Vascular endothelial growth factor activates nuclear factor of activated T cells in human endothelial cells: a role for tissue factor gene expression

Multifaceted regulatory mechanisms of the EGR family in tumours and prospects for therapeutic applications (Review)

The early growth response (EGR) family comprises four zinc finger transcription factors: EGR1, EGR2, EGR3 and EGR4. These transcription factors belong to the Cys2‑His2‑type zinc finger protein family and are essential in cell differentiation, proliferation, apoptosis and stress response. Initially, EGR1 was recognised for its essential regulatory role in tumourigenesis. Recent studies have identified similarities between other members of the EGR family and EGR1 in tumour regulation and the multifaceted regulatory mechanism employed by the EGR family to affect tumours. Therefore, the present review describes the dual roles of the EGR family in tumours and their regulatory mechanisms in immunity, metabolism and differentiation. Additionally, the present review offers a new perspective on relevant tumour therapeutic studies based on current EGR targeting.

HNRNPA2B1 stabilizes NFATC3 levels to potentiate its combined actions with FOSL1 to mediate vasculogenic mimicry in GBM cells

BACKGROUND

Vasculogenic mimicry (VM) is an enigmatic physiological feature that influences blood supply within glioblastoma (GBM) tumors for their sustained growth. Previous studies identify NFATC3, FOSL1 and HNRNPA2B1 as significant mediators of VEGFR2, a key player in vasculogenesis, and their molecular relationships may be crucial for VM in GBM.

AIMS

The aim of this study was to understand how NFATC3, FOSL1 and HNRNPA2B1 collectively influence VM in GBM.

METHODS

We have investigated the underlying gene regulatory mechanisms for VM in GBM cell lines U251 and U373 in vitro and in vivo. In vitro cell-based assays were performed to explore the role of NFATC3, FOSL1 and HNRNPA2B1 in GBM cell proliferation, VM and migration, in the context of RNA interference (RNAi)-mediated knockdown alongside corresponding controls. Western blotting and qRT-PCR assays were used to examine VEGFR2 expression levels. CO-IP was employed to detect protein-protein interactions, ChIP was used to detect DNA-protein complexes, and RIP was used to detect RNA-protein complexes. Histochemical staining was used to detect VM tube formation in vivo.

RESULTS

Focusing on NFATC3, FOSL1 and HNRNPA2B1, we found each was significantly upregulated in GBM and positively correlated with VM-like cellular behaviors in U251 and U373 cell lines. Knockdown of NFATC3, FOSL1 or HNRNPA2B1 each resulted in decreased levels of VEGFR2, a key growth factor gene that drives VM, as well as the inhibition of proliferation, cell migration and extracorporeal VM activity. Chromatin immunoprecipitation (ChIP) studies and luciferase reporter gene assays revealed that NFATC3 binds to the promoter region of VEGFR2 to enhance VEGFR2 gene expression. Notably, FOSL1 interacts with NFATC3 as a co-factor to potentiate the DNA-binding capacity of NFATC3, resulting in enhanced VM-like cellular behaviors. Also, level of NFATC3 protein in cells was enhanced through HNRNPA2B1 binding of NFATC3 mRNA. Furthermore, RNAi-mediated silencing of NFATC3, FOSL1 and HNRNPA2B1 in GBM cells reduced their capacity for tumor formation and VM-like behaviors in vivo.

CONCLUSION

Taken together, our findings identify NFATC3 as an important mediator of GBM tumor growth through its molecular and epistatic interactions with HNRNPA2B1 and FOSL1 to influence VEGFR2 expression and VM-like cellular behaviors.

Vascular Neoplasms With NFATC1/C2 Gene Alterations : Expanding the Clinicopathologic and Molecular Characteristics of a Distinct Entity

Despite significant advances in their molecular pathogenesis, skeletal vascular tumors remain diagnostically challenging due to their aggressive radiologic appearance and significant morphologic overlap. Within the epithelioid category and at the benign end of the spectrum, recurrent FOS/FOSB fusions have defined most epithelioid hemangiomas, distinguishing them from epithelioid hemangioendothelioma and angiosarcoma. More recently, the presence of EWSR1/FUS :: NFATC1/2 fusions emerged as the genetic hallmark of a novel group of unusual vascular proliferations, often displaying epithelioid morphology, with alternating vasoformative and solid growth, variable atypia, reminiscent of composite hemangioendothelioma. In this study, we further our understanding and morphologic spectrum of NFATC -fusion positive vascular neoplasms by describing 9 new cases, including soft tissue locations and novel fusion partners. Combining with the initial cohort of 5 cases, a total of 14 patients were analyzed, showing slight female predilection and an age range of 10 to 66 (mean 42 y). Twelve patients had solitary lesions, while 2 had multifocal polyostotic (pelvic bones) disease. Overall, 12 lesions were intra-osseous and 2 in soft tissue. By targeted RNA Fusion panels or FISH, there were 6 cases of EWSR1::NFATC1 , 4 EWSR1::NFATC2 , 2 FUS::NFATC2 , 1 EWSR1 rearrangement, and 1 with a novel FABP4::NFATC2 fusion. Follow-up was available in 4 patients. One patient experienced 2 local recurrences, 11 and 15 years postdiagnosis, and one patient experienced progressive disease despite multimodality treatment (curettings, embolization, radiation) over 3 years. In summary, our extended investigation confirms that NFATC -related fusions define a distinct group of vascular neoplasms with variable architecture, epithelioid phenotype, and cytologic atypia, commonly located in the bone, occasionally multifocal and with potential for local recurrence and aggressive behavior but no metastatic potential. Molecular analysis is recommended in diagnostically challenging cases with atypical histology to exclude malignancy.

G protein subunit alpha i2's pivotal role in angiogenesis

Here we explored the potential role of Gαi2 (G protein subunit alpha i2) in endothelial cell function and angiogenesis. Methods: Genetic methodologies such as shRNA, CRISPR/Cas9, dominant negative mutation, and overexpression were utilized to modify Gαi2 expression or regulate its function. Their effects on endothelial cell functions were assessed in vitro. In vivo, the endothelial-specific Gαi2 shRNA adeno-associated virus (AAV) was utilized to silence Gαi2 expression. The impact of this suppression on retinal angiogenesis in control mice and streptozotocin (STZ)-induced diabetic retinopathy (DR) mice was analyzed. Results: Analysis of single-cell RNA sequencing data revealed Gαi2 (GNAI2) was predominantly expressed in retinal endothelial cells and expression was increased in retinal endothelial cells following oxygen-induced retinopathy (OIR) in mice. Moreover, transcriptome analysis linking Gαi2 to angiogenesis-related processes/pathways, supported by increased Gαi2 expression in experimental OIR mouse retinas, highlighted its possible role in angiogenesis. In various endothelial cell types, shRNA-induced silencing and CRISPR/Cas9-mediated knockout (KO) of Gαi2 resulted in substantial reductions in cell proliferation, migration, invasion, and capillary tube formation. Conversely, Gαi2 over-expression in endothelial cells induced pro-angiogenic activities, enhancing cell proliferation, migration, invasion, and capillary tube formation. Furthermore, our investigation revealed a crucial role of Gαi2 in NFAT (nuclear factor of activated T cells) activation, as evidenced by the down-regulation of NFAT-luciferase reporter activity and pro-angiogenesis NFAT-targeted genes (Egr3, CXCR7, and RND1) in Gαi2-silenced or -KO HUVECs, which were up-regulated in Gαi2-overexpressing endothelial cells. Expression of a dominant negative Gαi2 mutation (S48C) also down-regulated NFAT-targeted genes, slowing proliferation, migration, invasion, and capillary tube formation in HUVECs. Importantly, in vivo experiments revealed that endothelial Gαi2 knockdown inhibited retinal angiogenesis in mice, with a concomitant down-regulation of NFAT-targeted genes in mouse retinal tissue. In contrast, Gαi2 over-expression in endothelial cells enhanced retinal angiogenesis in mice. Single-cell RNA sequencing data confirmed increased levels of Gαi2 specifically in retinal endothelial cells of mice with streptozotocin (STZ)-induced diabetic retinopathy (DR). Importantly, endothelial Gαi2 silencing ameliorated retinal pathological angiogenesis in DR mice. Conclusion: Our study highlights a critical role for Gαi2 in NFAT activation, endothelial cell activation and angiogenesis, offering valuable insights into potential therapeutic strategies for modulating these processes.

