Alpha 2-plasmin Inhibitor Research Articles

Lipoprotein (a) is a substrate for factor XIIIa and tissue transglutaminase.

The mechanisms which mediate deposition of lipoprotein (a) (Lp(a)), an atherogenic lipoprotein particle, onto the vessel wall and cell surfaces are unknown. An irreversible deposition of Lp(a) may require the presence of enzymes that catalyze its binding to surface-oriented structures. Transglutaminases catalyze cross-linking of proteins as well as incorporation of primary amines into protein substrates. We studied whether tissue transglutaminase and/or activated Factor XIII (plasma derived or recombinant FXIIIa) incorporate primary amines into Lp(a). In the presence of Ca2+, Factor XIIIa and tissue transglutaminase catalyze incorporation of monodansylcadaverine or [14C]putrescine into purified Lp(a) in a specific and time-dependent manner. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that monodansylcadaverine became incorporated into the apo(a) portion of Lp(a). Lp(a) purified from five different donors showing different apo(a) phenotypes were substrates for tissue transglutaminases (TG). Western blot analysis confirmed that apo(a) was the major monodansylcadaverine carrying protein moiety of Lp(a). Tissue TG also extensively cross-linked the apo(a) portion of the Lp(a) particle. Characterization of the specificity of tissue TG showed that fibronectin, alpha 2-plasmin inhibitor, and apo(a) could be readily labeled with monodansylcadaverine by tissue TG, but other proteins including low density lipoprotein, IgG, alpha 1-proteinase inhibitor, and albumin showed poor or no reactivity. Direct comparison of Lp(a) with low density lipoprotein showed that apoB 100 was a poor substrate for transglutaminases. Recombinant apolipoprotein (a) proved to be an excellent substrate for TGs in that 1 mol of recombinant apolipoprotein (a) incorporated as much as 15 mol of [14C]putrescine, which corresponded to five times the amount of amine incorporated into Lp(a). The susceptibility of Lp(a) to transglutaminases suggests a mechanism whereby the interaction of Lp(a) with surface receptors and other surface oriented structures could be enzymatically altered.

Extravascular fibrin formation and dissolution in synovial tissue of patients with osteoarthritis and rheumatoid arthritis

Fibrin deposition is a prominent finding in the synovium of patients with rheumatoid arthritis (RA). Macrophages are found in increased numbers in RA synovium, and these cells are known to produce a variety of procoagulant and anticoagulant molecules. Using immunohistologic techniques, the content and distribution of several important components of the coagulation system in the synovium of patients with RA, osteoarthritis (OA), or traumatic joint abnormalities requiring surgery were investigated. Samples from 3 patients from each category were examined in detail. RA synovium (compared with that of patients with OA or joint trauma) had increased numbers of macrophages and increased expression/content of fibrinogen, tissue factor, factor XIII, tissue transglutaminase, cross-linked fibrin (fibrin D dimer), urokinase-type plasminogen activator, and alpha 2-plasmin inhibitor. Macrophage content in RA synovium was increased in both the lining cell areas and the interstitial cell areas. Fibrinogen was distributed throughout the tissue in all samples and was greater in RA synovium. In trauma and OA synovia, tissue factor was seen only in association with vessels (endothelial cells), but in RA synovium, it was markedly increased throughout the tissues. While fibrin D dimer was seen in small amounts in synovial lining cell areas of trauma and OA synovia, it was present in increased amounts in the lining cell and interstitial cell areas of RA synovium. Factor XIII and tissue transglutaminase were present in scant amounts in trauma and OA synovia, but there were increased amounts of both (especially tissue transglutaminase) in RA synovium in the vessel, lining cell, and interstitial cell areas. Urokinase and alpha 2-plasmin inhibitor were also markedly increased in RA synovium. These results suggest that in inflamed synovium, there is ongoing extravascular tissue fibrin formation and dissolution that correlates with the degree of inflammation and macrophage content. Extravascular coagulation/fibrinolysis in RA represents a potential target for therapeutic intervention in this disease.

