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PubMed2001

The urokinase plasminogen activator receptor-associated protein/endo180 is coexpressed with its interaction partners urokinase plasminogen activator receptor and matrix metalloprotease-13 during osteogenesis.

The urokinase plasminogen activator receptor-associated protein/Endo180 (uPARAP/Endo180) is a newly discovered member of the macrophage mannose receptor family that was reported to interact with ligand-bound urokinase plasminogen activator receptor (uPAR), matrix metalloprotease-13 (MMP-13), and collagen V on the cell surface. We have determined the sites of expression of this novel receptor during murine postimplantation development. uPARAP/Endo180 was expressed in all tissues undergoing primary ossification, including the developing bones of the viscerocranium and calvarium that ossify intramembranously, and developing long bones undergoing endochondral ossification. uPARAP/Endo180 mRNA was expressed by both immature osteoblasts and by mature osteocalcin-producing osteoblasts-osteocytes, and was coexpressed with MMP-13. Interestingly, osteoblasts also expressed uPAR. Besides bone-forming tissues, uPARAP/Endo180 expression was detected only in a mesenchymal condensation of the midbrain and in the developing lungs. The data suggest a function of this novel protease receptor in bone development, possibly mediated through its interactions with uPAR, MMP-13, or collagen V.

Animals↗
PubMed1999

Effects of tissue plasminogen activator for acute ischemic stroke at one year. National Institute of Neurological Disorders and Stroke Recombinant Tissue Plasminogen Activator Stroke Study Group.

BACKGROUND: In 1995, the two-part National Institute of Neurological Disorders and Stroke (NINDS) Recombinant Tissue Plasminogen Activator Stroke Trial found that patients who were treated with tissue plasminogen activator (t-PA) within three hours after the onset of symptoms of acute ischemic stroke were at least 30 percent more likely than patients given placebo to have minimal or no disability three months after the stroke. It was unknown, however, whether the benefit would be sustained for longer periods. METHODS: In the NINDS Trial, a total of 624 patients with stroke were randomly assigned to receive either t-PA or placebo. We collected outcome data over a period of 12 months after the occurrence of stroke. The primary outcome measure was a "favorable outcome," defined as minimal or no disability as measured by the Barthel index, the modified Rankin Scale, and the Glasgow Outcome Scale. We assessed the treatment effect using a global statistic. RESULTS: Using an intention-to-treat analysis for the combined results of the two parts of the trial at 6 months and 12 months, we found that the global statistic favored the t-PA group (odds ratio for a favorable outcome at 6 months, 1.7; 95 percent confidence interval, 1.3 to 2.3; odds ratio at 12 months, 95 percent confidence interval, 1.7; 1.2 to 2.3). The patients treated with t-PA were at least 30 percent more likely to have minimal or no disability at 12 months than were the placebo-treated patients (absolute increase in the proportion with a favorable outcome, 11 to 13 percentage points). There was no significant difference in mortality at 12 months between the t-PA group and the placebo group (24 percent vs. 28 percent, P=0.29). There was no interaction between the type of stroke identified at base line and treatment with respect to the long-term response. The rate of recurrent stroke at 12 months was similar in the two groups. CONCLUSIONS: During 12 months of follow-up, the patients with acute ischemic stroke who were treated with t-PA within three hours after the onset of symptoms were more likely to have minimal or no disability, than the patients given placebo. These results indicate a sustained benefit of t-PA for such patients.

Activities of Daily Living↗
PubMed2005

Dynamic assembly of the urokinase-type plasminogen activator signaling receptor complex determines the mitogenic activity of urokinase-type plasminogen activator.

