Comparative Fibrinolytic Properties of Staphylokinase and Streptokinase in Animal Models of Venous Thrombosis

The thrombolytic and pharmacokinetic properties of staphylokinase were compared with those of streptokinase in hamsters with a pulmonary embolus produced from human plasma or from hamster plasma, and in rabbits with a jugular vein blood clot produced from rabbit blood. In both models, a continuous intravenous infusion of staphylokinase and streptokinase over 60 min in hamsters or over 4 h in rabbits, induced dose-dependent progressive clot lysis in the absence of significant systemic activation of the fibrinolytic system. The results of thrombolytic potency (clot lysis at 30 min after the end of the infusion, in percent, versus dose administered, in mg/kg) were fitted with an exponentially transformed sigmoidal function and the maximal percent clot lysis (c), the maximal rate of lysis (z = ¼ac · e b ) and the dose at which the maximal rate of lysis is achieved (b) were determined. In hamsters with a pulmonary embolus produced from human plasma, streptokinase had a somewhat higher thrombolytic potency than staphylokinase, as revealed by a higher z value (2,100 ± 1,100% lysis per mg/kg streptokinase administered versus 1,100 ± 330% lysis per mg/kg for staphylokinase). In hamsters with a pulmonary embolus produced from hamster plasma, staphylokinase had a somewhat higher thrombolytic potency than streptokinase (z = 1,600 ± 440 versus 1,200 ± 370% lysis per mg/kg). Staphylokinase had a higher thrombolytic potency than streptokinase in rabbits, as revealed by a higher z-value (950 ± 350% lysis per mg/kg staphylokinase administered versus 330 ± 39% lysis per mg/kg for streptokinase) and a lower b-value (0.035 ± 0.010 mg/kg staphylokinase versus 0.091 ± 0.008 mg/kg for streptokinase). The plasma clearance following bolus injection of staphylokinase or streptokinase in hamsters or rabbits was comparably rapid (1.1 to 1.4 ml/min in hamsters and 14 to 15 ml/min in rabbits) as a result of a short initial half-life (1.8 to 1.9 min in hamsters and 1.7 to 2.0 min in rabbits). These results in two quantitative rodent models of thrombolysis suggest that staphylokinase is a potent thrombolytic agent with an in vivo thrombolytic potency that is comparable to that of streptokinase. Further investigation of the thrombolytic potential of staphylokinase seems to be warranted.

Plasminogen Activator and Plasminogen Activator Inhibitor Associated with Granulomatous Inflammation: A Study with Murine Leprosy

Plasminogen activator that is associated with the development of hypersensitivity granulomas (gPA) was partially purified from a saline soluble fraction of murine lepromas elicited in “resistant” mice, C57BL/6N. The gPA was shown to consist of two subspecies (23,000 and 48,000 in molecular weight) with essentially identical enzymologic properties. The gPA was found to be a relatively heat stable weakly alkaline serine proteinase with trypsin-like characteristics in the specificity for synthetic substrates and proteinase inhibitors. It showed a high affinity for H- D-Ile-Pro-Arg-pNA (Km = 1.4 × 10-4 M) H-D-Val-Leu-Lys- pNA (Km = 5.2 × 10-4 M), and L-pyroGlu-Gly-Arg-pNA (Km = 9.3 × 10-4 M). The gPA did not demonstrate antigenic cross reaction with urokinase-type or tissue-type plasminogen activator.

Two distinct enzymatic regulators of the gPA were also demonstrated in the saline soluble fraction of the hypersensitivity granulomas. The gPA and its regulation are assumed to be correlated with macrophage activation in the hypersensitivity granulomas

Comparative Study of the Activity of High and Low Molecular Weight Urokinase in the Presence of Fibrin

The fibrinolytic or thrombolytic activity of low molecular weight urokinase (LMW-UK) and high molecular weight urokinase (HMW-UK) is not significantly different when measured in a bovine fibrin plate method, in a circulating plasma system containing a 125I-labelled human fibrin clot, or on 125I-fibrin films in culture plates using normal or α2-antiplasmin depleted human plasma.

In a human fibrin plate method however HMW-UK was found to be more active than LMW-UK. In a purified system on human 125I-fibrin films the activation of native or modified human plasminogen by HMW-UK was also found to be more effective than by LMW-UK.

Using a clot lysis test system we did not observe a different inhibition of LMW-UK and HMW-UK upon incubation in human plasma. This is in contrast with previous reports that HMW-UK is inhibited more rapidly in human plasma than LMW-UK.

In a purified system the inhibition rate of LMW-UK and HMW-UK by α2-antiplasmin is the same (rate constants at 25ΰC of 167 ± 9 M−1s−1 and 171 ± 5 M−1s−1 respectively).

The clinical trials available at present used doses of urokinase which were in excess of those required to obtain a maximal fibrinolytic effect. This might explain why in these trials no difference was observed between the thrombolytic effect of LMW-UK and HMW-UK, while in vitro HMW-UK appeared to be more effective. However, one should always be careful to extrapolate in vitro observations as such to the in vivo situation encountered during thrombolytic therapy.

Low Molecular Weight Trypsin-Plasmin Inhibitors Isolated from Papain Treated Urinary Trypsin Inhibitor

Papain treatment of human urinary trypsin inhibitor (UTI67; mol. wt. 43,000 by SDS-polyacrylamide gel electrophoresis, specific activity 1,897 U/mg protein) produced four new protease inhibitors, which were highly purified by gel chromatography on Sephadex G-100 and isoelectric focusing. The purified inhibitors (UTI26, UTI9-I, UTI9-II, and UTI9-III) were shown to be homogeneous by polyacrylamide disc gel electrophoresis, and had apparent molecular weights of 26,000, 9,000, 9,000, and 9,800, respectively, by sodium dodecyl sulfate gel electrophoresis. During enzymatic degradation of UTI67, the amino acid compositions changed to more basic, and the isoelectric point increased from pH 2.0 (UTI67) to pHs 4.4, 5.2, 6.6, and 8.3 (UTI26, UTI9-I, UTI9-II, and UTI9-III), respectively. Both the parent and degraded inhibitors had anti-plasmin activity as well as antitrypsin and anti-chymotrypsin activities. Much higher anti-plasmin/anti-trypsin and anti-plasmin/anti-chymotrypsin activities were observed in the degraded inhibitors than in the parent UTI67. They competitively inhibited human plasmin with Ki values of 1.13 X 10-7 - 2.12 X 10-6 M (H-D-Val-Leu-Lys-pNA substrate). The reactions were very fast and the active site of the inhibitors to plasmin was thought to be different from that to trypsin or chymotrypsin.

