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: EC:3.4.21.7 (plasmin)
9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured bovine capillary endothelial (BCE) cells synthesize heparan sulfate proteoglycans (HSPG), which are both secreted into the culture medium and deposited in the cell layer. The nonsoluble HSPGs can be isolated as two predominant species: a larger 800-kD HSPG, which is recovered from preparations of extracellular matrix, and a 250-kD HSPG, which is solubilized by nonionic detergent extraction of the cells. Both HSPG species bind bFGF. 125I-bFGF bound to BCE cell cultures is readily released by either heparinase or plasmin. When released by plasmin, the growth factor is recovered from the incubation medium as a complex with the partly degraded high molecular mass HSPG. Endogenous bFGF activity is released by a proteolytic treatment of cultured BCE cells. The bFGF-binding HSPGs are also released when cultures are incubated with the inactive proenzyme plasminogen. Under such experimental conditions, the release of the extracellular proteoglycans can be enhanced by treating the cells either with bFGF, which increases the plasminogen activating activity expressed by the cells, or decreased by treating the cells with transforming growth factor beta, which decreases the plasminogen activating activity of the cells. Specific immune antibodies raised against bovine urokinase also block the release of HSPG from BCE cell cultures. We propose that this plasminogen activator-mediated proteolysis provides a mechanism for the release of biologically active bFGF-HSPG complexes from the extracellular matrix and that bFGF release can be regulated by the balance between factors affecting the pericellular proteolytic activity.
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PMID:Release of basic fibroblast growth factor-heparan sulfate complexes from endothelial cells by plasminogen activator-mediated proteolytic activity. 213 29

The functional role of the fibrinolytic system in capillary growth was investigated using bovine capillary endothelial cells (BCEs) cultured on a Type I collagen gel matrix, into which the cells migrated to form capillary-like tubular structures. The length of the tubes formed were measured morphometrically using an image analyzer in the absence and presence of fibrinolytic proteases, namely plasminogen, plasminogen activators (PAs) and PA inhibitor (PAI). The addition of plasminogen (25 micrograms/ml) to the gel matrix significantly increased the length of BCE tubes found on the 9th day of culture (p less than 0.01), with a dose-dependent tendency. The simultaneous addition of a basic fibroblast growth factor (bFGF, 10 ng/ml) enhanced this tube formation as early as the 3rd day of culture (p less than 0.01). Cultured BCEs secreted both tissue-type and urokinase-type PAs (tPA and uPA) and PAI-1 into the culture medium, and the secretion of both PAs was enhanced by the addition of bFGF. However, the secreted tPA was composed mostly of an inactive form of tPA.PAI-1 complex, and the PA activity was derived mostly from uPA. Inhibitors of plasmin suppressed the enhancing effect of plasminogen on angiogenesis. In addition, anti-uPA IgG markedly inhibited the enhancing effect of plasminogen on the 4th and 7th days of culture (p less than 0.01), whereas anti-tPA IgG showed an inhibitory tendency only on the 4th day of culture (p less than 0.05). These findings indicate that the plasminogen-PAs system, especially uPA synthesized and secreted by BCEs, plays an important role in regulating angiogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A role of fibrinolytic activity in angiogenesis. Quantitative assay using in vitro method. 248 Nov 53

Angiogenesis is defined as a vascular neoformation usually of capillary origin. This phenomenon is important during development and under several physiological and or pathological conditions. In recent years, progress has been made to understand this phenomenon at the molecular level. This includes the identification of potent angiogenic factors, the appreciation of the role of proteases, the importance of the extracellular matrix, and the emerging characterisation of signal transduction pathways in endothelial cells. Two important participants in angiogenesis are molecules from the fibroblast growth factor (FGF) and the transforming growth factor-beta (TGF-beta) family. In our laboratory, we have extensively studied the roles and mechanisms of action of the major FGF prototype, FGF-2 and of the TGF-beta member, TGF-beta 1. Different isoforms of FGF-2 have been previously described, a high molecular weight (HMW) form associated with the nucleus and 18 kDa bFGF that is cytoplasmic. These two forms of FGF-2 also exhibit different functions when expressed endogenously. TGF-beta is formed from a latent complex by plasmin-dependent and plasmin-independent pathways. With the exception of macrophages, the plasmin-dependent pathway requires coculture conditions, urokinase, and the concentration of TGF-beta on the cell surface by the mannose-6-phosphate receptor and transglutaminase. Other important angiogenic modulators include vascular endothelial growth factor (VEGF) and angiostatin. The nature of the tumour angiogenesis factor is not yet known with certainty, but several identified and not yet identified angiogenic factors may act in concert. It is hoped that an angiostatic treatment for cancer will be derived from these molecular studies.
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PMID:Significance of angiogenesis in tumour progression and metastasis. 757

