The endothelial tumor suppressor p53 is essential for venous thrombus formation in aged mice

Endothelial PTP1B Deletion Promotes VWF Exocytosis and Venous Thromboinflammation

BACKGROUND

Endothelial activation promotes the release of procoagulant extracellular vesicles and inflammatory mediators from specialized storage granules. Endothelial membrane exocytosis is controlled by phosphorylation. We hypothesized that the absence of PTP1B (protein tyrosine phosphatase 1B) in endothelial cells promotes venous thromboinflammation by triggering endothelial membrane fusion and exocytosis.

METHODS

Mice with inducible endothelial deletion of PTP1B (End.PTP1B-KO) underwent inferior vena cava ligation to induce stenosis and venous thrombosis. Primary endothelial cells from transgenic mice and human umbilical vein endothelial cells were used for mechanistic studies.

RESULTS

Vascular ultrasound and histology showed significantly larger venous thrombi containing higher numbers of Ly6G (lymphocyte antigen 6 family member G)-positive neutrophils in mice with endothelial PTP1B deletion, and intravital microscopy confirmed the more pronounced neutrophil recruitment following inferior vena cava ligation. RT2 PCR profiler array and immunocytochemistry analysis revealed increased endothelial activation and adhesion molecule expression in primary End.PTP1B-KO endothelial cells, including CD62P (P-selectin) and VWF (von Willebrand factor). Pretreatment with the NF-κB (nuclear factor kappa B) kinase inhibitor BAY11-7082, antibodies neutralizing CD162 (P-selectin glycoprotein ligand-1) or VWF, or arginylglycylaspartic acid integrin-blocking peptides abolished the neutrophil adhesion to End.PTP1B-KO endothelial cells in vitro. Circulating levels of annexin V+ procoagulant endothelial CD62E+ (E-selectin) and neutrophil (Ly6G+) extracellular vesicles were also elevated in End.PTP1B-KO mice after inferior vena cava ligation. Higher plasma MPO (myeloperoxidase) and Cit-H3 (citrullinated histone-3) levels and neutrophil elastase activity indicated neutrophil activation and extracellular trap formation. Infusion of End.PTP1B-KO extracellular vesicles into C57BL/6J wild-type mice most prominently enhanced the recruitment of endogenous neutrophils, and this response was blunted in VWF-deficient mice or by VWF-blocking antibodies. Reduced PTP1B binding and tyrosine dephosphorylation of SNAP23 (synaptosome-associated protein 23) resulting in increased VWF exocytosis and neutrophil adhesion were identified as mechanisms, all of which could be restored by NF-κB kinase inhibition using BAY11-7082.

CONCLUSIONS

Our findings show that endothelial PTP1B deletion promotes venous thromboinflammation by enhancing SNAP23 phosphorylation, endothelial VWF exocytosis, and neutrophil recruitment.

Immune cell-mediated venous thrombus resolution

Herein, we review the current processes that govern experimental deep vein thrombus (DVT) resolution. How the human DVT resolves at the molecular and cellular level is not well known due to limited specimen availability. Experimentally, the thrombus resolution resembles wound healing, with early neutrophil-mediated actions followed by monocyte/macrophage-mediated events, including neovascularization, fibrinolysis, and eventually collagen replacement. Potential therapeutic targets are described, and coupling with site-directed approaches to mitigate off-target effects is the long-term goal. Similarly, timing of adjunctive agents to accelerate DVT resolution is an area that is only starting to be considered. There is much critical research that is needed in this area.

Deep sequencing of circulating miRNAs and target mRNAs level in deep venous thrombosis patients

Deep venous thrombosis is one of the most common peripheral vascular diseases that lead to major morbidity and mortality. The authors aimed to identify potential differentially expressed miRNAs and target mRNAs, which were helpful in understanding the potential molecule mechanism of deep venous thrombosis. The plasma samples of patients with deep venous thrombosis were obtained for the RNA sequencing. Differentially expressed miRNAs were identified, followed by miRNA-mRNA target analysis. Enrichment analysis was used to analyze the potential biological function of target mRNAs. GSE19151 and GSE173461 datasets were used for expression validation of mRNAs and miRNAs. 131 target mRNAs of 21 differentially expressed miRNAs were identified. Among which, 8 differentially expressed miRNAs including hsa-miR-150-5p, hsa-miR-326, hsa-miR-144-3p, hsa-miR-199a-5p, hsa-miR-199b-5p, hsa-miR-125a-5p, hsa-let-7e-5p and hsa-miR-381-3p and their target mRNAs (PRKCA, SP1, TP53, SLC27A4, PDE1B, EPHB3, IRS1, HIF1A, MTUS1 and ZNF652) were found associated with deep venous thrombosis for the first time. Interestingly, PDE1B and IRS1 had a potential diagnostic value for patients. Additionally, 3 important signaling pathways including p53, PI3K-Akt and MAPK were identified in the enrichment analysis of target mRNAs (TP53, PRKCA and IRS1). Identified circulating miRNAs and target mRNAs and related signaling pathways may be involved in the process of deep venous thrombosis.

