Platelet endothelial cell adhesion molecule in cell signaling and thrombosis

E2F2 modulates cell adhesion through the transcriptional regulation of PECAM1 in multiple myeloma

Multiple myeloma (MM) is the second most common haematological malignancy. Despite the development of new drugs and treatments in recent years, the therapeutic outcomes of patients are not satisfactory. It is necessary to further investigate the molecular mechanism underlying MM progression. Herein, we found that high E2F2 expression was correlated with poor overall survival and advanced clinical stages in MM patients. Gain- and loss-of-function studies showed that E2F2 inhibited cell adhesion and consequently activated cell epithelial-to-mesenchymal transition (EMT) and migration. Further experiments revealed that E2F2 interacted with the PECAM1 promoter to suppress its transcriptional activity. The E2F2-knockdown-mediated promotion of cell adhesion was significantly reversed by the repression of PECAM1 expression. Finally, we observed that silencing E2F2 significantly inhibited viability and tumour progression in MM cell models and xenograft mouse models respectively. This study demonstrates that E2F2 plays a vital role as a tumour accelerator by inhibiting PECAM1-dependent cell adhesion and accelerating MM cell proliferation. Therefore, E2F2 may serve as a potential independent prognostic marker and therapeutic target for MM.

Communication from the Scientific Standardization Committees of the International Society on Thrombosis and Haemostasis on vascular endothelium-related biomarkers in disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is not a disease criterion but a pathomechanistic process that accompanies various underlying diseases. According to the International Society on Thrombosis and Haemostasis definition, endothelial injury is an essential component in addition to systemic coagulation activation. Despite this definition, current diagnostic criteria for DIC do not include biomarkers for vascular endothelial injury. Endothelial cells are critical for hemostatic regulation because they produce various antithrombotic substances and express anticoagulant factors at the same time as facilitating coagulation, inflammatory reactions, platelet aggregation, and fibrinolysis with acute injury. Endothelial cells also exhibit various receptors, adhesion molecules, and the critical role of glycocalyx that regulates cellular interactions in thromboinflammation. For clinicians, biomarkers suitable for assessing endothelial injury are not readily available. Although we still do not have ideal biomarkers, antithrombin activity and von Willebrand factor can be candidates for the endothelium-related markers because those reflect the severity and are available in most clinical settings. Further, the dysfunction of endothelial cell in DIC arising from various underlying diseases is likely highly variable. For example, the involvement of endothelial dysfunction is significant in sepsis-induced coagulopathy, while moderate in trauma-induced coagulopathy, and variable in hematologic malignancy-associated coagulopathy. Because of the complexity of disease status associated with DIC, further research searching clinically available endothelium-related biomarkers is expected to establish individualized diagnostic criteria and potential therapeutic approaches.

Intracellular communication and immunothrombosis in sepsis

Inflammation and coagulation are the critical responses to infection that include leukocytes, platelets, and vascular endothelial cells responding in concert to eradicate the invading pathogen. In sepsis, a variety of cell surface receptors, including toll-like receptors, Fcγ-receptors, G-protein-coupled receptors, and adhesion receptors, detect the pathogens and elicit thromboinflammatory responses. Concurrently, the molecular patterns released from host damaged cells accelerate the immune responses through binding to the same pattern recognition receptors. Cytokines, chemokines, and extracellular vesicles are important mediators for amplifying the responses to distant cells as part of the systemic response to infections. At the same time, cells communicate with each other via direct contact, adhesion molecules, paracrine mediators, and tunneling nanotubes, which are important for regulating inflammation and thrombus formation. Despite increasing attention to immunothrombosis in sepsis, these close communication systems are less understood but play a critical role in host defense mechanisms. In this review, cellular activation and direct intercellular communication systems in sepsis with a focus on the coagulation response will be considered.

