Eph/Ephrin signaling in injury and inflammation

A conserved Eph family receptor-binding motif on the gH/gL complex of Kaposi's sarcoma-associated herpesvirus and rhesus monkey rhadinovirus

Kaposi’s sarcoma-associated herpesvirus (KSHV) is a human oncogenic virus associated with Kaposi’s sarcoma and two B-cell malignancies. The rhesus monkey rhadinovirus (RRV) is a virus of nonhuman primates that is closely related to KSHV. Eph family receptor tyrosine kinases (Ephs) are cellular receptors for the gH/gL glycoprotein complexes of both KSHV and RRV. Through sequence analysis and mutational screens, we identified conserved residues in the N-terminal domain of KSHV and RRV glycoprotein H that are critical for Eph-binding in vitro. Homology-based structural predictions of the KSHV and RRV gH/gL complexes based on the Epstein-Barr-Virus gH/gL crystal structure located these amino acids in a beta-hairpin on gH, which is likely stabilized by gL and is optimally positioned for protein-protein interactions. Guided by these predictions, we generated recombinant RRV and KSHV strains mutated in the conserved motif as well as an RRV gL null mutant. Inhibition experiments using these mutants confirmed that disruption of the identified Eph-interaction motif or of gL expression resulted in complete detargeting from Ephs. However, all mutants were infectious on all cell types tested, exhibiting normal attachment but a reduction in infectivity of up to one log order of magnitude. While Eph-binding-negative RRV mutants were replication-competent on fibroblasts, their infectivity was comparatively more reduced on endothelial cells with a substantial subpopulation of endothelial cells remaining resistant to infection. Together, this provides evidence for a cell type-specific use of Ephs by RRV. Furthermore, our results demonstrate that gL is dispensable for infection by RRV. Its deletion caused a reduction in infectivity similar to that observed after mutation of Eph-binding residues in gH. Our findings would be compatible with an ability of KSHV and RRV to use other, less efficient entry mediators in lieu of Ephs, although these host factors may not be uniformly expressed by all cells.

In immunocompromised individuals in general and in the context of HIV infection in particular, KSHV is a major cause of cancer and B-cell proliferative malignancies. We identified and mutated conserved residues in the N-terminal domain of the gH/gL glycoprotein complex of KSHV and the related monkey virus RRV that are critical for the interaction with cellular receptors from the Eph family. These findings provide important insight into the function of the γ-herpesviral entry machinery. Using recombinant KSHV and RRV carrying these mutations, we demonstrated that while not strictly essential, gH/gL-Eph interactions are important for efficient infection—for RRV also in a cell-specific manner—but not for attachment of KSHV and RRV. The Eph-detargeted virus mutants described in this study can be used to further dissect the requirements for KSHV and RRV entry and to identify potential alternative entry mediators. Domains and residues on the viral glycoproteins with critical roles in receptor recognition, such as the Eph-binding motif described in this paper, can be informative for the design of inhibitory monoclonal antibodies.

Clinical implications of the plasma EphA2 receptor level in critically ill patients with septic shock

The Eph/ephrin receptor ligand system is known to play a role in inflammation induced by infection, injury, and inflammatory diseases. The present study aimed to evaluate plasma EphA2 receptor levels in critically ill patients with sepsis. This study was a prospective cohort study evaluating samples and clinical data from the medical intensive care unit (MICU) of a 2000-bed university tertiary referral hospital in South Korea. Positive correlations of the plasma EphA2 receptor level with the acute physiology and chronic health evaluation (APACHE) II score and the sequential organ failure assessment (SOFA) score were observed. The area under the curve (AUC) for the plasma EphA2 receptor level on a receiver operating characteristic curve was 0.690 (95% confidence interval [CI], 0.608-0.764); the AUCs for the APACHE II score and SOFA scores were 0.659 (95% CI, 0.576-0.736) and 0.745 (95% CI, 0.666-0.814), respectively. A Cox proportional hazard model identified an association between an increased plasma EphA2 receptor level (>51.5 pg mL-1) and increased risk of 28-day mortality in the MICU (hazard ratio = 3.22, 95% CI, 1.709-6.049). An increased plasma EphA2 receptor level was associated with sepsis severity and 28-day mortality among sepsis patients.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

EPHA6 rs4857055 C > T polymorphism associates with hypertension through triglyceride and LDL particle size in the Korean population

BACKGROUND

Erythropoietin-producing human hepatocellular (Eph) receptors might contribute to the development of atherosclerosis. A genome-wide association study indicated that the Eph receptor A6 gene (EPHA6) associated with at least 1 blood pressure (BP) phenotype. The objective of the present study was to determine whether EPHA6 is a novel candidate gene for hypertension in a Korean population.

METHODS

A total 2146 study participants with normotension and hypertension were included. Genotype data were obtained using a Korean Chip. To assess the association between single-nucleotide polymorphisms (SNPs) and BP, we performed a linear regression analysis, which showed that rs4850755 in the EPHA6 gene was the SNP most highly associated with both systolic and diastolic BP.

RESULTS

The presence of the TT genotype of the EPHA6 rs4857055 C > T SNP was associated with a higher risk of hypertension after adjusting for age, sex, body mass index (BMI), smoking, and drinking [odds ratio 1.533, P = 0.001]. In the control group, significant associations were observed between systolic BP and the rs4857055 polymorphism and between diastolic BP and the rs4857055 polymorphism. In the hypertension group, a significant association was observed between systolic BP and the rs4857055 polymorphism. In the hypertension group, subjects with the TT genotype showed significantly higher systolic BP than CC subjects. Additionally, in the hypertension group, TT carriers showed a higher tendency of serum triglyceride (P = 0.069) and significantly higher apolipoprotein B (P = 0.015) and smaller low-density lipoprotein (LDL) particle size (P < 0.001) than either TC or CC subjects.

CONCLUSIONS

These results could suggest that the EPHA6 rs4857055 C > T SNP is a novel candidate gene for hypertension in the Korean population. Additionally, the TT genotype could be associated with hypertriglyceridemia and small LDL particle size in hypertension.