Upregulation of ERK-EGR1-heparanase axis by HDAC inhibitors provides targets for rational therapeutic intervention in synovial sarcoma

BACKGROUND

Synovial sarcoma (SS) is an aggressive soft tissue tumor with limited therapeutic options in advanced stage. SS18-SSX fusion oncogenes, which are the hallmarks of SS, cause epigenetic rewiring involving histone deacetylases (HDACs). Promising preclinical studies supporting HDAC targeting for SS treatment were not reflected in clinical trials with HDAC inhibitor (HDACi) monotherapies. We investigated pathways implicated in SS cell response to HDACi to identify vulnerabilities exploitable in combination treatments and improve the therapeutic efficacy of HDACi-based regimens.

METHODS

Antiproliferative and proapoptotic effects of the HDACi SAHA and FK228 were examined in SS cell lines in parallel with biochemical and molecular analyses to bring out cytoprotective pathways. Treatments combining HDACi with drugs targeting HDACi-activated prosurvival pathways were tested in functional assays in vitro and in a SS orthotopic xenograft model. Molecular mechanisms underlying synergisms were investigated in SS cells through pharmacological and gene silencing approaches and validated by qRT-PCR and Western blotting.

RESULTS

SS cell response to HDACi was consistently characterized by activation of a cytoprotective and auto-sustaining axis involving ERKs, EGR1, and the β-endoglycosidase heparanase, a well recognized pleiotropic player in tumorigenesis and disease progression. HDAC inhibition was shown to upregulate heparanase by inducing expression of the positive regulator EGR1 and by hampering negative regulation by p53 through its acetylation. Interception of HDACi-induced ERK-EGR1-heparanase pathway by cell co-treatment with a MEK inhibitor (trametinib) or a heparanase inhibitor (SST0001/roneparstat) enhanced antiproliferative and pro-apoptotic effects. HDAC and heparanase inhibitors had opposite effects on histone acetylation and nuclear heparanase levels. The combination of SAHA with SST0001 prevented the upregulation of ERK-EGR1-heparanase induced by the HDACi and promoted caspase-dependent cell death. In vivo, the combined treatment with SAHA and SST0001 potentiated the antitumor efficacy against the CME-1 orthotopic SS model as compared to single agent administration.

CONCLUSIONS

The present study provides preclinical rationale and mechanistic insights into drug combinatory strategies based on the use of ERK pathway and heparanase inhibitors to improve the efficacy of HDACi-based antitumor therapies in SS. The involvement of classes of agents already clinically available, or under clinical evaluation, indicates the transferability potential of the proposed approaches.

Extracellular Vesicles and Thrombosis: Update on the Clinical and Experimental Evidence

Extracellular vesicles (EVs) compose a heterogenous group of membrane-derived particles, including exosomes, microvesicles and apoptotic bodies, which are released into the extracellular environment in response to proinflammatory or proapoptotic stimuli. From earlier studies suggesting that EV shedding constitutes a cellular clearance mechanism, it has become evident that EV formation, secretion and uptake represent important mechanisms of intercellular communication and exchange of a wide variety of molecules, with relevance in both physiological and pathological situations. The putative role of EVs in hemostasis and thrombosis is supported by clinical and experimental studies unraveling how these cell-derived structures affect clot formation (and resolution). From those studies, it has become clear that the prothrombotic effects of EVs are not restricted to the exposure of tissue factor (TF) and phosphatidylserines (PS), but also involve multiplication of procoagulant surfaces, cross-linking of different cellular players at the site of injury and transfer of activation signals to other cell types. Here, we summarize the existing and novel clinical and experimental evidence on the role and function of EVs during arterial and venous thrombus formation and how they may be used as biomarkers as well as therapeutic vectors.

