© 1996 American Heart Association, Inc.
Articles |
Inhibitors of Fibrinolysis Are Elevated in Atherosclerotic Plaque
From the Department of Medicine and Therapeutics (L.A.R., B.B.), the Department of Molecular and Cell Biology (L.A.R., N.A.B.), and the Department of Pathology (P.A.J.B.), University of Aberdeen, Scotland, UK.
Correspondence to Dr L. A. Robbie, Department of Medicine and Therapeutics, University of Aberdeen, Foresterhill, Aberdeen AB9 2ZD, Scotland, UK. E-mail larobbie@abdn.ac.uk.
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Abstract |
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Abstract The proteins of the fibrinolytic system have been examined in the human normal and atherosclerotic arterial wall by immunohistochemical techniques and by quantitative immunoassay of extracts. The concentration of plasminogen activator inhibitor-1 (PAI-1) increased significantly during the progression from normal vessels to fatty streaks to the developed atherosclerotic plaque. Staining for PAI-1 was strongly positive, particularly in the areas adjacent to the plaque. In these areas, PAI-1 appeared to be colocalized with its binding protein vitronectin.
2-Antiplasmin
(2-AP) was present in the aorta at even higher
concentrations than PAI-1; a small but significant increase was seen in
some atherosclerotic compared with normal vessel walls. Tissue
plasminogen activator (TPA) showed the opposite
trend, being lowest in lesions with plaque. Thus, higher concentrations
of the two principal inhibitors of
fibrinolysis, PAI-1 and 2-AP, together
with lower levels of TPA, are characteristic of advanced
atheromatous lesions. Alteration in the balance of the
fibrinolytic system, favoring its inhibition, may predispose to the
development or maintenance of atherosclerotic plaque.
Key Words: atherosclerosis • fibrinolysis • PAI-1 • 2-AP
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Introduction |
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The fibrinolytic system is a highly regulated enzyme cascade that generates local proteolysis. Plasmin generation is not only responsible for the removal of fibrin deposits and incipient thrombi within blood vessels but is also involved in extraluminal phenomena such as cell migration and extracellular matrix degradation, which occur in processes including inflammation, tissue repair, angiogenesis, tumor invasion, and metastasis.1 Plasmin generation from plasminogen within or at the surface of the vessel wall is achieved by the plasminogen activators TPA and UPA. The plasminogen activators are regulated by specific inhibitors, PAI-1 and PAI-2. Fibrinolysis can also be regulated at the level of plasmin by the other major inhibitor of fibrinolysis,
2-AP.2
Both of the major inhibitors of
fibrinolysis, PAI-1 and 2-AP, are
present in plasma and platelets. 2-AP circulates
in plasma at a concentration of about 1 µmol/L, which is 2000- to
3000-fold greater than the concentration of PAI-1, at about 0.4 nmol/L.
The concentration of 2-AP in platelets is low,
representing less than 0.5% of that in plasma. In
contrast, platelet PAI-1 contributes over 90% of the circulating
PAI-1 antigen.3
A delicate balance between activation and inhibition of
fibrinolysis exists in the circulation.
Plasminogen and 2-AP are both present in
plasma at relatively stable concentrations in the µmol/L range. In
contrast, the concentrations of TPA and PAI-1, both of which are
present at much lower levels, in the picomole-per-liter
range, are much more variable. Increased TPA results in free active
TPA in the circulation, making plasmin generation possible and thus
favoring fibrin lysis. Low TPA and/or increased PAI-1 leads to
suppression of activity and decreased plasmin generation, so that lysis
cannot occur, favoring fibrin persistence and thrombosis. Elevated
levels of plasma PAI-1 have been found in many disease
states,4 5 and PAI-1 is considered to be among the risk
factors for arterial and thrombotic
disease.6 7 How these variations in equilibrium influence
more chronic processes within solid tissues, however, is not known.
Analyses of arterial wall specimens have indicated that fibrin is indeed present in developing atherosclerotic lesions.8 There is also evidence that fibrin(ogen) and its degradation products within the evolving plaque influence atherogenesis through several mechanisms, which include modulating endothelial cell permeability9 and providing an absorptive surface for the extracellular accumulation of LDL.10 11 Fibrin deposition, therefore, has roles in both the formation of thrombi within the lumen and the structure and development of atherosclerotic lesions in the vessel wall itself.
