Project description:Increased endothelial permeability and failure to repair is the hallmark of several vascular diseases including acute lung injury (ALI). However, little is known about the intrinsic pathways that activate endothelial cell (EC) regenerative programs and thereby tissue repair. Studies have invoked a crucial role of sphingosine-1-phosphate (S1P) in resolving endothelial hyperpermeability through activation of the G-protein coupled receptor, sphingosine-1-phosphate receptor 1 (S1PR1). Here, we addressed mechanisms of generation of S1PR1+ EC, which may prevent endothelial injury. Studies were made using inducible EC-S1PR1-/- (iEC-S1PR1-/-) mice and S1PR1-GFP reporter mice to trace the generation of S1PR1+ EC. We observed in a mouse model of endotoxemia that S1P generation induced the programming of S1PR1lo to S1PR1+ EC, which comprised 80% of lung EC. The transition of these cells was required for reestablishing the endothelial barrier. We also observed that conditional deletion of S1PR1 in EC increased vascular permeability. RNA-seq analysis of S1PR1+ EC showed enrichment of genes regulating S1P synthesis and transport, sphingosine kinase 1 (SPHK1) and SPNS2, respectively. The activation of transcription factors EGR1 and STAT3 were essential for transcribing SPHK1 and SPNS2, respectively, to increase S1P production that served to amplify S1PR1+ EC transition. Transplantation of S1PR1+ EC into injured lung vasculature restored endothelial integrity. Our findings show that generation of a S1PR1+ EC population activates the endothelial regenerative program mediating vascular endothelial repair, thus raising the possibility of harnessing this pathway to restore vascular homeostasis in inflammatory injury.
Project description:Understanding vascular growth and maturation in developing tumors has important implications for tumor progression, spread, and ultimately host survival. Modulating the signaling of endothelial G protein-coupled receptors (GPCRs) in blood and lymphatic vessels can enhance or limit tumor progression. Sphingosine 1-phosphate receptor 1 (S1PR1) is a GPCR for circulating lysophospholipid S1P that is highly expressed in blood and lymphatic vessels. Using the S1PR1- enhanced green fluorescent protein (eGFP) mouse model in combination with intravital imaging and pharmacologic modulation of S1PR1 signaling, we show that boundary conditions of high and low S1PR1 signaling retard tumor progression by enhancing or destabilizing neovasculature integrity, respectively. In contrast, midrange S1PR1 signaling, achieved by receptor antagonist titration, promotes abundant growth of small, organized vessels and thereby enhances tumor progression. Furthermore, in vivo S1PR1 antagonism supports lung colonization by circulating tumor cells. Regulation of endothelial S1PR1 dynamically controls vascular integrity and maturation and thus modulates angiogenesis, tumor growth, and hematogenous metastasis.
Project description:The M2 isoform of pyruvate kinase (PKM2) is highly expressed in most cancer cells, and has been studied extensively as a driver of oncogenic metabolism. In contrast, the role of PKM2 in nontransformed cells is little studied, and nearly nothing is known of its role, if any, in quiescent cells. We show here that endothelial cells express PKM2 almost exclusively over PKM1. In proliferating endothelial cells, PKM2 is required to suppress p53 and maintain cell cycle progression. In sharp contrast, PKM2 has a strikingly different role in quiescent endothelial cells, where inhibition of PKM2 leads to degeneration of tight junctions and barrier function. Mechanistically, PKM2 regulates barrier function independently of its canonical activity as a pyruvate kinase. Instead, PKM2 suppresses NF-kB and its downstream target, the vascular permeability factor angiopoietin 2. As a consequence, loss of endothelial cell PKM2 in vivo predisposes mice to VEGF-induced vascular leak, and to severe bacteremia and death in response to sepsis. Together, these data demonstrate new roles of PKM2 in quiescent cells, and highlight the need for caution in developing cancer therapies that target PKM2.