Identification of genes, pathways and transcription factor-miRNA-target gene networks and experimental verification in venous thromboembolism

Venous thromboembolism (VTE) is a complex, multifactorial life-threatening disease that involves vascular endothelial cell (VEC) dysfunction. However, the exact pathogenesis and underlying mechanisms of VTE are not completely clear. The aim of this study was to identify the core genes and pathways in VECs that are involved in the development and progression of unprovoked VTE (uVTE). The microarray dataset GSE118259 was downloaded from the Gene Expression Omnibus database, and 341 up-regulated and 8 down-regulated genes were identified in the VTE patients relative to the healthy controls, including CREB1, HIF1α, CBL, ILK, ESM1 and the ribosomal protein family genes. The protein–protein interaction (PPI) network and the transcription factor (TF)-miRNA-target gene network were constructed with these differentially expressed genes (DEGs), and visualized using Cytoscape software 3.6.1. Eighty-nine miRNAs were predicted as the targeting miRNAs of the DEGs, and 197 TFs were predicted as regulators of these miRNAs. In addition, 237 node genes and 4 modules were identified in the PPI network. The significantly enriched pathways included metabolic, cell adhesion, cell proliferation and cellular response to growth factor stimulus pathways. CREB1 was a differentially expressed TF in the TF-miRNA-target gene network, which regulated six miRNA-target gene pairs. The up-regulation of ESM1, HIF1α and CREB1 was confirmed at the mRNA and protein level in the plasma of uVTE patients. Taken together, ESM1, HIF1α and the CREB1-miRNA-target genes axis play potential mechanistic roles in uVTE development.

Mechanical Fingerprint of Senescence in Endothelial Cells

Endothelial senescence entails alterations of the healthy cell phenotype, which accumulate over time and contribute to cardiovascular disease. Mechanical aspects regulating cell adhesion, force generation, and the response to flow contribute to the senescence-associated drift; however, they remain largely unexplored. Here, we exploit force microscopy to resolve variations of the cell anchoring to the substrate and the tractions generated upon aging in the nanonewton (nN) range. Senescent endothelial cells display a multifold increase in the levels of basal adhesion and force generation supported by mature and strong focal adhesions. The enhanced mechanical interaction with the substrate yields static endothelial monolayers that polarize in response to flow but fail the process of coordinated cell shape remodeling and reorientation. The emerging picture indicates that senescence reinforces the local cell interaction with the substrate and may therefore prevent endothelial denudation; however, it compromises the ability to functionally adapt to the local hemodynamic conditions.

Effect of Heparanase and Heparan Sulfate Chains in Hemostasis

Heparanase, the only mammalian enzyme known to degrade heparan sulfate chains, affects the hemostatic system through several mechanisms. Along with the degrading effect, heparanase engenders release of syndecan-1 from the cell surface and directly enhances the activity of the blood coagulation initiator, tissue factor, in the coagulation system. Upregulation of tissue factor and release of tissue factor pathway inhibitor from the cell surface contribute to the prothrombotic effect. Tissue factor pathway inhibitor and the strongest physiological anticoagulant antithrombin are attached to the endothelial cell surface by heparan sulfate. Hence, degradation of heparan sulfate induces further release of these two natural anticoagulants from endothelial cells. Elevated heparanase procoagulant activity and heparan sulfate chain levels in plasma, demonstrated in cancer, pregnancy, oral contraceptive use, and aging, could suggest a potential mechanism for increased risk of thrombosis in these clinical settings. In contrast to the blood circulation, accumulation of heparan sulfate chains in transudate and exudate pleural effusions induces a local anticoagulant milieu. The anticoagulant effect of heparan sulfate chains in other closed spaces such as peritoneal or subdural cavities should be further investigated.

The expression level of COX7C associates with venous thromboembolism in colon cancer patients

Venous thromboembolism (VTE) is a common complication of colon cancer. In the present study, we aimed to explore the association of the oncogene COX7C to VTE in colon cancer patients. Samples from 580 patients were examined histologically for VTE and pathological characteristic of cancer. Gene mutation and expression analysis were performed using polymerase chain reaction-based assays to evaluate genes related to VTE, including COX7C. Univariate analysis between clinical pathological factors and VTE was conducted. Logistic regression analysis was performed for the prediction of VTE by pathological factors and gene expressions. Among patients investigated, a total of 56 patients had VTE. COX7C had a significant correlation with VTE (p < 0.001). Despite a correlation between tumor size, invasion depth of tumor, lymph node metastasis, lymph node metastasis, distant metastasis, lymphovascular invasion, histologic type and pathology type, Ki-67, and some other genes, to VTE (p > 0.05), only COX7C expression demonstrated significance in its ability to predict VTE. Here, we show that COX7C upregulation strongly correlates with VTE in colon cancer, which implicates its role as a biomarker and therapeutic target of VTE in colon cancer.