Dihydrodiosgenin inhibits endothelial cell-derived factor VIII and platelet-mediated hepatocellular carcinoma metastasis

Background: Our previous studies have demonstrated that diosgenin and diosgenin derivatives exhibit excellent antithrombotic activity via regulating platelet function and coagulation factor level. Platelets and blood coagulation system are highly associated with tumor hematogenous metastasis. Therefore, the purpose of this study was to evaluate whether dihydrodiosgenin (dydio) mediated-platelet inhibition or coagulation factor level modulation is involved in hepatocellular carcinoma cell (HCC) metastasis. Methods: Cell viability was examined by MTT and colony formation assays. Platelet aggregation text and morphology were used to assess dydio's role on tumor cell-induced platelet activation (TCIPA). Scratch assay, adhesion assay and Western blot were used to evaluate dydio's role on platelet-mediated metastasis. Western blot and fluorescence detection were performed to clarify dydio's role on endothelial cell (EC) function. The mice lung metastasis model was constructed to investigated dydio's function on coagulation factor and platelet-mediated metastasis. Results: This study found that pretreatment with dydio caused a significant inhibition of TCIPA. Platelets exposed to dydio significantly inhibited their adhesion to tumor cells, meanwhile, releasates of platelets that pretreated with dydio led to diminished cancer cell proliferation and migration along with the increase of epithelial markers E-cadherin and loss of mesenchymal phenotype. Additionally, ECs pretreated with dydio suppressed factor VIII (FVIII) level which in turn restrained the activation of platelets and the adhesion of cancer cells or platelets to ECs. Interestingly, our study demonstrated that FVIII could promote HCC proliferation. In vivo study revealed that mice intragastrical (i.g.) administration with dydio significantly inhibited the lung metastasis of hepal-6 cells which is highly correlated with the altered platelet function and coagulation level. Conclusion: Taken together, these results demonstrated that dydio altered platelet function and coagulation FVIII level, resulting in decreased metastatic potential of HCC. Thus, our study reveals that dydio exerts novel mechanisms of antitumor action beside its direct antitumor activity.

NEU1 sialidase regulates the sialylation state of CD31 and disrupts CD31-driven capillary-like tube formation in human lung microvascular endothelia

The highly sialylated vascular endothelial surface undergoes changes in sialylation upon adopting the migratory/angiogenic phenotype. We recently established endothelial cell (EC) expression of NEU1 sialidase (Cross, A. S., Hyun, S. W., Miranda-Ribera, A., Feng, C., Liu, A., Nguyen, C., Zhang, L., Luzina, I. G., Atamas, S. P., Twaddell, W. S., Guang, W., Lillehoj, E. P., Puché, A. C., Huang, W., Wang, L. X., Passaniti, A., and Goldblum, S. E. (2012) NEU1 and NEU3 sialidase activity expressed in human lung microvascular endothelia. NEU1 restrains endothelial cell migration whereas NEU3 does not. J. Biol. Chem. 287, 15966-15980). We asked whether NEU1 might regulate EC capillary-like tube formation on a Matrigel substrate. In human pulmonary microvascular ECs (HPMECs), prior silencing of NEU1 did not alter tube formation. Infection of HPMECs with increasing multiplicities of infection of an adenovirus encoding for catalytically active WT NEU1 dose-dependently impaired tube formation, whereas overexpression of either a catalytically dead NEU1 mutant, NEU1-G68V, or another human sialidase, NEU3, did not. NEU1 overexpression also diminished EC adhesion to the Matrigel substrate and restrained EC migration in a wounding assay. In HPMECs, the adhesion molecule, CD31, also known as platelet endothelial cell adhesion molecule-1, was sialylated via α2,6-linkages, as shown by Sambucus nigra agglutinin lectin blotting. NEU1 overexpression increased CD31 binding to Arachis hypogaea or peanut agglutinin lectin, indicating CD31 desialylation. In the postconfluent state, when CD31 ectodomains are homophilically engaged, NEU1 was recruited to and desialylated CD31. In postconfluent ECs, CD31 was desialylated compared with subconfluent cells, and prior NEU1 silencing completely protected against CD31 desialylation. Prior CD31 silencing and the use of CD31-null ECs each abrogated the NEU1 inhibitory effect on EC tube formation. Sialyltransferase 6 GAL-I overexpression increased α2,6-linked CD31 sialylation and dose-dependently counteracted NEU1-mediated inhibition of EC tube formation. These combined data indicate that catalytically active NEU1 inhibits in vitro angiogenesis through desialylation of its substrate, CD31.