The tissue-specific transcriptional landscape underlines the involvement of endothelial cells in health and disease

Endothelial cells (ECs) that line vascular and lymphatic vessels are being increasingly recognized as important to organ function in health and disease. ECs participate not only in the trafficking of gases, metabolites, and cells between the bloodstream and tissues but also in the angiocrine-based induction of heterogeneous parenchymal cells, which are unique to their specific tissue functions. The molecular mechanisms regulating EC heterogeneity between and within different tissues are modeled during embryogenesis and become fully established in adults. Any changes in adult tissue homeostasis induced by aging, stress conditions, and various noxae may reshape EC heterogeneity and induce specific transcriptional features that condition a functional phenotype. Heterogeneity is sustained via specific genetic programs organized through the combinatory effects of a discrete number of transcription factors (TFs) that, at the single tissue-level, constitute dynamic networks that are post-transcriptionally and epigenetically regulated. This review is focused on outlining the TF-based networks involved in EC specialization and physiological and pathological stressors thought to modify their architecture.

A genome-wide relay of signalling-responsive enhancers drives hematopoietic specification

Developmental control of gene expression critically depends on distal cis-regulatory elements including enhancers which interact with promoters to activate gene expression. To date no global experiments have been conducted that identify their cell type and cell stage-specific activity within one developmental pathway and in a chromatin context. Here, we describe a high-throughput method that identifies thousands of differentially active cis-elements able to stimulate a minimal promoter at five stages of hematopoietic progenitor development from embryonic stem (ES) cells, which can be adapted to any ES cell derived cell type. We show that blood cell-specific gene expression is controlled by the concerted action of thousands of differentiation stage-specific sets of cis-elements which respond to cytokine signals terminating at signalling responsive transcription factors. Our work provides an important resource for studies of hematopoietic specification and highlights the mechanisms of how and where extrinsic signals program a cell type-specific chromatin landscape driving hematopoietic differentiation.

Aberrant expression of miR-133a in endothelial cells inhibits angiogenesis by reducing pro-angiogenic but increasing anti-angiogenic gene expression

Angiogenesis is a multi-factorial physiological process deregulated in human diseases characterised by excessive or insufficient blood vessel formation. Emerging evidence highlights a novel role for microRNAs as regulators of angiogenesis. Previous studies addressing the effect of miR-133a expression in endothelial cells during blood vessel formation have reported conflicting results. Here, we have assessed the specific effect of mature miR-133a strands in angiogenesis and the expression of endothelial angiogenic genes. Transfection of miR-133a-3p or -5p mimics in primary human endothelial cells significantly inhibited proliferation, migration, and tubular morphogenesis of transfected cells. Screening of gene arrays related to angiogenic processes, and further validation by TaqMan qPCR, revealed that aberrant expression of miR-133a-3p led to a decrease in the expression of genes encoding pro-angiogenic molecules, whilst increasing those with anti-angiogenic functions. Ingenuity Pathway Analysis of a collection of genes differentially expressed in cells harbouring miR-133a-3p, predicted decreased cellular functions related to vasculature branching and cell cycle progression, underlining the inhibitory role of miR-133a-3p in angiogenic cellular processes. Our results suggest that controlled delivery of miR-133a-3p mimics, or antagomirs in diseased endothelial cells, might open new therapeutic interventions to treat patients suffering from cardiovascular pathologies that occur with excessive or insufficient angiogenesis.

Monitoring VEGF-Stimulated Calcium Ion Flux in Endothelial Cells

The endothelial response to vascular endothelial growth factor A (VEGF-A) regulates many aspects of animal physiology in health and disease. Such VEGF-A-regulated phenomena include vasculogenesis, angiogenesis, tumor growth and progression. VEGF-A binding to receptor tyrosine kinases such as vascular endothelial growth factor receptor 2 (VEGFR2 ) activates multiple signal transduction pathways and changes in homeostasis, metabolism, gene expression, cell proliferation, migration, and survival. One such VEGF-A-regulated response is a rapid rise in cytosolic calcium ion levels which modulates different biochemical events and impacts on endothelial-specific responses. Here, we present a series of detailed and robust protocols for evaluating ligand-stimulated cytosolic calcium ion flux in endothelial cells. By monitoring an endogenous endothelial transcription factor (NFATc2 ) which displays calcium-sensitive redistribution, we can assess the relevance of cytosolic calcium to protein function. This protocol can be easily applied to both adherent and non-adherent cultured cells to evaluate calcium ion flux in response to exogenous stimuli such as VEGF-A.

Vascular Health Triad in Humans With Hypertension-Not the Usual Suspects

Hypertension (HTN) affects more than one-third of the US population and remains the top risk factor for the development of cardiovascular disease (CVD). Identifying the underlying mechanisms for developing HTN are of critical importance because the risk of developing CVD doubles with ∼20 mmHg increase in systolic blood pressure (BP). Endothelial dysfunction, especially in the resistance arteries, is the primary site for initiation of sub-clinical HTN. Furthermore, inflammation and reactive oxygen and nitrogen species (ROS/RNS) not only influence the endothelium independently, but also have a synergistic influence on each other. Together, the interplay between inflammation, ROS and vascular dysfunction is referred to as the vascular health triad, and affects BP regulation in humans. While the interplay of the vascular health triad is well established, new underlying mechanistic targets are under investigation, including: Inducible nitric oxide synthase, hydrogen peroxide, hydrogen sulfide, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and nuclear factor activated T cells. This review outlines the role of these unusual suspects in vascular health and function in humans. This review connects the dots using these unusual suspects underlying inflammation, ROS and vascular dysfunction especially in individuals at risk of or with diagnosed HTN based on novel studies performed in humans.

Bioelectric signaling and the control of cardiac cell identity in response to mechanical forces

[Figure: see text].

Emerging roles of PLCγ1 in endothelial biology

Phospholipase C γ1 (PLCγ1) is a member of the PLC family that functions as signal transducer by hydrolyzing membrane lipid to generate second messengers. The unique protein structure of PLCγ1 confers a critical role as a direct effector of VEGFR2 and signaling mediated by other receptor tyrosine kinases. The distinct vascular phenotypes in PLCγ1-deficient animal models and the gain-of-function mutations of PLCγ1 found in human endothelial cancers point to a major physiological role of PLCγ1 in the endothelial system. In this review, we discuss aspects of physiological and molecular function centering around PLCγ1 in the context of endothelial cells and provide a perspective for future investigation.

A unique epithelioid vascular neoplasm of bone characterized by EWSR1/FUS-NFATC1/2 fusions

An increasing number of epithelioid vascular lesions, in particular tumors from the benign and low-grade end of the spectrum, have been characterized by recurrent gene fusions. As a result, the detection of these molecular markers have improved the classification of diagnostically challenging cases. However, despite the significant progress, there are occasional lesions that do not fit in known histologic or molecular groups. Herein, we present five such unclassified epithelioid vascular lesions, which occurred in the bone and showed a distinct morphology composed of alternating vasoformative and solid growth and mild to moderate nuclear pleomorphism. The variegated morphologic appearance resembled that of composite hemangioendothelioma, being distinct from both epithelioid hemangioma and epithelioid hemangioendothelioma, and consistently showed cytologic atypia. Due to their unusual morphologic appearance and negative molecular work-up, targeted transcriptome sequencing was performed in two cases showing the presence of NFATC2 fusions with either EWSR1 or FUS genes. Three additional bone tumors with EWSR1 gene rearrangements were identified by FISH screening of a large cohort of 45 fusion-negative epithelioid vascular neoplasms, one fused to NFATC2 while two others to NFATC1. There were three females and two males, with a wide age range at presentation, mean of 44 years. The lesions occurred in the pelvis, maxillary sinus, and humerus. Two patients presented with polyostotic disease, both located in the pelvic bones. Two patients had available follow-up, one developed two local recurrences in the humerus over a 15-year period, while the other showed no recurrence 4 years subsequent to an en-bloc resection. Tumors were positive for CD31 and ERG, while negative for EMA, CK, synaptophysin, and chromogranin. FISH confirmed this abnormality in all cases, none of them being associated with gene amplifications. Further studies are needed to establish the pathogenetic relationship of this rare molecular subset with other epithelioid vascular tumors and to determine its clinical behavior.

