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Different inhibitors of plasmin differentially affect angiostatin production and angiogenesis.

Plasmin is a broad-spectrum serine proteinase, which is presumed to cleave many extracellular proteins and affect angiogenesis. In the present work, we studied the effect of two different inhibitors of plasmin (epsilon-aminocaproic and alpha(2)-antiplasmin) on angiogenesis in vivo using the chicken embryo chorioallantoic membrane assay, and in vitro using human umbilical vein endothelial cells. Epsilon-aminocaproic acid inhibited, while alpha(2)-antiplasmin induced, angiogenesis, as well as human umbilical vein endothelial cell proliferation, migration and tube formation on matrigel in a dose-dependent manner. Since plasmin has been implicated in the production of angiostatin, we studied the effect of the two plasmin inhibitors on angiostatin protein amounts in the chicken embryo chorioallantoic membrane. In this tissue, the 38- and 45-kDa isoforms of angiostatin are differentially affected by the two inhibitors: epsilon-aminocaproic acid increased, while alpha(2)-antiplasmin decreased the amounts of both isoforms. These data suggest that plasmin may have an antiangiogenic role in vivo through generation of angiostatin. Moreover, plasmin inhibitors differentially affect in vivo angiogenesis, depending on the mechanism by which they inhibit plasmin activity.

Aminocaproic Acid↗

Osteonectin in matrix remodeling. A plasminogen-osteonectin-collagen complex.

Osteonectin is an adhesive glycoprotein synthesized constitutively by osteoblasts, endothelial cells, and megakaryocytes. Bone-derived and platelet-derived osteonectins differ in their electrophoretic mobility and carbohydrate content, and each displays different affinities for collagen matrices. Both types of osteonectin bind to plasminogen (Kd(app), of 4.7 +/- 1.0 x 10(-8) M for bone osteonectin and 1.2 +/- 0.1 x 10(-7) M for platelet osteonectin). The osteonectin-plasminogen interaction is inhibited by alpha 2-antiplasmin and epsilon-aminocaproic acid, suggesting that the interaction is mediated through the kringle 1 region of plasminogen. Both osteonectins enhance the rate of plasmin generation by tissue-type plasminogen activator to approximately the same extent as fibrinogen. Equilibrium binding measurements conducted using total internal reflection fluorescence spectroscopy indicate that plasminogen binds to collagen in the presence of bone osteonectin (Kd = 1.30 +/- 0.1 x 10(-7) M). No binding of plasminogen to collagen matrix was detected in the presence of platelet osteonectin or in the absence of bone osteonectin. Bone osteonectin-dependent binding of plasminogen to collagen matrix is reversed by the addition of epsilon-aminocaproic acid. The ability of both types of osteonectin to bind to and influence plasminogen activation and of bone osteonectin to anchor plasminogen on collagen matrices suggests that osteonectin may play a role in directing extracellular matrix proteolysis.

Aminocaproic Acid↗

Synthetic antifibrinolytics are not associated with an increased incidence of baffle fenestration closure after the modified Fontan procedure.

OBJECTIVE: To determine if the lysine analog antifibrinolytic agents, epsilon-aminocaproic acid and tranexamic acid, are associated with early closure of the baffle fenestration after the modified Fontan procedure. DESIGN: Retrospective chart review. SETTING: University hospital. PARTICIPANTS: Seventy-four successive patients underwent the modified Fontan procedure. Three patients received aprotinin and were excluded. A total of 71 patients were analyzed. INTERVENTIONS: Charts were examined for variables known to be associated with baffle fenestration closure in the modified Fontan procedure. MEASUREMENTS AND MAIN RESULTS: Occurrence of baffle fenestration closure, oxygen saturation, central venous pressure, left atrial pressure, transpulmonary gradient, chest tube drainage volume, chest tube drainage duration, intensive care unit (ICU) duration, and total inpatient duration were compared between the 33 patients who received antifibrinolytics and the 38 patients who did not. One patient of 71 had baffle fenestration closure in the first 48 hours after surgery. Oxygen saturation, central venous pressure, left atrial pressure, transpulmonary gradient, chest tube drainage volume, chest tube drainage duration, days in ICU, and total inpatient duration were not significantly different between the two groups. CONCLUSIONS: Use of epsilon-aminocaproic acid and tranexamic acid is not associated with early baffle fenestration closure after the modified Fontan procedure. It is concluded that these agents can be used without increasing the risk of spontaneous baffle fenestration closure.

