The expression of endothelial tissue plasminogen activator in vivo: a function defined by vessel size and anatomic location

1997 ◽  
Vol 110 (2) ◽  
pp. 139-148
Author(s):  
E.G. Levin ◽  
L. Santell ◽  
K.G. Osborn
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Plasminogen Activator ◽  
Lung Tissue ◽  
Vascular System ◽  
Vessel Size ◽  
Pulmonary Vessels ◽  
Pulmonary Endothelium ◽  
Tissue Plasminogen

Plasma tissue plasminogen activator (tPA) has long been considered to be the product of the endothelial cells that line the various parts of the vascular system regardless of vessel size or location. To determine whether this was truly the case in vivo, the distribution of tPA in the endothelium of the mouse lung and other tissues was evaluated. Immunohistochemical analysis of normal lung tissue showed positive staining limited to the endothelial cells of the bronchial arteries regardless of size with few cells of the pulmonary circulation associated with tPA. The pulmonary vessels that did contain endothelial cell-derived tPA were consistently between 7 and 30 microns in diameter. No capillary or large vessel pulmonary endothelium ever stained positive. These results were also observed in primate lung tissue where the bronchial endothelium of all vessels, even down to capillary size, contained tPA while none of the pulmonary endothelium did. Prolonged exposure of mice to hyperoxic conditions promotes acute lung injury and associated inflammation. Using this model, the effect of inflammation on endothelial cell tPA expression was evaluated. A 4.5-fold increase in the number of pulmonary vessels staining positive for tPA was observed after 66 hours with all of these vessels having a diameter between 7 and 30 microns. Again, none of the endothelium of large arteries or veins nor the capillaries had tPA. Whole tissue tPA mRNA increased dramatically with hyperoxia and in situ hybridization analysis showed tPA mRNA in the endothelium of the same types of vessels as antigen. The tPA localized to both the bronchial and pulmonary endothelium was active with neither tPA-PAI-1 complexes nor urokinase found in perfused lung tissue. These results indicate that endothelial cell tPA expression, either constitutive or induced by a pathologic event, is a function of a highly select group of endothelial cells which are defined by their association with vessels of discrete size and/or anatomic location. Thus, the widely held concept that the steady state level of plasma tPA is maintained through its constitutive production by all endothelial cells of the vascular system is invalid. Also suggested is the possibility that endothelial cell tPA might play a broader role than simply maintaining vessel patency as a component of the fibrinolytic pathway and contribute to complex dynamic processes such as inflammation.

Tissue Plasminogen Activator Expression in Endothelial Cells Exposed to Cyclic Strain in Vitro

1992 ◽  
Vol 1 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Toshiaki Iba ◽  
Bauer E. Sumpio
Keyword(s):  
Endothelial Cells ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Cyclic Strain ◽  
Neutral Position ◽  
Messenger Ribonucleic Acid ◽  
Tissue Plasminogen ◽  
Pai 1

The effects of cyclic strain on the production of tissue plasminogen activator (tPA) and type 1 plasminogen activator inhibitor (PAI-1) by cultured endothelial cells (EC) were examined. Human saphenous vein EC were seeded in selective areas of culture plates with flexible membrane bottoms (corresponding to specific strain regions) and grown to confluence. Membranes were deformed by vacuum (-20 kPa) at 60 cycles/min (0.5 s strain alternating with 0.5 s relaxation in the neutral position) for 5 days. EC grown in the periphery were subjected to 7-24% strain, while cells grown in the center experienced less than 7% strain. The results show a significant increase in immunoreactive tPA production on days 1, 3 and 5 compared to day 0 in EC subjected to more than 7% cyclic strain. There was no significant elevation of tPA in the medium of EC subjected to less than 7% strain. tPA activity could only be detected in the medium of EC subjected to more than 7% cyclic strain. PAI-1 levels in the medium were not significantly different in either group. In addition, immunocytochemical detection of intracellular tPA and messenger ribonucleic acid (mRNA) expression of tPA (assessed by the reverse transcriptase polymerase chain reaction utilizing tPA specific sense and antisense primers) was significantly increased in EC subjected to more than 7% cyclic strain. We conclude that a 60 cycles/min regimen of strain that is greater than 7% can selectively stimulate tPA production by EC in vitro and may contribute to the relative nonthrombogenicity of the endothelium in vivo.

