin-A1 is observed for memory cells (CD45RO(+)) and much weaker for naïve cells (CD45RA(+)). A signaling complex associated with the EphA4 receptor has also been isolated and includes EphA1, the Src family kinases Fyn and Lck, Slp76, and Vav1. To conclude, T cells express EphA1 and EphA4 receptors. Expression differences of EphA4 are observed in subpopulations of CD4(+) T cells. This is related to the cell migration potential after ephrin-A1 binding.

Guidance molecules in lung cancer

Guidance molecules were first described in the nervous system to control axon outgrowth direction. They are also widely expressed outside the nervous system where they control cell migration, tissue development and establishment of the vascular network. In addition, they are involved in cancer development, tumor angiogenesis and metastasis. This review is primarily focused on their functions in lung cancer and their involvement in lung development is also presented. Five guidance molecule families and their corresponding receptors are described, including the semaphorins/neuropilins/plexins, ephrins and Eph receptors, netrin/DCC/UNC5, Slit/Robo and Notch/Delta. In addition, the possibility to target these molecules as a therapeutic approach in cancer is discussed.

Mycobacterium tuberculosis interferes with the response to infection by inducing the host EphA2 receptor

BACKGROUND

Mycobacterium tuberculosis is an unusual pathogen, persisting for years in infected persons despite an immune response. Erythropoietin-producing hepatoma (Eph) receptors are critical for tissue organization. One hallmark of tuberculosis is the presence of granulomas consisting of organized immune cells. The importance of granuloma structure makes it likely that Eph receptors play a role in immunity to tuberculosis.

METHODS

We infected mice with low doses of M. tuberculosis by the aerosol method and examined the effects on ephA gene expression, pathology, composition of lymphocytes in the lungs (by flow cytometry), migration of CD4+ and CD8+ T cells, and numbers of cytokine-expressing cells.

RESULTS

Mice infected with M. tuberculosis displayed higher expression of ephA1 and ephA2 as well as ephrinA1, which encodes the ligand for EphA1 and EphA2. Interestingly, ephA2-/- mice displayed greater pathology, greater accumulation of T cells and dendritic cells, and higher levels of proinflammatory cytokines than did normal C57BL/6 mice. Furthermore, T cells from ephA2-/- mice migrated more efficiently than did those from C57BL/6 mice.

CONCLUSIONS

These observations suggest that ephA-related genes may provide a mechanism that M. tuberculosis uses to circumvent the host response, given that accumulation of T cells appears to be due to the inhibition of immune cell migration by EphA2. Ultimately, the absence of ephA2 results in greater clearance of M. tuberculosis during the chronic phase of infection, suggesting that induction of ephA2 is important for the survival of M. tuberculosis during latency.

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

Although the etiology of early events in rheumatoid arthritis (RA) remains undefined, an anomaly in T cell homeostasis and hyperproliferation of synovial-lining cells are involved in the disease process. Since it has been reported that the ephrin/Eph receptor system plays important signaling roles in inflammation processes, we attempted to examine ephrinB molecules in T cells and synovial cells derived from RA in this study. The expression level of ephrinB1 was significantly high in synovial fibroblasts and CD3-positive exudate lymphocytes in synovial tissues derived from patients with RA compared with those in osteoarthritis (OA). Protein and mRNA levels of ephrinB1 were also higher in peripheral blood lymphocytes (PBLs) prepared from patients with RA than those from normal controls. Similar results were obtained from an animal model of human RA, collagen antibody-induced arthritis mice. Moreover, a recombinant ephrinB1/Fc fusion protein stimulated normal PBLs to exhibit enhanced migration and production of TNF-alpha. EphrinB1/Fc also activated synovial cells established from patients with RA to produce IL-6. Tyrosine phosphorylation of EphB1 was induced in these cells by ephrinB1/Fc. The CpG islands in the 5' upstream regulatory region of the ephrinB1 gene were hypomethylated in RA patients compared with those of normal donors. These results suggest that ephrinB1 and EphB1 receptors play an important role in the inflammatory states of RA, especially by affecting the population and function of T cells. Inhibition of the ephrinB/EphB system might be a novel target for the treatment of RA.

Expression of ephrinB1 and its receptor in glaucomatous optic neuropathy

OBJECTIVE

To determine ephrinB1, ephrinB2 and EphB1 expression in the optic nerve head (ONH) and retina of monkeys with glaucoma and in human ONH astrocytes.

METHODS

Using immunohistochemistry, the localisation of ephrinB1, ephrinB2 and EphB1 was determined in the ONH and retina bilaterally in monkeys with monocular laser-induced glaucoma. RT-PCR, western blot and immunocytochemistry were used to study ephrinB1, ephrinB2 and EphB1 expression in cultured human ONH astrocytes from donors with and without glaucoma.