The urokinase-type plasminogen activator (uPA) receptor (uPAR) functions in concert with co-receptors, including integrins, FPR-like receptor-1/lipoxin A4 receptor, and the epidermal growth factor receptor (EGFR), to initiate cell signaling. uPAR co-receptors may be dynamically organized into a multiprotein signaling receptor complex. In Chinese hamster ovary-K1 (CHO-K1) cells, uPA-binding to uPAR activates ERK/MAP kinase, even though these cells do not express the EGFR; however, when CHO-K1 cells are transfected to express the EGFR, ERK activation becomes EGFR-dependent. In this study, we demonstrate that ERK activation in response to uPA follows equivalent biphasic kinetics in EGFR-expressing and -deficient CHO-K1 cells. In both cell types, the response is pertussis toxin-sensitive; however, uPA promotes cell proliferation exclusively in the EGFR-expressing cells. uPA-induced mitogenic activity requires activation of both STAT5b and ERK. STAT5b was tyrosine-phosphorylated, in response to uPA, only in EGFR-expressing cells. uPA-induced cell proliferation was blocked by dominant-negative MEK1, dominant-negative STAT5b, and by expression of an EGFR that is mutated at Tyr-845, which is essential for STAT5b activation. In two cell culture models of uPA-stimulated breast cancer growth, MDA-MB 468 cells treated with uPA and MCF-7 cells treated with uPA-plasminogen activator inhibitor-1 complex, proliferation was completely inhibited when EGFR expression or activity was blocked. We conclude that expression and assembly of uPAR co-receptors in a specific cell type determines the response to uPA. The EGFR selectively cooperates with uPAR to mediate mitogenesis.

Animals↗
PubMed1996

Hemostatic changes after thrombolytic therapy with saruplase (unglycosylated single-chain urokinase-type plasminogen activator) and urokinase (two-chain urokinase-type plasminogen activator).

Urokinase, or two-chain urokinase-type plasminogen activator (tcu-PA), is an effective thrombolytic agent. Its single-chain precursor (scu-PA), unlike tcu-PA, is able to selectively activate fibrin-bound plasminogen. The induced clot lysis is amplified by plasmin-triggered conversion of scu-PA to tcu-PA. The aim of our study was to compare the hemostatic effects of recombinant unglycosylated scu-PA, INN saruplase, and urokinase, at doses considered optimal (80 mg saruplase and 3 million units urokinase) in patients with acute myocardial infarction, within 6 h of onset of pain. Complete sample sets from more than 230 patients in each treatment group have been analyzed. The median hemostatic changes caused by saruplase and urokinase were virtually identical indicating that saruplase is converted early in vivo to its active tcu-PA derivative with the dose regimen used. Fibrinogen degradation products were higher for saruplase with a maximum at 2h. They rose markedly after saruplase from 0.43 mg/l at 0 h to a maximum of 160 mg/l at 2 h, whereas the increase after urokinase (from 0.45 mg/l to 89.0 mg/l) was significantly smaller (P < 0.001).

Double-Blind Method↗
PubMed2004

Investigation of residues in the fibrin(ogen) gamma chain involved in tissue plasminogen activator binding and plasminogen activation.

In order to characterize tissue plasminogen activator (t-PA) binding to gamma-chain residues in fibrinogen, we generated variant fibrinogens substituting alanine for gamma D316, gamma D318, gamma D320, and gamma K321. We measured thrombin-catalyzed polymerization and found normal polymerization with gamma K321A, no polymerization with gamma D316A, and, as reported by Lounes et al. in 2002, impaired polymerization with gamma D318A and gamma D320A. We measured t-PA binding in a solid-phase assay, and t-PA activity by the generation of plasmin. Comparing normal fibrin with fibrinogen, we found a seven-fold increase in binding and a two-fold increase in activity. Binding to all variant fibrinogens was the same as normal. In contrast, t-PA binding to all variant fibrins was weaker than binding to normal fibrin, 2.5-fold for gamma K321A, seven-fold for gamma D320A and 10-fold for gamma D316A and gamma D318A. Plasmin generation in the presence of variant fibrinogens was similar, although not identical, to normal, and plasmin generation in the presence of variant fibrins was impaired for the Asp to Ala variants. As the three variants with the weakest t-PA binding and least activity also showed impaired polymerization, our results support previous findings demonstrating the DD:E complex, found in the normal fibrin polymer, is necessary for the fibrin enhanced binding of t-PA and activation of plasminogen.