Expression of recombinant human plasminogen in mammalian cells is augmented by suppression of plasmin activity

We present evidence that over-expression of human plasminogen, the precursor to the serine protease plasmin, can be cytotoxic to mammalian cells. When an expression vector containing plasminogen cDNA is transfected into baby hamster kidney cells, the number of drug-resistant colonies as well as the levels of plasminogen secreted by those colonies is lower than observed in similar transfections of other protease precursor genes. The recombinant plasminogen accumulates intracellularly as degraded NH2-terminal fragments. In contrast, a mutant of plasminogen that produces inactive plasmin (active site Ser740 changed to Ala) is synthesized by these cells as a full-length plasminogen molecule, and the colony numbers and expression levels are normal. Thus, the generation of plasmin activity is responsible for the cytotoxic phenomena and the degradation associated with plasminogen expression. In addition, experiments using a plasminogen mutant that cannot be activated to plasmin (activation cleavage site Arg560 to Gly) or using coexpression of antisense urokinase RNA indicate that an endogenous plasminogen activator is responsible for converting newly synthesized plasminogen to plasmin. Finally, coexpression of plasminogen with alpha 2-plasmin inhibitor, a serpin which is the physiologic inhibitor of plasmin, prevents the toxic effects of intracellular plasmin activity and allows the synthesis and secretion of native human plasminogen.

Localization of blood coagulation factors and fibrinolysis factors within lymphoid germinal centers in human lymph nodes

The presence of nineteen blood coagulation factors and fibrinolysis factors was immunohistochemically evaluated in human lymph node germinal centers (GCs). Twelve of these factors were detected within lymphoid GCs. The predominant pattern was dendritic with occasional crescent-shaped, ring-shaped or 'moth-eaten' appearance. Immunostains of factor VIII-related antigen, factor I, protein C, tetranectin, antithrombin III, type 2-plasminogen activator inhibitor, and alpha 2-plasmin inhibitor were almost entirely absent from GCs, although they reacted in vascular wall and lumen, respectively. The immunostaining to high molecular weight kininogen, kallikrein, factors XII, X, V, II, XIIIa, XIIIs, plasminogen, tissue-plasminogen activator, and type 1-plasminogen activator inhibitor more frequently revealed a positive dendritic pattern. Immuno-electron microscopy demonstrated factor X and factor XIIIa attached to the cell surfaces of lymphocytes, macrophages, and follicular dendritic cells (FDCs); and in the intercellular space within GCs, especially attached to the labyrinthine-like structure of FDCs. No reaction products were observed in the perinuclear cisternae and rough endoplasmic reticulum in either lymphocytes or FDCs. Our data demonstrate that human lymphoid GCs really contain some of the proteins related to the blood coagulation and fibrinolysis cascades.

Activation of coagulation in acute cardioembolic stroke.

The hematologic disorders in patients with acute cardioembolic stroke are not fully understood, and no reliable measures are available to identify patients at high risk for recurrent embolism. We analyzed coagulation and fibrinolytic functions in 22 patients with cardiogenic cerebral embolism less than or equal to 24 hours after onset and in 25 age-matched controls. The levels of antithrombin III, protein C, and alpha 2-plasmin inhibitor were significantly lower in the patients than in the controls (p less than 0.001, 0.02, and 0.05, respectively). In contrast, the plasma concentrations of thrombin-antithrombin III complex and crosslinked D-dimer were markedly higher in the patients than in the controls (p less than 0.01 and 0.001, respectively). At the time of admission, the plasma concentrations of thrombin-antithrombin III complex and crosslinked D-dimer in the eight patients at high risk for recurrent embolization (one with prodromal embolism, three with intracardiac thrombi, and four with recurrent embolization) were 2.8 and 3.5 times, respectively, higher than those in the 14 patients without recurrence or thrombus formation. The lowest concentration of crosslinked D-dimer in the eight patients at high risk for recurrent embolization was 600 ng/ml on admission. Our results suggest that patients with acute cardioembolic stroke have various degrees of consumption coagulopathy and that the plasma concentrations of thrombin-antithrombin III complex and crosslinked D-dimer can be useful indicators of those who are prone to recurrent embolization during this stage.

