Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UNIPROT:P00750 (PLA)
16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasminogen activator inhibitor-1 (PAI-1), a unique member of the serpin superfamily, plays an important role in fibrinolysis and is an established risk factor for cardiovascular diseases. PAI-1 can occur in three interconvertible conformations: an active, a latent and a substrate form. To study conformational and functional relationships in PAI-1, a wide variety of monoclonal antibodies were evaluated for their influence on PAI-1 activity. Out of 77 monoclonal antibodies, directed against human PAI-1, six were selected for their strong inhibitory effect towards PAI-1 activity, i.e., 80 to 100% inhibition in the presence of a 1- to 16-fold molar excess of monoclonal antibody. Detailed analysis of the reaction products formed during the interaction between PAI-1 and its target proteinases tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA), in the presence of these monoclonal antibodies, revealed two distinct mechanisms of PAI-1 inactivation. Incubation of PAI-1 with one series of monoclonal antibodies resulted in the absence of any reaction indicative for direct interaction with the reactive-site loop or a facilitated conversion to the latent conformation. The loss of PAI-1 activity in the presence of the other group of monoclonal antibodies was associated with the concomitant formation of a 41 kDa cleavage product after interaction with the target proteinase. The latter observation demonstrates that binding of these antibodies induced a conformational change thereby converting the inhibitory, active conformation to the non-inhibitory substrate conformation. No conformational changes could be observed in latent PAI-1 under these conditions. Analysis of cross-reactivity revealed that some of these functionally important epitopes were conserved throughout PAI-1 obtained from various species including rabbit mouse and/or pig, resulting in similar functional and conformational effects induced by these antibodies. Thus, we have demonstrated the occurrence of two distinct mechanisms by which the inhibitory activity of PAI-1 can be neutralized. This may have implications for the design of therapeutic or preventive strategies to interfere with PAI-1 activity. Cross-reactivity of these inhibitory antibodies with PAI-1 from various species may also allow their application in experimental animal models studying the in vivo role of PAI-1 in various diseases (e.g. atherosclerosis, thrombosis, angiogenesis,...).
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PMID:Neutralization of plasminogen activator inhibitor-1 inhibitory properties: identification of two different mechanisms. 904 3

Plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of tissue-type plasminogen activator and urokinase, is abundantly expressed in atherosclerotic vascular wall. To determine the role of PAI-1 in vascular wall, we have used a novel inhibitor of PAI-1, (3E, 4E)-3-benzylidene-4-(3,4,5-trimethoxy-benzylidene) -pyrrolidine-2,5-dione (T-686). T-686 was given to human vascular endothelial cells in vitro and to rabbits subjected to high cholesterol diet and mechanical injury in vivo. T-686 attenuated the augmentation of PAI-1 antigen accumulation induced by transforming growth factor beta in conditioned medium from the human umbilical vein endothelial cells. In rabbits with aortic atherosclerosis induced by hypercholesterolemia and implantation of indwelling plastic tubing, oral administration of T-686 (30mg/kg body weight/day) for 8 weeks attenuated the increase in plasma PAI-1 activity induced by vascular injury without decreasing blood triglyceride and cholesterol. This was accompanied by the reduction in aortic PAI-1 mRNA expression and the inhibition of development of atherosclerosis lesions. Thus, T-686 not only decreased PAI-1 synthesis in vascular cells in vitro but also protected against the development of vascular lesions in vivo. This compound may be useful in defining the role of PAI-1 in atherothrombotic states.
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PMID:A new butadiene derivative, T-686, inhibits plasminogen activator inhibitor type-1 production in vitro by cultured human vascular endothelial cells and development of atherosclerotic lesions in vivo in rabbits. 906 54