EphrinB-mediated reverse signalling controls junctional integrity and pro-inflammatory differentiation of endothelial cells

The EphB/ephrinB receptor-ligand system is pivotal for the development of the embryonic vasculature and for angiogenesis in the adult organism. We observed that (i) the expression of ephrinB2 and ephrinB1 is up-regulated in capillaries during inflammation, that (ii) these ligands are localised on the luminal endothelial surface, and that (iii) they interact with the ephrinB-receptor EphB2 on monocyte/macrophages. This study delineates the impact of ephrinB-mediated reverse signalling on the integrity and proinflammatory differentiation of the endothelium. To this end, in vitro analyses with human cultured endothelial cells reveal that knockdown of ephrinB2 or ephrinB1 impairs monocyte transmigration through the endothelium. While ephrinB2 but not ephrinB1 interacts with PECAM-1 (CD31) in this context, reverse signalling by ephrinB1 but not ephrinB2 elicits a c-Jun N-terminal kinase (JNK)-dependent up-regulation of E-selectin expression. Furthermore, treatment of endothelial cells with soluble EphB2 receptor bodies or EphB2-overexpressing mouse myeloma cells links ephrinB2 to PECAM-1 and induces its Src-dependent phosphorylation while diminishing Src homology phosphotyrosyl phosphatase-2 (SHP-2) activity and increasing endothelial cell permeability. We conclude that extravasation of EphB2 positive leukocyte populations is facilitated by lowering the integrity of endothelial cell junctions and enhancing the pro-inflammatory phenotype of the endothelium through activation of ephrinB ligands.

Current Understanding of the Pathways Involved in Adult Stem and Progenitor Cell Migration for Tissue Homeostasis and Repair

With the advancements in the field of adult stem and progenitor cells grows the recognition that the motility of primitive cells is a pivotal aspect of their functionality. There is accumulating evidence that the recruitment of tissue-resident and circulating cells is critical for organ homeostasis and effective injury responses, whereas the pathobiology of degenerative diseases, neoplasm and aging, might be rooted in the altered ability of immature cells to migrate. Furthermore, understanding the biological machinery determining the translocation patterns of tissue progenitors is of great relevance for the emerging methodologies for cell-based therapies and regenerative medicine. The present article provides an overview of studies addressing the physiological significance and diverse modes of stem and progenitor cell trafficking in adult mammalian organs, discusses the major microenvironmental cues regulating cell migration, and describes the implementation of live imaging approaches for the exploration of stem cell movement in tissues and the factors dictating the motility of endogenous and transplanted cells with regenerative potential.

A neuroprotective astrocyte state is induced by neuronal signal EphB1 but fails in ALS models

Astrocyte responses to neuronal injury may be beneficial or detrimental to neuronal recovery, but the mechanisms that determine these different responses are poorly understood. Here we show that ephrin type-B receptor 1 (EphB1) is upregulated in injured motor neurons, which in turn can activate astrocytes through ephrin-B1-mediated stimulation of signal transducer and activator of transcription-3 (STAT3). Transcriptional analysis shows that EphB1 induces a protective and anti-inflammatory signature in astrocytes, partially linked to the STAT3 network. This is distinct from the response evoked by interleukin (IL)-6 that is known to induce both pro inflammatory and anti-inflammatory processes. Finally, we demonstrate that the EphB1-ephrin-B1 pathway is disrupted in human stem cell derived astrocyte and mouse models of amyotrophic lateral sclerosis (ALS). Our work identifies an early neuronal help-me signal that activates a neuroprotective astrocytic response, which fails in ALS, and therefore represents an attractive therapeutic target.

Identification of novel molecular signatures of IgA nephropathy through an integrative -omics analysis

IgA nephropathy (IgAN) is the most prevalent among primary glomerular diseases worldwide. Although our understanding of IgAN has advanced significantly, its underlying biology and potential drug targets are still unexplored. We investigated a combinatorial approach for the analysis of IgAN-relevant -omics data, aiming at identification of novel molecular signatures of the disease. Nine published urinary proteomics datasets were collected and the reported differentially expressed proteins in IgAN vs. healthy controls were integrated into known biological pathways. Proteins participating in these pathways were subjected to multi-step assessment, including investigation of IgAN transcriptomics datasets (Nephroseq database), their reported protein-protein interactions (STRING database), kidney tissue expression (Human Protein Atlas) and literature mining. Through this process, from an initial dataset of 232 proteins significantly associated with IgAN, 20 pathways were predicted, yielding 657 proteins for further analysis. Step-wise evaluation highlighted 20 proteins of possibly high relevance to IgAN and/or kidney disease. Experimental validation of 3 predicted relevant proteins, adenylyl cyclase-associated protein 1 (CAP1), SHC-transforming protein 1 (SHC1) and prolylcarboxypeptidase (PRCP) was performed by immunostaining of human kidney sections. Collectively, this study presents an integrative procedure for -omics data exploitation, giving rise to biologically relevant results.

Effect of magnolol on cerebral injury and blood brain barrier dysfunction induced by ischemia-reperfusion in vivo and in vitro

Magnolol, a neolignan compound isolated from traditional Chinese medicine Magnolia officinalis, has a potentially therapeutic influence on ischemic stroke. Previous studies have demonstrated that cerebral ischemia-reperfusion (I-R) and blood-brain barrier (BBB) are involved in the pathogeneses of stroke. Therefore, in vivo and in vitro studies were designed to investigate the effects of magnolol on I-R-induced neural injury and BBB dysfunction. In cerebral I-R model of mice, cerebral infarct volumes, brain water content, and the exudation of Evans blue were significantly reduced by intravenous injection with magnolol at the doses of 1.4, 7.0, and 35.0 μg/kg. When primary cultured microglial cells were treated with 1 μg/ml lipopolysaccharide (LPS) plus increasing concentrations of magnolol, ranging from 0.01 to 10 μmol/L, magnolol could statistically inhibit LPS-induced NO release, TNF-α secretion, and expression of p65 subunit of NF-κB in the nucleus of microglial cells. In the media of brain microvascular endothelial cells (BMECs), oxygen and glucose deprivation-reperfusion (OGD-R) could remarkably lead to the elevation of TNF-α and IL-1β levels, while magnolol evidently reversed these effects. In BBB model in vitro, magnolol dose- and time-dependently declined BBB hyperpermeability induced by oxygen and glucose deprivation (OGD), OGD-R, and ephrin-A1 treatment. More importantly, magnolol could obviously inhibit phosphorylation of EphA2 (p-EphA2) not only in ephrin-A1-treated BMECs but also in cerebral I-R model of mice. In contrast to p-EphA2, magnolol significantly increased ZO-1 and occludin levels in BMECs subjected to OGD. Taken together, magnolol can protect neural damage from cerebral ischemia- and OGD-reperfusion, which may be associated with suppressing cerebral inflammation and improving BBB function.