Project description:Vascular aging is based on the development of endothelial dysfunction, which is thought to be promoted by senescent cells accumulating in aged tissues and is possibly affected by their environment via inflammatory mediators and oxidative stress. Senescence appears to be closely interlinked with changes in cell metabolism. Here, we describe an upregulation of both glycolytic and oxidative glucose metabolism in replicative senescent endothelial cells compared to young endothelial cells by employing metabolic profiling and glucose flux measurements and by analyzing the expression of key metabolic enzymes. Senescent cells exhibit higher glycolytic activity and lactate production together with an enhanced expression of lactate dehydrogenase A as well as increases in tricarboxylic acid cycle activity and mitochondrial respiration. The latter is likely due to the reduced expression of pyruvate dehydrogenase kinases (PDHKs) in senescent cells, which may lead to increased activity of the pyruvate dehydrogenase complex. Cellular and mitochondrial ATP production were elevated despite signs of mitochondrial dysfunction, such as an increased production of reactive oxygen species and extended mitochondrial mass. A shift from glycolytic to oxidative glucose metabolism induced by pharmacological inhibition of PDHKs in young endothelial cells resulted in premature senescence, suggesting that alterations in cellular glucose metabolism may act as a driving force for senescence in endothelial cells.
Project description:Although more than 100 lipid metabolites have been identified, their bioactivities remain unknown. In a previous study, we discovered that the production of several lipid metabolites in the intestines dramatically changed in colitis. Of these metabolites, 5,6-dihydroxyeicosatetraenoic acid (DiHETE) possesses novel anti-inflammatory activity in the vasculature. In this study, we used mouse and human umbilical vein endothelial cell (HUVEC) models to elucidate the mechanisms underlying the vascular activity of lipid metabolites, particularly those related to the release of histamine, a major proinflammatory mediator that stimulates endothelial cells to produce NO, a mediator of vascular relaxation and hyperpermeability, by activating intracellular Ca2+ concentration-dependent signaling. In a mouse ear, the administration of 5,6-DiHETE did not induce inflammatory reactions, and pretreatment with 5,6-DiHETE inhibited histamine-induced inflammation, specifically vascular dilation and hyperpermeability. In an isolated mouse aorta, 5,6-DiHETE treatment did not influence vascular contraction but attenuated acetylcholine-induced vascular relaxation. In HUVECs, treatment with 5,6-DiHETE inhibited histamine-induced endothelial barrier disruption and inhibited the production of NO. Most notably, 5,6-DiHETE inhibited histamine-induced increases in intracellular Ca2+ concentrations in HUVECs. Our findings suggest that 5,6-DiHETE attenuates vascular hyperpermeability during inflammation by inhibiting endothelial Ca2+ elevation, which might lead to a novel pharmacological strategy against inflammatory diseases.
Project description:Many inflammatory diseases are associated with elevated blood concentration of fibrinogen (Fg) leading to vascular dysfunction. We showed that pathologically high (4 mg/ml) content of Fg disrupts integrity of endothelial cell (EC) layer and causes macromolecular leakage affecting tight junction proteins. However, role of adherence junction proteins, particularly vascular endothelial cadherin (VE-cadherin) and matrix metalloproteinase-9 (MMP-9) in this process is not clear. We tested the hypothesis that at high levels Fg affects integrity of mouse brain endothelial cell (MBEC) monolayer through activation of MMP-9 and downregulation of VE-cadherin expression and in part its translocation to the cytosol. The effect of Fg on cultured MBEC layer integrity was assessed by measuring transendothelial electrical resistance. Cellular expression and translocation of VE-cadherin were assessed by Western blot and immunohistochemical analyses, (respectively). Our results suggest that high content of Fg decreased VE-cadherin expression at protein and mRNA levels. Fg induced translocation of VE-cadherin to cytosol, which led to disruption of cell-to-cell interaction and cell to subendothelial matrix attachment. Fg-induced alterations in cell layer integrity and their attachment were diminished during inhibition of MMP-9 activity. Thus Fg compromises EC layer integrity causing downregulation and translocation of VE-cadherin and through MMP-9 activation. These results suggest that increased level of Fg could play a significant role in vascular dysfunction and remodeling.