The plasminogen activator (PA)-plasmin proteolytic system has recently received considerable attention because of its participation in a wide variety of biological activities and in pathological conditions involving tissue destruction. Excessive mechanical stress such as occlusal trauma is associated with alveolar bone loss in severe periodontitis. Therefore, mechanical stress may involve degradation of the extracellular matrix by occlusal trauma through activation of the PA-plasmin proteolytic system. We examined the effects of mechanical stress on PA activity, gene expressions of tissue type (t) PA, urokinase type (u) PA and PA inhibitor-1 (PAI-1) in human PDL cells. Human PDL cells were cultured on flexible-bottomed culture plates and placed on a Flexercell Strain Unit. The cells were flexed at 6 cycles (5 s strain, 5 s relaxation) at 9% and 18% elongation for 5 d. Application of tension-force induced significantly higher PA activity in stressed PDL cells than in non-stressed controls, and did so in a time- and magnitude-dependent manner (p < 0.001, ANOVA). Western-blot analysis revealed that the high level of activity was due to tPA and not uPA. Gene expression of tPA mRNA in stressed PDL cells, as examined by RT-PCR, increased on d 5. These findings suggest that tPA may be involved in periodontal metabolism in response to mechanical stress.
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PMID:Effect of tension-force on plasminogen activator activity from human periodontal ligament cells. 913 97

Plasminogen activator inhibitor-1 (PAI-1) is a unique member of the serpin superfamily. The alternative behavior of PAI-1 as an inhibitor, a non-inhibitory substrate, or a non-reactive latent form has been shown to be dependent on the initial conformation. In this study, we have evaluated the effect of a substitution outside the reactive site loop (P18) or in the reactive site loop (P6 and P10) on proteinase specificity and conformational transitions in PAI-1. Wild-type PAI-1 (wtPAI-1) revealed the same conformational distribution pattern toward tissue-type plasminogen activator (t-PA) as toward urokinase-type plasminogen activator (u-PA) (i.e. 53 +/- 6. 9% active, 36 +/- 6.8% latent, and 12 +/- 1.9% substrate). Inactivation of wtPAI-1 resulted in the conversion of the labile active form into the latent form while the stable substrate form remained unchanged. PAI-1-P6 (Val --> Pro at P6) revealed a target specificity for t-PA (39 +/- 7% versus 3 +/- 2% of the theoretical maximal value toward t-PA and u-PA, respectively), PAI-1-P10 (Ser --> Pro at P10) was 4-fold more active toward u-PA than toward t-PA, and PAI-1-P18 (Asn --> Pro at P18) exhibited inhibitory properties exclusively toward u-PA (41 +/- 10%). Surprisingly, inactivation of these mutants revealed functional and conformational transitions distinct from those observed for wtPAI-1. Inactivation of PAI-1-P6(Val --> Pro) resulted in a total conversion of the active form into the latent form and in a partial conversion of the substrate form into the latent form. The active forms of both PAI-1-P10(Ser --> Pro) and PAI-1-P18(Asn --> Pro) are also labile but, in contrast to the active form of wtPAI-1, convert into substrate forms. Based on the existence of various conformations of PAI-1, we propose an alternative reaction scheme describing the putative interactions between serpins and their target proteinases. The unusual conformational and functional flexibility of PAI-1 that, according to the current study, appears not to be restricted to the reactive site loop further underlines the importance of potential structural rearrangements (e.g. upon binding to cofactors) in PAI-1 (or serpins in general) for its functional behavior at particular biological sites.
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PMID:Proteinase specificity and functional diversity in point mutants of plasminogen activator inhibitor 1. 913 22

Plasminogen activator inhibitor-1 (PAI-1) is the primary physiological inhibitor of both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). Elevated plasma levels of PAI-1 have been associated with several important thrombotic diseases. A large number of studies have demonstrated that rats are suitable for in vivo investigations on thrombolysis and fibronolysis. In this study, we have expressed, in Escherichia coli, purified and characterized recombinant rat PAI-1 in comparison with human PAI-1. Subsequently this material was used to raise monoclonal antibodies using the hybridoma technology. Characterization of purified recombinant rat PAI-1 revealed that its functional and biochemical properties are similar to those of human PAI-1. Two fusions, with spleen cells from mice immunized with recombinant rat PAI-1, yielded 118 positive hybridomas. From these, 36 monoclonal antibodies were purified and evaluated for their applicability in the construction of sandwich-type ELISAs. Out of 860 combinations tested, 2 combinations were selected for the measurement of rat PAI-1 (antigen and activity) in biological samples (e.g., plasma, platelet lysates, cell-culture media, ...).
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PMID:Characterization of recombinant rat plasminogen activator inhibitor-1 and development of immunological tools for its quantitation. 931 43