Aminocaproic Acid↗

Crystallization and preliminary X-ray diffraction studies of an anti-4-hydroxy-3-nitrophenylacetic acid monoclonal antibody Fab fragment complexed with immunizing and heteroclitic haptens.

The Fab fragment of the anti-4-hydroxy-3-nitrophenylacetic acid monoclonal antibody, 88C6/12 has been crystallized in the presence of the eliciting hapten, 4-hydroxy-3-nitrophenacetyl-epsilon-aminocaproic acid (NP-aminocap) and the heteroclitic iodinated analog, 4-hydroxy-3-iodo-5-nitrophenylacetyl-epsilon-aminocaproic acid (NIP-aminocap). Crystals obtained by precipitation with 32% (w/v) polyethylene glycol 3400 in the presence of 40 to 400 microM of either NP-aminocap or NIP-aminocap, belong to the orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 81.2 A, b = 86.9 A, c = 131.1 A. The cell volume suggests the presence of two molecules of the complex per asymmetric unit. Analysis of the Patterson function indicates that these two molecules are related by a local 2-fold axis parallel to the crystallographic b axis located at x = 0.218 and z = 0.25.

Antibodies, Monoclonal↗

Continuous small-dose tranexamic acid reduces fibrinolysis but not transfusion requirements during orthotopic liver transplantation.

Tranexamic acid (TA) is a synthetic drug that inhibits fibrinolysis. It has been administered to decrease the use of blood products during cardiac surgery and orthotopic liver transplantation when infused in larger doses. A small-dose infusion of aprotinin causes a reduction in fibrinolysis and blood product requirement during orthotopic liver transplantation without apparent risk of intravascular thrombosis. This prospective study was designed to investigate whether a small-dose infusion of TA would be equally effective in reducing fibrinolysis and blood product transfusions during orthotopic liver transplantation. A double-blind, controlled study was undertaken to compare the efficacy of a small-dose TA infusion with that of a placebo. Thirty-two consecutive patients were randomized either to the TA group (n = 16), which received an intravenous infusion of 2 mg x kg(-1) x h(-1), or to the control group (n = 16), which received an identical volume of normal saline. Coagulation values were measured, a field rating was made by the surgeon, and a thromboelastogram was produced at four predetermined intervals throughout the case-before TA infusion was started, after portal vein ligation, 10 min after reperfusion, and at the end of surgery. Intraoperative transfusion requirements were recorded during the procedure and for the first 24 h postoperatively. A record was kept of any intraoperative epsilon-aminocaproic acid administered for uncontrolled fibrinolysis. The thromboelastogram clot lysis index was significant for lysis in the control group during both the anhepatic and the neohepatic phases (P < 0.01 and P < 0.05, respectively) when compared with the TA group. Fibrin degradation products were significantly increased (>20 microg/mL) in the control group at reperfusion (P < 0.03) and at the end of surgery (P < 0.01). D-dimers were also significantly increased (>1 mg/L) in the control group at the end of surgery (P < 0.04). Nine of the 16 control patients versus 3 of the 16 TA patients required epsilon-aminocaproic acid rescue for fibrinolysis. There were no other significant differences between groups. Transfusion requirements during surgery and for the first 24 h postoperatively did not differ significantly between the two groups. We conclude that the use of small-dose TA reduces fibrinolysis but not transfusion requirements during orthotopic liver transplantation.

Aminocaproic Acid↗

Conservative management of the recently ruptured aneurysm.

Antifibrinolytic drugs and subtotal occulusion of carotid artery have been investigated in a series of 168 patients with recently ruptured intracranial aneursyms. It is concluded that epsilon-aminocaproic acid offers effective treatment, that aggressive hypotensive therapy is dangerous in the severely obtunded patient, and that epsilon-aminocaproic acid plus subtotal carotid occlusion (supplemented by a moderate hypotensive regime) offer the best treatment, in this experience, in the prevention of recurrent hemmorrhages.