Characterization and Targeting of the Murine α2-Antiplasmin Gene

α2-Antiplasmin (α2-AP) is the main physiological plasmin inhibitor in mammalian plasma. As a first step toward the generation of α2-AP deficient mice, the murine α2-AP 1 gene was characterized and a targeting vector for homologous recombination in embryonic stem (ES) cells constructed. Alignment of nucleotide sequences obtained from genomic subclones allowed location of exons 2 through 10 of the α2-AP 1gene, but failed to identify the 5’ boundary of exon 1. Compared to the human gene, exons 2 through 9 in the murine gene have identical size and intron-exon boundaries obeying the GT/AG rule. The 5’ boundary of exon 10 is identical in both genes while the 3’ non-coding region is 64 bp longer in the human gene. Introns 2,3,6 and 8 have similar sizes in the mouse and human genes; intron 1 is 6-fold smaller, introns 5, 7 and 9 are 2- to 3-fold smaller, whereas intron 4 is about 2-fold larger in the mouse gene. Compared to the human 5’ flanking sequence, an insertion of a simple repeat region with sequence (TGG)n has occurred. The open reading frame of the mouse α2-AP gene encodes a 491-amino acid protein comprising the experimentally determined NH2-terminus of the mature protein Val-Asp-Leu-Pro-Gly-.

A targeting vector, ppPNT.α2-AP, was constructed by introducing a homologous sequence of 8.3 kb in total in the parental pPNT vector. In pPNT.α2-AP, the neomycin resistance expression cassette replaces a 7 kb genomic fragment comprising exon 2 through part of exon 10 (including the stop codon), which represents the entire sequence encoding the mature protein, including the fibrin-binding domain, the reactive site peptide bond and the plasmin(ogen)-binding region. Electroporation of 129R1 embryonic stem (ES) cells with the linearized vector pPNT.α2-AP yielded three targeted clones with correct homologous recombination at the 5’- and 3’-ends, as confirmed by Southern blot analysis of purified genomic DNA with appropriate restriction enzymes and probes. These targeted clones will be used to generate α2-AP deficient mice.

Comparison of the Relative Fibrinogenolytic, Fibrinolytic and Thrombolytic Properties of Tissue Plasminogen Activator and Urokinase in Vitro

The relative fibrinogenolytic, fibrinolytic and thrombolytic properties of human tissue plasminogen activator and human urokinase were compared in purified systems, in whole human plasma and in a system composed of a radioactive human blood clot (¹²⁵I-fibrinogen) hanging in circulating human plasma. The human tissue plasminogen activator was highly purified from the culture fluid of a human melanoma cell line.

In purified systems composed of fibrinogen or fibrin, plasminogen and α₂-antiplasmin as well as in whole plasma, tissue plasminogen activator digested fibrin without degrading fibrinogen significantly. Urokinase did not have this specific fibrinolytic effect.

In the circulating plasma system, the degree of fibrinolysis was proportional to the amount of activator added, tissue plasminogen activator being about 10 times more efficient than urokinase. In addition, tissue plasminogen activator appeared to cause negligible fibrinogen degradation. Tissue plasminogen activator still induced significant thrombolysis at a concentration of 10 IU per ml whereas no effect of urokinase was observed at 20 IU per ml. Infusion of 100 IU (1 (μg) of tissue plasminogen activator per ml resulted in moderate activation of the fibrinolytic system as judged from a decrease of plasminogen and α₂-antiplasmin to 40-50 percent. Nevertheless, extensive fibrinolysis (50 to 80 percent of radioactivity released after 12 hrs) and only very limited fibrinogenolysis were observed. An equivalent amount of urokinase (100 IU per ml) only induced approximately 15 percent lysis in 12 hrs. At higher concentrations of urokinase (260 IU per ml or more) extensive activation of the fibrinolytic system was obtained as evidenced by a depletion of plasminogen, α₂-antiplasmin and fibrinogen. This was associated with extensive fibrinolysis (approximately 60 percent after 12 hrs). It is concluded that human tissue plasminogen activator is a more specific and effective fibrinolytic-thrombolytic agent than human urokinase.

Hypofibrinolytic Activity after Total Joint Replacement

Tissue-type plasminogen activator (t-PA), tissue-type plasminogen activator inhibitor (t-PAI), and other factors (platelets, fibrinogen, fibrinogen degrada tion products, antithrombin-III, plasminogen, and α2-plasmin inhibitor [α2-PI]) related to the fibrinolytic system were studied in 21 patients undergoing total joint replacement.

Seventeen of the 21 patients revealed an impaired fibrinolytic activity from the first to seventh postoperative day and a subsequent return to the preopera tive level by the fourteenth postoperative day. There were accompanying increases in the level of α2-PI and in the t-PAI/t-PA ratio, and there was decrease in plas minogen level. Such hypofibrinolytic states may be related to a higher incidence of postoperative thrombosis in total joint replacement patients.

Urokinase-type plasminogen activator and plasminogen mediate activation of macrophage phagocytosis during liver repair in vivo

Urokinase-type plasminogen activator (u-PA) and plasminogen play a primary role in liver repair through the accumulation of macrophages and alteration of their phenotype. However, it is still unclear whether u-PA and plasminogen mediate the activation of macrophage phagocytosis during liver repair. Herein, we investigated the morphological changes in macrophages that accumulated at the edge of damaged tissue induced by a photochemical reaction or hepatic ischaemia-reperfusion in mice with u-PA ( u-PA-/- ) or plasminogen ( Plg-/- ) gene deficiency by using transmission electron and fluorescence microscopy. In wild-type mice, the macrophages aligned at the edge of the damaged tissue and extended a large number of long pseudopodia. These macrophages clearly engulfed cellular debris and showed well-developed organelles, including lysosome-like vacuoles, nuclei, and Golgi complexes. In wild-type mice, the distribution of the Golgi complex in these macrophages was biased towards the direction of the damaged tissue, indicating the extension of their pseudopodia in this direction. Conversely, in u-PA-/- and Plg-/- mice, the macrophages located at the edge of the damaged tissue had few pseudopodia and less developed organelles. The Golgi complex was randomly distributed in these macrophages in u-PA-/- mice. Furthermore, interferon γ and IL-4 were expressed at a low level at the border region of the damaged tissue in u-PA-/- mice. Our data provide novel evidence that u-PA and plasminogen are essential for the phagocytosis of cellular debris by macrophages during liver repair. Furthermore, u-PA plays a critical role in the induction of macrophage polarity by affecting the microenvironment at the edge of damaged tissue.

A synthetic peptide derived from staphylokinase enhances plasminogen activation by tissue-type plasminogen activator

BACKGROUND

A synthetic nonadecapeptide (SP; GPYLMVNVTGVDGKGNELL) previously enhanced the activation of plasminogen by the SAK/plasmin complex.

OBJECTIVES

To identify the binding site for SP on plasminogen and elucidate the effects of SP on plasminogen activation by the tissue-type plasminogen activator (t-PA).

METHODS

The effects of SP on plasminogen activation were estimated using a chromogenic substrate and from the cleavage of plasmin on SDS-PAGE under reduced conditions. The binding to SP of various peptides derived from the amino acid sequence of plasminogen was analyzed with an IAsys biosensor. The SP-mediated structural change to plasminogen was analyzed by circular dichroism (CD) spectroscopy. The thrombolytic effects of SP were examined using a mouse model of thrombosis.

RESULTS

SP enhanced the activation of plasminogen by t-PA. The catalytic efficiency (k(cat)/K(m)) of Glu-plasminogen activation by t-PA was 11.4-fold higher in the presence than absence of SP. The binding of SP to plasminogen was greatly inhibited by a synthetic peptide, FEKDKYILQGVTSWGLG, located close to the C-terminal of the plasminogen B region. Near-ultraviolet CD spectra of the complex between SP and Glu-plasminogen significantly differed from those of Glu-plasminogen. When SP was administered in a mouse model of thrombosis, early recanalization was observed in a dose-dependent manner. However, SP did not cause recanalization in t-PA gene-deficient mice.

