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The interaction of streptokinase.plasminogen activator complex, tissue-type plasminogen activator, urokinase and their acylated derivatives with fibrin and cyanogen bromide digest of fibrinogen. Relationship to fibrinolytic potency in vitro.

ABSTRACT: The effects of purified soluble fibrin and of fibrinogen fragments (fibrin mimic) on the activation of Lys-plasminogen (i.e. plasminogen residues 77-790) to plasmin by streptokinase.plasminogen activator complex and by tissue-type plasminogen activator were studied. Dissociation constants of both activators were estimated to lie in the range 90-160 nM (fibrin) and 16-60 nM (CNBr-cleavage fragments of fibrinogen). The kinetic mechanism for both types of activator comprised non-essential enzyme activation via a Rapid Equilibrium Ordered Bireactant sequence. In order to relate the fibrin affinity of plasminogen activators to their fibrinolytic potency, the rate of lysis of supported human plasma clots formed in the presence of unmodified or active-centre-acylated precursors of plasminogen activators was studied as a function of the concentration of enzyme derivative. The concentrations of unmodified enzyme giving 50% lysis/h in this assay were 0.9, 2.0 and 11.0 nM for tissue-type plasminogen activator, streptokinase.plasmin(ogen) and urokinase respectively. However, the potencies of active-centre-acylated derivatives of these enzymes suggested that acylated-tissue plasminogen activator and streptokinase.plasminogen complexes of comparable hydrolytic stability were of comparable potency. Both types of acyl-enzyme were significantly more potent than acyl-urokinases.

SUBMITTER: Cassels R

PROVIDER: S-EPMC1148422 | biostudies-other | 1987 Oct

REPOSITORIES: biostudies-other

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Project description:Data from clinical studies, cell culture, and animal models implicate the urokinase (uPA)/Plasminogen (Plg) system in the development of atherosclerosis and aneurysms. However, the mechanisms through which uPA/Plg stimulate these diseases are not yet defined. We used genetically modified, atherosclerosis-prone mice, including mice with macrophage-specific uPA overexpression to clarify mechanisms of uPA/Plg-accelerated atherosclerosis and aneurysm formation. Microarray studies were performed to identify potential mediators of uPA-accelerated atherosclerosis. These studies identified S100A8 and S100A9 mRNA as the most highly upregulated transcripts in uPA-overexpressing macrophages; upregulation of S100A9 protein in uPA-overexpressing macrophages was confirmed by Western blotting. S100A8/A9, which are atherogenic in mice and are expressed in human atherosclerotic plaques, are also upregulated in aortae of mice with uPA-overexpressing macrophages, and macrophage S100A9 mRNA is upregulated by exposure of wild-type macrophages to medium from uPA-overexpressing macrophages. Bioinformatics analysis of the microarray data suggest significant effects of uPA overexpression on cell migration and cell-matrix interactions. Our results confirm—in a second animal model—that macrophage-expressed uPA stimulates atherosclerosis and aortic dilation. They also implicate specific pathways in uPA/Plg-accelerated atherosclerosis and aneurysmal disease. Six independent biological replicate RNA samples were prepared from thioglycollate-elicited peritoneal macrophages from mice of two different genotypes: SR-uPA+/0 transgenic (overexpress uPA in macrophages) and nontransgenic, respectively), for a total of 12 independent RNA samples. Both transgenic and nontransgenic mice were Apoe-/- and were fed Western diet from 5-15 weeks before peritoneal macrophages were elicited. In addition, from the six samples of each genotype, a pooled sample was prepared by combining the six genotype-specific samples. Each of the two pooled samples was assayed on the BeadChip in two technical replicates, for a total of 16 hybridizations performed using two Illumina Mouse Ref-8 v1.1 chips.

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The interaction of streptokinase.plasminogen activator complex, tissue-type plasminogen activator, urokinase and their acylated derivatives with fibrin and cyanogen bromide digest of fibrinogen. Relationship to fibrinolytic potency in vitro.

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