RESULTS

There was an increase in ephrinB1 and EphB1 expression in mild to moderate glaucoma. In the ONH, both ephrinB1 and EphB1 were localised to astrocytes and EphB1 was also localised to lamina cribrosa cells and perivascular cells. In the retina, ephrinB1 localised to Muller cells and astrocytes, and EphB1 was found in retinal ganglion cells. In ONH astrocytes in humans with glaucoma, ephrinB1 and EphB1 were up-regulated but barely present in donors without glaucoma.

CONCLUSIONS

Ephrins are activated in early and moderate glaucoma in the ONH and retina. We postulate that the up-regulation of Eph/ephrin pathway may play a protective role by limiting axonal damage and inflammatory cell invasion. Loss of ephrin signalling in advanced glaucoma may explain macrophage activation.

Emerging roles of the Angiopoietin-Tie and the ephrin-Eph systems as regulators of cell trafficking

Vascular receptor tyrosine kinases (RTK) have been identified as critical regulatory signaling molecules of developmental and adult vascular morphogenic processes [vascular endothelial growth factor (VEGF) receptors=sprouting; EphB receptors=assembly; Tie2 receptor=maturation and quiescence]. It is intriguing that the same molecules that control the growth of blood and lymphatic vessels play critical roles in the adult to regulate maintenance functions related to vascular homeostasis. VEGF is among the most potent inducers of vascular permeability. The second vascular RTK system, the interaction of paracrine-acting Angiopoietin-1 with its cognate receptor Tie2, acts as an endothelial maintenance and survival-mediating molecular system, which stabilizes the vessel wall and controls endothelial cell quiescence. The third vascular RTK system, the interaction of Eph receptors with their Eph family receptor-interacting protein (ephrin) ligands, transduces positional guidance cues on outgrowing vascular sprouts, which are critical for proper arteriovenous assembly and establishment of blood flow. As such, Eph-ephrin interactions act as an important regulator of cell-cell interactions, exerting propulsive and repulsive functions on neighboring cells and mediating adhesive functions. This review summarizes recent findings related to the roles of the Angiopoietin-Tie and the Eph-ephrin systems as regulators of cell trafficking in the vascular system. The recognition of vascular homeostatic functions of vascular RTKs marks an important change of paradigm in the field of angiogenesis research as it relates angiogenesis-inducing molecules to vascular maintenance functions in the adult. This may also broaden the scope of vascular RTK-targeted therapies.

Putative dual role of ephrin-Eph receptor interactions in inflammation

Inflammation is associated with a decreased adhesion between endothelial cells in blood vessels and an increased adhesion of circulating leukocytes to vascular endothelium and to epithelia of internal organs. These changes lead to leukocyte extravasation and tissue transmigration. We propose that ephrins and Eph receptors play important, but underappreciated, signaling roles in these processes. At early stages of inflammation, EphA2 receptor and ephrin-B2 are overexpressed in endothelial and epithelial cells, thus leading to those events (expression of adhesion molecules on the cell surface and reorganization of the intracellular cytoskeleton) that cause cell repulsion and disruption of endothelial and epithelial barriers. At later stages of inflammation, expression of EphA1, EphA3, EphB3, and EphB4 on leukocytes and endothelial cells decreases, thus promoting adhesion of leukocytes to endothelial cells. Taking into consideration the abundance of ephrins and Eph receptors in tissues and the robustness of their signaling effects, the proposed involvement is likely to be substantial and may constitute a novel therapeutic target.

Molecular mechanisms underlying FOXP3 induction in human T cells

FOXP3 is playing an essential role for T regulatory cells and is involved in the molecular mechanisms controlling immune tolerance. Although the biological relevance of this transcription factor is well documented, the pathways responsible for its induction are still unclear. The current study reveals structure and function of the human FOXP3 promoter, revealing essential molecular mechanisms of its induction. The FOXP3 promoter was defined by RACE, cloned, and functionally analyzed using reporter-gene constructs in primary human T cells. The analysis revealed the basal, T cell-specific promoter with a TATA and CAAT box 6000 bp upstream the translation start site. The basal promoter contains six NF-AT and AP-1 binding sites, which are positively regulating the trans activation of the FOXP3 promoter after triggering of the TCR. The chromatin region containing the FOXP3 promoter was bound by NF-ATc2 under these conditions. Furthermore, FOXP3 expression was observed following TCR engagement. Promoter activity, mRNA, and protein expression of T cells were suppressed by addition of cyclosporin A. Taken together, this study reveals the structure of the human FOXP3 promoter and provides new insights in mechanisms of addressing T regulatory cell-inducing signals useful for promoting immune tolerance. Furthermore, the study identifies essential, positive regulators of the FOXP3 gene and highlights cyclosporin A as an inhibitor of FOXP3 expression contrasting other immunosuppressants such as steroids or rapamycin.