CONCLUSIONS

SP bound to the B region and promoted the activation of plasminogen by t-PA, and then induced effective thrombolysis.

Urokinase-type plasminogen activator contributes to heterogeneity of macrophages at the border of damaged site during liver repair in mice

Urokinase-type plasminogen activator (u-PA) plays an important role in tissue remodelling through the activation of plasminogen in the liver, but its mechanisms are less well known. Here, we investigated the involvement of u-PA in the accumulation and phenotypic heterogeneity of macrophages at the damaged site during liver repair. After induction of liver injury by photochemical reaction in mice, the subsequent pathological responses and expression of phenotypic markers in activated macrophages were analysed histologically. Fibrinolytic activity at the damaged site was also examined by fibrin zymography. In wild-type mice, the extent of damage decreased gradually until day 14 and was associated with an accumulation of macrophages at the border of the damaged site. In addition, the macrophages that accumulated near the damaged tissue expressed CD206, a marker of highly phagocytic macrophages, on day 7. Further, macrophages that were adjacent to CD206-positive cells expressed inducible nitric oxide synthase (iNOS), a pro-inflammatory marker. u-PA activity increased at the damaged site on days 4 and 7, which distributed primarily at the border region. In contrast, in u-PA-deficient mice, the decrease in damage size and the accumulation of macrophages were impaired. Further, neither CD206 nor iNOS was expressed in the macrophages that accumulated at the border region in u-PA-deficient mice. Mice deficient for the gene encoding either u-PA receptor (u-PAR) or tissue-type plasminogen activator experienced normal recovery during liver repair. These data indicate that u-PA mediates the accumulation of macrophages and their phenotypic heterogeneity at the border of damaged sites through u-PAR-independent mechanisms.

Plasminogen is essential for granulation tissue formation during the recovery process after liver injury in mice

SUMMARY BACKGROUND

The involvement of plasminogen in liver repair has been reported, but its exact role in promoting this process is unknown.

OBJECTIVE

To elucidate the underlying mechanism, we examined the dynamics of liver repair by using a reproducible liver injury model in plasminogen gene-deficient mice and their wild-type littermates.

METHODS

Liver injury was induced by photochemical reaction and the subsequent responses were histologically analyzed.

RESULTS

In wild-type animals, the area of the damage successively decreased, and the repair process was associated with macrophage accumulation at its border. Neutrophils were also attracted to the damaged region on day 1 and were evident only at its border by day 4, which spatially and temporally coincided with the expression of macrophage chemoattractant protein-1 (MCP-1). Neutrophil depletion suppressed recruitment of macrophages at the border between the damaged and the normal tissues. These changes were followed by activated hepatic stellate cell accumulation, collagen fiber deposition and angiogenesis at the boundaries of the injured zone. In contrast, in plasminogen gene-deficient mice, the decrease in the area of damage, macrophage accumulation, late-phase neutrophil recruitment, hepatic stellate cell accumulation, collagen fiber deposition and angiogenesis were all impaired.

CONCLUSION

Our data suggest that accumulated neutrophils at the border of the damaged area may contribute to macrophage accumulation at granulation tissue via the production of MCP-1 after liver injury. The plasminogen system is critical for liver repair by facilitating macrophage accumulation and triggering a cascade of subsequent repair events.

Alpha2-antiplasmin is involved in the production of transforming growth factor beta1 and fibrosis

BACKGROUND

Fibrotic disease occurs in most tissues. Transforming growth factor (TGF)-beta is the major inducer of fibrosis. The fibrinolytic system is considered to play an important role in the degradation of extracellular matrices. However, the detailed mechanism of how this system affects fibrosis remains unclear.

METHODS AND RESULTS

We examined experimental fibrosis in mice with a deficiency of alpha(2)-antiplasmin (alpha2AP), which is a potent and specific plasmin inhibitor. We found that the lack of alpha2AP attenuated bleomycin-induced TGF-beta(1) synthesis and fibrosis. In addition, the production of TGF-beta(1) from the explanted fibroblasts of alpha2AP(-/-) mice decreased dramatically as compared to that in wild-type mice. Moreover, we found that alpha2AP specifically induces the production of TGF-beta(1) in fibroblasts.

CONCLUSION

The lack of alpha2AP attenuated TGF-beta(1) synthesis, thereby resulting in attenuated fibrosis. This is the first report to describe the crucial role that alpha2AP plays in TGF-beta(1) synthesis during the process of fibrosis. Our results provide new insights into the role of alpha2AP in fibrosis.

A guide to murine fibrinolytic factor structure, function, assays, and genetic alterations

The components and functions of the murine fibrinolytic system are quite similar to those of humans. Because of these similarities and the adaptability of mice to genetic manipulation, murine fibrinolysis has been studied extensively. These studies have yielded important information regarding the function of the several components of fibrinolysis. This review presents information on the structure, function and assay of mouse fibrinolytic parameters and it discusses the results of the extensive studies of genetically modified mice. It is intended to be a convenient reference resource for investigators of fibrinolysis.

Lack of alpha2-antiplasmin improves cutaneous wound healing via over-released vascular endothelial growth factor-induced angiogenesis in wound lesions

BACKGROUND

The fibrinolytic system is supposed to play an important role in the degradation of extracellular matrices for physiological and pathological tissue remodeling; however, the detailed mechanism regarding how this system affects cutaneous wound healing remains to be clarified.

METHODS AND RESULTS

We performed experimental cutaneous wounding in mice with a deficiency of alpha(2)-antiplasmin (alpha(2)AP), which is a potent and specific plasmin inhibitor. We found that an accelerated wound closure was observed in alpha(2)AP-deficient (alpha(2)AP-/-) mice in comparison with wild type (WT) mice. Moreover, we observed that a greater increase of angiogenesis occurred in the process of wound healing in alpha(2)AP-/- mice than in the WT mice. Intriguingly, mRNA expression of vascular endothelial growth factor (VEGF), which is the best characterized positive regulator of angiogenesis, in wound lesions was found to show a greater increase in the early phase of the healing process in alpha(2)AP-/- mice than in WT mice. In addition, the amount of released-VEGF from the explanted fibroblasts of alpha(2)AP-/- mice increased dramatically more than in the WT mice. Finally, the intra-jugular administration of anti-VEGF antibody clearly suppressed the increased angiogenesis and accelerated wound closure in the wound lesion of alpha(2)AP-/- mice.

CONCLUSION

The lack of alpha(2)AP markedly causes an over-release of VEGF from the fibroblasts in cutaneous wound lesions, thereby inducing angiogenesis around the area, and thus resulting in an accelerated-wound closure.

CONCLUSIONS

This is the first report to describe the crucial role that alpha(2)AP plays following angiogenesis in the process of wound healing. Our results provide new insight into the role of alpha(2)AP on cutaneous wound healing.