A study on changes of coagulation inhibitors and fibrinolysis inhibitors in patients with liver cirrhosis and hepatoma.

The authors conducted an investigation focusing mainly on the activities of the inhibitory factors of the coagulation and fibrinolysis processes in 35 normal adults and 72 liver cirrhosis and/or hepatoma patients. The activities of antithrombin III, protein C, and alpha 2-plasmin inhibitor were reduced to less than 50% in patients with decreased hepatic synthetic function while lupus anticoagulant was detected in more than 50% of patients with decreased hepatic synthetic function. Hemostatic abnormalities in advanced lived diseases may be caused partly by a decrease of coagulation and fibrinolysis inhibitors and the presence of lupus anticoagulant.

Intramedullary Multiple Hematomas in Siblings with Congenital Alpha-2-Plasmin Inhibitor Deficiency: Orthopedic Surgery with Protection by Tranexamic Acid

Congenital alpha 2-plasmin inhibitor deficiency is very rare, but causes bleeding problems similar to hemophilia. Three young Japanese sisters affected with congenital alpha 2-plasmin inhibitor deficiency have been reported by us earlier. Recently we encountered a particular form of intramedullary multiple hematomas in the long bones in all of them which was not reported previously. In 2 of the sisters orthopedic operations were successfully performed by using an antiplasmin reagent: tranexamic acid. In this paper we describe the characteristics of the hematomas and the hemostatic management with tranexamic acid.

Intravenous recombinant tissue-type plasminogen activator (rt-PA) and urokinase (UK) in patients with evolving myocardial infarction. A multicenter double-blind, randomized trial in Japan.

Intravenous administrations of 2000 x 10(4)IU (33 mg) (rt-PA2) and 3000 x 10(4)IU (50 mg) (rt-PA3) of a new recombinant tissue plasminogen activator (rt-PA:TD-2061) derived from uterine endothelial cells and urokinase (UK) 96 x 10(4)IU were compared in a double blind, randomized trial of 198 patients with evolving myocardial infarction. All patients entered the trial within 6 h of the onset of symptoms and underwent baseline coronary angiography of the infarct-related coronary artery before thrombolytic therapy was instituted. Sixty minutes following thrombolytic therapy occluded infarct-related arteries were successfully reperfused in 41.5% of 66 patients in the UK, 76.4% of 72 patients in the rt-PA2, and 74.6% of 59 patients in the rt-PA3 group. Statistically significant differences were observed between the UK and rt-PA groups (p less than 0.01). Serum fibrinogen levels declined in all 3 groups at 60 min post-therapy by averages of 35.9 +/- 3.1% in the UK, 16.8 +/- 4.8% in the rt-PA2 and 17.5 +/- 4.5% in the rt-PA3 group. The difference between the UK and the rt-PA groups was statistically significant (p less than 0.01). Plasma plasminogen and alpha 2-plasmin inhibitor levels showed the same tendencies. Bleeding was the most commonly observed complication and was most commonly seen at the catheterization site. There was no difference in the incidence among the 3 groups. Hospital deaths occurred in 5.3%, 6.3%, and 4.7% of the cases in the UK, rt-PA2 and rt-PA3 groups, respectively. We conclude, therefore, that rt-PA achieves a significantly higher rate of recanalization with less extensive systemic fibrinogenolysis at the dose employed than does UK. The optimum intravenous dose of rt-PA for Japanese patients is considered to be 2000 x 10(4)IU (33 mg).

Blood Coagulation and Fibrinolysis in SART-Stressed (Repeated Cold-Stressed) Rats and Drug Effects on the Altered Hemostatic Parameters.