All-trans retinoic acid attenuates bleomycin-induced pulmonary fibrosis via downregulating EphA2-EphrinA1 signaling

The role of all-trans retinoic acid (ATRA) in pulmonary fibrosis is relatively unknown, although this metabolite modulates cell differentiation, proliferation, and development. We aimed to evaluate the role of ATRA in bleomycin-induced pulmonary fibrosis, and whether the mechanism involves EphA2-EphrinA1 and PI3K-Akt signaling. We evaluated three groups of mice: a control group (intraperitoneal DMSO injection 3 times weekly after PBS instillation), bleomycin group (intraperitoneal DMSO injection 3 times weekly after bleomycin instillation), and bleomycin + ATRA group (intraperitoneal ATRA injection 3 times weekly after bleomycin instillation). The cell counts and protein concentration in the bronchoalveolar lavage fluid (BALF), changes in histopathology, Ashcroft score, hydroxyproline assay, expression of several signal pathway proteins including EphA2-EphrinA1, and PI3K-Akt, and cytokine levels were compared among the groups. We found that bleomycin significantly increased the protein concentration in the BALF, Ashcroft score in lung tissue, and hydroxyproline contents in lung lysates. Furthermore, bleomycin upregulated EphA2, EphrinA1, PI3K 110γ, Akt, IL-6 and TNF-α. However, administration of ATRA attenuated the upregulation of EphA2-EphrinA1 and PI3K-Akt after bleomycin instillation, and decreased pulmonary fibrosis. In addition, ATRA suppressed IL-6 and TNF-α production induced by bleomycin-induced injury. Collectively, these data suggest that ATRA attenuates bleomycin-induced pulmonary fibrosis by regulating EphA2-EphrinA1 and PI3K-Akt signaling.

Pericytes are heterogeneous in their origin within the same tissue

Pericytes heterogeneity is based on their morphology, distribution, and markers. It is well known that pericytes from different organs may have distinct embryonic sources. Yamazaki et al. (2017) using several transgenic mouse model reveal by cell-lineage tracing that pericytes are even more heterogeneous than previously appreciated. This study shows that pericytes from within the same tissue may be heterogeneous in their origin. Remarkably, a subpopulation of embryonic dermal pericytes derives from the hematopoietic lineage, an unexpected source. Reconstructing the lineage of pericytes is central to understanding development, and also for the diagnosis and treatment of diseases in which pericytes play important roles.

Design and evaluation of EphrinA1 mutants with cerebral protective effect

The activation of EphA2 receptor by its natural ligand EphrinA1 causes blood brain barrier dysfunction, and inactivation of EphA2 reduces BBB damage in ischemic stroke. Thus, EphA2 targeted antagonists may serve as neuroprotective agents. We engineered four mutants of EphrinA1, EM1, EM2, EM3 and EM4, respectively. The computational analysis showed that these four mutants were capable of interacting with EphA2. Their potential neuroprotective effects were examined in mouse focal ischemia/reperfusion (I/R) model. EM2 exhibited strong neuroprotective effects, including reduced brain infarct volume, neuronal apoptosis, cerebral edema, and improved neurological scores. The EM2-mediated protection was associated with a comparative decrease in BBB leakage, inflammatory infiltration, and higher expression levels of tight junction proteins, such as zonula occludens-1 and Occludin. I/R-induced high expression of Rho-associated protein kinase 2 (ROCK2) was down-regulated after EM2 treatment. Moreover, EM2 reduced agonist doxazosin-induced EphA2 phosphorylation and cells rounding in PC3 cells, indicating EphA2-antagonizing activity of EM2. These finding provided evidences of the neuroprotection of EphA2 antagonist and a novel approach for ischemic stroke treatment. These results also suggested that a receptor agonist can be switched to an antagonist by substituting one or more relevant residues.

Clinical and molecular features of rapidly progressive chronic hypersensitivity pneumonitis

Background: Chronic hypersensitivity pneumonitis (CHP) is characterized by varying degrees of inflammation and fibrosis of the lungs caused by a variety of inhaled antigens. Despite extensive efforts to minimize exposure to the antigens, patients with CHP sometimes experience rapid deterioration of their pulmonary functions, resulting in death within a few years. Objectives: This study aimed to define clearly the clinical and molecular features of patients with rapidly progressive CHP. Methods: Annual decline in pulmonary functions and its association with clinical variables was evaluated in 43 patients with CHP. The RNA from frozen lung specimens of nine patients with rapidly progressive CHP and normal control subjects was profiled using Illumina HumanWG-6 v3 Expression BeadChips, and an Ingenuity Pathway Analysis was performed to identify the altered functional and canonical signaling pathways. Results: Patients with more than 10% annual decline in forced vital capacity and those with more than 15% annual decline in diffusion capacity for carbon monoxide showed significantly poor overall survival rates (p=0.002 and p=0.001, respectively). According to the gene expression analysis, 160 genes, including cystatin SN (CST1), ephrin-A2 (EFNA2), and wingless-type MMTV integration site family, member 7B (WNT7B) were upregulated, and pathways related to inflammatory responses and autoimmune diseases were differentially expressed. Conclusion: Greater annual decline in pulmonary function can predict poorer prognosis of patients with CHP. Genes and pathways related to inflammatory responses and autoimmune diseases have potential roles in the pathogenesis of rapidly progressive CHP, suggesting their potential as diagnostic biomarkers and/or therapeutic targets. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 48-57).

EphrinB2 Activation Enhances Vascular Repair Mechanisms and Reduces Brain Swelling After Mild Cerebral Ischemia

OBJECTIVE

Cerebral edema caused by the disruption of the blood-brain barrier is a major complication after stroke. Therefore, strategies to accelerate and enhance neurovascular recovery after stroke are of prime interest. Our main aim was to study the role of ephrinB2/EphB4 signaling in mediating the vascular repair and in blood-brain barrier restoration after mild cerebral ischemia occlusion/reperfusion.

APPROACH AND RESULTS

Here, we show that the guidance molecule ephrinB2 plays a key role in neurovascular protection and blood-brain barrier restoration after stroke. In a focal stroke model, we characterize the stroke-induced damage to cerebral blood vessels and their subsequent endogenous repair on a cellular, molecular, and functional level. EphrinB2 and its tyrosine kinase receptor EphB4 are upregulated early after stroke by endothelial cells and perivascular support cells, in parallel to their reassembly during neurovascular recovery. Using both retroviral and pharmacological approaches, we show that the inhibition of ephrinB2/EphB4 signaling suppresses post-middle cerebral artery occlusion neurovascular repair mechanisms resulting in an aggravation of brain swelling. In contrast, the activation of ephrinB2 after brain ischemia leads to an increased pericyte recruitment and increased endothelial-pericyte interaction, resulting in an accelerated neurovascular repair after ischemia.

CONCLUSIONS

We show that reducing swelling could result in improved outcome because of reduction in damaged brain tissue. We also identify a novel role for ephrinB2/EphB4 signaling in the maintenance of the neurovascular homeostasis and provide a novel therapeutic approach in reducing brain swelling after stroke.