Resolution of Deep Venous Thrombosis: Proposed Immune Paradigms

Venous thromboembolism (VTE) is a pathology encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE) associated with high morbidity and mortality. Because patients often present after a thrombus has already formed, the mechanisms that drive DVT resolution are being investigated in search of treatment. Herein, we review the current literature, including the molecular mechanisms of fibrinolysis and collagenolysis, as well as the critical cellular roles of macrophages, neutrophils, and endothelial cells. We propose two general models for the operation of the immune system in the context of venous thrombosis. In early thrombus resolution, neutrophil influx stabilizes the tissue through NETosis. Meanwhile, macrophages and intact neutrophils recognize the extracellular DNA by the TLR9 receptor and induce fibrosis, a complimentary stabilization method. At later stages of resolution, pro-inflammatory macrophages police the thrombus for pathogens, a role supported by both T-cells and mast cells. Once they verify sterility, these macrophages transform into their pro-resolving phenotype. Endothelial cells both coat the stabilized thrombus, a necessary early step, and can undergo an endothelial-mesenchymal transition, which impedes DVT resolution. Several of these interactions hold promise for future therapy.

Heparanase in the Coagulation System

The hemostatic cascade is initiated by the transmembrane coagulation protein - tissue factor (TF) and eventuates in fibrin formation. Heparanase protein was demonstrated to directly enhance TF activity resulting in increased activation of the coagulation system. In addition, heparanase was found to increase hemostatic system activation via two other mechanisms: up-regulating TF expression in endothelial cells and releasing the protein tissue factor pathway inhibitor (TFPI) from the cell surface. Peptides derived from TFPI-2, a protein similar to TFPI, were shown to inhibit the TF/heparanase complex as well as attenuate sepsis and tumor growth. Increased heparanase procoagulant activity was observed in several clinical settings, including women using oral contraceptives, women at delivery, patients following orthopedic surgery and patients with diabetic foot, shift work female nurses, patients with lung cancer, retinal vein thrombosis and prosthetic heart valve thrombosis. Remarkably, the heparanase profile was significantly different across the tested groups. Inhibition of TF / heparanase interaction may represent a new target for attenuating coagulation, cancer and inflammation.

By word of mouse: using animal models in venous thrombosis research

Deep vein thrombosis (DVT) is a disease with high prevalence and morbidity. It can lead to pulmonary embolism with severe respiratory insufficiency and risk of death. Mechanisms behind all stages of DVT, such as thrombosis commencement, propagation, and resolution, remain incompletely understood. Animal models represent an invaluable tool to explore these problems and identify new targets for DVT prevention and treatment. In this review, we discuss existing models of venous thrombosis, their advantages and disadvantages, and applicability to studying different aspects of DVT pathophysiology. We also speculate about requirements for an "ideal model" that would best recapitulate features of human DVT and discuss readouts of various models.

Unfolded Protein Response supports endothelial barrier function

Ongoing efforts are oriented towards the development of novel therapeutic agents to repress lung hyperpermeability responses due to inflammation. The endothelial barrier dysfunction triggered by such events, may eventually lead to severe cardiovascular complications, such as the Acute Respiratory Distress Syndrome. Hsp90 inhibitors are anticancer compounds, associated with strong anti-inflammatory responses in the endothelium. Our latest observations in experimental models of Acute Lung Injury suggest that P53 orchestrates, at least in part, such activities. Remarkably, both Hsp90 inhibition and P53 induction are associated with the activation of the Unfolded Protein Response element. The purpose of the current manuscript, is to introduce the hypotheses that UPR induction protects the vasculature against inflammation.

Cancer and Thrombosis-New Insights

Cancer patients have a pro-thrombotic state attributed to the ability of cancer cells to activate the coagulation system and interact with hemostatic cells, thus tilting the balance between pro- and anticoagulants. Mechanisms underlying the coagulation system activation involve tumor cells, endothelial cells, platelets, and white blood cells. Anti-cancer therapies, including anti-angiogenic drugs, significantly increase the risk of thrombosis during treatment. Along with the role of coagulation proteins in the hemostatic system, these proteins also serve as growth factors to the tumor. Heparanase is a pro-angiogenic and pro-metastatic protein. Our previous studies have demonstrated that it enhances tissue factor (TF) activity and is present at high levels in tumor cells and patients' blood. Strategies to attenuate heparanase effects by heparin mimetics or peptides interrupting the TF-heparanase interaction are good candidates to attenuate tumor growth and thrombotic manifestations.