Evidence for the Expression of Urokinase-type Plasminogen Activator by Human Venous Endothelial Cells In Vivo

1998 ◽  
Vol 80 (12) ◽  
pp. 961-967 ◽  
Author(s):  
L. Camoin ◽  
R. Pannell ◽  
F. Anfosso ◽  
J. P. Lefevre ◽  
J. Sampol ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Plasminogen Activator ◽  
Animal Studies ◽  
Normal Subjects ◽  
Immunomagnetic Beads ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Tissue Plasminogen

SummaryEndothelial cells (ECs) in culture synthesize and secrete urokinase-type plasminogen activator (u-PA), but the normal vascular endothelium is believed to synthesize only tissue plasminogen activator (t-PA), which is thought to be responsible for intravascular fibrinolysis. More recently, animal studies have shown that the biological role of u-PA in fibrinolysis has been underestimated, prompting a re-examination of its synthesis by the endothelium. In this study, we investigated whether u-PA was synthesized by non-atherosclerotic endothelial cells in vivo by testing ECs dislodged by venipuncture from 12 normal volunteers and 17 patients admitted for plasmapheresis. The ECs were isolated with an anti-endothelial monoclonal antibody coupled to immunomagnetic beads and characterized by morphology and by labelling for vWF, CD31, and UEA-1 binding. U-PA antigen was found in 50% of the ECs from the normal subjects and in 60% of those from patients. U-PA enzymatic activity on zymograms was detected in 50% of the normal samples and 60% of the patient samples, with the latter being more frequently and more strongly positive. U-PA mRNA was found in all the normal and patient samples tested. The results indicate that u-PA is synthesized by the venous endothelium in vivo but that its expression is highly variable.

Interaction of tissue plasminogen activator with a human endothelial cell 45-kilodalton plasminogen receptor

1994 ◽  
Vol 72 (3-4) ◽  
pp. 126-131 ◽  
Author(s):  
Anil K. Dudani ◽  
Agatha Pluskota ◽  
Peter R. Ganz
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Receptor Binding ◽  
Umbilical Vein ◽  
Annexin Ii ◽  
Cell Protein ◽  
Specific Manner ◽  
Tissue Plasminogen

We have investigated the interaction of tissue plasminogen activator (tPA) with endothelial cell proteins of the human umbilical vein using the technique of ligand blotting. It was observed that tPA interacted with a 45-kilodalton (kDa) endothelial cell protein which appeared to be similar to the 45-kDa plasminogen receptor. Binding of tPA to the 45-kDa protein could be inhibited by excess cold tPA. Morever, excess lysine could inhibit the binding of tPA to the 45-kDa protein in both coincubation and reversibility experiments. These studies indicated that like plasminogen, tPA interacts with the 45-kDa protein in a kringle-dependent and specific manner. To confirm that tPA and plasminogen are interacting with the same protein, we investigated the effect of excess cold plasminogen on tPA binding and excess cold tPA on plasminogen binding in reversibility experiments. It was observed that binding of tPA to the 45-kDa protein was reduced by plasminogen and vice versa. In addition, the 45-kDa protein did not cross-react with antibodies to annexin II, a 40-kDa protein that binds plasminogen and tPA. These latter properties distinguish the 45-kDa receptor from plasminogen/tPA-binding proteins described by others. Therefore, the above studies suggest that the 45-kDa protein represents a unique plasminogen/tPA receptor on human venous endothelial cells.Key words: plasminogen, tissue plasminogen activator, endothelial cells, receptors.