Considerable information is now available on the regulation of
plasminogen activators and
inhibitors by vascular cells and other cells in culture,
but little is known about the mechanisms governing local regulation of
plasminogen activators and
inhibitors in healthy and diseased arteries. Several
factors associated with inflammatory and atherosclerotic processes
increase the expression of PAI-1 in endothelial cells
in culture.12 The most important of these, in the context
of vascular disease, are the inflammatory mediators: tumor necrosis
factor-, interleukin-1, and transforming growth factor-ß, which
are released from activated platelets and
macrophages.13 Smooth muscle cells also synthesize
PAI-1, and its production can be increased in response to
the platelet-associated growth factors, platelet derived
growth factor and transforming growth factor-ß.14 15
We have already shown that human thrombi removed from vessels contain
high levels of both PAI-1 and 2-AP.16 They
may serve to stabilize fibrin deposits induced in vessel wall disease
and may also contribute to the inhibition of protease activity on other
potential substrates such as extracellular matrix. This study was
undertaken to examine the content and distribution of
inhibitors of the fibrinolytic system in normal and
atherosclerotic vessel walls to increase our understanding of their
contribution to the development and progression of
atherosclerosis.
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Methods |
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Pathological Specimens
Human normal and diseased aortas were obtained at autopsy within 24 hours of death. Periadventitial tissue was dissected free and the luminal surface examined; the vessels were divided into three categories and classified as apparently normal vessels, vessels with fatty streaks, and vessels with plaque. In no case was there a thrombus adjacent to the vessels examined. A clinical report was obtained for each specimen to eliminate any exceptional circumstances or disease processes. Specimens were washed three times with 0.9% (wt/vol) NaCl and blotted dry using filter paper. A piece of each sample was fixed in 10% neutral buffered formalin at room temperature for
24 hours
before cutting 5-µm cryostat sections. The remainder was cut into
small pieces (0.1 to 0.5 g) and frozen at -70°C until required
for the preparation of extracts. Extracts were prepared by grinding the
specimens to a fine powder using a Mikro-Dismembrator (B. Braun
Biotech) and resuspending them in extraction buffer consisting of 50
mmol/L phosphate at pH 7.0, 0.2 mol/L
-amino-n-caproic acid, 1 mol/L NaCl, and 0.01% Tween
20. The samples were then spun in a microfuge at 11 600g
for 10 minutes at room temperature. The pellet was resuspended twice in
500 µL extraction buffer and centrifuged. All extracts were
stored at -70°C until assayed.
ELISAs for PAI-1, TPA, and TPA–PAI-1 Complex
ELISAs for PAI-1,17 TPA,18 and
TPA–PAI-1 complex19 were performed as described
previously. The ELISAs for PAI-1 and TPA measure both free and
complexed forms of the antigens. The working range of the ELISA for
PAI-1 was 0.31 to 5 ng/mL and the effective limit for measurement of
PAI-1 in the extracts was 1.5 ng/mL. The intra-assay and interassay
coefficients of variation were 5.5% and 6.6%, respectively. The
working range of the TPA ELISA was 0.08 to 2.5 ng/mL and the limit of
detection 1 ng/mL in the extracts. The intra-assay and interassay
coefficients of variation were 6.0% and 9.5%, respectively. The
TPA–PAI-1 complex was measured in a two-site ELISA, using rabbit
anti-TPA as capture antibody and rabbit anti–PAI-1 biotin conjugate as
detecting antibody. The working range of the ELISA for the measurement
of TPA–PAI-1 complex was 0.48 to 7.7 ng/mL and the limit of detection
1.5 ng/mL in the extracts.
ELISA for 2-AP
The reagents used in the ELISA were as follows: rabbit IgG to
human 2-AP (DAKO) as coating antibody, purified
2-AP as standard (Biopool, supplied through Porton
Products Ltd), and rabbit anti-human 2-AP
conjugated to horseradish peroxidase, as described
previously,20 as the detecting antibody. The buffers,
incubation times, and working procedures were as detailed
previously.18 The working range of the 2-AP
ELISA was 0.63 to 10 ng/mL and the limit of detection 1 ng/mL in the
extracts. The intra-assay and interassay coefficients of variation
were 2% and 10%, respectively.