Blood coagulation and fibrinolytic activity was studied in SART (specific alternation of rhythm in temperature)-stressed animals found to exhibit thrombocytopenia and prolonged bleeding time, and drug effects on the abnormalities were evaluated. 1) SART-stressed rats revealed prolongation of activated partial thromboplastin and thrombin time, no change in prothrombin time, decreased plasma fibrinogen levels, and shortened euglobulin clot lysis time (ELT). Antithrombin III and alpha 2-plasmin inhibitor activity remained constant following stress exposure. 2) During stress, fibrinogen levels declined from day 5 and remained depressed up to day 14. Reduction in ELT developed in a similar manner to fibrinogen. 3) Decreased fibrinogen levels were prevented by consecutive doses of tranexamic acid, an antifibrinolytic, and Neurotropin, a sedative analgesic. Shortened ELT was counteracted by chronic treatment with Neurotropin and alprazolam, an anxiolytic. Single administrations of the above agents failed to affect either change. These results indicate that SART-stressed animals exhibit suppressed intrinsic coagulability and enhanced fibrinolytic activity, but normal extrinsic coagulability. Considering the previous report together with the above results, the hemostatic system under SART stress tends uniformly toward hemorrhage. Moreover, Neurotropin appears to improve and normalize hemostatic imbalance due to SART stress, a chronic form of stress.

低分子量Ｈｅｐａｒｉｎ（ＦＲ‐８６０）の実験的播種性血管内凝固症候群に対する効果

Effects of low molecular weight heparin (FR-860) on experimental disseminated intravascular coagulation (DIC) models in rats were compared with those of conventional unfractionated heparin (UF-heparin) and other anticoagulants. In the endotoxin-induced DIC model, FR-860 (12.5-200 U/kg/hr) and UF-heparin (25-200 U/kg/hr) inhibited dose-dependently the decreases in platelet counts, fibrinogen, antithrombin III activity and alpha 2-plasmin inhibitor activity, and they also inhibited the increases in fibrin de-products and thrombus formation in the glomerular capillary bed. Neither gabexate mesilate (FOY, 10 mg/kg/hr) nor nafamostat mesilate (FUT, 0.1 mg/kg/hr) improved endotoxin-induced DIC. FR-860 showed comparable potency to UF-heparin in plasma anti-factor Xa (F.Xa) activity. However, FR-860 was weaker than UF-heparin in prolongation of activated partial thromboplastin time. In the thrombin-induced DIC model, both FR-860 and UF-heparin significantly improved, as seen in the endotoxin-induced DIC model, the changes in coagulation and fibrinolytic parameters and suppressed the production of pulmonary thrombus. On the other hand, both FOY and FUT showed significant but weak improvement in this model. In addition, FR-860 inhibited the enhancement of fibrinolysis and the production of pulmonary thrombus in the lactic acid-induced DIC model. These results suggest that the efficacy of FR-860 on DIC in rats is comparable to that of UF-heparin and that the efficacy can be attributed to its anti-F.Xa activity. FR-860 can be expected to be a useful therapeutic drug for DIC.

The induction of a hypercoagulable state by medroxyprogesterone acetate in breast cancer patients

The effects of medroxyprogesterone acetate (MPA) on the mechanism of coagulation in postmenopausal patients were studied and compared with those of tamoxifen by a retrospective analysis. The coagulation test parameters tested included platelet count, bleeding time, clotting time, prothrombin time, activated partial thromboplastin time, and the levels of fibrinogen, fibrin degradation products, factor II, factor V, plasminogen, alpha 2-plasmin inhibitor (alpha 2-PI) and alpha 2-plasmin inhibitor-plasmin complex (alpha 2-PI-P). A shortened APTT was noted and the levels of factors II, V, alpha 2-PI and alpha 2-PI-P were also out of the normal range during treatment in the MPA-treated group. However, these abnormal parameters recovered to within the normal range from 6 months or more after the commencement of treatment without any termination of drug administration. The patients were all asymptomatic. In contrast, a slight prolongation of bleeding time which persisted for more than 6 months was observed in the patients treated with tamoxifen. These data suggest that MPA causes a hypercoagulable state and that any change must be carefully monitored during treatment with either MPA or tamoxifen.