Recently, a novel class of angiostatic steroids which block angiogenesis in several systems has been described. Since the elaboration of proteases is believed to be an important component of angiogenesis, we tested whether these steroids blocked the fibrinolytic response of endothelial cells to the angiogenic protein, basic fibroblast growth factor [bFGF]). Cultured bovine aortic endothelial (BAE) cells were incubated with bFGF and/or medroxyprogesterone acetate (MPA), an angiostatic steroid which has been shown to inhibit vascularization, collagenolysis, and tumor growth. When bFGF (3 ng/ml) was added to confluent monolayers of BAE cells, plasminogen activator (PA) activity in the medium was increased threefold. In contrast, MPA at 10(-6) M, 10(-7) M, 10(-8) M, and 10(-9) M decreased PA levels in the medium by 83%, 83%, 75%, and 39%, respectively. The stimulation of PA levels in BAE cells by bFGF (3 ng/ml) was abrogated by the presence of 10(-6) M MPA. This decrease in PA activity was found to be mediated by a significant increase in plasminogen activator inhibitor type-1 (PAI-1) production. MPA, therefore, negated one of the important enzymatic activities associated with the angiogenic process. In contrast to the decreased levels of secreted PA in cultures exposed simultaneously to MPA and bFGF, cell-associated PA levels remained high, consistent with earlier observations indicating that PAI-1 does not inhibit cell-associated PA. Thus, angiostatic steroids may exert their inhibitory effects on angiogenesis by increasing the synthesis of PAI-1. This, in turn, inhibits PA activity and, therefore, plasmin generation, which is essential for the invasive aspect of angiogenesis.
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PMID:Mechanism of action of angiostatic steroids: suppression of plasminogen activator activity via stimulation of plasminogen activator inhibitor synthesis. 768 43

Cartilage degradation is mediated by activated matrix metalloproteinases (MMP). Since the plasmin/plasminogen cascade may activate latent MMP during cartilage catabolism, we determined if protease nexin-1 (PN-1), an inhibitor of plasminogen, plasmin, and urokinase could prevent cartilage degradation. Using a rabbit model, we induced cartilage glycosaminoglycan (GAG) loss by intraarticular (IA) injection of IL-1 beta and bFGF. PN-1 was given IA for 4 days, once before IL-1 beta/bFGF and daily for 3 days. Three days after IL-1 beta/bFGF, we determined GAG loss. PN-1 significantly inhibited GAG loss at 2.8, 2.5 mg, and 2.0 mg/knee (p < 0.03). These data suggest the role of the plasmin/plasminogen enzymatic cascade in the cartilage catabolism that occurs during IL-1-induced inflammation and demonstrates the potential of PN-1 to prevent cartilage degradation.
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PMID:Recombinant human protease nexin-1 prevents articular cartilage-degradation in the rabbit. 838 2

In angiogenesis associated with tissue repair and disease, fibrin and inflammatory mediators are often involved. We have used three-dimensional fibrin matrices to investigate the humoral requirements of human microvascular endothelial cells (hMVEC) to form capillary-like tubular structures. bFGF and VEGF165 were unable to induce tubular structures by themselves. Simultaneous addition of one or both of these factors with TNFalpha induced outgrowth of tubules, the effect being the strongest when bFGF, VEGF165, and TNFalpha were added simultaneously. Exogenously added u-PA, but not its nonproteolytic amino-terminal fragment, could replace TNFalpha, suggesting that TNFalpha-induced u-PA synthesis was involved. Soluble u-PA receptor (u-PAR) or antibodies that inhibited u-PA activity prevented the formation of tubular structures by 59-99%. epsilon-ACA and trasylol which inhibit the formation and activity of plasmin reduced the extent of tube formation by 71-95%. TNFalpha or u-PA did not induce tubular structures without additional growth factors. bFGF and VEGF165 enhanced of the u-PAR by 72 and 46%, but TNFalpha itself also increased u-PAR in hMVEC by 30%. Induction of mitogenesis was not the major contribution of bFGF and VEGF165 because the cell number did not change significantly in the presence of TNFalpha, and tyrphostin A47, which inhibited mitosis completely, reduced the formation of tubular structures only by 28-36%. These data show that induction of cell-bound u-PA activity by the cytokine TNFalpha is required in addition to the angiogenic factors VEGF165 and/or bFGF to induce in vitro formation of capillary-like structures by hMVEC in fibrin matrices. These data may provide insight in the mechanism of angiogenesis as occurs in pathological conditions.
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PMID:Cooperative effect of TNFalpha, bFGF, and VEGF on the formation of tubular structures of human microvascular endothelial cells in a fibrin matrix. Role of urokinase activity. 860 93

The binding of urokinase (u-PA) to its cell surface receptor (u-PAR) is critical for tumor cell invasion. Here, we report that the distribution of this binding by a u-PAR antagonist ATF-HSA inhibits in vitro the motility of endothelial cells in a dose-dependent manner. This inhibition was also observed when the cells were first stimulated with potent angiogenic factors, including bFGF or VEGF. [3H]thymidine incorporation assay demonstrated that ATF-HSA did not affect the cell proliferation. ATF-HSA was more potent than plasmin inhibitors, suggesting that it exerts its effects not solely by inhibiting the remodeling of the extracellular matrix. In fact, analysis of the cell shape change during migration revealed for the first time that its effect is related to a decrease in cell deformability. These results suggest that u-PAR antagonist may be a new approach to control angiogenesis.
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PMID:Blockage of urokinase receptor reduces in vitro the motility and the deformability of endothelial cells. 860 39