Alpha2-antiplasmin plays a significant role in acute pulmonary embolism

The importance of pulmonary embolism (PE) due to venous thrombosis is recognized in the treatment of vascular diseases. We have investigated the physiological effects of plasmin generation in experimental acute PE using mice deficient in plasminogen (Plg-/-) or alpha2-antiplasmin (alpha2-AP-/-). PE was induced by continuous induction of venous thrombus in the left jugular vein by endothelial injury due to photochemical reaction. The mortality of wild-type mice was 68.8% at 2 h after the initiation of venous thrombosis and it was significantly reduced in alpha2-AP-/- mice (41.7%). In contrast, Plg-/- mice did not survive. Histological evidence of thromboembolism in the lung was obtained in all mice. However, whereas a strict thromboembolism was observed in Plg-/- mice, only a few thrombi were detected in the lungs of alpha2-AP-/- mice. Plasma fibrinogen levels measured in mice were not different. When alpha2-AP was infused in alpha2-AP-/- mice, the mortality was indistinguishable from wild-type mice. Tissue-type plasminogen activator (tPA) did not reduce the mortality due to acute PE in wild-type mice. However, in alpha2-AP-/- mice, tPA (0.52 mg x kg-1) significantly decreased the mortality compared with that of alpha2-AP-/- mice without tPA. The bleeding time was not significantly prolonged in either type of mice treated with tPA. The lack of plasminogen increases the mortality due to acute PE while a lack of alpha2-AP decreases the mortality rate, which can be further reduced by tPA administration. Therefore, the combination of inhibition of alpha2-AP with thrombolytic therapy could be beneficial in the treatment of acute PE.

Mechanism of retarded liver regeneration in plasminogen activator-deficient mice: impaired activation of hepatocyte growth factor after Fas-mediated massive hepatic apoptosis

Urokinase-type plasminogen activator (uPA) is implicated in the regulation of hepatic regeneration by activating hepatocyte growth factor (HGF). Here, we investigated its role in the hepatic regeneration after Fas-mediated massive hepatocyte death employing mice deficient in either uPA or its inhibitor, plasminogen activator inhibitor-1 (PAI-1). We measured kinetics of hepatic levels of proliferating cell nuclear antigen (PCNA)-labeling index, plasmin activity, mature HGF, and its phosphorylated receptor, c-Met. In the genetically targeted and wild-type mice, hepatocytes fell into the same extent of apoptosis 6 to 12 hours after an intraperitoneal injection with anti-Fas antibody, as judged from histologic analysis and a histon-DNA enzyme-linked immunosorbent assay (ELISA). In the wild-type mice, mature HGF emerged in the liver 6 hours following anti-Fas injection, and hepatic PCNA-labeling index started to increase following 24 hours and peaked at 48 hours. In the uPA(-/-) mice, emergence of mature HGF was delayed 12 hours and hepatic regeneration peaked at 96 hours. Supplementation with the uPA gene to the uPA(-/-) mice by in vivo lipofection restored hepatic plasmin levels, and improved a delay in the expression of both mature HGF and phosphorylated c-Met, accompanying a normal rate of liver regeneration. In contrast, PAI-1(-/-) mice showed accelerated liver regeneration; mature HGF emerged as early as 3 hours, and PCNA-labeling index increased at 24 hours. This accelerated regeneration was abolished by administration with anti-HGF antibody. These results strongly suggest a physiologic role of uPA in the proteolytic maturation of HGF, and thereby in hepatic regeneration after Fas-mediated massive hepatocyte death.

Roles of urokinase type plasminogen activator in a brain stab wound

Urokinase type plasminogen activator (uPA) may influence brain pathophysiology after injury. We studied disruption of the blood-brain barrier (BBB) and changes in the vasculature after a brain stab wound in uPA-deficient, uPA receptor-deficient, and PA inhibitor-1 (PAI-1) deficient mice. The extravasation of immunoglobulin was greater in PAI-1 deficient mice; less pronounced in uPA-deficient mice; similar to controls in uPA receptor-deficient mice. Vasculatures in the wound proliferated in PAI-1 deficient mice. Our study shows that uPA affects BBB disruption. PA enhances angiogenesis after brain injury.

tPA, but not uPA, significantly affects antithrombotic therapy by a glycoprotein IIb/IIIa antagonist, but not by a factor Xa inhibitor

To define the interaction of fibrinolytic components with platelets or coagulation factors on thrombus formation, we investigated mouse deficient in tissue plasminogen activator (tPA -/-) or urokinase plasminogen activator (uPA -/-) and in their wild-type control (tPA +/+, uPA +/+). A thrombus was induced in the murine carotid artery using photochemical reaction. Blood flow was monitored and the time needed before the vessel became completely obstructed was within 12 min in all types of mice. When DX-9065a, a selective factor Xa inhibitor, or GR144053, a platelet glycoprotein (GP) complex IIb/IIIa antagonist was applied, the time required to occlusion was prolonged in a dose-dependent manner in all types of mice. When a factor Xa inhibitor was injected in tPA -/- mice, the estimated ED50 was not changed. However, when GR144053 was injected in tPA -/- mice, the most significant changes were observed: the estimated ED51 was 19.6 times higher than the one in tPA +/+ mice. Platelet aggregation, hemostasis tests, and bleeding times were not significantly different among the different types of mice. In conclusion, the antithrombotic effect of platelet inhibition by a GPIIb/IIIa antagonist, is severely affected by the absence or presence of tPA production. On the contrary, the inhibition of factor Xa shows a stable antithrombotic effect with or without tPA. Thus the lack of tPA, but not of uPA, significantly affects antithrombotic efficacy.

The effect of argatroban on injured endothelial cells by thrombin

When endothelial cells are exposed to thrombin, they become perturbed and acquire thrombogenic properties. Argatroban is an arginine derivative, synthetic small molecule that binds to the active site of thrombin and inhibits its catalytic activity. Therefore, the effects of argatroban on endothelial cells, which had been injured by thrombin, were investigated. The established endothelial cell line, TKM-33, which had been cloned from human umbilical vein endothelial cells, was used. Endothelial cells produce plasminogen activator (PA) to prevent thrombosis and maintain the blood flow. When the endothelial cells were injured by thrombin, secretion of plasminogen activator inhibitor-1 (PAI-1) increased and then the PA activity proportionally decreased. The treatment of endothelial cells with argatroban after thrombin injury did not restore their reduced PA activity. However, the treatment of endothelial cells with argatroban prior to thrombin injury resulted in inhibiting the induction of PAI-1 secretion. Thus, pretreatment of endothelial cells with argatroban suppresses the inhibition of their PA activity by thrombin. Since the effect of thrombolytic agent may be modified by the fibrinolytic factors produced by the endothelial cells, the activity of staphylokinase (SAK) was measured in the presence of endothelial cells that had been injured by thrombin. SAK is a newly developed thrombolytic agent. SAK activity in the presence of injured endothelial cells by thrombin was lower than that in the presence of endothelial cells without thrombin injury. However, treatment of endothelial cells with argatroban prior to thrombin injury revealed higher SAK activity than that after thrombin injury. These findings indicate that argatroban pretreatment prevents thrombin injury of endothelial cells, which may then maintain their physiological function.