Store-operated Ca2+ entry as a key oncogenic Ca2+ signaling driving tumor invasion-metastasis cascade and its translational potential

Tumor metastasis is the primary cause of treatment failure and cancer-related deaths. Store-operated Ca²⁺ entry (SOCE), which is mediated by stromal interaction molecules (STIM) and ORAI proteins, has been implicated in the tumor invasion-metastasis cascade. Epithelial-mesenchymal transition (EMT) is a cellular program that enables tumor cells to acquire the capacities needed for migration and invasion and the formation of distal metastases. Tumor-associated angiogenesis contributes to metastasis because aberrantly developed vessels offer a path for tumor cell dissemination as well as supply sufficient nutrients for the metastatic colony to develop into metastasis. Recently, increasing evidence has indicated that SOCE alterations actively participate in the multi-step process of tumor metastasis. In addition, the dysregulated expression of STIM/ORAI has been reported to be a predictor of poor prognosis. Herein, we review the latest advances about the critical role of SOCE in the tumor metastasis cascade and the underlying regulatory mechanisms. We emphasize the contributions of SOCE to the EMT program, tumor cell migration and invasion, and angiogenesis. We further discuss the possibility of modulating SOCE or intervening in the downstream signaling pathways as a feasible targeting therapy for cancer treatment.

Lessons from dermatology about inflammatory responses in Covid-19

The SARS-Cov-2 is a single-stranded RNA virus composed of 16 non-structural proteins (NSP 1-16) with specific roles in the replication of coronaviruses. NSP3 has the property to block host innate immune response and to promote cytokine expression. NSP5 can inhibit interferon (IFN) signalling and NSP16 prevents MAD5 recognition, depressing the innate immunity. Dendritic cells, monocytes, and macrophages are the first cell lineage against viruses' infections. The IFN type I is the danger signal for the human body during this clinical setting. Protective immune responses to viral infection are initiated by innate immune sensors that survey extracellular and intracellular space for foreign nucleic acids. In Covid-19 the pathogenesis is not yet fully understood, but viral and host factors seem to play a key role. Important points in severe Covid-19 are characterized by an upregulated innate immune response, hypercoagulopathy state, pulmonary tissue damage, neurological and/or gastrointestinal tract involvement, and fatal outcome in severe cases of macrophage activation syndrome, which produce a 'cytokine storm'. These systemic conditions share polymorphous cutaneous lesions where innate immune system is involved in the histopathological findings with acute respiratory distress syndrome, hypercoagulability, hyperferritinemia, increased serum levels of D-dimer, lactic dehydrogenase, reactive-C-protein and serum A amyloid. It is described that several polymorphous cutaneous lesions similar to erythema pernio, urticarial rashes, diffuse or disseminated erythema, livedo racemosa, blue toe syndrome, retiform purpura, vesicles lesions, and purpuric exanthema or exanthema with clinical aspects of symmetrical drug-related intertriginous and flexural exanthema. This review describes the complexity of Covid-19, its pathophysiological and clinical aspects.

Loss of Down Syndrome Critical Region-1 Mediated-Hypercholesterolemia Accelerates Corneal Opacity Via Pathological Neovessel Formation

OBJECTIVE

The calcineurin-NFAT (nuclear factor for activated T cells)-DSCR (Down syndrome critical region)-1 pathway plays a crucial role as the downstream effector of VEGF (vascular endothelial growth factor)-mediated tumor angiogenesis in endothelial cells. A role for DSCR-1 in different organ microenvironment such as the cornea and its role in ocular diseases is not well understood. Corneal changes can be indicators of various disease states and are easily detected through ocular examinations. Approach and Results: The presentation of a corneal arcus or a corneal opacity due to lipid deposition in the cornea often indicates hyperlipidemia and in most cases, hypercholesterolemia. Although the loss of Apo (apolipoprotein) E has been well characterized and is known to lead to elevated serum cholesterol levels, there are few corneal changes observed in ApoE^-/- mice. In this study, we show that the combined loss of ApoE and DSCR-1 leads to a dramatic increase in serum cholesterol levels and severe corneal opacity with complete penetrance. The cornea is normally maintained in an avascular state; however, loss of Dscr-1 is sufficient to induce hyper-inflammatory and -oxidative condition, increased corneal neovascularization, and lymphangiogenesis. Furthermore, immunohistological analysis and genome-wide screening revealed that loss of Dscr-1 in mice triggers increased immune cell infiltration and upregulation of SDF (stromal derived factor)-1 and its receptor, CXCR4 (C-X-C motif chemokine ligand receptor-4), potentiating this signaling axis in the cornea, thereby contributing to pathological corneal angiogenesis and opacity.

CONCLUSIONS

This study is the first demonstration of the critical role for the endogenous inhibitor of calcineurin, DSCR-1, and pathological corneal angiogenesis in hypercholesterolemia induced corneal opacity.

Nanoclay-based 3D printed scaffolds promote vascular ingrowth ex vivo and generate bone mineral tissue in vitro and in vivo

Acellular soft hydrogels are not ideal for hard tissue engineering given their poor mechanical stability, however, in combination with cellular components offer significant promise for tissue regeneration. Indeed, nanocomposite bioinks provide an attractive platform to deliver human bone marrow stromal cells (HBMSCs) in three dimensions producing cell-laden constructs that aim to facilitate bone repair and functionality. Here we present the in vitro, ex vivo and in vivo investigation of bioprinted HBMSCs encapsulated in a nanoclay-based bioink to produce viable and functional three-dimensional constructs. HBMSC-laden constructs remained viable over 21 d in vitro and immediately functional when conditioned with osteogenic media. 3D scaffolds seeded with human umbilical vein endothelial cells (HUVECs) and loaded with vascular endothelial growth factor (VEGF) implanted ex vivo into a chick chorioallantoic membrane (CAM) model showed integration and vascularisation after 7 d of incubation. In a pre-clinical in vivo application of a nanoclay-based bioink to regenerate skeletal tissue, we demonstrated bone morphogenetic protein-2 (BMP-2) absorbed scaffolds produced extensive mineralisation after 4 weeks (p < 0.0001) compared to the drug-free and alginate controls. In addition, HBMSC-laden 3D printed scaffolds were found to significantly (p < 0.0001) support bone tissue formation in vivo compared to acellular and cast scaffolds. These studies illustrate the potential of nanoclay-based bioink, to produce viable and functional constructs for clinically relevant skeletal tissue regeneration.

N-terminal syndecan-2 domain selectively enhances 6-O heparan sulfate chains sulfation and promotes VEGFA165-dependent neovascularization

The proteoglycan Syndecan-2 (Sdc2) has been implicated in regulation of cytoskeleton organization, integrin signaling and developmental angiogenesis in zebrafish. Here we report that mice with global and inducible endothelial-specific deletion of Sdc2 display marked angiogenic and arteriogenic defects and impaired VEGFA165 signaling. No such abnormalities are observed in mice with deletion of the closely related Syndecan-4 (Sdc4) gene. These differences are due to a significantly higher 6-O sulfation level in Sdc2 versus Sdc4 heparan sulfate (HS) chains, leading to an increase in VEGFA165 binding sites and formation of a ternary Sdc2-VEGFA165-VEGFR2 complex which enhances VEGFR2 activation. The increased Sdc2 HS chains 6-O sulfation is driven by a specific N-terminal domain sequence; the insertion of this sequence in Sdc4 N-terminal domain increases 6-O sulfation of its HS chains and promotes Sdc2-VEGFA165-VEGFR2 complex formation. This demonstrates the existence of core protein-determined HS sulfation patterns that regulate specific biological activities.