ELISA for Plasminogen
The ELISA for plasminogen used in-house
affinity-purified rabbit IgG to human plasminogen as
coating antibody, plasminogen purified from outdated plasma
as described previously21 as standard, and in-house
affinity-purified rabbit IgG to human plasminogen
conjugated to horseradish peroxidase20 as detecting
antibody. Buffers, incubation procedures, and wash procedures were as
described previously.19 The working range of the
plasminogen ELISA was 0.63 to 20 ng/mL and the limit of
detection 1 ng/mL in the extracts. The intra-assay and interassay
coefficients of variation were 2% and 10%, respectively. The
plasminogen-related protein lipoprotein(a) was not
detected by the affinity-purified rabbit IgG to human
plasminogen, even though present at concentrations 100
times those of the highest plasminogen standard.
Immunohistochemical Staining
Sections of the vessel wall were stained with monoclonal
antibodies to PAI-1 (ESPI-4, SNBTS22 ), 2-AP
(American Diagnostica Inc), TPA (ESP-5; kindly provided by
Dr I.R. MacGregor, SNBTS Headquarters Laboratory,
Edinburgh18 ), and UPA (MUK-1; Biopool, supplied through
Porton Products Ltd) using the APAAP technique as described
previously.23 Vitronectin was detected within
the vessel wall with rabbit antiserum to human vitronectin
by use of an indirect (two-stage) immunoalkaline phosphatase
technique.16
SDS-PAGE With Zymography
SDS-PAGE with zymography for detection of the
plasminogen activators was performed as
described previously.24 Goat IgG to human melanoma TPA and
goat IgG to human UPA, for the identification of the
plasminogen activators, were purchased from
Biopool, supplied through Porton Products Ltd.
Statistical Analysis
Statistical analysis was performed using the
Mann-Whitney U test. This is a nonparametric
test suitable for data involving unequal group variance. A probability
level of .05 or less was considered to be significant.
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Results |
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Extracts of human aorta were analyzed for PAI-1, TPA, TPA–PAI-1 complex, plasminogen, and
2-AP.
All these antigens were found to be quantitatively extracted from the
aorta, in that 85% was typically recovered in the first extract, with
10% to 15% in the second, and only 0% to 5% in the third.
Examination of the extraction pellets by SDS-PAGE followed by
zymography revealed only minor traces of PAI-1 and TPA in the pellets
and no evidence for 2-AP (data not shown). All data
shown are the sums of the three extracts. The ELISAs for
TPA18 and PAI-117 each recognized all known
forms of these proteins to equal extents.
High levels of PAI-1 antigen were detected in extracts, especially in
plaque (Fig 1a
). The difference in PAI-1 concentration
between the normal arteries and the arteries with plaque was highly
significant (P=.003). The difference between PAI-1 in normal
vessels compared with vessels with fatty streaks was not significant.
2-AP, the other main inhibitor of
fibrinolysis, was detected in the vessels at even
higher levels than PAI-1 (Fig 1b). There was considerable overlap
between levels of 2-AP in the three groups, but the mean
value in vessels with plaque was significantly greater than for normal
vessels (P=.009). Statistical comparisons between levels of
2-AP in the normal vessels and vessels with fatty
streaks were not significant. Plasminogen was present
in the vessels at concentrations similar to those of
2-AP, in the microgram per gram range (Fig 1c).
Plasminogen levels were not significantly different in the
three groups, although as for 2-AP, elevated levels were
detected in a small number of plaque extracts.