Amino Acid Substitution↗
PubMed2001

4G/5G polymorphism of the plasminogen activator inhibitor-1 gene and insertion/deletion polymorphism of the tissue-type plasminogen activator gene in atherothrombotic stroke.

BACKGROUND AND PURPOSE: Decreased fibrinolytic capacity due to increased plasminogen activator inhibitor-1 (PAI-1) activity and decreased tissue-type plasminogen activator (t-PA) activity has been associated with hypertension or atherothrombotic disorders. The aims of this study were to observe associations of the genetic polymorphism for PAI-1 and t-PA with hypertension and atherothrombotic stroke, and to elucidate whether impaired fibrinolytic activity in atherothrombotic stroke was related to atherothrombosis per se or to other risk factors such as hypertension. METHODS: Patients with atherothrombotic stroke (n = 60), hypertension (n = 100), and control subjects (n = 100) were enrolled. We genotyped all subjects for 4G/5G polymorphism in the promoter region of the PAI-1 gene and the Alu-repeat insertion/deletion (I/D) polymorphism in intron h of the t-PA gene by polymerase chain reaction and endonuclease digestion. RESULTS: The frequency of the 4G/4G genotype of PAI-1 was significantly higher in the atherothrombotic stroke patients than the control subjects (41.7 versus 21%; p = 0.005), but not in the hypertensive subjects. There was a significant association between 4G/4G genotype of PAI-1 and atherothrombotic stroke (adjusted odds ratio = 3.11, 95% confidence interval 1.18-8.15), adjusting for age, sex, total cholesterol, low-density lipoprotein, triglyceride, and body mass index. However, the number of the I/I genotype of t-PA in the atherothrombotic stroke or hypertensive patients was virtually identical to the control subjects. CONCLUSION: Our results suggest that the 4G/4G genotype of the PAI-1 gene is significantly associated with an increased risk of atherothrombotic stroke. This finding also supports that impaired fibrinolytic activity in atherothrombotic stroke is related to atherothrombosis per se, but not to hypertension, one of the most important risk factors of atherothrombotic stroke.

Adult↗
PubMedDate not supplied

Genetic variation at the plasminogen activator inhibitor-1 locus is associated with altered levels of plasma plasminogen activator inhibitor-1 activity.

Plasminogen activator inhibitor-1 (PAI-1), a rapid inhibitor of tissue-type plasminogen activator, has been shown to be an independent risk factor for recurrent myocardial infarction (MI) at a young age. To investigate whether genetic variation in the PAI-1 gene is affecting plasma PAI-1 levels, a sample of 145 patients with an MI before the age of 45 years was genotyped for two polymorphisms at the PAI-1 locus, together with a sample of 95 healthy individuals of a similar age. All individuals were measured for plasma PAI-1 levels as well as for other fibrinolytic and metabolic risk indicators. A HindIII restriction fragment length polymorphism (RFLP) was used in this study in conjunction with a previously unreported eight-allele dinucleotide repeat polymorphism at the PAI-1 locus. The dinucleotide repeat polymorphism and HindIII RFLP were in strong linkage disequilibrium. There was no difference in the frequency of alleles of either polymorphism between patient and control groups. However, the smaller dinucleotide repeat alleles were significantly associated (p = 0.03) with higher plasma PAI-1 levels in the patient sample. This association was also apparent in the control sample but not at significant levels. Differences in regression coefficients for the effect of triglycerides on plasma PAI-1 levels suggest that triglyceride regulation of PAI-1 is genotype specific. Our data suggest that genetic variation at this locus contributes to between-individual differences in the level of plasma PAI-1, which is important in fibrinolysis and the pathogenesis of MI.

Adult↗
PubMed1990

Studies of recombinant plasminogen activator inhibitor-1 in rabbits. Pharmacokinetics and evidence for reactivation of latent plasminogen activator inhibitor-1 in vivo.