Overexpression of protease-activated receptor type 1 (PAR-1) in glioblastoma multiforme WHO IV cells and blood vessels revealed by NCAM-assisted glioblastoma border labeling

Glioblastomas are neuroepithelial tumors with lost cellular differentiation and tenfold increased growth rates compared to low-grade gliomas. Despite of very aggressive treatment options based on surgery, irradiation, and chemotherapy, the prognosis of affected patients has remained poor and showed only slight improvements during the last 30 years. Research on glioblastoma border zone was hindered by the tumor's intense invasion into the brain parenchyma and the lack of suitable tumor cell markers. Nevertheless, the compact tumor mass and tumor invasion zone are composed of distinct cell types that need to be distinguished from each other to be addressed selectively. As the isoform 140 of the neural cell adhesion molecule (NCAM-140) was recently demonstrated to be lost in human gliomas with rising WHO grade, human multiform glioblastomas were characterized as a NCAM-140 negative entity displaying three main distinct invasion patterns. Evaluation of putative therapy targets within the tumor tissue and tumor invasion zone has been made possible through NCAM-140 negativity. In the present study, brain tissue controls and human glioblastoma samples with compact tumor mass and invasion areas were analyzed for their vascularization at the tumor border and the expression of thrombin receptor protease-activated receptor type 1 (PAR-1) within tumor tissue and vascular vessel walls. Use of NCAM-140 enabled the identification of the tumor invasion zone and its experimental investigation. Tissue vascularization was found to be significantly increased in the compact tumor mass of glioblastomas compared to their invasion zone and tumor-free controls with a significantly high and specific overexpression of PAR-1 within tumor cells and within tumor blood vessels depending upon the tumor area. This suggests thereby a functional role of the thrombin receptor PAR-1 in glioma cell malignancy and glioblastoma neoangiogenesis.

A glimpse of the glomerular milieu: from endothelial cell to thrombotic disease in nephrotic syndrome

Patients with nephrotic syndrome (NS) carry a high risk of venous thromboembolism (VTE) due to the abnormalities in coagulation and fibrinolysis. Although massive urine protein loss is considered to trigger the cascade of hypercoagulation, the exact nature of VTE in NS patients still remains obscure, especially in some cases when VTE occurs far before the presence of nephrotic proteinuria. Recent findings illustrate that loss of local glomerular homeostasis, like disturbance of cytokine profiles in endothelial cells or aberrant cellular crosstalks in glomerulus, is sufficient to initiate the development of thrombotic disease in glomerulonephropathy. Emerging data have highlighted the glomerular endothelial cell as a key regulator of local homeostasis, which might mediate the haemostatic derangement in the beginning of glomerular disease by expression of numerous prothrombotic factors and result in the subsequent predilection of VTE in NS. As the glomerulus-derived circulating factors are all collected and flushed into the renal vein directly, it is reasonable to suggest that increased release of glomerulus-derived thrombotic regulators, particularly from endothelial cells, may play a significant role in the highest proclivity for the renal vein as the site of thrombosis in NS. In this review, we thus discuss the current understandings of thromboembolism in NS with focus on how the glomerular endothelial cell involves in the pathogenesis of VTE, which may help to increase our understandings in the anti-thrombotic therapy for patients with NS.