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In contrast to the marked elevations in PAI-1 in diseased vessels
compared with normal vessels, TPA was lower in vessels with plaque (Fig 1d
). Statistical analysis revealed a significant difference
between vessels with plaque and normal vessels (P=.005) and
vessels with fatty streaks compared with vessels with plaque
(P=.02). TPA in complex with its primary
inhibitor PAI-1 was present at much higher
concentrations in vessels with plaque compared with normal vessels
(P=.0001; Fig 1e). The relative concentrations of TPA–PAI-1
complex and of total TPA antigen suggested that some TPA in the artery
was in free form. This was confirmed by SDS-PAGE followed by zymography
(Fig 2). Antibodies to TPA and UPA, incorporated into
the fibrin/agarose gel, showed the presence of TPA at 65 kD and UPA at
54 kD. Two distinct bands of complex were also evident, both removed by
antibodies to TPA. The 110-kD band corresponded to TPA–PAI-1 complex,
while the 180-kD was identified as TPA–C1-inh complex by comparison
with complexes prepared from purified components (data not
shown).
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Immunohistochemical staining demonstrated PAI-1 in all three layers of
the vessel wall (Fig 3a and 3b).
Endothelial cells covering the luminal surface of the
vessel stained positively, as did the smooth muscle cells within the
media. Positivity for PAI-1 was also observed in association with
collagen fibers in the adventitia (Fig 3b).
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The distribution of PAI-1 in lesions with plaque was quite different.
Strong focal staining for PAI-1 was present around the sides and
base of lesions, most notably in fatty streaks. Similar but less
defined peripheral positivity was noted in established and
late atheromatous plaques, with strong staining also
present in the necrotic cores (Fig 3c). Positive staining was also
associated with the smooth muscle cell areas of the vessels. Staining
for vitronectin was detected in both normal and diseased
vessels. A vessel with an early lesion is shown in Fig 3d. Positive
staining can be seen in apparently normal areas of the vessel but is
clearly most intense at the shoulder regions of the developing lesion
and not in the plaque core itself.
2-AP was detected in normal and diseased vessels. As for
PAI-1, 2-AP positivity in the arteries with plaque was
strongest in the areas surrounding the plaque itself, less intense
staining being observed in the media (Fig 3e). TPA was fairly evenly
distributed throughout the layers of normal arteries. In diseased
vessels, TPA appeared to be located predominantly within the areas
around the lesion itself (Fig 3f). UPA was also detected in normal and
diseased arteries, but staining was markedly enhanced in arteries with
plaque compared with normal arteries. Strong focal positivity was
present in the vicinity of the plaque itself, with less intense
staining in the media (Fig 3g). A control slide for which the primary
antibody was omitted is shown in Fig 3h.
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Discussion |
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This study examines the major inhibitors of fibrinolysis in normal and diseased vessel walls. PAI-1, the major inhibitor of the plasminogen activators, was evenly distributed throughout the intima and media of normal vessels. In arteries with plaque, however, the concentration of PAI-1 was elevated significantly compared with normal arteries. In these vessels, strong positive staining for PAI-1 was detected in the necrotic core of plaques and in the thickened intima around plaques and, as in normal vessels, appeared to be associated with the smooth muscle cell areas of the media, in good agreement with other studies.25 26 Macrophages and smooth muscle cells in diseased arteries have been shown to express PAI-1 mRNA,27 suggesting that they may contribute to the accumulation of PAI-1 noted here. The presence of elevated levels of PAI-1 in diseased artery walls may promote the persistence of adjacent intravascular fibrin or reduce extracellular matrix breakdown.28
Vitronectin, an extracellular matrix and plasma protein that binds and stabilizes PAI-1 activity,29 30 was examined. In early lesions, in which the intima was only slightly raised, positive staining for vitronectin was detected at the sides and base of the lesion. Vitronectin may accumulate in the vessel wall from remote sites31 by direct diffusion from the plasma or by local synthesis by the macrophages in the plaque.32 Platelets store vitronectin in their granules33 and therefore provide another potential source. Vitronectin colocalized with PAI-1 around the sides and base of lesions but did not concentrate in the necrotic core in established lesions, as did PAI-1 antigen.