Positive effects of intermittent fasting in ischemic stroke

Intermittent fasting (IF) is a dietary protocol where energy restriction is induced by alternate periods of ad libitum feeding and fasting. Prophylactic intermittent fasting has been shown to extend lifespan and attenuate the progress and severity of age-related diseases such as cardiovascular (e.g. stroke and myocardial infarction), neurodegenerative (e.g. Alzheimer's disease and Parkinson's disease) and cancerous diseases in animal models. Stroke is the second leading cause of death, and lifestyle risk factors such as obesity and physical inactivity have been associated with elevated risks of stroke in humans. Recent studies have shown that prophylactic IF may mitigate tissue damage and neurological deficit following ischemic stroke by a mechanism(s) involving suppression of excitotoxicity, oxidative stress, inflammation and cell death pathways in animal stroke models. This review summarizes data supporting the potential hormesis mechanisms of prophylactic IF in animal models, and with a focus on findings from animal studies of prophylactic IF in stroke in our laboratory.

The role of Eph/ephrin molecules in stromal–hematopoietic interactions

Bone marrow mesenchymal stromal/stem cells(BMSC) are fundamental regulatory elements of the hematopoietic stem cell niche; however, the molecular signals that mediate BMSC support of hematopoiesis are poorly understood. Recent studies indicate that BMSC and hematopoietic stem/progenitors cells differentially express the Eph cell surface tyrosine kinase receptors, and their ephrinligands. Eph/ephrin interactions are thought to mediate cross-talk between BMSC and different hematopoietic cell populations to influence cell development, migration and function. This review summarizes Eph/ephrin interactions in the regulation of BMSC communication with hematopoietic stem/progenitor cells and discusses Eph/ephrintargeted therapeutic strategies that are currently being pursued or various hematotological malignancies.

EPHA4-FC TREATMENT REDUCES ISCHEMIA/REPERFUSION-INDUCED INTESTINAL INJURY BY INHIBITING VASCULAR PERMEABILITY

The inflammatory response is characterized by increased endothelial permeability, which permits the passage of fluid and inflammatory cells into interstitial spaces. The Eph/ephrin receptor ligand system plays a role in inflammation through a signaling cascade, which modifies Rho-GTPase activity. We hypothesized that blocking Eph/ephrin signaling using an EphA4-Fc would result in decreased inflammation and tissue injury in a model of ischemia/reperfusion (I/R) injury. Mice undergoing intestinal I/R pretreated with the EphA4-Fc had significantly reduced intestinal injury compared to mice injected with the control Fc. This reduction in I/R injury was accompanied by significantly reduced neutrophil infiltration, but did not affect intestinal inflammatory cytokine generation. Using microdialysis, we identified that intestinal I/R induced a marked increase in systemic vascular leakage, which was completely abrogated in EphA4-Fc-treated mice. Finally, we confirmed the direct role of Eph/ephrin signaling in endothelial leakage by demonstrating that EphA4-Fc inhibited tumor necrosis factor-α-induced vascular permeability in human umbilical vein endothelial cells. This study identifies that Eph/ephrin interaction induces proinflammatory signaling in vivo by inducing vascular leak and neutrophil infiltration, which results in tissue injury in intestinal I/R. Therefore, therapeutic targeting of Eph/ephrin interaction using inhibitors, such as EphA4-Fc, may be a novel method to prevent tissue injury in acute inflammation by influencing endothelial integrity and by controlling vascular leak.

The intragraft microenvironment as a central determinant of chronic rejection or local immunoregulation/tolerance

PURPOSE OF REVIEW

Chronic rejection is associated with persistent mononuclear cell recruitment, endothelial activation and proliferation, local tissue hypoxia and related biology that enhance effector immune responses. In contrast, the tumor microenvironment elicits signals/factors that inhibit effector T cell responses and rather promote immunoregulation locally within the tissue itself. The identification of immunoregulatory check points and/or secreted factors that are deficient within allografts is of great importance in the understanding and prevention of chronic rejection.

RECENT FINDINGS

The relative deficiency of immunomodulatory molecules (cell surface and secreted) on microvascular endothelial cells within the intragraft microenvironment, is of functional importance in shaping the phenotype of rejection. These regulatory molecules include coinhibitory and/or intracellular regulatory signals/factors that enhance local activation of T regulatory cells. For example, semaphorins may interact with endothelial cells and CD4 T cells to promote local tolerance. Additionally, metabolites and electrolytes within the allograft microenvironment may regulate local effector and regulatory cell responses.

SUMMARY

Multiple factors within allografts shape the microenvironment either towards local immunoregulation or proinflammation. Promoting the expression of intragraft cell surface or secreted molecules that support immunoregulation will be critical for long-term graft survival and/or alloimmune tolerance.

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.

Truncated EphA2 likely potentiates cell adhesion via integrins as well as infiltration and/or lodgment of a monocyte/macrophage cell line in the red pulp and marginal zone of the mouse spleen, where ephrin-A1 is prominently expressed in the vasculature

We previously established a J774.1 monocyte/macrophage subline expressing a truncated EphA2 construct lacking the kinase domain. We demonstrated that following ephrin-A1 stimulation, endogenous EphA2 promotes cell adhesion through interaction with integrins and integrin ligands such as ICAM1 and that truncated EphA2 potentiates the adhesion and becomes associated with the integrin/integrin ligand complex. Based on these findings, we hypothesized that the EphA/ephrin-A system, particularly EphA2/ephrin-A1, regulates transendothelial migration/tissue infiltration of monocytes/macrophages, because ephrin-A1 is widely recognized to be upregulated in inflammatory vasculatures. To evaluate whether this hypothesis is applicable in the spleen, we screened for EphA2/ephrin-A1 expression and reexamined the cellular properties of the J774.1 subline. We found that ephrin-A1 was expressed in the vasculature of the marginal zone and the red pulp and that its expression was upregulated in response to phagocyte depletion; further, CD115, F4/80, and CXCR4 were expressed in J774.1 cells, which serve as a usable substitute for monocytes/macrophages. Moreover, following ephrin-A1 stimulation, truncated EphA2 did not detectably interfere with the phosphorylation of endogenous EphA2, and it potentiated cell adhesion possibly through modulation of integrin avidity. Accordingly, by intravenously injecting mice with equal numbers of J774.1 and the subline cells labeled with distinct fluorochromes, we determined that truncated EphA2 markedly potentiated preferential cell infiltration into the red pulp and the marginal zone. Thus, modulation of EphA2 signaling might contribute to effective transplantation of tissue-specific resident macrophages and/or monocytes.