Hemostatic and fibrinolytic parameters in patients with acute myeloid leukemia: Activation of blood coagulation, fibrinolysis and unspecific proteolysis

Blood coagulation, fibrinolytic and unspecific proteolytic parameters were investigated in 34 patients with acute myeloid leukemia. An increased activity of the coagulation system, documented by elevated thrombin-antithrombin III-complex (TAT) plasma levels, was found in 91% of the patients; 50% had increased elastase plasma levels. Hyperfibrinolysis, as shown by elevated fibrin split-product D-Dimer plasma levels, was detected in 91% of AML patients. Activation of these enzyme systems was not associated with relevant defects in blood coagulation or fibrinolysis in the majority of the patients investigated. In selected cases of promyelocytic M3 and monoblastic M5 leukemia, however, hypofibrinogenemia and alpha 2-plasmininhibitor deficiency was found, most likely due to depletion of these proteins in the course of disseminated intravascular coagulation and secondary hyperfibrinolysis. Significant correlations were calculated between TAT and fibrinogen (r = -0.57, P less than 0.005), TAT and D-Dimer (r = 0.89, P less than 0.0005), and D-Dimer and alpha 2-plasmininhibitor (r = -0.77, P less than 0.0005) levels. Indications of a pathogenetic importance of primary hyperfibrinolysis or unspecific proteolysis for hypofibrinogenemia and alpha 2-PI deficiency were not found.

Histidine-Rich Glycoprotein and Plasminogen Plasma Levels in Term and Preterm Newborns

The newborn's fibrinolytic system is not the same as that in the adult. Hypoplasminogenemia with normal (adult) levels of alpha 2-plasmin inhibitor and plasminogen activator inhibitor are characteristic of the newborn's lytic system. This combination suggests that the newborn may have an impaired lytic system that may explain, in part, the thrombotic events that are frequently observed. Histidine-rich glycoprotein (HRG), another fibrinolytic inhibitor, retards fibrinolysis by interfering with plasminogen's binding to fibrin. Levels of HRG have been reported to be reduced in term newborns. This finding has not been studied recently and to our knowledge, there are no reports of HRG levels in premature infants. The purpose of this study was to measure the plasma levels of HRG and plasminogen in three groups of patients: normal adults (n = 48), normal term newborns (n = 43), and normal premature newborns (n = 18). The protein levels were determined by electroimmunoassay. Cross-immunoelectrophoresis was also performed for HRG. Cord blood was employed for obtaining newborn citrated plasma. The newborns had significantly lower plasminogen and HRG levels when compared with those of the adults. Also, the HRG levels of the premature newborns were lower than those of the term newborns. In conclusion, the newborns had lower levels of HRG than adults, with premature newborns having the lowest levels. This may allow for more plasminogen to be available for fibrin binding even though newborns have hypoplasminogenemia.

Tissue plasminogen activator catalyzed Lys-Plasminogen activation on heparin-inserted phospholipid liposomes

We prepared heparin-inserted phospholipid liposomes as a functional model of heparan sulfate present on the vascular surface and examined tissue plasminogen activator (t-PA) catalyzed plasminogen activation on the liposome surface. Kinetic analyses showed a marked increase in the affinity of t-PA for Lys-plasminogen in the presence of heparin-inserted phosphatidylcholine (PC) liposomes. The catalytic efficiency (kcat/Km) of t-PA for the plasminogen activation on the surface of heparin-inserted PC liposomes was 5.4 times that on the surface of heparin-free PC liposomes. This stimulatory action of immobilized heparin was apparently affected by changing the phospholipid component of liposomes. Phosphatidylethanolamine or stearylamine, having a positively charged group, reduced the catalytic efficiency of t-PA by raising its Km value (10-fold), whereas negatively charged phospholipids, phosphatidylserine and phosphatidylinositol, did not affect the efficiency. t-PA and generated plasmin bound to the liposome surface heparin were protected from inhibition by plasminogen activator inhibitor type 1 and alpha 2-plasmin inhibitor, respectively. t-PA-induced clot lysis of euglobulin or whole plasma, which contained native (Glu-) plasminogen and the above inhibitors, was also accelerated by addition of heparin-inserted PC liposomes. These results suggest that the vascular surface heparin-like molecules may play an important role in modulating fibrinolytic events. The principles of conjugation of t-PA with a biologically active liposome will be applied to the construction of better thrombolytic agents.