Analysis of plasminogen activation by the plasmin-staphylokinase complex in plasma of alpha2-antiplasmin-deficient mice

Staphylokinase (SAK) expresses plasminogen activator (PA) activity by forming a complex with plasmin; this PA activity is inhibited by alpha2-antiplasmin (alpha2-AP) in plasma. However, SAK's activity is protected against inhibition by alpha2-AP in the presence of fibrin because the plasmin-SAK complex binds to fibrin. In the present study, the interaction between SAK and murine plasminogen was investigated in the plasma of alpha2-AP-deficient (alpha2-AP-/-) mice or plasminogen-deficient (Plg-/-) mice. Although the human plasmin-SAK complex was formed in equimolar mixtures of plasmin and SAK, the murine plasmin-SAK complex was not formed. Human plasminogen was activated by the human plasmin-SAK complex, although equimolar mixtures of murine plasmin and SAK did not activate murine plasminogen. These findings suggest that SAK does not react with murine plasmin. However, the murine plasminogen was activated by the human plasmin-SAK complex, although this activation was approximately 100-fold weaker than human plasminogen. Human and wild-type mouse plasminogens were not activated by the human plasmin-SAK complex in their plasma. In alpha2-AP-/- mouse plasma, murine plasminogen was activated by the human plasmin-SAK complex. Human or murine plasminogen, which had been added to Plg-/- mouse plasma, was not activated by the human plasmin-SAK complex. However, plasma clot lysis by the human plasmin-SAK complex was observed in both human and murine plasma. These findings indicate that: (1) murine plasmin does not react with SAK, (2) human plasmin-SAK complex activates murine plasminogen, (3) this activation is inhibited by murine alpha2-AP, but (4) this activation is not inhibited by murine alpha2-AP in the presence of fibrin.

Antithrombotic regulation in human endothelial cells by fibrinolytic factors

Vascular endothelial cells (ECs) modulate the blood fibrinolytic system by secreting tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and their inhibitor, type-1 plasminogen activator inhibitor (PAI-1). ECs also express t-PA receptors (t-PAR) and u-PA receptors (u-PAR) on their cell surfaces, assembling both enzymes to regulate the cellular fibrinolytic activity. In addition, ECs modulate these factors in response to several stimuli. Fibrin clots on ECs induce the up- and downregulation of t-PA and PAI-1 production, respectively, thus causing an effective lysis of the fibrin clot. Heat shock (43 degrees C) increases the expression of u-PA, t-PA, PAI-1, and u-PAR by which ECs become more fibrinolytic around the cells. Furthermore, because ECs possess t-PAR and u-PAR on their cell surfaces, the binding of t-PA and u-PA is a critical event, which affords ECs the localized and condensed fibrinolytic potential. Therefore, ECs play a central role in antithrombotic activity by regulating the levels of these fibrinolytic factors.

Binding of mutant tissue-type plasminogen activators to human endothelial cells and their extracellular matrix

We previously demonstrated that tissue-type plasminogen activator (t-PA) specifically bound to its receptor (t-PAR) on human umbilical vein endothelial cells (HUVEC). In addition to analyses of t-PA binding to plasminogen activator inhibitor-1 (PAI-1) in the extracellular matrix (ECM) and to the t-PAR, we further evaluated the binding of three t-PA mutants, deltaFE1X t-PA lacking finger (F), epidermal growth factor-like (E) domains and one sugar chain at Asn177 thus comprising two kringles (K1 and K2) and protease (P) domains, deltaFE3X t-PA with three glycosylation sites deleted at Asn117, 184, and 448, and deltaFEK1 t-PA comprising K2 and P domains without glycosylation. Wild-type t-PA bound to ECM with high affinity, which was completely blocked by anti-PAI-1 IgG. Wild-type t-PA, deltaFE1X t-PA and deltaFEK1 t-PA bound to two classes of binding sites with high and low affinities on monolayer HUVEC. However, all t-PAs bound to a single class of binding site in the presence of anti-PAI-1 IgG. DeltaFEK1 t-PA bound t-PAR maximally among these t-PAs. These results suggested that the high affinity binding of t-PA mainly occurred with PAI-1 on ECM while the low affinity binding was with t-PAR. The deletion of F, E domains and sugar chains had no effect on binding with t-PAR. However, since only K1-missing t-PA (deltaFEK1) exhibited significantly increased binding sites among these t-PAs, it was suggested that the binding to t-PAR was mediated mainly by K2 domain and that the increase of binding was due to direct exposure of K2 domain.

Effect of hyperthermia on the viability and the fibrinolytic potential of human cancer cell lines

The effects of heat treatment on the viability and fibrinolytic potential of four cultured human carcinoma cell lines, fibrosarcoma cells (HT-1080), lung adenocarcinoma cells with highly metastatic potential (HAL-8), melanoma cells (Bowes) and osteosarcoma cells (NY), determined by measuring their levels of urokinase-type plasminogen activator (u-PA) and its specific receptor (u-PAR), were investigated by comparing them with those of human umbilical vein endothelial cells (HUVECs). HUVECs incubated at 43 degrees C for 120 min exhibited no decrease in viability but exhibited an increase in both u-PA and u-PAR. HT-1080 and HAL-8 showed a moderately high heat-resistance (viability, 60-90%) that correlated with the reduction of u-PAR but not u-PA. On the other hand, Bowes and NY cells, with poor heat-resistance (viability, 20-50%), exhibited stronger cell-associated u-PA activity when they survived at 43 degrees C for 120 min. Since the u-PA/u-PAR system is directly involved in the invasiveness and metastatic potential of carcinoma cells, hyperthermia would alter the biological activity of these carcinoma cells.

Lack of tPA significantly affects antithrombotic therapy by a GPIIb/IIIa antagonist, but not by a thrombin inhibitor in mice

The interaction of fibrinolytic components with platelets or coagulation factors after endothelial injury, was investigated in mouse deficient in tissue type plasminogen activator (tPA -/-), or urokinase (uPA -/-) and in their wild type control (tPA +/+, uPA +/+). A thrombus was induced in the murine carotid artery using the photochemical reaction. Blood flow was continuously monitored and the time needed before the vessel became completely obstructed was within 11 min in all types of mice. When GR144053, a platelet glycoprotein IIb/IIIa antagonist, or argatroban, a thrombin inhibitor, was applied, the time required to occlusion was prolonged in a dose-dependent manner in all types of mice. However, when GR144053 was injected in tPA -/- mice, the most significant changes were observed: that is the estimated ED50 was 14.8 times higher than the one in tPA +/+ mice. On the other hand, when argatroban was injected in tPA -/- mice, the estimated ED50 was not changed. Platelet aggregation, haemostasis tests and bleeding times were not significantly different among the different types of mice. In conclusion, the antithrombotic effect of platelet inhibition by a GPIIb/IIIa antagonist, is severely affected by the absence or presence of tPA-production. Thus, the lack of tPA significantly reduces the antithrombotic efficacy.