Genomic characteristics of adhesion molecules in patients with symptomatic pulmonary embolism

The aim of this study was to identify the differences in the expression of cell adhesion molecule-related mRNAs between symptomatic pulmonary embolism (PE) and a control group, and to investigate the interactions among activated leukocytes, platelets and endothelial cells. Whole human gene chip was applied to detect the expression of cell adhesion molecule-related mRNAs in symptomatic PE and in the control group, and statistical analysis was performed. In patients with PE, the expression of the majority of integrin mRNAs located on leukocytes and platelets was significantly upregulated. The expression of mRNAs related to L-selectin and P-selectin glycoprotein ligand was significantly upregulated, while the expression of mRNA related to E-selectin was significantly downregulated. The expression of mRNAs related to classic cadherins and protocadherins was downregulated, and the expression of mRNAs related to vascular endothelial cadherin was significantly downregulated; the expression of mRNAs related to the immunoglobulin superfamily had no obvious difference between the 2 groups. In conclusion, we demonstrated that, in symptomatic PE patients, the adhesion of leukocytes and platelets was enhanced; the activation of endothelial cells was obviously weakened; the adherens junctions among endothelial cells were weakened, with the endothelium becoming more permeable.

Vanadium pentoxide induces activation and death of endothelial cells

Vanadium is a transition metal released into the atmosphere, as air-suspended particles, as a result of the combustion of fossil fuels and some metallurgic industry activities. Air-suspended particle pollution causes inflammation-related processes such as thrombosis and other cardiovascular events. Our aim was to evaluate the effect of vanadium pentoxide (V2O5) on endothelial cells since they are key participants in the pathogenesis of several cardiovascular and inflammatory diseases. Cell adhesion, the expression of adhesion molecules and oxidative stress, as well as proliferation, morphology and cell death of human umbilical vein endothelial cells (HUVECs) exposed to V2O5, were evaluated. Vanadium pentoxide at a 3.12 µg cm(-2) concentration induced an enhanced adhesion of the U937 macrophage cell line to HUVECs, owing to an increased expression of late adhesion molecules. HUVECs exposed to V2O5 showed an increase in ROS and nitric oxide production, and a diminished proliferation. These changes in vanadium-treated HUVECs were accompanied by severe morphological changes and apoptotic cell death. Vanadium pentoxide induced serious endothelial cell damage, probably related to the increased cardiovascular morbidity and mortality observed in individuals living in highly air-polluted areas.

The phosphorylation of vascular endothelial growth factor receptor-2 (VEGFR-2) by engineered surfaces with electrostatically or covalently immobilized VEGF

Growth factors are a class of signaling proteins that direct cell fate through interaction with cell-surface receptors. Although a myriad of possible cell fates stems from a growth factor binding to its receptor, the signaling cascades that result in one fate over another are still being elucidated. One possible mechanism by which nature modulates growth factor signaling is through the method of presentation of the growth factor--soluble or immobilized (matrix bound). Here we present the methodology to study signaling of soluble versus immobilized VEGF through VEGFR-2. We have designed a strategy to covalently immobilize VEGF using its heparin-binding domain to orient the molecule (bind) and a secondary functional group to mediate covalent binding (lock). This bind-and-lock approach aims to allow VEGF to assume a bioactive orientation before covalent immobilization. Surface plasmon resonance (SPR) demonstrated heparin and VEGF binding with surface densities of 60 ng/cm2 and 100 pg/cm2, respectively. ELISA experiments confirmed VEGF surface density and showed that electrostatically bound VEGF releases in cell medium and heparin solutions while covalently bound VEGF remains immobilized. Electrostatically bound VEGF and covalently bound VEGF phosphorylate VEGFR-2 in both VEGFR-2 transfected cells and VEGFR-2 endogenously producing cells. HUVECs plated on VEGF functionalized surfaces showed different morphologies between surface-bound VEGF and soluble VEGF. The surfaces synthesized in these studies allow for the study of VEGF/VEGFR-2 signaling induced by covalently bound, electrostatically bound, and soluble VEGF and may provide further insight into the design of materials for the generation of a mature and stable vasculature.