EGR-mediated control of STIM expression and function

Ca²⁺ is a ubiquitous, dynamic and pluripotent second messenger with highly context-dependent roles in complex cellular processes such as differentiation, proliferation, and cell death. These Ca²⁺ signals are generated by Ca²⁺-permeable channels located on the plasma membrane (PM) and endoplasmic reticulum (ER) and shaped by PM- and ER-localized pumps and transporters. Differences in the expression of these Ca²⁺ homeostasis proteins contribute to cell and context-dependent differences in the spatiotemporal organization of Ca²⁺ signals and, ultimately, cell fate. This review focuses on the Early Growth Response (EGR) family of zinc finger transcription factors and their role in the transcriptional regulation of Stromal Interaction Molecule (STIM1), a critical regulator of Ca²⁺ entry in both excitable and non-excitable cells.

Genetic variation determines VEGF-A plasma levels in cancer patients

Angiogenesis is essential in tumor biology and is regulated by vascular endothelial growth factor (VEGF) ligands and receptors. Here we aimed to discover genetic variants associated with levels of circulating angiogenic proteins in cancer patients. Plasma was collected at baseline in 216 pancreatic and 114 colorectal cancer patients. Thirty-one angiogenic proteins were measured by ELISA. 484,523 Single Nucleotide Polymorphisms (SNP) were tested for association with plasma levels for each protein in pancreatic cancer patients. Three top-ranked hits were then genotyped in colorectal cancer patients, where associations with the same proteins were measured. The results demonstrated rs2284284 and MCP1 (P-value = 6.7e–08), rs7504372 and VEGF-C (P-value = 9.8e–09), and rs7767396 and VEGF-A (P-value = 5.8e–09) were SNP-protein pairs identified in pancreatic cancer patients. In colorectal cancer patients, only rs7767396 (A > G) and VEGF-A was validated (P-value = 5.18e–05). The AA genotype of rs7767396 exhibited 2.04–2.3 and 2.7–3.4-fold higher VEGF-A levels than those with AG and GG genotypes. The G allele of rs7767396 reduces binding of the NF-AT1 transcription factor. In conclusion, a common genetic variant predicts the plasma levels of VEGF-A in cancer patients through altered binding of NF-AT1.

Tacrolimus inhibits angiogenesis and induces disaggregation of endothelial cells in spheroids - Toxicity testing in a 3D cell culture approach

The administration of immunosuppressive drugs is a necessary therapeutic measure in organ transplantation to prevent rejections. However, the use of temporarily high dosed immunosuppressive drugs is associated with cytotoxicity and adverse side effects that could induce endothelial dysfunction. The aim of this work is to evaluate the effect of the administrated drugs tacrolimus and mycophenolic acid (MPA) on human umbilical vein endothelial cells (HUVECs). Whereas MPA showed no significant toxicity in a dose-dependent manner, a dose-response curve of tacrolimus treatment could be obtained in 2D monolayer. Due to limited cell-cell and cell-extracellular matrix (ECM) interactions in 2D monolayers, 3D spheroids have been established. The comparison of IC₅₀ values demonstrated that tacrolimus is more toxic towards endothelial cells in 3D spheroids (IC₅₀ value = 27.19 μg/ml) than in 2D monolayers (IC₅₀ value = 40.23 μg/ml). Moreover, the maximal trough level of tacrolimus achieved in immunosuppressive therapy (18 ng/ml) resulted in low disaggregation of the spheroids and decreased vessel areas with increased number of end points of tubular-like structures in the angiogenesis assay even if no toxic effect could be detected. Thus, our approach unseals very sensitive cytotoxic effects of tacrolimus on the vasculature in organ recipients after immunosuppressive therapy.

Curcumin exerts anti-inflammatory and vasoprotective effects through amelioration of NFAT-dependent endothelin-1 production in mice with acute Chagas cardiomyopathy

BACKGROUND

The anti-inflammatory and cardioprotective properties of curcumin (Cur), a natural polyphenolic flavonoid isolated from the rhizomes of Curcuma longa, are increasingly considered to have beneficial effects on the progression of Chagas heart disease, caused by the protozoan parasite Trypanosoma cruzi.

OBJECTIVE

To evaluate the effects of oral therapy with Cur on T. cruzi-mediated cardiovasculopathy in acutely infected mice and analyse the in vitro response of parasite-infected human microvascular endothelial cells treated with this phytochemical.

METHODS

Inflammation of heart vessels from Cur-treated and untreated infected mice were analysed by histology, with benznidazole (Bz) as the reference compound. Parasitaemia was monitored by the direct method. Capillary permeability was visualised by Evans-blue assay. Myocardial ET-1, IL-6, and TNF-α mRNA expressions were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Microvascular endothelial HMEC-1 cells were infected in vitro with or without addition of Cur or Bz. Induction of the Ca2+/NFAT pathway was assessed by fluorometry, immunoblotting, and reporter assay.

FINDINGS

Oral Cur therapy of recently infected mice reduced inflammatory cell infiltration of myocardial arteries without lowering parasite levels. Compared to that of the phosphate-buffered saline-receiving group, hearts from Cur-treated mice showed significantly decreased vessel inflammation scores (p < 0.001), vascular permeabilities (p < 0.001), and levels of IL-6/TNF-α (p < 0.01) and ET-1 (p < 0.05) mRNA. Moreover, Cur significantly (p < 0.05 for transcript; p < 0.01 for peptide) downregulated ET-1 secretion from infected HMEC-1 cells. Remarkably, Cur addition significantly (p < 0.05 at 27.0 μM) interfered with T. cruzi-dependent activation of the Ca2+/NFATc1 signalling pathway that promotes generation of inflammatory agents in HMEC-1 cells.

CONCLUSIONS

Oral treatment with Cur dampens cardiovasculopathy in acute Chagas mice. Cur impairs the Ca2+/NFATc1-regulated release of ET-1 from T. cruzi-infected vascular endothelium. These findings identify new perspectives for exploring the potential of Cur-based interventions to ameliorate Chagas heart disease.

Treatment of voluminous and complicated superficial slow-flow vascular malformations with sirolimus (PERFORMUS): protocol for a multicenter phase 2 trial with a randomized observational-phase design

BACKGROUND

Slow-flow superficial vascular malformations (VMs) are rare congenital anomalies that can be responsible for pain and functional impairment. Currently, we have no guidelines for their management, which can involve physical bandages, sclerotherapy, surgery, anti-inflammatory or anti-coagulation drugs or no treatment. The natural history is progressive and worsening. Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that acts as a master switch in cell proliferation, apoptosis, metabolism and angio/lymphangiogenesis. Sirolimus directly inhibits the mTOR pathway, thereby inhibiting cell proliferation and angio/lymphangiogenesis. Case reports and series have reported successful use of sirolimus in children with different types of vascular anomalies, with heterogeneous outcomes.

OBJECTIVE

The objective of this trial is to evaluate the efficacy and safety of sirolimus in children with complicated superficial slow-flow VMs.

METHODS/DESIGN

This French multicenter randomized observational-phase, phase 2 trial aims to include 50 pediatric patients 6 to 18 years old who have slow-flow (lymphatic, venous or lymphatico-venous) voluminous complicated superficial VM. Patients will be followed up for 12 months. All patients will start with an observational period (no treatment). Then at a time randomly selected between month 4 and month 8, they will switch to the experimental period (switch time), when they will receive sirolimus until month 12. Each child will undergo MRI 3 times: at baseline, at the switch time, and at month 12. For both periods (observational and treatment), we will calculate the relative change in volume of the VM divided by the study period duration. This relative change weighted by the study period duration will constitute the primary endpoint. VM will be measured by MRI images, which will be centralized and interpreted by the same radiologist who will be blinded to the study period. Hence, each patient will be his/her own control. Secondary outcomes will include assessment of safety and efficacy by viewing standardized digital photographs and according to the physician, the patient or proxy; impact on quality of life; and evolution of biological makers (coagulation factors, vascular endothelial growth factor, tissue factor).

DISCUSSION

The main benefit of the study will be to resolve uncertainty concerning the efficacy of sirolimus in reducing the volume of VMs and limiting related complications and the safety of the drug in children with slow-flow VMs. This trial design is interesting in these rare conditions because all included patients will have the opportunity to receive the drug and the physician can maintain it after the end of the protocol if is found efficient (which would not be the case in a classical cross-over study).