A peptide mimic of E-selectin ligand inhibits sialyl Lewis X-dependent lung colonization of tumor cells

Selectins bind to carbohydrate ligands in a calcium-dependent manner and play critical roles in host defense and possibly in tumor metastasis. To isolate peptides that mimic E-selectin ligands, we screened a phage peptide library using E-selectin as a target molecule. This attempt unexpectedly failed, probably because the binding affinity of E-selectin to its ligand is low. We then took an approach that is analogous to the isolation of anti-idiotype antibodies and were able to isolate peptides that bound to anticarbohydrate antibodies recognizing E-selectin ligands. These peptides, enriched for their binding to anti-Lewis A antibody, were found to bind to E-, P- and L-selectins in a calcium-dependent manner. Phage harboring the identified peptide IELLQAR and synthetic peptides having the same sequence inhibited the binding of sialyl Lewis X or sialyl Lewis A oligosaccharides to E-selectin. The adhesion of HL-60 and B16 melanoma cells expressing sialyl Lewis X to E-selectin was also inhibited by the phage-displaying IELLQAR peptide. Moreover, i.v. injected IELLQAR peptide inhibited the lung colonization of mouse B16 melanoma and human lung tumor cells expressing sialyl Lewis X. These results demonstrate that it is possible to isolate peptides mimicking carbohydrate ligands by screening the peptides for binding to anticarbohydrate antibodies and then using them to inhibit carbohydrate-dependent experimental tumor metastasis.

Nigral degeneration following striato-pallidal lesion in tissue type plasminogen activator deficient mice

Tissue type plasminogen activator (tPA) has been suggested as a key factor in excitotoxic neuronal death in the hippocampus. Transneuronal degeneration of the substantia nigra pars reticulata (SNR) neurons after striato-pallidal lesions is attributable to excess excitatory glutamatergic inputs into the SNR following inhibitory GABAergic deafferentation and tPA may contribute to the mechanism of transneuronal degeneration of the SNR. To examine this possibility, we studied pathological changes in the SNR following striato-pallidal lesions produced by electrocoagulation in tPA-deficient mice. There was no difference in the degree of SNR degeneration, or in microglial activation and proliferation in the degenerating SNR of tPA-deficient and control mice. Our results indicate that tPA does not contribute to transneuronal degeneration in the SNR following striato-pallidal lesions in mice.

Differential role of components of the fibrinolytic system in the formation and removal of thrombus induced by endothelial injury

The role of fibrinolytic system components in thrombus formation and removal in vivo was investigated in groups of six mice deficient in urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), or plasminogen activator inhibitor-1 (PAI-1) (u-PA-/-, t-PA-/- or PAI-1-/-, respectively) or of their wild type controls (u-PA+/+, t-PA+/+ or PAI-1+/+). Thrombus was induced in the murine carotid artery by endothelial injury using the photochemical reaction between rose bengal and green light (540 nm). Blood flow was continuously monitored for 90 min on day 0 and for 20 min on days 1, 2 and 3. The times to occlusion after the initiation of endothelial injury in u-PA+/+, t-PA+/+ or PAI-1+/+ mice were 9.4+/-1.3, 9.8+/-1.1 or 9.7+/-1.6 min, respectively. u-PA-/- and t-PA-/- mice were indistinguishable from controls, whereas that of PAI-1-/- mice were significantly prolonged (1 8.4+/-3.7 min). Occlusion persisted for the initial 90 min observation period in 10 of 18 wild type mice and was followed by cyclic reflow and reocclusion in the remaining 8 mice. At day 1, persistent occlusion was observed in 1 wild type mouse, 8 mice had cyclic reflow and reocclusion and 9 mice had persistent reflow. At day 2, all injured arteries had persistent reflow. Persistent occlusion for 90 min on day 0 was observed in 3 u-PA-/-, in all t-PA-/- mice at day 1 and in 2 of the t-PA-/-mice at day 2 (p <0.01 versus wild type mice). Persistent patency was observed in all PAI-1-/- mice at day 1 and in 5 of the 6 u-PA-/- mice at day 2 (both p <0.05 versus wild type mice). In conclusion, t-PA increases the rate of clot lysis after endothelial injury, PAI-1 reduces the time to occlusion and delays clot lysis, whereas u-PA has little effect on thrombus formation and spontaneous lysis.

Alpha2-antiplasmin gene deficiency in mice is associated with enhanced fibrinolytic potential without overt bleeding

alpha2-antiplasmin (alpha2-AP) is the main physiologic plasmin inhibitor in mammalian plasma. Inactivation of the murine alpha2-AP gene was achieved by replacing, through homologous recombination in embryonic stem cells, a 7-kb genomic sequence encoding the entire murine protein (exon 2 through part of exon 10, including the stop codon) with the neomycin resistance expression cassette. Germline transmission of the mutated allele was confirmed by Southern blot analysis. Mendelian inheritance of the inactivated alpha2-AP allele was observed, and homozygous deficient (alpha2-AP-/-) mice displayed normal fertility, viability, and development. Reverse transcription-polymerase chain reaction confirmed the absence of alpha2-AP mRNA in kidney and liver from alpha2-AP-/- mice, in contrast to wild-type (alpha2-AP+/+) mice. Immunologic and functional alpha2-AP levels were undetectable in plasma of alpha2-AP-/- mice, and were about half of wild-type in heterozygous littermates (alpha2-AP+/-). Other hemostasis parameters, including plasminogen activator inhibitor-1, plasminogen, fibrinogen, hemoglobin, hematocrit, and blood cell counts were comparable for alpha2-AP+/+, alpha2-AP+/-, and alpha2-AP-/- mice. After amputation of tail or toe tips, bleeding stopped spontaneously in alpha2-AP+/+, as well as in alpha2-AP+/- and alpha2-AP-/- mice. Spontaneous lysis after 4 hours of intravenously injected 125I-fibrin-labeled plasma clots was significantly higher in alpha2-AP-/- than in alpha2-AP+/+ mice when injecting clots prepared from alpha2-AP+/+ plasma (78% +/- 5% v 46% +/- 9%; mean +/- SEM, n = 6 to 7; P =.02) or from alpha2-AP-/- plasma (81% +/- 5% v 46% +/- 5%; mean +/- SEM, n = 5; P =.008). Four to 8 hours after endotoxin injection, fibrin deposition in the kidneys was significantly reduced in alpha2-AP-/- mice, as compared with alpha2-AP+/+ mice (P </=.005). Thus, alpha2-AP-/- mice develop and reproduce normally; they have an enhanced endogenous fibrinolytic capacity without overt bleeding.

Co-localization of urokinase and its receptor on established human umbilical vein endothelial cell

Vascular endothelial cells possess antithrombotic properties, which are determined by the balance between plasminogen activators (PAs) and PA inhibitors (PAls). A cell line, TKM-33, has been established and cloned from human umbilical vein endothelial cells, was previously reported to produce a large amount of urokinase-type PA (u-PA) and small amounts of tissue-type plasminogen activator (t-PA) and PA inhibitor-1 (PAI-1). Moreover, TKM-33 expressed the u-PA receptor (u-PAR) which plays an important role in the localization of fibrinolytic activity on cell surface. In the present study, we investigated the localization of u-PA, t-PA, PAI-1 and u-PAR in TKM-33 by using immunofluorescence staining technique. The endothelial cells were strongly stained with anti-PAI-1, anti-u-PA and anti-u-PAR IgGs, and slightly with anti-t-PA IgG. The double immunofluorescence staining with mouse anti-u-PA IgG and rabbit anti-u-PAR IgG followed by rhodamine-conjugated anti-mouse IgG and FITC-conjugated anti-rabbit IgG showed the co-localization of u-PA and u-PAR on the same section of endothelial cells. Although u-PA antigen also existed in the cytoplasm of endothelial cells, u-PAR antigen did not. The treatment of endothelial cells with phorbol-myristate-acetate (PMA) upregulated the expression of u-PA and u-PAR antigens. In this stimulation, u-PAR antigen was detected not only on the surface of the cells but also in the cytoplasm. Thus, the binding of u-PA to u-PAR was confirmed by double immunofluorescence staining.