The initial step in atherosclerosis is the rapid targeting of monocytes to the sites of inflammation and endothelial injury. Serum levels of intercellular adhesion molecule-1 were found to be increased in ischaemic heart disease patients and polymorphisms in the E-selectin gene were associated with accelerated atherosclerosis in young (age < 40 years) patients, further suggesting a role of inflammation in atherosclerosis. Cholesterol loading in macrophages was found to induce interleukin-8 expression, suggesting an association between foam cell formation and beta 2-integrin-dependent adhesion of leukocytes. Enhanced endothelium-platelet interaction induced by hypercholesterolaemia is mediated by von Willebrand factor, whereas platelet adhesion to subendothelial matrix is mediated by fibulin-fibrinogen complexes. Activated platelets mediate the homing of leukocytes by interaction with the subendothelial matrix under shear stresses that do not allow neutrophil adhesion. They may also contribute to the oxidative modification of LDL, provide a source of lipids for foam cell generation and contribute to smooth muscle cell proliferation. Oxidized LDL induces tissue factor in macrophages that also provide sites for fibrin polymerization and decreases the anticoagulant activity of endothelium by interfering with thrombomodulin expression and inactivating tissue factor pathway inhibitor. Intravascular fibrinolysis induced by tissue-type plasminogen activator or urokinase may contribute to the initiation of atherosclerosis by inducing P-selectin and platelet activating factor as well as to plaque rupture, either directly or indirectly, by activating metalloproteinases. Plasminogen activator inhibitor-1 inhibits smooth muscle cell migration and, in the presence of vitronectin, promotes the clearance of thrombin by LDL receptor-related protein at sites of endothelial injury.
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PMID:Thrombosis and atherosclerosis. 933 57

Induction of in vitro angiogenesis and upregulation of urokinase- and tissue type-plasminogen activator (uPA, tPA) expression are two hallmarks of vascular endothelial growth factor (VEGF) activity on cultured endothelial cells. We report here that neutralizing antibodies to basic fibroblast growth factor (bFGF) inhibit VEGF-induced in vitro angiogenesis in bovine microvascular endothelial (BME) cells. Analysis of VEGF receptor-2 (VEGFR-2) expression revealed no alteration in VEGFR-2 mRNA or total protein in anti-bFGF antibody-treated BME or bovine aortic endothelial (BAE) cells. Ethidium bromide/agarose gel electrophoresis on the cytosolic fraction of BME cells revealed a basal level of fragmented DNA that was increased by anti-bFGF antibodies to an extent not exceeding that observed in parallel cultures incubated with concentrations of transforming growth factor-ss1 that increase VEGF-induced in vitro angiogenesis. In both BME and BAE cells, antibodies to bFGF also decreased basal levels of cell-associated uPA activity, and completely blocked the VEGF-mediated increase in uPA and tPA expression observed in parallel cultures incubated with VEGF alone. In contrast, PA inhibitor-1 expression was strongly upregulated in BME and BAE cells incubated with antibodies to bFGF, either alone or in combination with VEGF. These findings demonstrate that: (1) VEGF-induced in vitro angiogenesis and PA expression are dependent on endogenous bFGF, (2) that this phenomenon is not mediated by a decrease in VEGFR-2 expression and that apoptosis does not necessarily correlate with inhibition of invasion, and (3) that inhibition of endogenous bFGF in VEGF-treated cells results in a net antiproteolytic (and possibly also anti-adherent) effect, which could account in part for the inhibitory effect of the anti-bFGF antibodies. These findings point to a novel and unsuspected role for endogenous bFGF in regulating VEGF-induced in vitro angiogenesis.
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PMID:Vascular endothelial growth factor-induced in vitro angiogenesis and plasminogen activator expression are dependent on endogenous basic fibroblast growth factor. 937 78