In contrast to the elevated levels of PAI-1 in atherosclerotic arteries, total TPA levels were lower in affected vessel walls than normal vessels. Our immunohistochemical studies of the arteries demonstrated positivity for TPA within the thickened intimas of diseased vessels compared with normal vessels. In one study on intima, fibrinolytic activity was increased in the intima of atherosclerotic vessels34 despite the high levels of PAI-1 detected in diseased arteries found in the study described here and by others.26 27
The ratio of PAI-1 to TPA within the vessels increased in the diseased arteries, from about 3:1 in normal vessels, to in some cases as much as 18:1 in diseased vessels. In normal circulating blood, the ratio of PAI-1 to TPA is about 5:1. Clearly there is some shift in the balance of fibrinolytic activity in diseased vessels that may contribute to the persistence of intravascular fibrin, thrombosis, or indeed the development of atherosclerotic lesions. The pattern of TPA–PAI-1 complex formation in the arteries reflects the elevations of PAI-1 seen in the diseased arteries, demonstrating its dominant effect as an inhibitor.
TPA was also present in the vessel wall in complex with C1-inh, which is known to inhibit TPA.35 36 37 Endothelial cells in culture synthesize functionally active C1-inh, and the C1-inh in the arteries may result from local synthesis or direct uptake from plasma.
Traces of UPA activity were also detected within the extracts of aorta by zymography following SDS-PAGE. Immunohistochemical staining demonstrated positivity for UPA within the atherosclerotic arteries, especially in the plaques. Quantitative information for UPA antigen in the vessels was not achieved, since the levels were below the limit of detection by ELISA. The UPA present within the intima of diseased arteries may be a result of synthesis by macrophages that accumulate within the intima of diseased vessels.38
Plasminogen was detected in the arteries in the microgram per gram range, representing about 10% of the concentration found in normal circulating blood. These levels of plasminogen are sufficient to provide adequate substrate for the generation of plasmin by the plasminogen activators. Indeed, it has been shown in mouse vessel wall that the plasminogen present is activated to plasmin.39
2-AP was present in the arteries at concentrations
substantially higher than those of PAI-1. There was a noticeable
overlap in the level of 2-AP between the normal and
diseased vessels, but levels were significantly elevated in some
lesions with plaque. This finding may reflect plaque rupture in these
specimens and subsequent direct exposure of the inner layers of the
vessel wall to the circulating blood. Staining for 2-AP
was also most positive in the regions surrounding the plaque.
In an earlier study, we demonstrated that human thrombi formed in vivo
contain very high levels of both the major inhibitors of
fibrinolysis, PAI-1 and
2-AP.16 The concentration of
2-AP in thrombi was about 25% of the plasma level,
whereas PAI-1 was present at concentrations up to 30 times that
found in the normal circulating blood, presumably reflecting
platelet accumulation. As we have shown here, human artery walls
contain high levels of PAI-1 and clearly have the capacity to
contribute to the PAI-1 content of an adjacent thrombus, especially if
the vessel has been distorted by the processes of
atherosclerosis.
The pathological processes involved in thrombosis and atherosclerosis are complex. This study examines one contributory mechanism, fibrinolysis, and provides new information on the concentration and distribution of some of the key components of this system in normal and atherosclerotic arteries. The presence of plasminogen activators and inhibitors of fibrinolysis in arteries and the differences noted between normal and diseased vessels suggest that local fibrin deposition, and persistence of such fibrin may be influenced by the relative levels of activators and inhibitors. Clearly, the overall activity of the fibrinolytic system in the vessel wall is an interesting question and merits further investigation. These observations also raise important questions concerning the origin of these proteins, their function in the arteries, and their role in the development and progression of vessel wall disease or thrombotic occlusion of such vessels.
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Selected Abbreviations and Acronyms |
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Acknowledgments |
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We thank the British Heart Foundation and Aberdeen Royal Hospitals NHS Trust for their support.
Received June 12, 1995; accepted November 3, 1995.