EphA2 promotes cell adhesion and spreading of monocyte and monocyte/macrophage cell lines on integrin ligand-coated surfaces

Eph signaling, which arises following stimulation by ephrins, is known to induce opposite cell behaviors such as promoting and inhibiting cell adhesion as well as promoting cell-cell adhesion and repulsion by altering the organization of the actin cytoskeleton and influencing the adhesion activities of integrins. However, crosstalk between Eph/ephrin with integrin signaling has not been fully elucidated in leukocytes, including monocytes and their related cells. Using a cell attachment stripe assay, we have shown that, following stimulation with ephrin-A1, kinase-independent EphA2 promoted cell spreading/elongation as well as adhesion to integrin ligand-coated surfaces in cultured U937 (monocyte) and J774.1 (monocyte/macrophage) cells as well as sublines of these cells expressing dominant negative EphA2 that lacks most of the intracellular region. Moreover, a pull-down assay showed that dominant negative EphA2 is recruited to the β2 integrin/ICAM1 and β2 integrin/VCAM1 molecular complexes in the subline cells following stimulation with ephrin-A1-Fc. Notably, this study is the first comprehensive analysis of the effects of EphA2 receptors on integrin-mediated cell adhesion in monocytic cells. Based on these findings we propose that EphA2 promotes cell adhesion by an unknown signaling pathway that largely depends on the extracellular region of EphA2 and the activation of outside-in integrin signaling.

Targeted Sequencing Reveals Low-Frequency Variants in EPHA Genes as Markers of Paclitaxel-Induced Peripheral Neuropathy

Purpose: Neuropathy is the dose-limiting toxicity of paclitaxel and a major cause for decreased quality of life. Genetic factors have been shown to contribute to paclitaxel neuropathy susceptibility; however, the major causes for interindividual differences remain unexplained. In this study, we identified genetic markers associated with paclitaxel-induced neuropathy through massive sequencing of candidate genes.Experimental Design: We sequenced the coding region of 4 EPHA genes, 5 genes involved in paclitaxel pharmacokinetics, and 30 Charcot-Marie-Tooth genes, in 228 cancer patients with no/low neuropathy or high-grade neuropathy during paclitaxel treatment. An independent validation series included 202 paclitaxel-treated patients. Variation-/gene-based analyses were used to compare variant frequencies among neuropathy groups, and Cox regression models were used to analyze neuropathy along treatment.Results: Gene-based analysis identified EPHA6 as the gene most significantly associated with paclitaxel-induced neuropathy. Low-frequency nonsynonymous variants in EPHA6 were present exclusively in patients with high neuropathy, and all affected the ligand-binding domain of the protein. Accumulated dose analysis in the discovery series showed a significantly higher neuropathy risk for EPHA5/6/8 low-frequency nonsynonymous variant carriers [HR, 14.60; 95% confidence interval (CI), 2.33-91.62; P = 0.0042], and an independent cohort confirmed an increased neuropathy risk (HR, 2.07; 95% CI, 1.14-3.77; P = 0.017). Combining the series gave an estimated 2.5-fold higher risk of neuropathy (95% CI, 1.46-4.31; P = 9.1 × 10^-4).Conclusions: This first study sequencing EPHA genes revealed that low-frequency variants in EPHA6, EPHA5, and EPHA8 contribute to the susceptibility to paclitaxel-induced neuropathy. Furthermore, EPHA's neuronal injury repair function suggests that these genes might constitute important neuropathy markers for many neurotoxic drugs. Clin Cancer Res; 23(5); 1227-35. ©2016 AACR.

Inhibition of EphA2/EphrinA1 signal attenuates lipopolysaccharide-induced lung injury

Eph-Ephrin signalling mediates various cellular processes, including vasculogenesis, angiogenesis, cell migration, axon guidance, fluid homoeostasis and repair after injury. Although previous studies have demonstrated that stimulation of the EphA receptor induces increased vascular permeability and inflammatory response in lung injury, the detailed mechanisms of EphA2 signalling are unknown. In the present study, we evaluated the role of EphA2 signalling in mice with lipopolysaccharide (LPS)-induced lung injury. Acute LPS exposure significantly up-regulated EphA2 and EphrinA1 expression. Compared with LPS+IgG mice (IgG instillation after LPS exposure), LPS+EphA2 mAb mice [EphA2 monoclonal antibody (mAb) instillation posttreatment after LPS exposure] had attenuated lung injury and reduced cell counts and protein concentration of bronchoalveolar lavage fluid (BALF). EphA2 mAb posttreatment down-regulated the expression of phosphoinositide 3-kinases (PI3K) 110γ, phospho-Akt, phospho-NF-κB p65, phospho-Src and phospho-S6K in lung lysates. In addition, inhibiting the EphA2 receptor augmented the expression of E-cadherin, which is involved in cell-cell adhesion. Our study identified EphA2 receptor as an unrecognized modulator of several signalling pathways-including PI3K-Akt-NF-kB, Src-NF-κB, E-cadherin and mTOR-in LPS-induced lung injury. These results suggest that EphA2 receptor inhibitors may function as novel therapeutic agents for LPS-induced lung injury.

Development of Specific, Irreversible Inhibitors for a Receptor Tyrosine Kinase EphB3

Erythropoietin-producing human hepatocellular carcinoma (Eph) receptor tyrosine kinases (RTKs) regulate a variety of dynamic cellular events, including cell protrusion, migration, proliferation, and cell-fate determination. Small-molecule inhibitors of Eph kinases are valuable tools for dissecting the physiological and pathological roles of Eph. However, there is a lack of small-molecule inhibitors that are selective for individual Eph isoforms due to the high homology within the family. Herein, we report the development of the first potent and specific inhibitors of a single Eph isoform, EphB3. Through structural bioinformatic analysis, we identified a cysteine in the hinge region of the EphB3 kinase domain, a feature that is not shared with any other human kinases. We synthesized and characterized a series of electrophilic quinazolines to target this unique, reactive feature in EphB3. Some of the electrophilic quinazolines selectively and potently inhibited EphB3 both in vitro and in cells. Cocrystal structures of EphB3 in complex with two quinazolines confirmed the covalent linkage between the protein and the inhibitors. A "clickable" version of an optimized inhibitor was created and employed to verify specific target engagement in the whole proteome and to probe the extent and kinetics of target engagement of existing EphB3 inhibitors. Furthermore, we demonstrate that the autophosphorylation of EphB3 within the juxtamembrane region occurs in trans using a specific inhibitor. These exquisitely specific inhibitors will facilitate the dissection of EphB3's role in various biological processes and disease contribution.

Activation of ephrinB-EphB receptor signalling in rat spinal cord contributes to maintenance of diabetic neuropathic pain

BACKGROUND

Diabetic neuropathic pain (DNP) is severe and intractable in clinic. The specific cellular and molecular mechanisms underlying DNP remain elusive and its treatment are limited. We investigated roles of EphB1 receptor in the development of DNP.

METHODS

Diabetic neuropathic pain was produced in male, adult, Sprague-Dawley rats by a single i.p. streptozotocin (STZ) or alloxan. Western blot analysis and immunohistochemistry were used to analyse expression of EphB1 receptor as well as the activation of the glial cells and the pro-inflammatory cytokines in the spinal cord. DNP manifested as mechanical allodynia, which was determined by measuring incidence of foot withdrawal in response to mechanical indentation of the hind paw by an electro von Frey filament.