Aminocaproates↗

Regulation of macrophage receptor-bound plasmin by autoproteolysis.

The activation of plasminogen by macrophage is regulated by their expression of receptors for urokinase and plasmin(ogen). In these studies we have examined plasmin(ogen) binding to adherent human THP-1 macrophage. Plasmin bound to the THP-1 cells in a time- and dose-dependent manner (Kd 15.8 +/- 6.2 nM; Bmax 1.4 +/- 0.3 x 10(6)/cell). The lysine analog epsilon-aminocaproic acid competitively inhibited plasmin binding. The fraction of membrane-bound plasmin, however, became increasingly resistant to displacement with epsilon-aminocaproic acid. Over a 24-h period, membrane-bound plasmin activity fell 80% despite the presence of catalytically active plasmin in the incubation media. The loss of receptor-bound plasmin activity was not due to proteolytic alterations of its receptor since 125I-Lys-plasminogen bound to THP-1 cells pretreated with plasmin with similar affinity as to untreated cells. Following a 24-h incubation of 125I-Lys-plasminogen or 125I-plasmin with THP-1 cells, several degradative fragments were apparent in their conditioned media. The smaller degradative fragments (28 and 36 kDa) lacked cell binding activity and were demonstrated to be active by casein-zymography. A 48-kDa fragment bound to cells in a lysine-dependent manner but was not active. In contrast, phenylmethylsulfonyl fluoride-inactivated 125I-plasmin retained its binding activity over 24 h, and degradative fragments were not present in the conditioned media. The binding of 125I-Lys-plasmin(ogen) to THP-1 cells was also examined in the presence of excess alpha 2 plasmin inhibitor. Despite the absence of fluid-phase plasmin activity, membrane-bound 125I-Lys-plasmin(ogen) decreased over 24 h. At 24 h a radiolabeled 48-kDa fragment was observed in the conditioned media and together with 125I-Lys-plasmin(ogen) was bound to cells. Unlike 125I-Lys-plasmin, the 48-kDa fragment did not form a complex with alpha 2 plasmin inhibitor. Thus, autoproteolysis of receptor-bound plasmin results in fragments with truncated physiologic properties that possess either cell binding or catalytic activities. We propose that autoproteolysis is a mechanism for regulating membrane-bound plasmin activity.

Catalysis↗

[A trial of adiuretin-SD use in von Willebrand's disease].

In healthy volunteer donors, intranasal instillation of adiuretin-SD in doses of 0.0002-0.001 mg/kg a day provoked an increase of the activity VIII:WF in the plasma and acceleration of euglobulin lysis. Out of 15 patients suffering from Willebrand's disease, the activity of Willebrand's factor rose in 9 patients. Activated partial thromboplastic time became shorter in all the patients. In addition, acceleration of euglobulin lysis was noted. In view of that fact adiuretin was used later in combination with aminocaproic acid (0.2 g/kg a day). All the patients suffering from menorrhagias demonstrated the lowering of hemorrhagic diathesis. The data obtained allow recommending the use of adiuretin combined with aminocaproic acid in patients suffering from Willebrand's disease.

Adult↗

Biochemical properties of the kringle 2 and protease domains are maintained in the refolded t-PA deletion variant BM 06.022.

BM 06.022 is a t-PA deletion variant which comprises the kringle 2 and the protease domain. Production of BM 06.022 in Escherichia coli leads to the formation of inactive inclusion bodies, which have to be refolded by an in vitro refolding process to achieve activity and proper structure of the domains. We analysed the biochemical properties of BM 06.022 to obtain some information about the structure of kringle 2 and the protease as compared with the structure of these domains in the intact t-PA molecule. The kinetic analysis of the amidolytic activity of BM 06.022 and CHO-t-PA yielded similar values for kcat (13.9 s-1 and 11.4 s-1 for the single chain forms and 33.9 s-1 and 27.1 s-1 for the two chain forms of BM 06.022 and CHO-t-PA, respectively) and for Km (2.5 mM and 2.1 mM for the single chains forms and 0.5 mM and 0.3 mM for the two chain forms of BM 06.022 and CHO-t-PA, respectively). BM 06.022 and CHO-t-PA have the same plasminogenolytic activity in the absence of CNBr fragments of fibrinogen. However, BM 06.022 has a lower plasminogenolytic activity in the presence of CNBr fragments of fibrinogen and a lower affinity to fibrin as compared with CHO-t-PA. The affinity of BM 06.022 for fibrin is completely suppressed by 0.3 mM epsilon-aminocaproic acid, while the intact t-PA has a residual affinity of approximately 30%. The dissociation constants for the interaction with the lysine analogue epsilon-aminocaproic acid are 0.10 mM and 0.09 mM for BM 06.022 and the intact t-PA, respectively. Furthermore, BM 06.022 and CHO-t-PA are inhibited by PAI-1 in a similar manner.