OP-1 injection increases VEGF expression but not angiogenesis in a rabbit model of distraction osteogenesis

We have previously shown that a single injection of rhBMP-7 (OP-1) applied to the regenerate early during distraction accelerates bone consolidation in a rabbit model of distraction osteogenesis. In the present study, we hypothesised that the injection of OP-1 improves bone consolidation by increasing blood flow to the distracted site. Blood flow into the regenerate of a rabbit model was measured and vascular endothelial growth factor (VEGF) expression was tested using semi-quantitative PCR. Immunohistochemistry was used for assessing the temporal and spatial expression of platelet endothelial cell adhesion molecule (PECAM), VEGF and its receptors following OP-1 injection. We observed a higher expression of VEGF and its receptors in the regenerate with OP-1 treatment. However, there was no difference in the increase in bone blood flow nor PECAM expression between the treated and control groups of animals. Interestingly, the increased expression of VEGF and its receptors was associated with chondrocyte and fibroblast-like cells, but not with endothelial cells. These results suggest that accelerated ossification by OP-1 may depend on a non-vascular mechanism, possibly involving a non-angiogenic function of VEGF signalling.

Effects of flavonoids on the expression of the pro-inflammatory response in human monocytes induced by ligation of the receptor for AGEs

Increasing evidence has shown advanced glycation end products (AGEs) receptor ligation (RAGE) to be an important part of complex interactions of the oxidative stress and pro-inflammatory responses. In this study, flavonoids were used to monitor the protective effects against the oxidative damage and inflammation mediated by AGEs in human monocytes. S100B (RAGE ligand) treatment in human THP-1 monocytic cells (THP-1) significantly increased gene expression of the pro-inflammatory cytokines TNF-alpha and IL-1beta; chemokines MCP-1 and IP-10; adhesion factors platelet endothelial cell adhesion molecule (PECAM-1) and beta2-integrin; and pro-inflammatory cyclooxygenase-2 (COX-2). S100B treatment with quercetin and catechin in THP-1 cells had inhibitory effects on the expression of pro-inflammatory genes and protein levels. Quercetin and catechin could regulate S100B-activated oxidant stress-sensitive pathways through blocking p47phox protein expression. Treatment with quercetin and catechin could eliminate reactive oxygen species (ROS) to reduce oxidative stress stimulated by S100B in THP-1 cells. Quercetin and catechin also showed different regulatory abilities on mitogen-activated protein kinase (MAPK) signaling pathways by inhibiting protein expression in S100B-stimulated inflammatory responses in THP-1 cells. This study suggests that quercetin and catechin may be of benefit for diabetic vascular complications due to its antioxidant abilities against AGE-mediated oxidative stress through oxidative stress-sensitive and oxidative stress-responsive signaling pathways, which lead to inflammation in human monocytes.

Blocking endothelial adhesion molecules: a potential therapeutic strategy to combat atherogenesis

PURPOSE OF REVIEW

This review provides a concise update of the involvement of endothelial adhesion molecules in atherogenesis, an overview of current advances in the development of adhesion molecule blocking agents, as well as an insight into the potential of these molecules in cardiovascular therapy.

RECENT FINDINGS

As endothelial adhesion molecules are deemed to play an important role in the development and progression of atherosclerotic lesions, they are interesting targets for therapeutic intervention in this process. In particular, P-selectin and vascular cell adhesion molecule 1 are widely considered to hold promise in this regard. Current research efforts centre on the design of agents that directly block the interaction of the receptor with its ligand (e.g. soluble P-selectin glycoprotein ligand 1, blocking antibodies, EWVD-based peptides) or that interfere with their synthesis (e.g. antisense oligonucleotides) or their regulatory control by nuclear factor kappa B or peroxisome proliferator-activated receptor gamma. Furthermore, adhesion molecules have been exploited as a target for the specific delivery of drug carriers (e.g. biodegradable particles with entrapped dexamethasone) or therapeutic compounds (e.g. dexamethasone) to the plaque. All approaches have been shown to be effective in blocking adhesion molecule function in in-vitro studies and in-vivo models for inflammation or atherosclerosis.

SUMMARY

Although the field has achieved considerable progress in recent years, leading to the development of a number of interesting leads, final proof of their efficacy in cardiovascular therapy is eagerly awaited.