RESULTS

Diabetic neuropathic pain and high blood glucose were exhibited simultaneously in around 70% of animals that received i.p. STZ or alloxan. Phosphorylation of EphB1, activation of the astrocytes and microglial cells, and level of tumour necrosis factor (TNF)-α and interleukin (IL)-1β in the spinal cord were significantly increased in rats with DNP. Spinal blocking EphB1 receptor activation in the late phase after STZ injection significantly suppressed the established mechanical allodynia as well as activation of the astrocytes and microglial cells and activity of TNF-α and IL-1β. However, spinal treatment of EphB1-Fc in the early phase after STZ injection did not prevent the induction of DNP.

CONCLUSIONS

EphB1 receptor activation in the spinal cord is critical to the maintenance, but not induction of diabetic pain. EphB1 receptor may be a potential target for relieving the established diabetic pain.

SIGNIFICANCE

Activation of EphB1 receptor in the spinal cord is critical to maintaining the established diabetic neuropathic pain, but not to diabetic pain induction. Spinal blocking EphB1 receptor activation suppresses ongoing diabetic neuropathic pain.

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.

Dysregulation of EGFR Pathway in EphA2 Cell Subpopulation Significantly Associates with Poor Prognosis in Colorectal Cancer

PURPOSE

EphA2 receptor is involved in multiple cross-talks with other cellular networks, including EGFR, FAK, and VEGF pathways, with which it collaborates to stimulate cell migration, invasion, and metastasis. Colorectal cancer (CRC) EphA2 overexpression has also been correlated to stem-like properties of cells and tumor malignancy. We investigated the molecular cross-talk and miRNAs modulation of the EphA2 and EGFR pathways. We also explored the role of EphA2/EGFR pathway mediators as prognostic factors or predictors of cetuximab benefit in patients with CRC.

EXPERIMENTAL DESIGN

Gene expression analysis was performed in EphA2_high cells isolated from CRC of the AOM/DSS murine model by FACS-assisted procedures. Six independent cohorts of patients were stratified by EphA2 expression to determine the potential prognostic role of a EphA2/EGFR signature and its effect on cetuximab treatment response.

RESULTS

We identified a gene expression pattern (EphA2, Efna1, Egfr, Ptpn12, and Atf2) reflecting the activation of EphA2 and EGFR pathways and a coherent dysregulation of mir-26b and mir-200a. Such a pattern showed prognostic significance in patients with stage I-III CRC, in both univariate and multivariate analysis. In patients with stage IV and WT KRAS, EphA2/Efna1/Egfr gene expression status was significantly associated with poor response to cetuximab treatment. Furthermore, EphA2 and EGFR overexpression showed a combined effect relative to cetuximab resistance, independently from KRAS mutation status.

CONCLUSIONS

These results suggest that EphA2/Efna1/Egfr genes, linked to a possible control by miR-200a and miR-26b, could be proposed as novel CRC prognostic biomarkers. Moreover, EphA2 could be linked to a mechanism of resistance to cetuximab alternative to KRAS mutations. Clin Cancer Res; 23(1); 159-70. ©2016 AACR.

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.

Astrocytic Ephrin-B1 Regulates Synapse Remodeling Following Traumatic Brain Injury

Traumatic brain injury (TBI) can result in tissue alterations distant from the site of the initial injury, which can trigger pathological changes within hippocampal circuits and are thought to contribute to long-term cognitive and neuropsychological impairments. However, our understanding of secondary injury mechanisms is limited. Astrocytes play an important role in brain repair after injury and astrocyte-mediated mechanisms that are implicated in synapse development are likely important in injury-induced synapse remodeling. Our studies suggest a new role of ephrin-B1, which is known to regulate synapse development in neurons, in astrocyte-mediated synapse remodeling following TBI. Indeed, we observed a transient upregulation of ephrin-B1 immunoreactivity in hippocampal astrocytes following moderate controlled cortical impact model of TBI. The upregulation of ephrin-B1 levels in hippocampal astrocytes coincided with a decline in the number of vGlut1-positive glutamatergic input to CA1 neurons at 3 days post injury even in the absence of hippocampal neuron loss. In contrast, tamoxifen-induced ablation of ephrin-B1 from adult astrocytes in ephrin-B1^loxP/yERT2-Cre^GFAP mice accelerated the recovery of vGlut1-positive glutamatergic input to CA1 neurons after TBI. Finally, our studies suggest that astrocytic ephrin-B1 may play an active role in injury-induced synapse remodeling through the activation of STAT3-mediated signaling in astrocytes. TBI-induced upregulation of STAT3 phosphorylation within the hippocampus was suppressed by astrocyte-specific ablation of ephrin-B1 in vivo, whereas the activation of ephrin-B1 in astrocytes triggered an increase in STAT3 phosphorylation in vitro. Thus, regulation of ephrin-B1 signaling in astrocytes may provide new therapeutic opportunities to aid functional recovery after TBI.

Molecular, cellular and functional events in axonal sprouting after stroke

Stroke is the leading cause of adult disability. Yet there is a limited degree of recovery in this disease. One of the mechanisms of recovery is the formation of new connections in the brain and spinal cord after stroke: post-stroke axonal sprouting. Studies indicate that post-stroke axonal sprouting occurs in mice, rats, primates and humans. Inducing post-stroke axonal sprouting in specific connections enhances recovery; blocking axonal sprouting impairs recovery. Behavioral activity patterns after stroke modify the axonal sprouting response. A unique regenerative molecular program mediates this aspect of tissue repair in the CNS. The types of connections that are formed after stroke indicate three patterns of axonal sprouting after stroke: reactive, reparative and unbounded axonal sprouting. These differ in mechanism, location, relationship to behavioral recovery and, importantly, in their prospect for therapeutic manipulation to enhance tissue repair.

Periostin: A Downstream Mediator of EphB4-Induced Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Erythropoietin-producing hepatocyte B4 (EphB4) has been reported to be a key molecular switch in the regulation of bone homeostasis, but the underlying mechanism remains poorly understood. In this study, we investigated the role of EphB4 in regulating the expression of periostin (POSTN) within bone marrow-derived mesenchymal stem cells (MSCs) and assessed its effect and molecular mechanism of osteogenic induction in vitro. Treatment with ephrinB2-FC significantly increased the expression of POSTN in MSCs, and the inhibition of EphB4 could abrogate this effect. In addition, osteogenic markers were upregulated especially in MSCs overexpressing EphB4. To elucidate the underlying mechanism of cross talk between EphB4 and the Wnt pathway, we detected the change in protein expression of phosphorylated-glycogen synthase kinase 3β-serine 9 (p-GSK-3β-Ser9) and β-catenin, as well as the osteogenic markers Runx2 and COL1. The results showed that GSK-3β activation and osteogenic marker expression levels were downregulated by ephrinB2-FC treatment, but these effects were inhibited by blocking integrin αvβ3 in MSCs. Our findings demonstrate that EphB4 can promote osteogenic differentiation of MSCs via upregulation of POSTN expression. It not only helps to reveal the interaction mechanism between EphB4 and Wnt pathway but also brings a better understanding of EphB4/ephrinB2 signaling in bone homeostasis.