High-Altitude Climate Therapy Reduces Local Airway Inflammation and Modulates Lymphocyte Activation

High-altitude climate therapy is a well-established therapeutic option, which improves clinical symptoms in asthma. However, little is known about the underlying immunological mechanisms. The study investigates the influence of high-altitude climate therapy on airway inflammation and cellular components of specific and unspecific immune response. Exhaled NO significantly decreased within 3 weeks of therapy in patients with allergic and intrinsic, moderate and severe asthma. Interleukin-10 (IL-10)-secreting peripheral blood mononuclear cells (PBMC) increased within 3 weeks of therapy in six of 11 patients, whereas transforming growth factor-beta(1)-secreting PBMC remained stable. Furthermore, monocyte activation, assessed by CD80 expression significantly decreased during therapy. The frequency of CRTH2-expressing T cells decreased, while regulatory T cells (T(reg)) remained stable. FOXP3 and GATA-3 mRNA expression in CD4(+) T cells did not change, while interferon-gamma and IL-13 mRNA expression decreased in eight of 10 patients. The current data demonstrate that high-altitude climate therapy reduces local airway inflammation. Furthermore, monocytes switch towards a tolerogenic phenotype under high-altitude climate therapy. The T(reg)/Th2 ratio increases; however, because of the absence of antigens/allergens, no de novo differentiation of Th2 nor T(reg) cells is observed. The high-altitude climate therapy therefore may form the immunological basis for the endogenous control of allergen-driven diseases.

Recent advances on T-cell regulation by receptor tyrosine kinases

PURPOSE OF REVIEW

This review summarizes recent knowledge on the role of receptor tyrosine kinases, particularly erythropoietin-producing hepatocyte kinases (Ephs), in T-cell function and development.

RECENT FINDINGS

Erythropoietin-producing hepatocyte kinase function and signaling in the immune system have been recently investigated. Cross-linking some Ephs results in T-cell costimulation and reduces the response threshold of T-cell receptor activation. In vivo, T-cell-mediated responses are compromised in EphB6-/- mice. Some Ephs are shown to control T-cell migration and adhesion, as well as the integrity of lymphoid organ structure.

SUMMARY

Ephs are the largest family of receptor tyrosine kinases. Some Ephs are expressed in the lymphoid organs. Ephrins, ligands of Ephs, are also cell surface molecules. Cross-linking of certain Ephs facilitates T-cell activation and proliferation. Under physiologic conditions, such cross-linking by ephrins likely occurs in lymphoid organs, where ephrins on T cells interact with ephrins on the surface of neighboring fraternal T cells or antigen-presenting cells; this may explain why T-cell responses are more effectively initiated in the lymphoid organs. Certain Ephs are also critical for lymphocyte adhesion and migration and for proper lymphoid organ structure. Ephs and ephrins are highly redundant and their interactions promiscuous, suggesting pivotal roles of these molecules in biology. Conversely, such redundancy represents a major challenge to further dissection of the function of individual Ephs. Multiple tissue-specific gene null mutations on Ephs or ephrins will likely reveal more interesting immune-related phenotypes.

Ephrin A receptors and ligands in lesions and normal-appearing white matter in multiple sclerosis

Complexes of the tyrosine kinase ephrin ligands (ephrins) and their receptors (Ephs) provide critical cell recognition signals in CNS development. Complementary ephrin/Eph expression gradients present topographic guidance cues that may either stimulate or repulse axon growth. Some ephrin/Ephs are upregulated in adult CNS injury models. To assess their involvement in multiple sclerosis (MS), ephrin A1-5 and Eph A1-8 expression was analyzed in CNS tissues using immunohistochemistry. Control samples showed distinct expression patterns for each ephrin/Eph on different cell types. Perivascular mononuclear inflammatory cells, reactive astrocytes and macrophages expressed ephrin A1-4, Eph A1, -A3, -A4, -A6 and -A7 in active MS lesions. Axonal ephrin A1 and Eph A3, -A4, and -A7 expression was increased in active lesions and was greater in normal-appearing white matter (NAWM) adjacent to active lesions than within or adjacent to chronic MS lesions, in contralateral NAWM, or in control samples. As in development, therefore, there are temporally dynamic, lesion-associated axonal ephrin/Eph A expression gradients in the CNS of MS patients. These results indicate that ephrin/Eph As are useful cell markers in human CNS tissue samples; they likely are involved in the immunopathogenesis of active lesions and in neurodegeneration in MS NAWM; and they represent potential therapeutic targets in MS.