Effect of Lipoprotein(a) and LDL on Plasminogen Binding to Extracellular Matrix and on Matrix-dependent Plasminogen Activation by Tissue Plasminogen Activator

1996 ◽  
Vol 75 (03) ◽  
pp. 497-502 ◽  
Author(s):  
Hadewijch L M Pekelharing ◽  
Henne A Kleinveld ◽  
Pieter F C.C.M Duif ◽  
Bonno N Bouma ◽  
Herman J M van Rijn
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Plasminogen Activator ◽  
Binding Sites ◽  
Umbilical Vein ◽  
Single Step ◽  
Plasminogen Activation ◽  
Structural Homology ◽  
Tissue Plasminogen ◽  
Umbilical Vein Endothelial Cells

SummaryLp(a) is an LDL-like lipoprotein plus an additional apolipoprotein apo(a). Based on the structural homology of apo(a) with plasminogen, it is hypothesized that Lp(a) interferes with fibrinolysis. Extracellular matrix (ECM) produced by human umbilical vein endothelial cells was used to study the effect of Lp(a) and LDL on plasminogen binding and activation. Both lipoproteins were isolated from the same plasma in a single step. Plasminogen bound to ECM via its lysine binding sites. Lp(a) as well as LDL were capable of competing with plasminogen binding. The degree of inhibition was dependent on the lipoprotein donor as well as the ECM donor. When Lp(a) and LDL obtained from one donor were compared, Lp(a) was always a much more potent competitor. The effect of both lipoproteins on plasminogen binding was reflected in their effect on plasminogen activation. It is speculated that Lp(a) interacts with ECM via its LDL-like lipoprotein moiety as well as via its apo(a) moiety.

Localization of Fibrinolytic Activators and Inhibitors in Normal and Atherosclerotic Vessels

1996 ◽  
Vol 75 (06) ◽  
pp. 933-938 ◽  
Author(s):  
Marten Fålkenberg ◽  
Johan Tjärnstrom ◽  
Per Örtenwall ◽  
Michael Olausson ◽  
Bo Risberg
Keyword(s):  
Endothelial Cells ◽  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Vasa Vasorum ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Tissue Plasminogen ◽  
The Media ◽  
Activator Inhibitor ◽  
Pai 1

SummaryLocal fibrinolytic changes in atherosclerotic arteries have been suggested to influence plaque growth and promote mural thrombosis on ruptured or ulcerated plaques. Increased levels of plasminogen activator inhibitor (PAI-1) have been found in atherosclerotic arteries. In this study tissue plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA) and PAI-1 were localized in arterial biopsies of healthy and atherosclerotic vessels by immunohistochemis-try. The expression of fibrinolytic regulators was related to the distribution of endothelial cells (EC) and macrophages. Results: t-PA was expressed in vasa vasorum. PAI-1 was positive in endothelial cells, in the media and in the adventitia. Increased expression of t-PA, u-PA and PAI-1 was found in atherosclerotic vessels. t-PA, u-PA, PAI-1 and macrophages were co-localized in plaques. These results support the concept that macrophages can be important in the local regulation of fibrinolysis in atherosclerotic vessels.

An Electron Microscopic Study of Platelet Thrombus Formation in the Rabbit with Particular Regard to 5-Hydroxytryptamine Release

1967 ◽  
Vol 18 (03/04) ◽  
pp. 592-604 ◽  
Author(s):  
H. R Baumgartner ◽  
J. P Tranzer ◽  
A Studer
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Vessel Wall ◽  
Thrombus Formation ◽  
Endothelial Damage ◽  
Electron Microscopic ◽  
Rabbit Ear ◽  
Basement Lamina ◽  
Platelet Thrombus

SummaryElectron microscopic and histologic examination of rabbit ear vein segments 4 and 30 min after slight endothelial damage have yielded the following findings :1. Platelets do not adhere to damaged endothelial cells.2. If the vessel wall is denuded of the whole endothelial cell, platelets adhere to the intimai basement lamina as do endothelial cells.3. The distance between adherent platelets as well as endothelial cells and intimai basement lamina measures 10 to 20 mµ, whereas the distance between aggregated platelets is 30 to 60 mµ.4. 5-hydroxytryptamine (5-HT) is released from platelets during viscous metamorphosis at least in part as 5-HT organelles.It should be noted that the presence of collagen fibers is not necessary for platelet thrombus formation in vivo.