Eph receptor and ephrin function in breast, gut, and skin epithelia

Epithelial cells are tightly coupled together through specialized intercellular junctions, including adherens junctions, desmosomes, tight junctions, and gap junctions. A growing body of evidence suggests epithelial cells also directly exchange information at cell-cell contacts via the Eph family of receptor tyrosine kinases and their membrane-associated ephrin ligands. Ligand-dependent and -independent signaling via Eph receptors as well as reverse signaling through ephrins impact epithelial tissue homeostasis by organizing stem cell compartments and regulating cell proliferation, migration, adhesion, differentiation, and survival. This review focuses on breast, gut, and skin epithelia as representative examples for how Eph receptors and ephrins modulate diverse epithelial cell responses in a context-dependent manner. Abnormal Eph receptor and ephrin signaling is implicated in a variety of epithelial diseases raising the intriguing possibility that this cell-cell communication pathway can be therapeutically harnessed to normalize epithelial function in pathological settings like cancer or chronic inflammation.

EphA2 Receptor Signaling Mediates Inflammatory Responses in Lipopolysaccharide-Induced Lung Injury

Background

Eph receptors and ephrin ligands have several functions including angiogenesis, cell migration, axon guidance, fluid homeostasis, oncogenesis, inflammation and injury repair. The EphA2 receptor potentially mediates the regulation of vascular permeability and inflammation in response to lung injury.

Methods

Mice were divided into 3 experimental groups to study the role of EphA2 signaling in the lipopolysaccharide (LPS)-induced lung injury model i.e., IgG+phosphate-buffered saline (PBS) group (IgG instillation before PBS exposure), IgG+LPS group (IgG instillation before LPS exposure) and EphA2 monoclonal antibody (mAb)+LPS group (EphA2 mAb pretreatment before LPS exposure).

Results

EphA2 and ephrinA1 were upregulated in LPS-induced lung injury. The lung injury score of the EphA2 mAb+LPS group was lower than that of the IgG+LPS group (4.30±2.93 vs. 11.45±1.20, respectively; p=0.004). Cell counts (EphA2 mAb+LPS: 11.33×10⁴±8.84×10⁴ vs. IgG+LPS: 208.0×10⁴±122.6×10⁴; p=0.018) and total protein concentrations (EphA2 mAb+LPS: 0.52±0.41 mg/mL vs. IgG+LPS: 1.38±1.08 mg/mL; p=0.192) were decreased in EphA2 mAb+LPS group, as compared to the IgG+LPS group. In addition, EphA2 antagonism reduced the expression of phospho-p85, phosphoinositide 3-kinase 110γ, phospho-Akt, nuclear factor κB, and proinflammatory cytokines.

Conclusion

This results of the study indicated a role for EphA2-ephrinA1 signaling in the pathogenesis of LPS-induced lung injury. Furthermore, EphA2 antagonism inhibits the phosphoinositide 3-kinase-Akt pathway and attenuates inflammation.

Oleic acid enhances the motility of umbilical cord blood derived mesenchymal stem cells through EphB2-dependent F-actin formation

The role of unsaturated fatty acids (UFAs) is essential for determining stem cell functions. Eph/Ephrin interactions are important for regulation of stem cell fate and localization within their niche, which is significant for a wide range of stem cell behavior. Although oleic acid (OA) and Ephrin receptors (Ephs) have critical roles in the maintenance of stem cell functions, interrelation between Ephs and OA has not been explored. Therefore, the present study investigated the effect of OA-pretreated UCB-MSCs in skin wound-healing and underlying mechanism of Eph expression. OA promoted the motility of UCB-MSCs via EphB2 expression. OA-mediated GPR40 activation leads to Gαq-dependent PKCα phosphorylation. In addition, OA-induced phosphorylation of GSK3β was followed by β-catenin nuclear translocation in UCB-MSCs. Activation of β-catenin was blocked by PKC inhibitors, and OA-induced EphB2 expression was suppressed by β-cateninsiRNA transfection. Of those Rho-GTPases, Rac1 was activated in an EphB2-dependent manner. Accordingly, knocking down EphB2 suppressed F-actin expression. In vivo skin wound-healing assay revealed that OA-treated UCB-MSCs enhanced skin wound repair compared to UCB-MSCs pretreated with EphB2siRNA and OA. In conclusion, we showed that OA enhances UCB-MSC motility through EphB2-dependent F-actin formation involving PKCα/GSK3β/β-catenin and Rac1 signaling pathways.

EphB2 Promotes Progression of Cutaneous Squamous Cell Carcinoma

Keratinocyte-derived skin cancer, cutaneous squamous cell carcinoma (cSCC), is the most common metastatic skin cancer. We have examined the role of Eph/ephrin signaling in the progression of cSCC. Analysis of the expression of EPH and EFN families in cSCC cells and normal epidermal keratinocytes revealed overexpression of EPHB2 mRNA in cSCC cells and cSCC tumors in vivo. Tumor cell-specific overexpression of EphB2 was detected in human cSCCs and in chemically induced mouse cSCCs with immunohistochemistry, whereas the expression of EphB2 was low in premalignant lesions and normal skin. Knockdown of EphB2 expression in cSCC cells suppressed growth and vascularization of cSCC xenografts in vivo and inhibited proliferation, migration, and invasion of cSCC cells in culture. EphB2 knockdown downregulated expression of genes associated with biofunctions cell viability, migration of tumor cells, and invasion of tumor cells. Among the genes most downregulated by EphB2 knockdown were MMP1 and MMP13. Moreover, activation of EphB2 signaling by ephrin-B2-Fc enhanced production of invasion proteinases matrix metalloproteinase-13 (MMP13) and MMP1, and invasion of cSCC cells. These findings provide mechanistic evidence for the role of EphB2 in the early progression of cSCC to the invasive stage and identify EphB2 as a putative therapeutic target in this invasive skin cancer.

Identification of the soluble form of tyrosine kinase receptor Axl as a potential biomarker for intracranial aneurysm rupture

Background

Subarachnoid hemorrhage caused by a ruptured intracranial aneurysm (RIA) is a devastating condition with significant morbidity and mortality. Despite the fact that RIAs can be prevented by microsurgical clipping or endovascular coiling, there are no reliable means of effectively predicting IA patients at risk for rupture. The purpose of our study was to discover differentially-expressed glycoproteins in IAs with or without rupture as potential biomarkers to predict rupture.