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02509468 , first received: 28 July 2015. EU Clinical Trials Register EudraCT Number: 2015-001096-43.

EphA2 stimulates VCAM-1 expression through calcium-dependent NFAT1 activity

Endothelial cell activation by proinflammatory stimuli drives leukocyte recruitment through enhanced expression of counter-receptors such as vascular cell adhesion molecule-1 (VCAM-1). We previously demonstrated that activation of the receptor tyrosine kinase EphA2 with its ligand ephrin-A1 induces VCAM-1 expression. Here, we sought to characterize the proinflammatory signaling pathways involved. Analysis of over-represented transcription factors in ephrin-A1-induced genes identified multiple potential transcriptional regulators, including the Rel family members nuclear factor-κB (NF-κB/p65) and nuclear factor of activated T-cells (NFAT). While ephrin-A1 failed to induce endothelial NF-κB activation, NF-κB inhibitors prevented ephrin-A1-induced VCAM-1 expression, suggesting basal NF-κB activity is required. In contrast, ephrin-A1 induced a robust EphA2-dependent increase in NFAT activation, and mutation of the NF-κB/NFAT-binding sites in the VCAM-1 promoter blunted ephrin-A1-induced promoter activity. NFAT activation classically occurs through calcium-dependent calcineurin activation, and inhibiting NFAT signaling with calcineurin inhibitors (cyclosporine A, FK506) or direct NFAT inhibitors (A-285222) was sufficient to block ephrin-A1-induced VCAM-1 expression. Consistent with robust NFAT activation, ephrin-A1-induced an EphA2-dependent calcium influx in endothelial cells that was required for ephrin-A1-induced NFAT activation and VCAM-1 expression. This work provides the first data showing EphA2-dependent calcium influx and NFAT activation and identifies NFAT as a novel EphA2-dependent proinflammatory pathway in endothelial activation.

Regulator of calcineurin 1 modulates vascular contractility and stiffness through the upregulation of COX-2-derived prostanoids

Cyclooxygenase-2 (COX-2) derived-prostanoids participate in the altered vascular function and mechanical properties in cardiovascular diseases. We investigated whether regulator of calcineurin 1 (Rcan1) participates in vascular contractility and stiffness through the regulation of COX-2. For this, wild type (Rcan1^+/+) and Rcan1-deficient (Rcan1^-/-) mice untreated or treated with the COX-2 inhibitor rofecoxib were used. Vascular function and structure were analysed by myography. COX-2 and phospo-p65 expression were studied by western blotting and immunohistochemistry and TXA₂ production by ELISA. We found that Rcan1 deficiency increases COX-2 and IL-6 expression and NF-κB activation in arteries and vascular smooth muscle cells (VSMC). Adenoviral-mediated re-expression of Rcan1.4 in Rcan1^-/- VSMC normalized COX-2 expression. Phenylephrine-induced vasoconstrictor responses were greater in aorta from Rcan1^-/- compared to Rcan1^+/+ mice. This increased response were diminished by etoricoxib, furegrelate, SQ 29548, cyclosporine A and parthenolide, inhibitors of COX-2, TXA₂ synthase, TP receptors, calcineurin and NF-κB, respectively. Endothelial removal and NOS inhibition increased phenylephrine responses only in Rcan1^+/+ mice. TXA₂ levels were greater in Rcan1^-/- mice. In small mesenteric arteries, vascular function and structure were similar in both groups of mice; however, vessels from Rcan1^-/- mice displayed an increase in vascular stiffness that was diminished by rofecoxib. In conclusion, our results suggest that Rcan1 might act as endogenous negative modulator of COX-2 expression and activity by inhibiting calcineurin and NF-kB pathways to maintain normal contractility and vascular stiffness in aorta and small mesenteric arteries, respectively. Our results uncover a new role for Rcan1 in vascular contractility and mechanical properties.

Inhibition of Orai1-mediated Ca2+ entry limits endothelial cell inflammation by suppressing calcineurin-NFATc4 signaling pathway

Orai1-dependent Ca²⁺ entry plays an essential role in inflammatory response through regulating T cell and macrophage activation and neutrophil infiltration. However, whether Orai1 Ca²⁺ entry contributes to endothelial activation, one of the early steps of vascular inflammation, remains elusive. In the present study, we observed that knockdown of Orai1 reduced, whereas overexpression of Orai1 potentiated, TNFα-induced expression of adhesion molecules such as ICAM-1 and VCAM-1 in HUVECs, and subsequently blocked adhesion of monocyte to HUVECs. In vivo, Orai1 downregulation attenuated TNFα-induced ICAM-1 and VCAM-1 expression in mouse aorta and the levels of pro-inflammatory cytokines in the serum. In addition, Orai1 knockdown also dramatically decreased the expression of pro-inflammatory cytokines and neutrophil infiltration in the lung after TNFα treatment, and thus protected lung tissue injury. Notably, among all isoforms of nuclear factor of activated T cells (NFATs), TNFα only triggered NFATc4 nuclear accumulation in HUVECs. Knockdown of Orai1 or inhibition of calcineurin prevented TNFα-induced NFATc4 nuclear translocation and reduced ICAM-1 and VCAM-1 expression in HUVECs. Overexpression of NFATc4 further enhanced ICAM-1 and VCAM-1 expression induced by TNFα. Our study demonstrates that Orai1-Ca²⁺-calcineurin-NFATc4 signaling is an essential inflammatory pathway required for TNFα-induced endothelial cell activation and vascular inflammation. Therefore, Orai1 may be a potential therapeutic target for treatment of inflammatory diseases.

Selective inhibition of plasma membrane calcium ATPase 4 improves angiogenesis and vascular reperfusion

AIMS

Ischaemic cardiovascular disease is a major cause of morbidity and mortality worldwide. Despite promising results from pre-clinical animal models, VEGF-based strategies for therapeutic angiogenesis have yet to achieve successful reperfusion of ischaemic tissues in patients. Failure to restore efficient VEGF activity in the ischaemic organ remains a major problem in current pro-angiogenic therapeutic approaches. Plasma membrane calcium ATPase 4 (PMCA4) negatively regulates VEGF-activated angiogenesis via inhibition of the calcineurin/NFAT signalling pathway. PMCA4 activity is inhibited by the small molecule aurintricarboxylic acid (ATA). We hypothesize that inhibition of PMCA4 with ATA might enhance VEGF-induced angiogenesis.

METHODS AND RESULTS

We show that inhibition of PMCA4 with ATA in endothelial cells triggers a marked increase in VEGF-activated calcineurin/NFAT signalling that translates into a strong increase in endothelial cell motility and blood vessel formation. ATA enhances VEGF-induced calcineurin signalling by disrupting the interaction between PMCA4 and calcineurin at the endothelial-cell membrane. ATA concentrations at the nanomolar range, that efficiently inhibit PMCA4, had no deleterious effect on endothelial-cell viability or zebrafish embryonic development. However, high ATA concentrations at the micromolar level impaired endothelial cell viability and tubular morphogenesis, and were associated with toxicity in zebrafish embryos. In mice undergoing experimentally-induced hindlimb ischaemia, ATA treatment significantly increased the reperfusion of post-ischaemic limbs.

CONCLUSIONS

Our study provides evidence for the therapeutic potential of targeting PMCA4 to improve VEGF-based pro-angiogenic interventions. This goal will require the development of refined, highly selective versions of ATA, or the identification of novel PMCA4 inhibitors.