Amidohydrolases↗

Fibrin binding. An essential property of anisoylated plasminogen streptokinase activator complex.

Use of an immobilised lysine column as a model system to assess the fibrin binding properties of plasminogen and its derivatives showed that anisoylated plasminogen streptokinase activator complex (APSAC) behaved in a manner similar to that of lys-plasminogen, the adsorption being inhibited in the presence of epsilon-aminocaproic acid. In 3 experimental systems using fibrin as the adsorbant, however, APSAC was more firmly bound than plasminogen and was not readily eluted by epsilon-aminocaproic acid.

Anistreplase↗

[Procoagulant and proteolytic activities of leukocytes in the foci of acute abscesses and gangrene of the lungs].

Essential role in development of acute purulent destruction of the lungs in attributed to proteinases of polimorphonuclear leukocytes. Poor localization of the destruction focus seems to result from low procoagulant activity of pulmonary macrophages. If the activity of purulent and destructive process stands high the ability of phagocytes to synthesize and release proteinases is realized fully. epsilon-Aminocaproic acid prohibits phagocytic proteolytic activity from growing under the influence of stimulators. Correction of defective leukocytic proteolysis and mononuclear activity can be done with prodigiozan, streptokinase and epsilon-aminocaproic acid.

Acute Disease↗

Role of tryptophan-74 of the recombinant kringle 2 domain of tissue-type plasminogen activator in its omega-amino acid binding properties.

The role of W74 in stabilization of the binding of omega-amino acids to the recombinant (r) kringle 2 domain (residues 180-261) of tissue-type plasminogen activator ([K2tPA]) has been assessed by examination of the binding (dissociation) constants (Kd) of epsilon-aminocaproic acid (EACA) and one of its structural analogues, 7-aminoheptanoic acid (7-AHpA), to variants of r-[K2tPA] generated by site-directed mutagenesis of the wild-type kringle domain. Two nonconservative mutations at W74 of r-[K2tPA] have been constructed, expressed, and purified, resulting in one variant molecule containing a W74L mutation (r-[K2tPA/W74L]) and another containing a W74S mutation (r-[K2tPA/W74S]). In both cases, binding of EACA and 7-AHpA was virtually eliminated in the mutated kringles. Two additional conservative mutations at W74 of r-[K2tPA] have been similarly generated, resulting in r-[K2tPA/W74F] and r-[K2tPA/W74Y]. For these mutants, binding of the same ligands to the variant recombinant kringle domain is retained, although it is significantly weaker in nature. The 1H-NMR spectra of each of the variant kringles demonstrates that all retain the general gross conformations of their wild-type counterpart but that some environmental changes of proton resonances occur at particular aromatic amino acid residues that may be involved in omega-amino acid binding. Differential scanning calorimetric analyses of each of the variant kringles suggest that none of the mutations led to substantial destabilization of their structures, again suggestive of gross conformational similarities in all r-[K2tPA] molecules constructed. We conclude that the aromatic character present at position 74 of wild-type r-[K2tPA] is of great importance to its ability to interact with omega-amino acid ligands, with tryptophan being the most effective amino acid at that position.

Amino Acid Sequence↗

Comparative analyses of the lysine binding site properties of apolipoprotein(a) kringle IV types 7 and 10.