Methods

Forty age/gender-matched patients with RIA, unruptured IA (UIA), healthy controls (HCs) and disease controls (DCs) (discovery cohort, n = 10 per group) were recruited and a multiplex quantitative proteomic method, iTRAQ (isobaric Tagging for Relative and Absolute protein Quantification), was used to quantify relative changes in the lectin-purified glycoproteins in CSF from RIAs and UIAs compared to HCs and DCs. Then we verified the proteomic results in an independent set of samples (validation cohort, n = 20 per group) by enzyme-linked immunosorbent assay. Finally, we evaluated the specificity and sensitivity of the candidate marker with receiver operating characteristic (ROC) curve methods.

Results

The proteomic findings identified 294 proteins, 40 of which displayed quantitative changes unique to RIA, 13 to UIA, and 20 to IA. One of these proteins, receptor tyrosine kinase Axl, was significantly increased in RIA, as confirmed in CSF from the discovery cohort as well as in CSF and plasma from the validation cohort (p <0.05). Spearman’s correlation analysis revealed that the CSF and plasma Axl levels were strongly correlated (r = 0.93, p <0.0001). The ROC curve indicated an optimal CSF Axl threshold of 0.12 nM for discriminating RIA from UIA with corresponding sensitivity/specificity of 73.33%/90% and an area under the curve (AUC) of 0.89 (95% CI: 0.80-0.97, p < 0.0001). The optimal threshold for plasma Axl was 1.7 nM with corresponding sensitivity/specificity of 50%/80% and an AUC of 0.71 (95% CI: 0.54-0.87, p = 0.027).

Conclusions

Both CSF and plasma Axl levels are significantly elevated in RIA patients. Axl might serve as a promising biomarker to predict the rupture of IA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-015-0282-8) contains supplementary material, which is available to authorized users.

ADAM-family metalloproteinases in lung inflammation: potential therapeutic targets

Acute and chronic lung inflammation is driven and controlled by several endogenous mediators that undergo proteolytic conversion from surface-expressed proteins to soluble variants by a disintegrin and metalloproteinase (ADAM)-family members. TNF and epidermal growth factor receptor ligands are just some of the many substrates by which these proteases regulate inflammatory or regenerative processes in the lung. ADAM10 and ADAM17 are the most prominent members of this protease family. They are constitutively expressed in most lung cells and, as recent research has shown, are the pivotal shedding enzymes mediating acute lung inflammation in a cell-specific manner. ADAM17 promotes endothelial and epithelial permeability, transendothelial leukocyte migration, and inflammatory mediator production by smooth muscle and epithelial cells. ADAM10 is critical for leukocyte migration and alveolar leukocyte recruitment. ADAM10 also promotes allergic asthma by driving B cell responses. Additionally, ADAM10 acts as a receptor for Staphylococcus aureus (S. aureus) α-toxin and is crucial for bacterial virulence. ADAM8, ADAM9, ADAM15, and ADAM33 are upregulated during acute or chronic lung inflammation, and recent functional or genetic analyses have linked them to disease development. Pharmacological inhibitors that allow us to locally or systemically target and differentiate ADAM-family members in the lung suppress acute and asthmatic inflammatory responses and S. aureus virulence. These promising results encourage further research to develop therapeutic strategies based on selected ADAMs. These studies need also to address the role of the ADAMs in repair and regeneration in the lung to identify further therapeutic opportunities and possible side effects.

Matrix metalloproteinases and protein tyrosine kinases: potential novel targets in acute lung injury and ARDS

Acute lung injury (ALI) and ARDS fall within a spectrum of pulmonary disease that is characterized by hypoxemia, noncardiogenic pulmonary edema, and dysregulated and excessive inflammation. While mortality rates have improved with the advent of specialized ICUs and lung protective mechanical ventilation strategies, few other therapies have proven effective in the management of ARDS, which remains a significant clinical problem. Further development of biomarkers of disease severity, response to therapy, and prognosis is urgently needed. Several novel pathways have been identified and studied with respect to the pathogenesis of ALI and ARDS that show promise in bridging some of these gaps. This review will focus on the roles of matrix metalloproteinases and protein tyrosine kinases in the pathobiology of ALI in humans, and in animal models and in vitro studies. These molecules can act independently, as well as coordinately, in a feed-forward manner via activation of tyrosine kinase-regulated pathways that are pivotal in the development of ARDS. Specific signaling events involving proteolytic processing by matrix metalloproteinases that contribute to ALI, including cytokine and chemokine activation and release, neutrophil recruitment, transmigration and activation, and disruption of the intact alveolar-capillary barrier, will be explored in the context of these novel molecular pathways.

Ephs and Ephrins in malignant gliomas

Eph receptor tyrosine kinases and the corresponding ephrin ligands play a pivotal role in the glioma development and progression. Aberrant protein expression levels of the Eph receptors and ephrins are often associated with higher tumor grade and poor prognosis. Their function in tumorigenesis is complex due to the intricate network of possible co-occurring interactions between neighboring tumor cells and tumor microenvironment. Both Ephs and ephrins localize on the surface of tumor cells, tumor vasculature, glioma stem cells, tumor cells infiltrating brain, and immune cells infiltrating tumors. They can both promote and inhibit tumorigenicity depending on the downstream forward and reverse signalling generated. All the above-mentioned features make the Ephs/ephrins system an intriguing candidate for the development of new therapeutic strategies in glioma treatment. This review will give a general overview on the structure and the function of Ephs and ephrins, with a particular emphasis on the state of the knowledge of their role in malignant gliomas.

Eph receptors and ephrins: therapeutic opportunities

The erythropoietin-producing hepatocellular carcinoma (Eph) receptor tyrosine kinase family plays important roles in developmental processes, adult tissue homeostasis, and various diseases. Interaction with Eph receptor-interacting protein (ephrin) ligands on the surface of neighboring cells triggers Eph receptor kinase-dependent signaling. The ephrins can also transmit signals, leading to bidirectional cell contact-dependent communication. Moreover, Eph receptors and ephrins can function independently of each other through interplay with other signaling systems. Given their involvement in many pathological conditions ranging from neurological disorders to cancer and viral infections, Eph receptors and ephrins are increasingly recognized as attractive therapeutic targets, and various strategies are being explored to modulate their expression and function. Eph receptor/ephrin upregulation in cancer cells, the angiogenic vasculature, and injured or diseased tissues also offer opportunities for Eph/ephrin-based targeted drug delivery and imaging. Thus, despite the challenges presented by the complex biology of the Eph receptor/ephrin system, exciting possibilities exist for therapies exploiting these molecules.

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.