Basic fibroblast growth factor (bFGF or FGF-2) is an angiogenic and pleiotropic growth factor involved in the proliferation and differentiation of numerous cell types. It is expressed mostly in tissues of mesoderm and neuroectoderm origin, and is thought to play an important role in the mesoderm induction. Although hematopoietic cells derive from the mesoderm, relatively few studies have, until recently, addressed the role of FGF-2 in hematopoiesis. FGF-2 is expressed in cells of the bone marrow including stromal cells, and possibly cells from several hematopoietic cell lineages. It is stored in the bone marrow extra-cellular matrix and released by enzymes such as heparanase, plasmin, or phospholipase C and D. FGF-receptors (FGF-Rs) are expressed in leukemic cell lines and in hematopoietic cells. FGF-2 positively regulates hematopoiesis, by acting on stromal cells, on early and committed hematopoietic progenitors, and possibly on some mature blood cells. The action of FGF-2 is most likely indirect since its action, on megakaryocytopoiesis for example, is abrogated by anti-IL6 antibodies. It synergizes with hematopoietic cytokines, or antagonizes the negative regulatory effects of TGF-beta. Taken together, these results demonstrate that FGF-2 is a potent hematopoietic growth factor that is likely to play an important role in physiological and pathological hematopoiesis.
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PMID:The role of fibroblast growth factor-2 (FGF-2) in hematopoiesis. 871 68

During immune injury, activation of endothelial cells by inflammatory cytokines stimulates leukocyte adhesion to the endothelium, turns the endothelium from an anticoagulant surface to one that is frankly procoagulant, and results in the release of vasoactive mediators and growth factors. Cytokine activation of endothelial cells also results in increased endothelial cell TGF-beta 1 synthesis and enhanced activation of latent TGF-beta, the latter involving a shift of plasmin production from the apical to subendothelial surface. In cytokine-stimulated endothelial cells, TGF-beta hinders leukocyte adhesion and transmigration via inhibition of IL-8 and E-selectin expression. TGF-beta also profoundly diminishes cytokine-stimulated inducible nitric oxide synthase production and instead augments endothelial nitric oxide synthase expression. Thus, some of the TGF-beta actions on endothelium during immune activation can viewed as immunosuppressive. TGF-beta also influences mechanisms of vascular remodeling during the healing phase of immune injury. It stimulates PDGF-B synthesis by endothelial cells, causes bFGF release from subendothelial matrix, and promotes VEGF synthesis by non-endothelial cells. Together these mediators control angiogenesis, a critical component of the vascular repair phenomenon. Further, endothelial cell derived PDGF-B and bFGF influence the proliferation and migration of neighboring cells. Thus, endothelial cells and TGF-beta actions on the endothelium play important roles both during the initial phase of immune injury and during the later remodeling phase.
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PMID:TGF-beta and the endothelium during immune injury. 915 Apr 51

We previously reported that a 16-kDa proteolytic fragment of IGF Binding Protein-3 (IGFBP-3), which is devoid of affinity for IGFs, inhibits the mitogenic effects of IGF-I on chick embryo fibroblasts. Here, we set out to determine if the fragment had biological effects on fibroblasts from mouse embryos homozygous for a targeted disruption of the Type 1 IGF receptor gene. In the cell clone used, bFGF (but not IGF, EGF or PDGF) was mitogenic in serum-free medium, increasing 14C-thymidine uptake by a factor of 10-15 within 24 hours and doubling cell proliferation. The 16-kDa fragment, isolated by HPLC following limited proteolysis of recombinant human (rh) IGFBP-3 by plasmin, in both assays dose-dependently (20 to 100 ng/ml) inhibited (up to 100%) maximal stimulation induced by 25 ng/ml bFGF, whereas intact IGFBP-3 had virtually no effect. Similar results were obtained with control wild-type cells. In the latter, the mitogenic activity of 1% fetal calf serum (equal to that of 25 ng/ml bFGF) was inhibited by only 25-30% by 100 ng/ml 16-kDa fragment or 200 ng/ml rhIGFBP-3. This agrees with an antagonistic action, affecting the mitogenic activity of serum that is attributable to IGFs. The 16-kDa IGFBP-3 fragment therefore appears to be a potent inhibitor of mitogenic signals resulting from activation of both the type 1 IGF and FGF receptors.
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PMID:The 16-kDa proteolytic fragment of insulin-like growth factor (IGF) binding protein-3 inhibits the mitogenic action of fibroblast growth factor on mouse fibroblasts with a targeted disruption of the type 1 IGF receptor gene. 920 55


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