Analysis of tissue-type plasminogen activator receptor (t-PAR) in human endothelial cells

Vascular endothelial cells regulate the fibrinolytic system in blood by expressing cell-surface receptors for plasminogen and plasminogen activators (PAs) as well as secreting PAs and their inhibitors. Although several receptors for plasminogen and PAs have been identified in many cell types, little is known about tissue-type PA (t-PA)-specific receptor (t-PAR) on endothelial cells except a few reports. By using suspended human umbilical vein endothelial cells (HUVEC), which are free from the formation of extracellular matrix (ECM)--where type-1 plasminogen activator inhibitor (PAI-1) preferably accumulates and interacts with t-PA with high affinity--we demonstrated a relatively low affinity binding site for t-PA on the cells and identified a novel t-PAR. The isolation and characterization of HUVEC-derived t-PAR was performed in the present study. A 20-kDa t-PAR was successively isolated and purified by high performance liquid chromatography system from HUVEC which specifically binds t-PA and not plasminogen forming a 90-kDa complex with t-PA. When t-PA binds the immobilized t-PAR stoichiometrically 1:1, the enzymatic activity of t-PA was enhanced 90-fold. Thus, it is suggested that the t-PAR may function as a t-PA-enhancing molecule expressed on the surface of endothelial cells.

Transcriptional regulation of urokinase-type plasminogen activator receptor by cyclic AMP in PL-21 human myeloid leukemia cells: comparison with the regulation by phorbol myristate acetate

We investigated the effect of dibutyryl cyclic AMP (Bt2-cAMP) on urokinase-type plasminogen activator receptor (uPAR) expression in human PL-21 myeloid leukemia cells and compared it with the effect of phorbol myristate acetate (PMA). Flow cytometric analysis clearly demonstrated that Bt2-cAMP and PMA both induced the cell surface expression of uPAR. Northern analysis and nuclear run-on assay revealed that cAMP and PMA activated the uPAR gene transcription and both additively increased the uPAR mRNA level. However, actinomycin-D decay experiment showed that PMA, but not cAMP, prolonged the uPAR mRNA half-life. Furthermore, inhibition of the ongoing protein synthesis with cycloheximide abrogated completely the PMA-induced uPAR mRNA accumulation but only partially the induction by PMA plus cAMP, whereas the induction by cAMP alone was rather amplified, indicating that the de novo protein synthesis is necessary in the induction by PMA but not in the induction by cAMP and that the cAMP pathway may be dominant in uPAR gene expression in the PL-21 cells as compared to the PMA pathway. These results suggest that cAMP induces the uPAR expression exclusively through activating the gene transcription in which a preexisting transcriptional factor may be involved, whereas PMA transcriptionally and posttranscriptionally regulates the uPAR gene expression.

Characterization and targeting of the murine alpha2-antiplasmin gene

Alpha2-Antiplasmin (alpha2-AP) is the main physiological plasmin inhibitor in mammalian plasma. As a first step toward the generation of alpha2-AP deficient mice, the murine alpha2-AP gene was characterized and a targeting vector for homologous recombination in embryonic stem (ES) cells constructed. Alignment of nucleotide sequences obtained from genomic subclones allowed location of exons 2 through 10 of the alpha2-AP gene, but failed to identify the 5' boundary of exon 1. Compared to the human gene, exons 2 through 9 in the murine gene have identical size and intron-exon boundaries obeying the GT/AG rule. The 5' boundary of exon 10 is identical in both genes while the 3' non-coding region is 64 bp longer in the human gene. Introns 2, 3, 6 and 8 have similar sizes in the mouse and human genes; intron 1 is 6-fold smaller, introns 5, 7 and 9 are 2- to 3-fold smaller, whereas intron 4 is about 2-fold larger in the mouse gene. Compared to the human 5' flanking sequence, an insertion of a simple repeat region with sequence (TGG)n has occurred. The open reading frame of the mouse alpha2-AP gene encodes a 491-amino-acid protein comprising the experimentally determined NH2-terminus of the mature protein Val-Asp-Leu-Pro-Gly-. A targeting vector, pPNT.alpha2-AP, was constructed by introducing a homologous sequence of 8.3 kb in total in the parental pPNT vector. In pPNT.alpha2-AP, the neomycin resistance expression cassette replaces a 7 kb genomic fragment comprising exon 2 through part of exon 10 (including the stop codon), which represents the entire sequence encoding the mature protein, including the fibrin-binding domain, the reactive site peptide bond and the plasmin(ogen)-binding region. Electroporation of 129R1 embryonic stem (ES) cells with the linearized vector pPNT.alpha2-AP yielded three targeted clones with correct homologous recombination at the 5'- and 3'-ends, as confirmed by Southern blot analysis of purified genomic DNA with appropriate restriction enzymes and probes. These targeted clones will be used to generate alpha2-AP deficient mice.

Enhancement of tissue-type plasminogen activator (t-PA) activity by purified t-PA receptor expressed in human endothelial cells

We demonstrated previously that tissue-type plasminogen activator (t-PA) bound to its specific receptor (t-PAR) on human umbilical vein endothelial cells (HUVEC) in suspension and that t-PAR of mol wt. 20 kDa interacted only with t-PA to form 90 kDa complex (Fukao, H., Hagiya, Y., Nonaka, T., Okada, K., and Matsuo, O. (1992) Biochem. Biophys. Res. Commun. 187, 956-962). In the present study, 20 kDa t-PAR was purified from HUVEC and the function of the t-PAR was investigated by analyzing its effect on plasminogen activation by t-PA. About 2.2 microg t-PAR protein was purified from cell lysate of 1.0 X 10(9) HUVEC as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) by gel filtration with TSK-3000SW and reversed phase separation with high performance liquid chromatography (HPLC). 125I-t-PA but not 125I-plasminogen specifically bound to the purified t-PAR in ligand blot assay. Plasminogen activation by t-PA in the presence of purified t-PAR in solution was increased. Furthermore, t-PA bound to immobilized t-PAR efficiently expressed its plasminogen activation activity. Kinetic analysis revealed that t-PA in the presence of soluble t-PAR and t-PA bound to immobilized t-PAR exhibited 34- and 90-fold increase in plasminogen activation, respectively. The t-PAR did not interact with anti-annexin II antibody. These findings indicate that the 20 kDa t-PAR is a novel molecule which immobilizes t-PA and enhances its proteolytic activity on the cell surface of endothelial cells.