The pharmacokinetics of human recombinant plasminogen activator inhibitor-1 (rPAI-1) was studied in rabbits. Latent rPAI-1 (0-2 units of tissue-type plasminogen activator neutralizing activity per microgram protein); reactivated rPAI-1 (approximately 150 units/micrograms); and chloramine T-oxidized, nonreactivatable rPAI-1 (approximately 0.7 units/microgram) were studied. The pharmacokinetic parameters for the disposition of rPAI-1 antigen after an intravenous bolus injection of 1.0 or 2.5 mg/kg rPAI-1 were very similar for all three forms: the initial volume of distribution was approximately 60 ml/kg, the initial half-life in plasma was 6 minutes, and the plasma clearance was approximately 4 ml/kg/min. The disposition of PAI activity after injection of reactivated rPAI-1 was similar to that of rPAI-1 antigen. Injection of latent rPAI-1 was associated with a nearly threefold increase in the specific activity of circulating PAI-1 from 2 units/micrograms to 5.0 +/- 1.1 units/micrograms (p less than 0.01) within 1 minute, followed by a cumulative 25-fold increase in specific activity over 1 hour (p = 0.01). In contrast, the specific activity of oxidized or reactivated preparations of rPAI-1 did not increase in the first several minutes after injection. These findings support the existence of a fast-acting but low-capacity mechanism for the reactivation of rPAI-1 in vivo.

Analysis of Variance↗
PubMed1992

Cultured rat aortic vascular smooth muscle cells digest naturally produced extracellular matrix. Involvement of plasminogen-dependent and plasminogen-independent pathways.

Vascular smooth muscle (VSM) cell migration and proliferation play a major role in the development of atherosclerotic lesions, graft occlusion, and restenosis after angioplasty. Cell migration implies the digestion of the surrounding extracellular matrix. Cell-associated proteolysis has been extensively studied in neoplastic and inflammatory cells, but very little is known about the proteolytic properties of VSM. We have evaluated the ability of rat cultured VSM cells to solubilize [3H]amino acid-labeled extracellular matrices produced by bovine VSM. When plated at a density of 30,000 cells per well in 24 multiwell plates, VSM cells were able to solubilize 63.3 +/- 7.0% of the extracellular matrix after 10 days in culture. Extracellular matrix digestion occurred also when the cells were cultured in plasminogen-depleted serum but was higher in the presence of 10 micrograms/ml purified plasminogen (net percent digestion after the subtraction of the appropriate control, 8.6 +/- 3.0% versus 21.2 +/- 3.5% after 3 days in culture, p less than 0.005, respectively). The involvement of other enzymes in addition to plasmin is confirmed by the ability of VSM cells to degrade extracellular matrices from which the plasmin-sensitive component was removed with plasmin pretreatment. Rat VSM cells were able to solubilize 52.3 +/- 2.0% of this residual extracellular matrix-associated radioactivity after 6 days in culture versus 26.1 +/- 1.5% in the control dishes (p less than 0.01, n = 5). Cell contact was required for extracellular matrix degradation: cell-conditioned medium did not have any effect on extracellular matrix digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Aspirin inhibits vascular plasminogen activator activity in vivo. Studies utilizing a new assay to quantify plasminogen activator activity.

Vascular or tissue-type plasminogen activator (TPA) is a key enzyme in physiologic fibrinolysis. To study the role of prostaglandins in modulating the synthesis and release of TPA in vivo, we prospectively studied the effect of aspirin (650 mg/d X 2) on TPA activity in 13 human subjects before and after 10 min of forearm venous occlusion. TPA activity was quantified by a newly developed enzyme-linked immunosorbent assay that both measures and differentiates between TPA and urokinase (UK)-like plasminogen activator activity. This assay is based on the observation that the concentration of alpha 2-plasmin inhibitor-plasmin complexes in Reptilase-clotted plasma increases linearly in proportion to the amount of activator added. Resting TPA activity was higher in women than in men (0.56 +/- 0.59 vs. 0.15 +/- 0.11 U/ml, P = 0.049). Venous occlusion induced an eightfold rise in TPA activity in women (to 4.5 U/ml, P = 0.006) and a 15-fold rise in men (to 2.28 U/ml, P = 0.004), whereas UK activity was not detected. Aspirin inhibited the rise in TPA activity after venous occlusion by 69% in men (P = 0.004) and 70% in women (P = 0.014). In contrast, aspirin had no effect on pre- or post-occlusion hematocrits or Factor VIII-related antigen levels. There was no correlation between plasma salicylate level and percentage inhibition of TPA. Neither exogenous aspirin (0-1 microgram/ml) nor salicylate (0-70 micrograms/ml) inhibited the generation of alpha 2-plasmin inhibitor-plasmin complexes by exogenous TPA or interfered with the assay system. We conclude that aspirin may have an antifibrinolytic effect in man that has not been previously described.