Deletion polymorphism of angiotensin I-converting enzyme (ACE) gene has been reported to be an independent risk factor for myocardial infarction. Plasminogen activator inhibitor-1 (PAI-1) was proposed to be a link between the renin-angiotensin system and thrombotic risk. This study was undertaken to investigate the possible association between the insertion/deletion (I/D) polymorphism of the ACE gene and plasma PAI-1 levels in 160 patients with mild-to-moderate hypertension. The I/D genotypes were determined by polymerase chain reaction with oligonucleotide primers flanking the polymorphic region in intron 16 of the ACE gene. Baseline levels of PAI-1 antigen and activity and tissue plasminogen activator (t-PA) antigen were determined in fasting morning plasma samples. It was found that patients with homozygote deletion (DD, n = 37) ACE genotype did not have significantly higher plasma levels of PAI-1 antigen (31.2 +/- 15.6 ng/mL v 28.4 +/- 15.1 ng/mL or 27.2 +/- 13.2 ng/mL, P = .42), PAI-1 activity (16.2 +/- 10.6 IU/mL v 14.1 +/- 9.4 IU/ mL or 15.0 +/- 9.9 IU/mL, P = .60), or t-PA antigen (14.6 +/- 6.0 ng/mL v 13.4 +/- 4.9 ng/mL or 14.6 +/- 5.7 ng/mL, P = .40) as compared to those with heterozygote (DI, n = 67) or homozygote insertion (II, n = 56) genotypes. On multiple regression analysis, the ACE genotypes did not appear to be significant predictors for plasma PAI-1 levels and t-PA antigen after adjustment with age, sex, body mass index, plasma triglyceride, cholesterol, and glucose. In conclusion, the results indicated that the I/D polymorphism of the ACE gene was not related to plasma PAI-1 levels in a Chinese population with hypertension. The ACE genotypes may not have a role in influencing the fibrinolysis in hypertension.
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PMID:Plasminogen activator inhibitor-1 and angiotensin I converting enzyme gene polymorphism in patients with hypertension. 952 54

The plasminogen activator (PA)-plasmin proteolytic system has recently received considerable attention because of its participation in a wide variety of biological activities and in pathological conditions involving tissue destruction. We examined the effects of interleukin-6 (IL-6) on PA activity and the gene expressions of tissue type (t) PA and PA inhibitor-1 (PAI-1) in human dental pulp (HDP) cells. IL-6 treatment induced significantly high PA activity in the HDP cells in a time- and dose-dependent manner, compared with nontreated controls. Western-blot analysis showed that tPA protein in the conditioned medium was stimulated by IL-6, compared with the control. The tPA and PAI-1 mRNA levels were increased in HDP cells treated with IL-6, as shown by reverse transcriptase-polymerase chain reaction. These results suggest that IL-6 stimulated PA activity through an enhancement of tPA gene expression and may be involved in extracellular matrix degradation through the stimulation of the PA-plasmin system of HDP cells.
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PMID:Stimulatory effect of interleukin-6 on plasminogen activator activity from human dental pulp cells. 964 Nov 8

In the present study, we determined the plasma and tissue concentrations of tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1, plasminogen activator inhibitor-2 and urokinase-type plasminogen activator receptor in 32 patients with pathology-proved gastric cancer. The plasma levels of the same markers were compared in 37 patients with benign gastric ulcer in order to find out if these plasma levels could be used to evaluate the prognostic value in patients with gastric cancer. Plasma plasminogen activator inhibitor-1 was significantly higher in gastric cancer than in benign gastric disease (p < 0.0005), whereas plasma urokinase-type plasminogen activator was significantly lower in patients with gastric cancer than in those with benign ulcer (p = 0.003). There was no significant correlation between tissue and plasma concentrations of the same parameters. The plasma and tissue levels of fibrinolytic parameters were not affected by tumor size or distant metastasis, whereas tumor tissue concentration of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-2 were significantly higher in N0 than in N1 and N2, and tissue plasminogen activator inhibitor-1 was significantly higher in N0 than in N1. Plasma levels of the five fibrinolytic parameters could not take the place of the corresponding tissue concentrations on the diagnosis and prediction of prognosis in patients with gastric cancer. Tissue concentrations of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-2, especially the latter, can be used to predict lymph node involvement in patients with gastric cancer.
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PMID:Diagnostic and prognostic values of plasma levels of fibrinolytic markers in gastric cancer. 970 Aug 49


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