Apolipoprotein(a) [apo(a)] shares extensive sequence similarity with plasminogen and consists of multiple tandem repeats of domains similar to plasminogen kringle IV (KIV), followed by domains homologous to the plasminogen KV and protease domains. The apo(a) KIV domains can be classified into 10 types on the basis of amino acid sequence (KIV(1)-KIV(10)) of which KIV(10) contains a canonical lysine binding site (LBS); KIV(10) mediates the lysine-dependent interaction of Lp(a) with certain biological substrates. Molecular modeling studies indicated the presence of weak LBS in each of KIV(5)-KIV(8), and subsequent biochemical studies have revealed contributions of these kringles to lysine-mediated interactions involving apo(a). The present study describes the direct demonstration of a weak LBS within KIV(7), as well as the first characterization of the ligand specificity of an LBS outside that of KIV(10). We have expressed both KIV(7) and KIV(10) from bacterial cells and purified them to homogeneity from cell lysates. Equilibrium binding analyses of the KIV(7) LBS using intrinsic fluorescence revealed an affinity for L-lysine and its analogues approximately 10-fold weaker (K(D) = 230 +/- 42 microM for epsilon-aminocaproic acid) than that of KIV(10) (K(D) = 33 +/- 4 microM for epsilon-aminocaproic acid). Moreover, we demonstrated differences in specificity of the LBS of KIV(7) in comparison with KIV(10) in that KIV(7) preferentially bound L-proline. Both kringles bind 4-aminobutyric acid with similar affinities albeit with apparently different mechanisms. Key Phe(62) --> Tyr and Asp(56) --> Glu substitutions in the KIV(7) LBS result in alterations in the size of the LBS and in the spatial relationship between the cationic and anionic centers in the LBS and thus account for the differences in the binding properties of KIV(7) and KIV(10).

Apolipoproteins↗

Correlation of the serial-dilution protamine sulfate test with models of "hypercoagulability" and thrombosis in dogs.

In a dog model, combinations of venous-injury thrombosis, homologous serum-induced "hypercoagulability," and fibrinolytic blockade were evaluated to determine the factors involved in the generation of a positive serial-dilution protamine sulfate test. Stasis and operative procedures did not produce a positive test. Small local thrombi induced by electrical current produced a positive test that tended to persist only during the initial formation and propagation of the thrombus, and was blocked by pretreatment with epsilon-aminocaproic acid, suggesting in this model that the test was detecting mainly early fibrin degradation products. Homologous serum infusion without venous-injury thrombosis also produced positive serial-dilution protamine sulfate test results that could not be blocked with epsilon-aminocaproic acid suggesting here that the serial-dilution protamine sulfate test was detecting mainly soluble complexes of fibrin monomer rather than early fibrin degradation products. The serial-dilution protamine sulfate test is therefore capable of detecting both small local thrombi and serum-induced "hypercoagulability" without thrombosis in the dog model.

Animals↗

Thermodynamic properties of the binding of alpha-, omega-amino acids to the isolated kringle 4 region of human plasminogen as determined by high sensitivity titration calorimetry.

The binding of alpha-, omega-amino acids, which are important effectors of human plasminogen activation, to the isolated kringle 4 (K4) peptide region of this protein has been investigated by high sensitivity titration calorimetry. The titration curve of the heat changes accompanying binding of the widely employed ligand, epsilon-aminocaproic acid (EACA), to K4 were deconvoluted to yield the following binding characteristics: n = 0.87 +/- 0.08 mol/mol; Ka = 3.82 +/- 0.37 x 10(4) M-1; delta H = -4.50 +/- 0.22 kcal/mol; delta S = 6.01 +/- 0.7 entropy units; and delta G = 6.29 +/- 0.06 kcal/mol. Here, both delta H and delta S provide the driving force of the interaction, with both hydrogen bonds and hydrophobic interactions, the latter which may result from an induced conformational change in K4 upon ligand binding, as well as possible alterations in peptide-bound water structure, providing the stabilizing forces for complex formation. The thermodynamic binding parameters were not greatly influenced by pH between the values of 5.5 and 8.2, suggesting that titratable groups on K4 in this pH region did not influence the binding. Investigations of the binding properties of structural analogues of EACA to K4 demonstrated that definable steric requirements existed for a maximal interaction, with spacing between the functional groups on EACA, as well as a hydrophobic region of this molecule, being important. This rapid and reliable method for measuring all thermodynamic parameters of formation of this complex at a given temperature can now be employed to investigate this important interaction with a wide variety of kringles and modified kringles to provide a more complete understanding of the necessary factors for this binding to occur.