Clinical and prognostic significance of prokineticin 1 in human gliomas

The objective of this study was to explore the expression and the clinical and prognostic significance of prokineticin 1 (PROK1) in human gliomas. The expression of PROK1 in 60 patients with glioma and in eight control cases (patients with traumatic brain injury) by immunohistochemistry (IHC). The associations between the differences in expression and pathology grades were analyzed statistically. The positive rates of PROK1 expression in normal brain and glioma tissue were 25.0% (2/8) and 93.3% (56/60), respectively. PROK1 expression in glioma tissue was higher than that in normal tissue (P<0.05). The positive rates of PROK1 expression in low-grade gliomas (LGGs, grades I and II) and high-grade gliomas (HGGs, grades III and IV) were 66.7% (8/12) and 100% (48/48), respectively, the positive rates in HGG were higher than those in LGG (P<0.01). PROK1 is an angiogenic growth factor that is related with metastatic ability of tumor, we also correlated PROK1 expression with NFAT expression. Expression of PROK1correlated significantly with expression of NFAT (r=0.524, P<0.01), but not with patient sex and age. Glioma patients with higher expressing PROK1 had a significantly shorter progression-free survival time, increasing levels of PROK1 expression significantly correlated with reduced survival times when all patients with glioma were considered (P<0.01). These results suggested that PROK1 positivity and protein expression levels are of significant clinical and prognostic value in human gliomas, which significantly correlates with the survival in gliomas, PROK1 may regulate the progression of glioma via the NFAT pathway.

Transcriptional and Post-Transcriptional Regulation of Thrombospondin-1 Expression: A Computational Model

Hypoxia is an important physiological stress signal that drives angiogenesis, the formation of new blood vessels. Besides an increase in the production of pro-angiogenic signals such as vascular endothelial growth factor (VEGF), hypoxia also stimulates the production of anti-angiogenic signals. Thrombospondin-1 (TSP-1) is one of the anti-angiogenic factors whose synthesis is driven by hypoxia. Cellular synthesis of TSP-1 is tightly regulated by different intermediate biomolecules including proteins that interact with hypoxia-inducible factors (HIFs), transcription factors that are activated by receptor and intracellular signaling, and microRNAs which are small non-coding RNA molecules that function in post-transcriptional modification of gene expression. Here we present a computational model that describes the mechanistic interactions between intracellular biomolecules and cooperation between signaling pathways that together make up the complex network of TSP-1 regulation both at the transcriptional and post-transcriptional level. Assisted by the model, we conduct in silico experiments to compare the efficacy of different therapeutic strategies designed to modulate TSP-1 synthesis in conditions that simulate tumor and peripheral arterial disease microenvironment. We conclude that TSP-1 production in endothelial cells depends on not only the availability of certain growth factors but also the fine-tuned signaling cascades that are initiated by hypoxia.

Modulation of VEGF receptor 2 signaling by protein phosphatases

Phosphorylation of serines, threonines, and tyrosines is a central event in signal transduction cascades in eukaryotic cells. The phosphorylation state of any particular protein reflects a balance of activity between kinases and phosphatases. Kinase biology has been exhaustively studied and is reasonably well understood, however, much less is known about phosphatases. A large body of evidence now shows that protein phosphatases do not behave as indiscriminate signal terminators, but can function both as negative or positive regulators of specific signaling pathways. Genetic models have also shown that different protein phosphatases play precise biological roles in health and disease. Finally, genome sequencing has unveiled the existence of many protein phosphatases and associated regulatory subunits comparable in number to kinases. A wide variety of roles for protein phosphatase roles have been recently described in the context of cancer, diabetes, hereditary disorders and other diseases. In particular, there have been several recent advances in our understanding of phosphatases involved in regulation of vascular endothelial growth factor receptor 2 (VEGFR2) signaling. The receptor is the principal signaling molecule mediating a wide spectrum of VEGF signal and, thus, is of paramount significance in a wide variety of diseases ranging from cancer to cardiovascular to ophthalmic. This review focuses on the current knowledge about protein phosphatases' regulation of VEGFR2 signaling and how these enzymes can modulate its biological effects.

Epithelial calcineurin controls microbiota-dependent intestinal tumor development

Inflammation-associated pathways are active in intestinal epithelial cells (IECs) and contribute to the pathogenesis of colorectal cancer (CRC). Calcineurin, a phosphatase required for the activation of the nuclear factor of activated T cells (NFAT) family of transcription factors, shows increased expression in CRC. We therefore investigated the role of calcineurin in intestinal tumor development. We demonstrate that calcineurin and NFAT factors are constitutively expressed by primary IECs and selectively activated in intestinal tumors as a result of impaired stratification of the tumor-associated microbiota and toll-like receptor signaling. Epithelial calcineurin supports the survival and proliferation of cancer stem cells in an NFAT-dependent manner and promotes the development of intestinal tumors in mice. Moreover, somatic mutations that have been identified in human CRC are associated with constitutive activation of calcineurin, whereas nuclear translocation of NFAT is associated with increased death from CRC. These findings highlight an epithelial cell-intrinsic pathway that integrates signals derived from the commensal microbiota to promote intestinal tumor development.

AP-1 transcription factor mediates VEGF-induced endothelial cell migration and proliferation

VEGF, upon binding to its endothelial cell specific receptors VEGF-R1 and VEGF-R2, can induce endothelial cell migration, proliferation and angiogenesis. However, the molecular mechanism of these effects still remains unclear. In this study, we investigated whether VEGF promotes human umbilical vascular endothelial cell (HUVEC) migration and proliferation through activator protein-1 transcription factor (AP-1) family. We first showed that VEGF induces immediate-early genes AP-1 family gene expression differentially with the profound induction of JunB (both mRNA and protein) under various conditions (PBS, DMSO or control adenoviruses). The increase in AP-1 mRNA expression occurs primarily at the transcriptional level. Inhibition of AP-1 DNA binding activity by adenovirus expressing a potent dominant negative form of c-Fos (Afos) significantly attenuated VEGF-induced HUVEC migration and proliferation and cyclin D1 expression. Knockdown of JunB with adenovirus expressing JunB shRNA reduces VEGF-induced JunB expression and attenuated HUVEC migration. However the shJunB-expressing virus has no effect on VEGF-induced cyclin D1 protein expression and proliferation. These results suggest that VEGF-induced endothelial migration is mediated primarily by induction of JunB whereas the promotion of endothelial proliferation by VEGF is mediated by JunB-independent AP-1 family members.

SOCE and cancer: Recent progress and new perspectives

Ca²⁺ acts as a universal and versatile second messenger in the regulation of a myriad of biological processes, including cell proliferation, differentiation, migration and apoptosis. Store‐operated Ca²⁺ entry (SOCE) mediated by ORAI and the stromal interaction molecule (STIM) constitutes one of the major routes of calcium entry in nonexcitable cells, in which the depletion of intracellular Ca²⁺ stores triggers activation of the endoplasmic reticulum (ER)‐resident Ca²⁺ sensor protein STIM to gate and open the ORAI Ca²⁺ channels in the plasma membrane (PM). Accumulating evidence indicates that SOCE plays critical roles in cancer cell proliferation, metastasis and tumor neovascularization, as well as in antitumor immunity. We summarize herein the recent advances in our understanding of the function of SOCE in various types of tumor cells, vascular endothelial cells and cells of the immune system. Finally, the therapeutic potential of SOCE inhibitors in the treatment of cancer is also discussed.

Feedback Mechanisms Regulate Ets Variant 2 (Etv2) Gene Expression and Hematoendothelial Lineages

Etv2 is an essential transcriptional regulator of hematoendothelial lineages during embryogenesis. Although Etv2 downstream targets have been identified, little is known regarding the upstream transcriptional regulation of Etv2 gene expression. In this study, we established a novel methodology that utilizes the differentiating ES cell and embryoid body system to define the modules and enhancers embedded within the Etv2 promoter. Using this system, we defined an autoactivating role for Etv2 that is mediated by two adjacent Ets motifs in the proximal promoter. In addition, we defined the role of VEGF/Flk1-Calcineurin-NFAT signaling cascade in the transcriptional regulation of Etv2. Furthermore, we defined an Etv2-Flt1-Flk1 cascade that serves as a negative feedback mechanism to regulate Etv2 gene expression. To complement and extend these studies, we demonstrated that the Flt1 null embryonic phenotype was partially rescued in the Etv2 conditional knockout background. In summary, these studies define upstream and downstream networks that serve as a transcriptional rheostat to regulate Etv2 gene expression.