Project description:Maintenance of vascular integrity in the adult animal is needed for survival, and it is critically dependent on the endothelial lining, which controls barrier function, blood fluidity, and flow dynamics. However, nodal regulators that coordinate endothelial identity and function in the adult animal remain poorly characterized. Here, we show that endothelial KLF2 and KLF4 control a large segment of the endothelial transcriptome, thereby affecting virtually all key endothelial functions. Inducible endothelial-specific deletion of Klf2 and/or Klf4 reveals that a single allele of either gene is sufficient for survival, but absence of both (EC-DKO) results in acute death from myocardial infarction, heart failure, and stroke. EC-DKO animals exhibit profound compromise in vascular integrity and profound dysregulation of the coagulation system. Collectively, these studies establish an absolute requirement for KLF2/4 for maintenance of endothelial and vascular integrity in the adult animal.
Project description:Exosomes play a critical role in intercellular communication since they contain signalling molecules and genetic materials. During tumorigenesis, tumour-derived exosomes have been demonstrated to promote tumour angiogenesis and metastasis. However, how the exosomes facilitate tumour metastasis is not clear. Here we explored the effect of HeLa cell-derived exosomes (ExoHeLa) on endothelial tight junctions (TJ) and the related mechanisms. After human umbilical vein endothelial cells (HUVEC) were treated with ExoHeLa, TJ proteins zonula occludens-1 (ZO-1) and Claudin-5 in HUVEC were significantly reduced as compared with that treated with exosomes from human cervical epithelial cells, while mRNA levels of ZO-1 and Claudin-5 remained unchanged. Consequently, permeability of endothelial monolayer was increased after the treatment with ExoHeLa. Injection of ExoHeLa into mice also increased vascular permeability and tumour metastasis in vivo. Neither knocking down of Dicer nor use of inhibitors of microRNAs targeting at mRNAs of ZO-1 and Claudin-5 could block the inhibitory effect of ExoHeLa on ZO-1 and Claudin-5. The expression of genes involved in endoplasmic reticulum (ER) stress was significantly increased in HUVECs after treated with ExoHeLa. Inhibition of ER stress by knocking down protein kinase RNA-like endoplasmic reticulum kinase prevented the down-regulation of ZO-1 and Claudin-5 by ExoHeLa. Our study found that HeLa cell-derived exosomes promote metastasis by triggering ER stress in endothelial cells and break down endothelial integrity. Such effect of exosomes is microRNA-independent.
Project description:The vascular endothelial barrier, which supports balanced plasma solute and macromolecule composition, controls hemostasis, and limits leukocyte extravasation at homeostasis, is frequently disrupted in inflammation associated with sepsis and other critical illness. Monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS, Clarkson disease) is a rare and devastating disorder characterized by relapsing-remitting episodes of spontaneous, profound microvascular hyper-permeability. A loss of function (LOF) mutation (G628R) in the mono ADP-ribosyltransferase PARP15, a protein of unknown function that is absent in mice, is associated with ISCLS and correlates with clinical markers of severe vascular leakage. In vascular endothelial cells, PARP15 suppresses cytokine-induced barrier disruption by ADP-ribosylating the scaffold protein JNK-interacting protein 3 (JIP3) and inhibiting p38 MAP kinase activation. Mice expressing human wild type (WT) PARP15 have curtailed inflammation-associated vascular leakage compared to mice expressing PARP15(G628R) in a p38-dependent fashion. Thus, PARP15 is essential for vascular endothelial barrier function under inflammatory stress.
Project description:Members of the ETS family of transcription factors are involved in several developmental processes including endothelial cell specification and blood vessel formation, but their exact roles remain unclear. The family member Erg is highly expressed in endothelial cells as compared to other developing cell types including chondrocytes, hematopoietic cells and mesodermal cells. To study the specific roles ERG plays in endothelial cell specification and function during early embryogenesis, we conditionally ablated it by mating ErgloxP/loxP and Tie2-Cre mice. We found that mutant embryos died by mid-gestation and that angiogenesis and vascular integrity were highly compromised. Our study reveals that ERG has essential and cell autonomous roles in endothelial cell development and blood vessel maintenance.