Aspirin↗
PubMed2002

Influence of plasminogen deficiency on the contribution of polymorphonuclear leucocytes to fibrin/ogenolysis: studies in plasminogen knock-out mice.

Plasminogen knock-out (PG(-/-)) mice provide an unique opportunity for the study of alternative mediators of fibrinolysis. Polymorpho-nuclear leucocytes (PMNs) contain non-plasmin fibrinolytic proteases, however the degree to which these cells contribute to fibrin(ogen) degradation in these animals is not known. Thrombi were generated in carotid arteries and jugular veins of PG(-/-) and wild type (PG(+/+)) mice following adventitial application of a 20% ferric chloride solution. PMNs, identified histologically on H&E staining and by immunohistochemistry using anti-mouse PMN RB6-8C5 antibody, accumulated within the thrombus by 6 h after the injury and peaked at 24 h. There was significantly greater retention of PMNs within the thrombi of PG(-/-) mice from 48 to 72 h than in the PG(+/+) controls (at 72 h: PG(-/-)255 +/- 41 cell/mm(2) (n = 5), PG(+/+) 61 +/- 10 cell/mm(2) (n = 5), p<0.01 in the arterial thrombi; PG(-/-) 252 +/- 50 cell/mm(2) (n = 5), PG(+/+) 100 +/- 36 cell/mm(2) (n = 5), p<0.05 in the venous thrombi), providing potential for more PMN derived fibrinolytic enzymes to be present at late times after a thrombotic challenge in PG(-/-) mice relative to the PG(+/+) controls. Intact PMNs were elicited from the peritoneal cavities of PG(-/-) and PG(+/+) mice following 4% thioglycolate stimulation. In vitro studies showed PMNs from PG(-/-) mice to release greater quantities of 10% trichloroacetic acid (TCA)-soluble fibrinopeptides from I(125)-labeled fibrinogen, than cells from PG(+/+) controls although these differences did not become apparent until after 24 h of incubation (at 72 h incubation: PG(-/-) 918 n/10 x 10(6) cells/0.5 ml, PG(+/+) 589 ng/10 10(6) cells/0.5 ml p = 0.005). Furthermore, autoradiographic analysis of the I(125)-labeled fibrinogen degradation products showed the cleavage pattern by PG(-/-) PMNs to be distinct from that produced by PG(+/+) PMNs. These data suggest that a relatively greater role for PMNs-initiated fibrinolysis exists in the setting of plasminogen deficiency, although this prominence only becomes evident more than 24 h after the thrombotic insult. In addition, mechanisms responsible for the process in PG(-/-) mice may be distinct from those primarily responsible for the process in PMNs from PG(+/+) mice.

Animals↗
PubMed1991

The endothelial cell tissue plasminogen activator receptor. Specific interaction with plasminogen.