Specificity of the Thrombin-Induced Release of Tissue Plasminogen Activator from Cultured Human Endothelial Cells

1986 ◽  
Vol 56 (02) ◽  
pp. 115-119 ◽  
Author(s):  
Eugene G Levin ◽  
David M Stern ◽  
Peter P Nawroth ◽  
Richard A Marlar ◽  
Daryl S Fair ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Protein C ◽  
Primary Cultures ◽  
Activated Protein C ◽  
Specific Inhibitor ◽  
Factor Xa ◽  
Human Endothelial Cells ◽  
Tissue Plasminogen

SummaryThe addition of thrombin (9 nM) to primary cultures of human endothelial cells induces a 6- to 7-fold increase in the rate of release of tissue plasminogen activator (tPA). Several other serine proteases which specifically interact with endothelial cells were also analyzed for their effect on tPA release. Gamma-thrombin, an autocatalytic product of α-thrombin, promoted tPA release but was less effective than α-thrombin. A maximum increase of 5.5-fold was observed, although a concentration of γ-thrombin 20 times greater than α-thrombin was required. The response to Factor Xa was similar to α-thrombin, although the stimulation was significantly reduced by the addition of hirudin or DAPA suggesting that prothrombin activation was occurring. The simultaneous addition of prothrombin with Factor Xa resulted in enhanced tPA release equal to that observed with an equimolar concentration of active α-thrombin. Thus, under these conditions, Factor Xa-cell surface mediated activation of prothrombin can lead to a secondary effect resulting from cell-thrombin interaction. Activated protein C, which has been implicated as a profibrinolytic agent, was also tested. No change in tPA release occurred after the addition of up to 325 nM activated protein C in the presence or absence of proteins. Factor IXa and plasmin were also ineffective. The effect of thrombin on the endothelial cell derived plasminogen activator specific inhibitor was also studied. Thrombin produced a small but variable release of the inhibitor with an increase of less than twice that of non-thrombin treated controls.

Signal transduction and regulation of lung endothelial cell permeability. Interaction between calcium and cAMP

1998 ◽  
Vol 275 (2) ◽  
pp. L203-L222 ◽  
Author(s):  
Timothy M. Moore ◽  
Paul M. Chetham ◽  
John J. Kelly ◽  
Troy Stevens
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Intracellular Signaling ◽  
Endothelial Permeability ◽  
Cell Permeability ◽  
Gap Formation ◽  
Pulmonary Endothelium ◽  
Intracellular Signals ◽  
Endothelial Cell Permeability ◽  
Cell Cell

Pulmonary endothelium forms a semiselective barrier that regulates fluid balance and leukocyte trafficking. During the course of lung inflammation, neurohumoral mediators and oxidants act on endothelial cells to induce intercellular gaps permissive for transudation of proteinaceous fluid from blood into the interstitium. Intracellular signals activated by neurohumoral mediators and oxidants that evoke intercellular gap formation are incompletely understood. Cytosolic Ca2+ concentration ([Ca2+]i) and cAMP are two signals that importantly dictate cell-cell apposition. Although increased [Ca2+]ipromotes disruption of the macrovascular endothelial cell barrier, increased cAMP enhances endothelial barrier function. Furthermore, during the course of inflammation, elevated endothelial cell [Ca2+]idecreases cAMP to facilitate intercellular gap formation. Given the significance of both [Ca2+]iand cAMP in mediating cell-cell apposition, this review addresses potential sites of cross talk between these two intracellular signaling pathways. Emerging data also indicate that endothelial cells derived from different vascular sites within the pulmonary circulation exhibit distinct sensitivities to permeability-inducing stimuli; that is, elevated [Ca2+]ipromotes macrovascular but not microvascular barrier disruption. Thus this review also considers the roles of [Ca2+]iand cAMP in mediating site-specific alterations in endothelial permeability.

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