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References |
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 K. Schafer, K. Muller, A. Hecke, E. Mounier, J. Goebel, D. J. Loskutoff, and S. Konstantinides Enhanced Thrombosis in Atherosclerosis-Prone Mice Is Associated With Increased Arterial Expression of Plasminogen Activator Inhibitor-1 Arterioscler Thromb Vasc Biol, November 1, 2003; 23(11): 2097 - 2103. [Abstract] [Full Text] [PDF]
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S. Konstantinides, K. Schafer, and D. J. Loskutoff Do PAI-1 and Vitronectin Promote or Inhibit Neointima Formation?: The Exact Role of the Fibrinolytic System in Vascular Remodeling Remains Uncertain Arterioscler Thromb Vasc Biol, December 1, 2002; 22(12): 1943 - 1945. [Full Text] [PDF]
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 T. Hryszko, J. Malyszko, J. S. Malyszko, S. Brzosko, K. Pawlak, and M. Mysliwiec A possible role of thrombin-activatable fibrinolysis inhibitor in disturbances of fibrinolytic system in renal transplant recipients Nephrol. Dial. Transplant., August 1, 2001; 16(8): 1692 - 1696. [Abstract] [Full Text] [PDF]
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 L. Sironi, A. M. Calvio, L. Arnaboldi, A. Corsini, A. Parolari, M. de Gasparo, E. Tremoli, and L. Mussoni Effect of Valsartan on Angiotensin II-Induced Plasminogen Activator Inhibitor-1 Biosynthesis in Arterial Smooth Muscle Cells Hypertension, March 1, 2001; 37(3): 961 - 966. [Abstract] [Full Text] [PDF]
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 J. Orbe, J. A Rodriguez, A. Calvo, A. Grau, M. S Belzunce, D. Martinez-Caro, and J. A Paramo Vitamins C and E attenuate plasminogen activator inhibitor-1 (PAI-1) expression in a hypercholesterolemic porcine model of angioplasty Cardiovasc Res, February 1, 2001; 49(2): 484 - 492. [Abstract] [Full Text] [PDF]
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 P. H. A. Quax, M. L. M. Lamfers, J. H. P. Lardenoye, J. M. Grimbergen, M. R. de Vries, J. Slomp, M. C. de Ruiter, M. M. Kockx, J. H. Verheijen, and V. W. M. van Hinsbergh Adenoviral Expression of a Urokinase Receptor-Targeted Protease Inhibitor Inhibits Neointima Formation in Murine and Human Blood Vessels Circulation, January 30, 2001; 103(4): 562 - 569. [Abstract] [Full Text] [PDF]
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S. Konstantinides, K. Schafer, T. Thinnes, and D. J. Loskutoff Plasminogen Activator Inhibitor-1 and Its Cofactor Vitronectin Stabilize Arterial Thrombi After Vascular Injury in Mice Circulation, January 30, 2001; 103(4): 576 - 583. [Abstract] [Full Text] [PDF]
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 V. A. Ploplis, I. Cornelissen, M. J. Sandoval-Cooper, L. Weeks, F. A. Noria, and F. J. Castellino Remodeling of the Vessel Wall after Copper-Induced Injury Is Highly Attenuated in Mice with a Total Deficiency of Plasminogen Activator Inhibitor-1 Am. J. Pathol., January 1, 2001; 158(1): 107 - 117. [Abstract] [Full Text] [PDF]
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T. Uchiyama, M. Kurabayashi, Y. Ohyama, T. Utsugi, N. Akuzawa, M. Sato, S. Tomono, S. Kawazu, and R. Nagai Hypoxia Induces Transcription of the Plasminogen Activator Inhibitor-1 Gene Through Genistein-Sensitive Tyrosine Kinase Pathways in Vascular Endothelial Cells Arterioscler Thromb Vasc Biol, April 1, 2000; 20(4): 1155 - 1161. [Abstract] [Full Text] [PDF]
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S. Lopez, F. Peiretti, B. Bonardo, I. Juhan-Vague, and G. Nalbone Tumor Necrosis Factor alpha Up-regulates in an Autocrine Manner the Synthesis of Plasminogen Activator Inhibitor Type-1 during Induction of Monocytic Differentiation of Human HL-60 Leukemia Cells J. Biol. Chem., February 4, 2000; 275(5): 3081 - 3087. [Abstract] [Full Text] [PDF]