Human endothelial cells (EC) assemble plasmin-generating proteins on their surface. We have previously identified an EC membrane protein (Mr approximately 40,000) which specifically binds tissue plasminogen activator (t-PA) but not urokinase (Hajjar, K.A., and Hamel, N. M. (1990) J. Biol. Chem. 265, 2908-2916). In the present study, t-PA receptor protein (t-PA-R) was purified to apparent homogeneity from a detergent extract of human placental tissue by diisopropyl fluorophosphate-t-PA affinity chromatography and preparative gel electrophoresis. In a solid phase binding assay wells coated with t-PA-R bound both 125I-t-PA and 125I-Lys-plasminogen (PLG), but not 125I-urokinase in a specific, reversible, and noncompetitive fashion. Binding of 125I-Lys-PLG, but not 125I-t-PA, to t-PA-R was 80% inhibited by a 20-100-fold molar excess of the PLG-like lipoprotein(a), or by the lysine analog, epsilon-aminocaproic acid (50 mM). A polyclonal anti-t-PA-R antibody inhibited 66 and 79% of the specific 125I-t-PA and 125I-Lys-PLG binding, respectively, to EC monolayers. Biosynthetically labeled 40-kDa protein coprecipitated with t-PA- or Lys-PLG-Sepharose beads, but not with unconjugated Sepharose. In a functional assay, t-PA associated with immobilized t-PA-R generated 6.4 times more plasmin than an equivalent amount of t-PA in the fluid phase. These results suggest that t-PA-R can bind both t-PA and Lys-PLG in a manner that mimics the EC surface. This protein may play a role in modulating plasmin generation on cell surfaces.

Binding, Competitive↗
PubMed1991

[Unstable angina: tissue plasminogen activator, tissue plasminogen activator inhibitors, protein C and other factors of the blood fibrinolytic system].

The authors examined the activities of plasminogen activator, its inhibitor, the levels of C protein, antithrombin III, alpha 2-antiplasmin, plasminogen, fibrinogen, fibrinogen/fibrin degradation products in 22 patients with unstable angina by using the vein occlusive test. No significant differences were found in the examined parameters while comparing the group of stable angina patients and healthy subjects. It was concluded that thrombogenesis disturbances in unstable angina were regional and the recording of peripheral blood fibrinolytic parameters failed to detect any changes characteristic of unstable angina.

Adult↗
PubMed1997

Angiotensin II increases plasminogen activator inhibitor-1 and tissue factor mRNA expression without changing that of tissue type plasminogen activator or tissue factor pathway inhibitor in cultured rat aortic endothelial cells.

Angiotensin converting enzyme inhibitors (ACE-I) have been reported to prevent the recurrence of cardiovascular events. The mechanism of this decrease, however, can not be completely explained by anti-hypertensive and anti-hypertrophic effects of ACE-I. To investigate the mechanism of this decrease, we studied the regulation of plasminogen activator inhibitor-1 (PAI-1), tissue type plasminogen activator (TPA), tissue factor (TF), and tissue factor pathway inhibitor (TFPI) by angiotensin II (Ang II) in cultured rat aortic endothelial cells. Ang II increased PAI-1 and TF mRNA expression without affecting that of TPA or TFPI. These inductions were accompanied by increases in PAI-1 and TF activities and were inhibited by a type I Ang II receptor antagonist. The results suggest that Ang II decreases the antithrombotic properties of endothelial cells which increases the chance of thrombosis. Thus, inhibition of the renin-angiotensin system may be beneficial to prevent thrombus formation in treatment of ischemic heart disease.

Angiotensin II↗
PubMed1992

Plasminogen activator regulation in osteoblasts: parathyroid hormone inhibition of type-1 plasminogen activator inhibitor and its mRNA.

In order to determine the mechanism by which parathyroid hormone (PTH) stimulates plasminogen activator (PA) activity in rat osteoblasts, we investigated the effect of human PTH(1-34) [hPTH(1-34)] on the synthesis of mRNAs for tissue-type PA (tPA), urokinase-type PA (uPA), and PA inhibitor-1 (PAI-1), and on release of PA activity and PAI-1 protein in both normal rat calvarial osteoblasts and UMR 106-01 osteogenic sarcoma cells. hPTH(1-34) (0.25-25 nM) decreased PAI-1 mRNA and protein, and increased PA activity in both cell types in a dose-dependent manner with ED50 of about 1 nM for both responses. Forskolin and isobutylmethylxanthine also stimulated PA activity and decreased PAI-1 protein and mRNA in both cell types. hPTH(1-34) did not show any consistent effect on tPA and uPA mRNA in calvarial osteoblasts, but a modest (two-fold) increase of both mRNAs was observed in UMR 106-01 cells treated with 25 nM hPTH(1-34). However, when protein synthesis was inhibited with 100 microM cycloheximide, the increase of tPA and uPA mRNA by hPTH(1-34) was enhanced in UMR 106-01 cells and became evident in calvarial osteoblasts. Fibrin autography also revealed that hPTH(1-34) increases tPA and uPA activity, especially after cycloheximide treatment in UMR 106-01 cells. These results strongly suggest that PTH increases PA activity predominantly by decreasing PAI-1 protein production through a cyclic adenosine monophosphate (cAMP)-dependent mechanism in rat osteoblasts. The reduction of PAI-1 protein by PTH results in enhanced action of both tPA and uPA, and would contribute to the specific roles of these PAs in bone.