Amino Acid Sequence↗

Lysine/fibrin binding sites of kringles modeled after the structure of kringle 1 of prothrombin.

The Lys binding site of kringle 1 and 4 (K1 and K4) of plasminogen (PG) has been modeled on the basis of the three-dimensional structure of kringle 1 of prothrombin and 300- and 600-MHZ proton nuclear magnetic resonance observations. These structures were then compared to the corresponding regions of modeled kringle 1 and 2 of tissue plasminogen activator (PA). The coordinates of the modeled structures have been refined by energy minimization in the presence and absence of epsilon-aminocaproic acid ligand in order basically to remove unacceptable van der Waals contacts. The binding site is characterized by an apparent dipolar surface, the polar parts of which are separated by a hydrophobic region of highly conserved aromatic residues. Zwitterionic ligands such as Lys and epsilon-aminocaproic acid form ion pair interactions with Asp55 and Asp57 located on the dipolar surface; the latter are also conserved in all the Lys binding kringles. The cationic center of the dipolar surface is Arg71, in the case of PGK4, and is composed of Arg34 and Arg71 in PGK1. The doubly charged anionic/cationic interaction centers of the latter might account for the larger binding constants of PGK1 for like-ligands but the modeling suggests that PGK4 might be kinetically faster in binding bulkier ligands. The binding site region of PAK2, which also binds Lys, resembles those of PGK1 and PGK4. Since PAK2 lacks both cationic center Arg residues, ligand carboxylate binding appears to be accomplished though an imidazolium ion of His64, which is located just below the outer surface of the kringle.

Amino Acid Sequence↗

Predictors of pericardial effusion after orthotopic heart transplantation.

OBJECTIVES: Pericardial effusion occurs frequently after orthotopic heart transplantation, but the causes of this complication have not been well described. This study was designed to identify factors predisposing toward the development of significant postoperative pericardial effusions in a large, single-institution population of orthotopic heart transplant recipients. METHODS: A retrospective review of more than 90 preoperative, intraoperative, and postoperative variables was conducted for 241 patients undergoing orthotopic heart transplantation from September 1988 to December 1999. Patients who had significant postoperative pericardial effusions develop were identified from postoperative echocardiograms by standard criteria. Factors associated with the development of significant pericardial effusions were determined by multivariate logistic regression analysis. RESULTS: Echocardiographic data were available for 203 of 241 transplant recipients. Forty-two patients (21%) had significant effusions develop. According to multivariate analysis, pericardial effusions were less likely to occur in recipients with a history of previous cardiac surgery (odds ratio 0.13, 95% confidence interval 0.05-0.36, P <.0001) and with greater weight (odds ratio 0.96, 95% confidence interval 0.94-0.99, P <.0048). Pericardial effusions were more likely to occur in patients who had received aminocaproic acid during the operation (odds ratio 5.92, 95% confidence interval 2.23-15.72, P <.0008). Patient survival and hospital length of stay did not differ between patients with and without postoperative pericardial effusions. CONCLUSIONS: Postoperative pericardial effusions develop in approximately 20% of patients undergoing orthotopic cardiac transplantation. On the basis of the risk factors identified in this study, prevention may prove difficult, although avoidance of the intraoperative use of aminocaproic acid may be helpful.

Aminocaproates↗

Severe intraoperative coagulopathy following routine aortobi-iliac bypass with knitted Dacron graft.

Coagulopathy associated with aortic operation is generally described in patients undergoing supraceliac aortic clamping or ruptured abdominal aortic aneurysm repair. This intraoperative complication is managed with component blood replacement and occasional use of aminocaproic acid. The presence of intraoperative coagulopathy associated with aortic reconstruction for occlusive disease is not described. We report a case of severe intraoperative coagulopathy associated with aortobi-iliac artery bypass with a knitted Dacron prosthesis. Management of this complication was accomplished with administration of blood components, aminocaproic acid and explant of the Dacron prosthesis with polytetrafluoroethylene graft placement. The possibility of fibrinolysis induced by the knitted Dacron prosthesis is suggested.

Aged↗