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T. Bourcier and P. Libby HMG CoA Reductase Inhibitors Reduce Plasminogen Activator Inhibitor-1 Expression by Human Vascular Smooth Muscle and Endothelial Cells Arterioscler Thromb Vasc Biol, February 1, 2000; 20(2): 556 - 562. [Abstract] [Full Text] [PDF]
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 T. Kietzmann, U. Roth, and K. Jungermann Induction of the Plasminogen Activator Inhibitor-1 Gene Expression by Mild Hypoxia Via a Hypoxia Response Element Binding the Hypoxia-Inducible Factor-1 in Rat Hepatocytes Blood, December 15, 1999; 94(12): 4177 - 4185. [Abstract] [Full Text] [PDF]
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I. M. Lang, K. M. Moser, and R. R. Schleef Elevated Expression of Urokinase-like Plasminogen Activator and Plasminogen Activator Inhibitor Type 1 During the Vascular Remodeling Associated With Pulmonary Thromboembolism Arterioscler Thromb Vasc Biol, May 1, 1998; 18(5): 808 - 815. [Abstract] [Full Text] [PDF]
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Y.-Q. Chen, M. Su, R. R. Walia, Q. Hao, J. W. Covington, and D. E. Vaughan Sp1 Sites Mediate Activation of the Plasminogen Activator Inhibitor-1 Promoter by Glucose in Vascular Smooth Muscle Cells J. Biol. Chem., April 3, 1998; 273(14): 8225 - 8231. [Abstract] [Full Text] [PDF]
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H. Tomiyama, Y. Kimura, H. Mitsuhashi, T. Kinouchi, H. Yoshida, T. Kushiro, and N. Doba Relationship Between Endothelial Function and Fibrinolysis in Early Hypertension Hypertension, January 1, 1998; 31(1): 321 - 327. [Abstract] [Full Text] [PDF]
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S. M. Kanse, O. Benzakour, C. Kanthou, C. Kost, H. R. Lijnen, and K. T. Preissner Induction of Vascular SMC Proliferation by Urokinase Indicates a Novel Mechanism of Action in Vasoproliferative Disorders Arterioscler Thromb Vasc Biol, November 1, 1997; 17(11): 2848 - 2854. [Abstract] [Full Text]
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T. Padro, M. Steins, C.-X. Li, R. M Mesters, D. Hammel, H. H Scheld, and J. Kienast Comparative analysis of plasminogen activator inhibitor-1 expression in different types of atherosclerotic lesions in coronary arteries from human heart explants Cardiovasc Res, October 1, 1997; 36(1): 28 - 36. [Abstract] [Full Text] [PDF]
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P. Kauhanen, V. Siren, O. Carpen, A. Vaheri, M. Lepantalo, and R. Lassila Plasminogen Activator Inhibitor-1 in Neointima of Vein Grafts : Its Role in Reduced Fibrinolytic Potential and Graft Failure Circulation, September 16, 1997; 96(6): 1783 - 1789. [Abstract] [Full Text]
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T. J. Podor, S. G. Shaughnessy, M. N. Blackburn, and C. B. Peterson New Insights into the Size and Stoichiometry of the Plasminogen Activator Inhibitor Type-1{middle dot}Vitronectin Complex J. Biol. Chem., August 11, 2000; 275(33): 25402 - 25410. [Abstract] [Full Text] [PDF]
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S. Stefansson, E. Petitclerc, M. K. K. Wong, G. A. McMahon, P. C. Brooks, and D. A. Lawrence Inhibition of Angiogenesis in Vivo by Plasminogen Activator Inhibitor-1 J. Biol. Chem., March 9, 2001; 276(11): 8135 - 8141. [Abstract] [Full Text] [PDF]
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W.-Y. Zhang, I. Ishii, and H. S. Kruth Plasmin-mediated Macrophage Reversal of Low Density Lipoprotein Aggregation J. Biol. Chem., October 13, 2000; 275(42): 33176 - 33183. [Abstract] [Full Text] [PDF]
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 A. Gorlach, I. Diebold, V. B. Schini-Kerth, U. Berchner-Pfannschmidt, U. Roth, R. P. Brandes, T. Kietzmann, and R. Busse Thrombin Activates the Hypoxia-Inducible Factor-1 Signaling Pathway in Vascular Smooth Muscle Cells : Role of the p22phox-Containing NADPH Oxidase Circ. Res., July 6, 2001; 89(1): 47 - 54. [Abstract] [Full Text] [PDF]
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