Animals↗
PubMed1995

Urokinase binding and catabolism by Hep G2 cells is plasminogen activator inhibitor-1 dependent, analogous to interactions of tissue-type plasminogen activator with these cells.

The adherent human hepatoma cell line Hep G2 exhibits receptor mediated endocytosis and catabolism of tissue-type plasminogen activator.plasminogen activator inhibitor type-1 (t-PA.PAI-1) complexes formed when exogenous t-PA combines with endogenous PAI-1 in the extracellular matrix. To determine whether the other major PA, urokinase (u-PA), which also complexes with PAI-1, is metabolised via the same mechanism, 125I-labelled high (hmw) and low (lmw) molecular weight forms of u-PA were incubated with Hep G2 cells at 4 degrees C for 2 hr in the absence and presence of a 100-fold excess of unlabelled ligand in order to detect specific binding. Both hmw and lmw 125I-u-PA formed complexes with PAI-1 and these bound specifically and with high affinity (apparent Kd 3.9 and 4.1 nM, with Bmax 78 x 10(3) and 83 x 10(3) binding sites/cell respectively). Binding by each form of radiolabelled u-PA was inhibited in a dose-dependent fashion by unlabelled t-PA, hmw-u-PA, lmw-u-PA, and by monoclonal anti-PAI-1 antibody. At 37 degrees C, bound hmw and lmw 125I-u-PA.PAI-1 complexes were internalised and degraded rapidly. These findings indicate that the specificity of the previously described receptor which mediates PAI-1 dependent catabolism of t-PA by Hep G2 cells extends to complexes of u-PA with this inhibitor.

Antibodies, Monoclonal↗
PubMed2003

Expression and regulation of plasminogen activators, plasminogen activator inhibitor type-1, and steroidogenic acute regulatory protein in the rhesus monkey corpus luteum.

The corpus luteum (CL) is a transient endocrine organ that secretes progesterone to support early pregnancy. Using primate materials obtained from rhesus monkeys, we have in this study investigated the expression and regulation of the plasminogen activators (PAs) and PA inhibitor type 1 (PAI-1) during CL development and regression. Adult (5-7 yr old) female rhesus monkeys were treated with pregnant mare serum gonadotropin/human chorionic gonadotropin to induce ovulation and follicular luteinization. At various luteal developmental stages, CL or whole ovaries were obtained for preparing luteal cells, Northern blot, in situ hybridization, and immunohistochemistry. We demonstrated that luteal cells from the rhesus monkey were able to produce both tissue type PA (tPA) and urokinase type PA, as well as the physiological PAI-1. During luteal development in the monkey, urokinase type PA was the major PA species taking part in the active angiogenesis and tissue remodeling processes in the forming CL. However, the mRNA as well as the enzymatic activity levels of tPA increased dramatically in monkey CL with the advent of luteolysis. This change of tPA levels was in a temporal coordination with the regulation of PAI-1 expression, resulting in an increased tPA activity at the initiation of luteolysis. Therefore, we suggest that tPA might be a luteolytic factor to the monkey CL. A PAI-1 modulated tPA activity might be important for the initiation of luteolysis in the monkey. In addition, we have also demonstrated that the expression of steroidogenic acute regulatory protein in the monkey CL was in accordance with the changes of progesterone production, suggesting that steroidogenic acute regulatory protein expression may be considered as a reliable marker for CL function in primates.

Animals↗