Effects of fibrin and alpha2-antiplasmin on plasminogen activation by staphylokinase

Staphylokinase obtains plasminogen activating activity by forming a complex with plasminogen. Although the enzymatic activity of staphylokinase is enhanced by fibrin, how fibrin enhances enzymatic activity has not been determined yet. The effects of fibrin, or fibrinogen fragments, on the activation of plasminogen by staphylokinase was investigated using CNBr-digested fibrinogen fragments (FCB-2 and FCB-5) and plasmin-degraded cross-linked fibrin fragments ((DD)E complex, DD fragments and E fragments). Kinetic analysis of the activity of staphylokinase revealed that its plasminogen activating activity, which was expressed as kcat/Km, was enhanced by FCB-2 (10-fold) and FCB-5 (5-fold). These fibrin fragments caused 38-, 30-, and 8.5-fold increases in activity for the DD fragment, (DD)E complex and E fragment, respectively. Although alpha2-antiplasmin inhibited the activation of plasminogen by staphylokinase, FCB-2 abolished its inhibitory effects, and the plasminogen activating activity of staphylokinase was restored. The inhibitory effects of alpha2-antiplasmin on the activation of mini-plasminogen by staphylokinase were less than for Glu- or Lys-plasminogen, and the inhibitory effect of alpha2-antiplasmin was not altered by fibrin or EACA. These findings indicate that the staphylokinase/plasmin(ogen) complex reacts with fibrin even in the presence of alpha2-antiplasmin, and efficient plasminogen activation takes place on the surface of fibrin.

Comparative studies of thrombolysis with single-chain and two-chain recombinant tissue-type plasminogen activators in canine coronary thrombosis

Tissue-type plasminogen activator (t-PA) can occur in two different forms, single- and two-chain t-PA. Such a difference in structure of the t-PA molecule may induce different biological functions. We compared the thrombolytic efficacy of single-chain t-PA with that of two-chain t-PA and urokinase in a canine thrombosis model. The thrombolytic properties of single- and two-chain recombinant t-PA and urokinase with equivalent activity in vitro after intravenous infusion were examined in 24 anesthetized, open-chest dogs with intracoronary thrombi. Repeated coronary angiography showed that the time to reperfusion was 29.0 +/- 4.8, 32.5 +/- 6.3, and 39.2 +/- 6.8 min, respectively. One dog in the single-chain t-PA group and all dogs in the vehicle group showed no recanalization. Plasma t-PA antigen reached similar plateau levels within 15. min in both the single- and two-chain t-PA groups. The infusion of single- and two-chain t-PA was not associated with systemic fibrinolytic activation, except for a decrease in alpha 2-plasmin inhibitor in single-chain t-PA. However, the infusion of urokinase was associated with significant depletion of fibrinogen. These findings suggest that single-chain t-PA has potent thrombolytic effect without systemic fibrinolytic activity similar to that of two-chain t-PA in a canine coronary artery thrombosis model.

Enhanced urokinase-type plasminogen activator activity by extracellular matrix protein obtained from highly metastatic human lung adenocarcinoma cell line

A protein which enhanced urokinase-type plasminogen activator (u-PA) activity was purified from the extracts of extracellular matrix of highly metastatic cell line HAL-8 derived from human lung adenocarcinoma. The protein showed a single band with molecular weight of 65 kDa after the purification by Sephadex G-150 and diethylaminoethyl-cellulose followed by reversed phase separation in a high performance liquid chromatography system. The purified protein in the immobilized conditions enhanced u-PA activity in both plasminogen activation and S-2444 amidolysis by 4.6- and 2.8-fold increases in the second order rate constants (Kcat/K(m)), respectively. This protein was related to neither plasminogen nor single-chain u-PA by the immunological studies and with respect to retention time on reversed phase analysis. These results suggest that the purified material acts as an enhancer of u-PA in extracellular matrix of the cancer cells, inducing an effective tissue destruction and cell invasion and possessing a highly metastatic potential.

Effects of endothelial cells on activity of staphylokinase

Staphylokinase (SAK), produced by Staphylococcus aureus, induces fibrinolytic activity in circulation without systemic fibrinolytic activation. Since the effect of blood vessels on the activity of SAK has not yet been clarified, plasminogen activator (PA) activity of SAK in the presence or absence of endothelial cells was analyzed. The endothelial cells used in this experiment were of a cloned established cell line (TKM-33). In the expression of PA activity by SAK or streptokinase (SK), the kinetic constants revealed as Vmax/km were increased about 1.5-fold in the presence of endothelial cells. Furthermore, an initial lag phase which was observed during the plasminogen activation by SAK was markedly shortened in the presence of endothelial cells. In the case of SK, an initial lag phase was not observed in the absence or presence of endothelial cells. Although PA activity of SAK was inhibited by alpha 2-antiplasmin (alpha 2-AP), the inhibitory effect of alpha 2-AP in the presence of endothelial cells was weaker than in the absence of endothelial cells. The cyanogen bromide digested fibrinogen fragment-2 (FCB-2) distinctly enhanced the PA activity of SAK in the absence and the presence of endothelial cells. However, alpha 2-AP and FCB-2 did not cause a significant alteration of PA activity of SK even in the absence or presence of endothelial cells. These findings suggest that PA activity of SAK is enhanced by endothelial cells, but inhibited by alpha 2-AP. Moreover, PA activity of SAK is further enhanced by fibrin clot in the presence of endothelial cells.

Effects of lipopolysaccharide on the expression of fibrinolytic factors in an established cell line from human endothelial cells

Human endothelial cells express antithrombotic properties by producing prostacyclin, heparan sulphate and plasminogen activator (PA). Bacterial extract, such as lipopolysaccharide (LPS), damaged the blood vessels and destroyed the balance between the antithrombotic and thrombotic functions of endothelial cells. The fibrinolytic system is involved in antithrombotic functions. The TKM-33 cell line was established from human endothelial cells. In order to determine whether TKM-33 is a good fibrinolytic system endothelial cell expression model, the expression of fibrinolytic factors in TKM-33 cells treated with or without LPS was studied. The endothelial cells which had not been treated with LPS produced and secreted a large amount of urokinase-type PA (u-PA), and small amounts of tissue-type PA (t-PA) and PA inhibitor-1 (PAI-1), which were identified immunohistochemically and by electrophoretic enzymography. Diisopropylfluorophosphate-treated 125I-u-PA bound specifically to acid-treated monolayered endothelial cells with a Kd of 2.83 +/- 0.61 nM, and Bmax of (0.11 +/- 0.01) x 10(6) sites/cell. u-PAR expression was detected in endothelial cells by Northern blot analysis. Thus, endothelial cells was shown to express u-PAR which binds u-PA specifically. In the binding assay, the stimulation of endothelial cells with 0.1, 1.0 and 10 micrograms/ml of LPS altered the Kd values to 6.04 +/- 0.71, 7.03 +/- 1.55 and 7.38 +/- 1.03 nM, respectively. However the Bmax values did not change significantly. Although LPS treatment increased u-PAR expression in endothelial cells in a dose-dependent manner, the expression of u-PA and t-PA mRNAs was not altered significantly. LPS stimulation (10 micrograms/ml) increased the expression of PAI-1 mRNA, significantly. The PA activity recovered from the cell surface fraction was not affected by LPS stimulation, but the PAI-1 activity was increased. These findings suggest that the established endothelial cell line, TKM-33, possesses the characteristics of endothelial cells and they express u-PAR on their cell surface, which is occupied by intrinsic u-PA secreted from the cells, and that treatment of endothelial cells with LPS changes the cell surface characteristics and inhibited the u-PAR expression thus promoting the prothrombotic function concomitantly with increased PAI-1 activity.