C/EBPβ and Nuclear Factor of Activated T Cells Differentially Regulate Adamts-1 Induction by Stimuli Associated with Vascular Remodeling

Emerging evidence indicates that the metalloproteinase Adamts-1 plays a significant role in the pathophysiology of vessel remodeling, but little is known about the signaling pathways that control Adamts-1 expression. We show that vascular endothelial growth factor (VEGF), angiotensin-II, interleukin-1β, and tumor necrosis factor α, stimuli implicated in pathological vascular remodeling, increase Adamts-1 expression in endothelial and vascular smooth muscle cells. Analysis of the intracellular signaling pathways implicated in this process revealed that VEGF and angiotensin-II upregulate Adamts-1 expression via activation of differential signaling pathways that ultimately promote functional binding of the NFAT or C/EBPβ transcription factors, respectively, to the Adamts-1 promoter. Infusion of mice with angiotensin-II triggered phosphorylation and nuclear translocation of C/EBPβ proteins in aortic cells concomitantly with an increase in the expression of Adamts-1, further underscoring the importance of C/EBPβ signaling in angiotensin-II-induced upregulation of Adamts-1. Similarly, VEGF promoted NFAT activation and subsequent Adamts-1 induction in aortic wall in a calcineurin-dependent manner. Our results demonstrate that Adamts-1 upregulation by inducers of pathological vascular remodeling is mediated by specific signal transduction pathways involving NFAT or C/EBPβ transcription factors. Targeting of these pathways may prove useful in the treatment of vascular disease.

VEGF-A isoform-specific regulation of calcium ion flux, transcriptional activation and endothelial cell migration

Vascular endothelial growth factor A (VEGF-A) regulates many aspects of vascular physiology such as cell migration, proliferation, tubulogenesis and cell-cell interactions. Numerous isoforms of VEGF-A exist but their physiological significance is unclear. Here we evaluated two different VEGF-A isoforms and discovered differential regulation of cytosolic calcium ion flux, transcription factor localisation and endothelial cell response. Analysis of VEGF-A isoform-specific stimulation of VEGFR2-dependent signal transduction revealed differential capabilities for isoform activation of multiple signal transduction pathways. VEGF-A₁₆₅ treatment promoted increased phospholipase Cγ1 phosphorylation, which was proportional to the subsequent rise in cytosolic calcium ions, in comparison to cells treated with VEGF-A₁₂₁. A major consequence of this VEGF-A isoform-specific calcium ion flux in endothelial cells is differential dephosphorylation and subsequent nuclear translocation of the transcription factor NFATc2. Using reverse genetics, we discovered that NFATc2 is functionally required for VEGF-A-stimulated endothelial cell migration but not tubulogenesis. This work presents a new mechanism for understanding how VEGF-A isoforms program complex cellular outputs by converting signal transduction pathways into transcription factor redistribution to the nucleus, as well as defining a novel role for NFATc2 in regulating the endothelial cell response.

Nuclear factor of activated T cells in cancer development and treatment

Since nuclear factor of activated T cells (NFAT) was first identified as a transcription factor in T cells, various NFAT isoforms have been discovered and investigated. Accumulating studies have suggested that NFATs are involved in many aspects of cancer, including carcinogenesis, cancer cell proliferation, metastasis, drug resistance and tumor microenvironment. Different NFAT isoforms have distinct functions in different cancers. The exact function of NFAT in cancer or the tumor microenvironment is context dependent. In this review, we summarize our current knowledge of NFAT regulation and function in cancer development and treatment. NFATs have emerged as a potential target for cancer prevention and therapy.

Analysis of protein kinase C theta inhibitors for the control of HIV-1 replication in human CD4+ T cells reveals an effect on retrotranscription in addition to viral transcription

HIV-1 infection cannot be cured due to reservoirs formed early after infection. Decreasing the massive CD4+ T cell activation that occurs at the beginning of the disease would delay reservoir seeding, providing a better prognosis for patients. CD4+ T cell activation is mediated by protein kinase C (PKC) theta (θ), which is involved in T-cell proliferation, as well as NF-κB, NF-AT, and AP-1 activation. We found that PKCθ activity increased viral replication, but also that HIV-1 induced higher activation of PKCθ in infected CD4+ T cells, creating a feedback loop. Therefore, specific inhibition of PKCθ activity could contribute to control HIV-1 replication. We tested the efficacy of seven PKCθ specific inhibitors to control HIV-1 replication in CD4+ T cells and selected two of the more potent and safer: CGX1079 and CGX0471. They reduced PKCθ phosphorylation at T538 and its translocation to the plasma membrane, which correlated with decreased HIV-1 retrotranscription through partial inhibition of SAMHD1 antiviral activity, rendering lower proviral integration. CGX1079 and CGX0471 also interfered with viral transcription, which would reduce the production of new virions, as well as the subsequent spread and infection of new targets that would increase the reservoir size. CGX1079 and CGX0471 did not completely abrogate T-cell functions such as proliferation and CD8-mediated release of IFN-γ in PBMCs from HIV-infected patients, thereby avoiding general immunosuppresion. Consequently, using PKCθ inhibitors as adjuvant of antiretroviral therapy in recently infected patients would decrease the pool of activated CD4+ T cells, thwarting proviral integration and reducing the reservoir size.

NFAT1 promotes intratumoral neutrophil infiltration by regulating IL8 expression in breast cancer

NFAT transcription factors are key regulators of gene expression in immune cells. In addition, NFAT1-induced genes play diverse roles in mediating the progression of various solid tumors. Here we show that NFAT1 induces the expression of the IL8 gene by binding to its promoter and leading to IL8 secretion. Thapsigargin stimulation of breast cancer cells induces IL8 expression in an NFAT-dependent manner. Moreover, we show that NFAT1-mediated IL8 production promotes the migration of primary human neutrophils in vitro and also promotes neutrophil infiltration in tumor xenografts. Furthermore, expression of active NFAT1 effectively suppresses the growth of nascent and established tumors by a non cell-autonomous mechanism. Evaluation of breast tumor tissue reveals that while the levels of NFAT1 are similar in tumor cells and normal breast epithelium, cells in the tumor stroma express higher levels of NFAT1 compared to normal stroma. Elevated levels of NFAT1 also correlate with increased neutrophil infiltrate in breast tumors. These data point to a mechanism by which NFAT1 orchestrates the communication between breast cancer cells and host neutrophils during breast cancer progression.

Characterization of the host response to pichinde virus infection in the Syrian golden hamster by species-specific kinome analysis

The Syrian golden hamster has been increasingly used to study viral hemorrhagic fever (VHF) pathogenesis and countermeasure efficacy. As VHFs are a global health concern, well-characterized animal models are essential for both the development of therapeutics and vaccines as well as for increasing our understanding of the molecular events that underlie viral pathogenesis. However, the paucity of reagents or platforms that are available for studying hamsters at a molecular level limits the ability to extract biological information from this important animal model. As such, there is a need to develop platforms/technologies for characterizing host responses of hamsters at a molecular level. To this end, we developed hamster-specific kinome peptide arrays to characterize the molecular host response of the Syrian golden hamster. After validating the functionality of the arrays using immune agonists of defined signaling mechanisms (lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α), we characterized the host response in a hamster model of VHF based on Pichinde virus (PICV(1)) infection by performing temporal kinome analysis of lung tissue. Our analysis revealed key roles for vascular endothelial growth factor (VEGF), interleukin (IL) responses, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling, and Toll-like receptor (TLR) signaling in the response to PICV infection. These findings were validated through phosphorylation-specific Western blot analysis. Overall, we have demonstrated that hamster-specific kinome arrays are a robust tool for characterizing the species-specific molecular host response in a VHF model. Further, our results provide key insights into the hamster host response to PICV infection and will inform future studies with high-consequence VHF pathogens.