Impaired secretion of mutant alpha 2-plasmin inhibitor (alpha 2 PI- Nara) from COS-7 and HepG2 cells: molecular and cellular basis for hereditary deficiency of alpha 2-plasmin inhibitor

The elongated mutant of alpha 2-plasmin inhibitor (alpha 2 PI) designated as alpha 2 PI-Nara is caused by a frameshift mutation found near the 3' end of the coding region of the alpha 2 PI gene. To elucidate the mechanism by which this molecular abnormality leads to alpha 2 PI deficiency in plasma, we transfected an expression plasmid for alpha 2 PI-Nara into a monkey kidney cell line COS-7 or human hepatoma cell line HepG2 synthesizing alpha 2 PI, and analyzed the secretory process of the expressed alpha 2 PI-Nara by radioimmunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography. The results obtained showed that the recombinant alpha 2 PI-Nara was retained within the cells for prolonged periods as an endoglycosidase H-sensitive precursor form, and only a small portion of the recombinant protein was secreted into the medium as a neuraminidase-sensitive mature form. These results suggest that instead of being secreted from the cells, most of the alpha 2 PI-Nara undergoes degradation within the cells while its transport is retarded in the intracellular secretory pathway; thus, alpha 2 PI-Nara should lead to the alpha 2 PI deficiency primarily by causing a block in the intracellular transport from the endoplasmic reticulum to the Golgi complex.

Impaired secretion of mutant alpha 2-plasmin inhibitor (alpha 2 PI- Nara) from COS-7 and HepG2 cells: molecular and cellular basis for hereditary deficiency of alpha 2-plasmin inhibitor

Abstract The elongated mutant of alpha 2-plasmin inhibitor (alpha 2 PI) designated as alpha 2 PI-Nara is caused by a frameshift mutation found near the 3′ end of the coding region of the alpha 2 PI gene. To elucidate the mechanism by which this molecular abnormality leads to alpha 2 PI deficiency in plasma, we transfected an expression plasmid for alpha 2 PI-Nara into a monkey kidney cell line COS-7 or human hepatoma cell line HepG2 synthesizing alpha 2 PI, and analyzed the secretory process of the expressed alpha 2 PI-Nara by radioimmunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography. The results obtained showed that the recombinant alpha 2 PI-Nara was retained within the cells for prolonged periods as an endoglycosidase H- sensitive precursor form, and only a small portion of the recombinant protein was secreted into the medium as a neuraminidase-sensitive mature form. These results suggest that instead of being secreted from the cells, most of the alpha 2 PI-Nara undergoes degradation within the cells while its transport is retarded in the intracellular secretory pathway; thus, alpha 2 PI-Nara should lead to the alpha 2 PI deficiency primarily by causing a block in the intracellular transport from the endoplasmic reticulum to the Golgi complex.

Anti-plasmin inhibitor. VI. Structure of phlorofucofuroeckol A, a novel phlorotannin with both dibenzo-1,4-dioxin and dibenzofuran elements, from Ecklonia kurome Okamura.

Phlorofucofuroeckol A (1), a novel phlorotannin with both dibenzo-1,4-dioxin and dibenzofuran elements, has been isolated from the brown alga Ecklonia kurome OKAMURA as a potent anti-plasmin inhibitor. Its structure has been elucidated to be 1,11-di(3,5-dihydroxyphenoxy)- benzofuro[3,2-a]dibenzo[b,e][1,4]dioxin-2,4,8,10,14-pentaol on the basis of the spectral data, in particular, by means of negative nuclear Overhauser effect (NOE) and long-range carbon-proton couplings (2JCH and 3JCH). Phlorofucofuroeckol A inhibited the action of alpha 2-macroglobulin (IC50 = 1.0 micrograms/ml) and alpha 2-plasmin inhibitor (IC50 = 0.3 micrograms/ml), the main plasmin inhibitors in plasma.

Changes in coagulative and fibrinolytic activities in Triton WR-1339-induced hyperlipidemia in rats.