Visualizing cancer and response to therapy in vivo using Cy5.5-labeled factor VIIa and anti-tissue factor antibody

We have developed a specific technique for imaging cancer in vivo using Cy5.5-labeled factor VIIa (fVIIa), clotting-deficient FFRck-fVIIa, paclitaxel-FFRck-fVIIa, and anti-tissue factor (TF) antibody. FVIIa is the natural ligand for TF. We took advantage of the fact that vascular endothelial cells (VECs) in cancer, but not normal tissue, aberrantly express TF due to its induction by vascular endothelial growth factor (VEGF). Under physiological conditions, TF is expressed by stromal cells and outer blood vessel layers (smooth muscle and adventitia), but not by VECs. We hypothesized that labeled fVIIa or anti-TF antibodies could be used to image the tumor vasculature in vivo. To test this, Cy5.5-labeled fVIIa, FFRck-fVIIa, paclitaxel-FFRck-fVIIa, and anti-TF antibody were developed and administered to athymic nude mice carrying xenografts including glioma U87EGFRviii, pancreatic cancer ASPC-1 and Mia PaCa-2, and squamous cell carcinoma KB-V1. Cy5.5 labeled with these targeting proteins specifically localized to the tumor xenografts for at least 14 days but unconjugated Cy5.5 did not localize to any xenografts or organs. This method of imaging TF in the tumor VECs may be useful in detecting primary tumors and metastases as well as monitoring in vivo therapeutic responses.

Tumor angiogenesis therapy using targeted delivery of Paclitaxel to the vasculature of breast cancer metastases

Breast cancer aberrantly expresses tissue factor (TF) in cancer tissues and cancer vascular endothelial cells (VECs). TF plays a central role in cancer angiogenesis, growth, and metastasis and, as such, is a target for therapy and drug delivery. TF is the cognate receptor of factor VIIa (fVIIa). We have coupled PTX (paclitaxel, also named Taxol) with a tripeptide, phenylalanine-phenylalanine-arginine chloromethyl ketone (FFRck) and conjugated it with fVIIa. The key aim of the work is to evaluate the antiangiogenic effects of PTX-FFRck-fVIIa against a PTX-resistant breast cancer cell line. Matrigel mixed with VEGF and MDA-231 was injected subcutaneously into the flank of athymic nude mice. Animals were treated by tail vein injection of the PTX-FFRck-fVIIa conjugate, unconjugated PTX, or PBS. The PTX-FFRck-fVIIa conjugate significantly reduces microvessel density in matrigel (p < 0.01–0.05) compared to PBS and unconjugated PTX. The breast cancer lung metastasis model in athymic nude mice was developed by intravenous injection of MDA-231 cells expressing luciferase. Animals were similarly treated intravenously with the PTX-FFRck-fVIIa conjugate or PBS. The conjugate significantly inhibits lung metastasis as compared to the control, highlighting its potential to antagonize angiogenesis in metastatic carcinoma. In conclusion, PTX conjugated to fVIIa is a promising therapeutic approach for improving selective drug delivery and inhibiting angiogenesis.

Plasma membrane calcium ATPase isoform 4 inhibits vascular endothelial growth factor-mediated angiogenesis through interaction with calcineurin

OBJECTIVE

Vascular endothelial growth factor (VEGF) has been identified as a crucial regulator of physiological and pathological angiogenesis. Among the intracellular signaling pathways triggered by VEGF, activation of the calcineurin/nuclear factor of activated T cells (NFAT) signaling axis has emerged as a critical mediator of angiogenic processes. We and others previously reported a novel role for the plasma membrane calcium ATPase (PMCA) as an endogenous inhibitor of the calcineurin/NFAT pathway, via interaction with calcineurin, in cardiomyocytes and breast cancer cells. However, the functional significance of the PMCA/calcineurin interaction in endothelial pathophysiology has not been addressed thus far.

APPROACH AND RESULTS

Using in vitro and in vivo assays, we here demonstrate that the interaction between PMCA4 and calcineurin in VEGF-stimulated endothelial cells leads to downregulation of the calcineurin/NFAT pathway and to a significant reduction in the subsequent expression of the NFAT-dependent, VEGF-activated, proangiogenic genes RCAN1.4 and Cox-2. PMCA4-dependent inhibition of calcineurin signaling translates into a reduction in endothelial cell motility and blood vessel formation that ultimately impairs in vivo angiogenesis by VEGF.

CONCLUSIONS

Given the importance of the calcineurin/NFAT pathway in the regulation of pathological angiogenesis, targeted modulation of PMCA4 functionality might open novel therapeutic avenues to promote or attenuate new vessel formation in diseases that occur with angiogenesis.

An EMMPRIN-γ-catenin-Nm23 complex drives ATP production and actomyosin contractility at endothelial junctions

Cell-cell adhesions are important sites through which cells experience and resist forces. In endothelial cells, these forces regulate junction dynamics and determine endothelial barrier strength. We identify the Ig superfamily member EMMPRIN (also known as basigin) as a coordinator of forces at endothelial junctions. EMMPRIN localization at junctions correlates with endothelial junction strength in different mouse vascular beds. Accordingly, EMMPRIN-deficient mice show altered junctions and increased junction permeability. Lack of EMMPRIN alters the localization and function of VE-cadherin (also known as cadherin-5) by decreasing both actomyosin contractility and tugging forces at endothelial cell junctions. EMMPRIN ensures proper actomyosin-driven maturation of competent endothelial junctions by forming a molecular complex with γ-catenin (also known as junction plakoglobin) and Nm23 (also known as NME1), a nucleoside diphosphate kinase, thereby locally providing ATP to fuel the actomyosin machinery. These results provide a novel mechanism for the regulation of actomyosin contractility at endothelial junctions and might have broader implications in biological contexts such as angiogenesis, collective migration and tissue morphogenesis by coupling compartmentalized energy production to junction assembly.

The involvement of NFAT transcriptional activity suppression in SIRT1-mediated inhibition of COX-2 expression induced by PMA/Ionomycin

SIRT1, a class III histone deacetylase, acts as a negative regulator for many transcription factors, and plays protective roles in inflammation and atherosclerosis. Transcription factor nuclear factor of activated T cells (NFAT) has been previously shown to play pro-inflammatory roles in endothelial cells. Inhibition of NFAT signaling may be an attractive target to regulate inflammation in atherosclerosis. However, whether NFAT transcriptional activity is suppressed by SIRT1 remains unknown. In this study, we found that SIRT1 suppressed NFAT-mediated transcriptional activity. SIRT1 interacted with NFAT, and the NHR and RHR domains of NFAT mediated the interaction with SIRT1. Moreover, we found that SIRT1 primarily deacetylated NFATc3. Adenoviral over-expression of SIRT1 suppressed PMA and calcium ionophore Ionomycin (PMA/Io)-induced COX-2 expression in human umbilical vein endothelial cells (HUVECs), while SIRT1 RNAi reversed the effects in HUVECs. Moreover, inhibition of COX-2 expression by SIRT1 in PMA/Io-treated HUVECs was largely abrogated by inhibiting NFAT activation. Furthermore, SIRT1 inhibited NFAT-induced COX-2 promoter activity, and reduced NFAT binding to the COX-2 promoter in PMA/Io-treated HUVECs. These results suggest that suppression of NFAT transcriptional activity is involved in SIRT1-mediated inhibition of COX-2 expression induced by PMA/Io, and that the negative regulatory mechanisms of NFAT by SIRT1 may contribute to its anti-inflammatory effects in atherosclerosis.

Regulation of tissue factor gene expression in monocytes and endothelial cells: Thromboxane A2 as a new player

Tissue factor (TF) is the primary activator of the coagulation cascade. Under normal conditions, endothelial cells (ECs) and blood cells, such as monocytes, do not express TF. However, bacterial lipopolysaccharide (LPS) induces TF expression in monocytes and this leads to disseminated intravascular coagulation during endotoxemia and sepsis. A variety of stimuli induce TF expression in ECs in vitro, although it is unclear how much TF is expressed by the endothelium in vivo. LPS induction of TF gene expression in monocytic cells and ECs is mediated by various intracellular signaling pathways and the transcription factors NF-ĸB, AP-1 and Egr-1. In contrast, vascular endothelial cell growth factor (VEGF) induces TF gene expression in ECs via the transcription factors NFAT and Egr-1. Similarly, oxidized phospholipids (such as 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine) induce TF expression in ECs and possibly monocytes via NFAT and Egr-1. Thromboxane A2 (TXA2) can now be added to the list of stimuli that induce TF gene expression in both monocytes and ECs. Interestingly, inhibition of the TX-prostanoid (TP) receptor also reduces TF expression in with tumor necrosis factor (TNF)-α stimulated ECs and LPS stimulated monocytes, which suggests that TP receptor antagonist may be useful in reducing pathologic TF expression in the vasculature and blood.