Changes in coagulative and fibrinolytic activities were studied in rats with hyperlipidemia induced by Triton WR-1339 (T-WR). After intravenous injection of T-WR (150, 200 or 300 mg/kg) into S.D. rats, dose-related increases in plasma lipids (total cholesterol, triglyceride, free cholesterol and phospholipid) were observed. In hyperlipidemic rats that received 300 mg/kg of T-WR, decreases in red blood cell count and Hb value were found. Significant increases in the ma value of the thromboelastogram and the fibrinogen level were observed in these T-WR treated rats. The alpha 2-plasmin inhibitor activity was found to decrease dose-relatedly. These results indicate that T-WR induced hyperlipidemia in rats is accompanied with an increase in coagulative activity and an indirect enhancement of fibrinolytic activity.

Clot lysis induced by a monoclonal antibody against alpha 2-plasmin inhibitor

A monoclonal antibody (MoAb) to alpha 2-plasmin inhibitor designated JTPI-1 inhibited antiplasmin activity by interfering with formation of alpha 2-plasmin inhibitor (alpha 2-PI)-plasmin complex. With this MoAb, we observed plasma clot lysis in vitro and evaluated the potential of JTPI-1 to serve as a new therapeutic agent for thrombolysis. After adding 125I-labeled fibrinogen to plasma, clots were made by adding thrombin and calcium and were then resuspended in normal plasma containing various concentrations of JTPI-1. The presence of JTPI-1 enhanced release of the soluble 125I-labeled fibrin degradation fragment from the clots in a dose-dependent manner. With tissue plasminogen activator (t-PA)-depleted plasma, we showed that induction of clot lysis by JTPI-1 was dependent on fibrin-bound endogenous t-PA. Regulation of fibrinolysis initiated on the fibrin surface by fibrin- bound t-PA and plasminogen is mediated by alpha 2-PI cross-linked to fibrin by activated factor XIII. JTPI-1 bound to this cross-linked alpha 2-PI neutralized its activity and induced partial digestion of fibrin by plasmin. This resulted in additional binding of Glu- plasminogen to fibrin during the incubation. When 1.2 mumol/L JTPI-1 and 5 U/mL exogenous t-PA were present in the suspending plasma, the rate of clot lysis was essentially the same as that induced by 60 U/mL exogenous t-PA alone. These results suggest that JTPI-1 may be useful in reducing the amount of t-PA administered for thrombolytic therapy.

Clot Lysis Induced by a Monoclonal Antibody Against α2-Plasmin Inhibitor

A monoclonal antibody (MoAb) to alpha 2-plasmin inhibitor designated JTPI-1 inhibited antiplasmin activity by interfering with formation of alpha 2-plasmin inhibitor (alpha 2-PI)-plasmin complex. With this MoAb, we observed plasma clot lysis in vitro and evaluated the potential of JTPI-1 to serve as a new therapeutic agent for thrombolysis. After adding 125I-labeled fibrinogen to plasma, clots were made by adding thrombin and calcium and were then resuspended in normal plasma containing various concentrations of JTPI-1. The presence of JTPI-1 enhanced release of the soluble 125I-labeled fibrin degradation fragment from the clots in a dose-dependent manner. With tissue plasminogen activator (t-PA)-depleted plasma, we showed that induction of clot lysis by JTPI-1 was dependent on fibrin-bound endogenous t-PA. Regulation of fibrinolysis initiated on the fibrin surface by fibrin-bound t-PA and plasminogen is mediated by alpha 2-PI cross-linked to fibrin by activated factor XIII. JTPI-1 bound to this cross-linked alpha 2-PI neutralized its activity and induced partial digestion of fibrin by plasmin. This resulted in additional binding of Glu-plasminogen to fibrin during the incubation. When 1.2 mumol/L JTPI-1 and 5 U/mL exogenous t-PA were present in the suspending plasma, the rate of clot lysis was essentially the same as that induced by 60 U/mL exogenous t-PA alone. These results suggest that JTPI-1 may be useful in reducing the amount of t-PA administered for thrombolytic therapy.