Plasmin-alpha 2-antiplasmin Research Articles

Trauma induced coagulopathy is limited to only one out of four shock induced endotheliopathy (SHINE) phenotypes among moderate-severely injured trauma patients: an exploratory analysis

BackgroundTrauma induced coagulopathy remains to be an important cause of high transfusion requirements and mortality and shock induced endotheliopathy (SHINE) has been implicated.MethodsEuropean multicenter observational study of adult trauma patients with injury severity score ≥ 16 arriving within 2 h from injury to the trauma centers. Admission blood samples obtained were used for analysis of the SHINE biomarkers (syndecan-1, soluble thrombomodulin, adrenaline) and extensive analysis of coagulation, -and fibrinolytic factors together with collection of clinical data. Hierarchical clustering of the SHINE biomarkers was used to identify the SHINE phenotypes.ResultsThe 313 patients clustered into four SHINE phenotypes. Phenotype 2, having the highest glycocalyx shedding, encompassing 22% of the whole cohort, had severe coagulopathy with lower levels of prothrombin, FV, IX, X, XI and severe hyperfibrinolysis with higher plasmin – alpha 2-antiplasmin (PAP) – and tPA levels and lower alpha2 – antiplasmin levels. This phenotype had significantly higher transfusion requirements and higher mortality (39% vs. 23%, 15% and 14%) but similar injury severity score (ISS) compared to the others phenotypes.ConclusionsHierarchical clustering identified four SHINE phenotype in a cohort of trauma patients. Trauma induced coagulopathy was confined to only one of the SHINE phenotypes, encompassing 22% of the total cohort. This phenotype was characterized by severe hypocoagulability and hyperfibrinolysis, which translated to significantly higher transfusion requirements and higher mortality compared to the other SHINE phenotypes with similar injury severity, warranting further investigation.

Fibrinolysis in normal vitreous liquid

Plasmin is the key enzyme of fibrinolysis. Plasmin-alpha2-antiplasmin (PAP) complexes are biomarkers of fibrinolysis activation. The purpose of our investigation was to evaluate the activity of fibrinolysis in normal human eyes, that is in eyes without blood-retina barrier breakdown (BRB), which has not been investigated so far. Twenty-two vitreal samples were harvested at the beginning of a standard 23-gauge three-port pars plana vitrectomy for macular pucker removal, macular hole closure or vitreal floater removal from the central vitreous body. These samples were immediately stabilized with human albumin (2.5% final conc.) and arginine (1.25 mmol/l final conc.) and subsequently frozen. Plasminogen was functionally determined in an ultra-sensitive pNA reaction after activation with streptokinase (100% = functional plasminogen in pooled normal citrated plasma). PAP concentrations were measured by enzyme immune assay (EIA). Intravitreal functional plasminogen exhibited to be 1 ± 0.65% (range: 0.2-2.49%). PAP concentrations ranged at levels of 14 ± 9ng/ml (range: 2-33 ng/ml). Pearson's correlation quotient between functional plasminogen and PAP revealed to be r equal to -0.27 (P = 0.221). No adverse events or serious side effects occurred. Sampling vitreous fluid at the beginning of a standard 23-gauge three-port pars plana vitrectomy is a well tolerated procedure. A strict stabilization procedure for extracted vitreous specimen is necessary to obtain activities and concentrations that are close to the true intraocular value. There is a basal intraocular fibrinolysis, a possible target for intravitreal pharmacological therapy.

In vitro effects of detergent sclerosants on fibrinolytic enzymes and inhibitors

Objective To investigate the effects of Sodium Tetradecyl Sulphate (STS) and Polidocanol (POL) on fibrinolytic mechanisms. Materials and methods Measurements were done with serial dilutions of sclerosants in whole blood (WB), platelet rich (PRP) and platelet poor plasma (PPP). Control experiments were done in 5% bovine serum albumin (BSA), spiked with the enzyme/inhibitor. Plasminogen was measured with a chromogenic assay. Alpha-2-antiplasmin (AP) activity, plasmin-alpha-2-antiplasmin (PAP) complexes, plasminogen activator inhibitor-1 (PAI-1) activity, tissue plasminogen activator (t-PA) total antigen, t-PA activity, t-PA/PAI-1 complexes, thrombin activatable fibrinolysis inhibitor (TAFI) antigen and activated TAFI (TAFIa) were measured by ELISA. Results At high concentrations (> 0.3%), STS destroyed plasminogen, PAI-1, t-PA/PAI-1 complexes and total t-PA antigen but increased t-PA activity. At low concentrations (< 0.3%), both agents reduced PAP complexes while increasing AP activity. Low concentration STS increased PAI-1 activity, t-PA/PAI-1 complexes, TAFI and TAFIa. Low concentration POL mildly increased the total t-PA antigen and TAFI. Conclusion At low concentrations, both agents demonstrated a prothrombotic, antifibrinolytic (increase in PAI-1, total t-PA antigen, AP, TAFI and TAFIa) activity. At high concentrations, STS demonstrated non-prothrombotic (destruction of PAI-1, t-PA/PAI-1 complexes), antifibrinolytic (destruction of plasminogen, increase in AP) activity while POL had minimal effect.

Hyperglycemia modulates plasminogen activator inhibitor-1 expression and aortic diameter in experimental aortic aneurysm disease

Extracellular matrix degradation is a sentinel pathologic feature of abdominal aortic aneurysm (AAA) disease. Diabetes mellitus, a negative risk factor for AAA, may impair aneurysm progression through its influence on the fibrinolytic system. We hypothesize that hyperglycemia limits AAA progression through effects on endogenous plasminogen activator inhibitor-1 (PAI-1) levels and subsequent reductions in plasmin generation. Experimental AAAs were induced in diabetic and control mice via the intra-aortic elastase infusion method. Serial transabdominal high-frequency ultrasound examinations were performed to monitor aortic diameter following elastase infusion. Circulating PAI-1 and plasmin alpha2-antiplasmin (PAP) complex concentrations were determined by ELISA and local expression of PAI-1 levels was examined by RT-PCR and immunohistochemistry. Hyperglycemia was associated with reduced AAA diameter, increased plasma PAI-1 concentration and reduced plasmin generation. Aneurysmal aortic PAI-1 gene expression increased in parallel with plasma concentration, with peak expression occurring early after aneurysm initiation. Hyperglycemia increases PAI-1 expression and attenuates AAA diameter in experimental AAA disease. These results emphasize the role of the fibrinolytic pathway in AAA pathophysiology, and suggest a candidate mechanism for hyperglycemic inhibition of AAA disease.

Pregnancy outcome and fibrinolytic, endothelial and coagulation markers in women undergoing uterine artery Doppler screening at 23 weeks.

Pre-eclampsia (PET) and/or fetal growth restriction (FGR) remain a major cause of maternal and fetal morbidity and mortality. In pregnancy, fibrinolysis is controlled by the maternal endothelium and placenta, both of which are central to the pathogenesis of PET/FGR. Clinically, uterine artery Doppler screening at 23 weeks is used to predict PET/FGR. An abnormal uterine artery Doppler finding is defined as early diastolic bilateral uterine artery notching (BN) in the waveform. However, about 50% of mothers with BN do not develop PET/FGR. We investigated fibrinolytic changes and uterine artery Doppler findings in the second trimester, and related them to pregnancy outcome; in particular assessing whether fibrinolytic markers could discriminate between normal and abnormal outcome in mothers with BN. Plasma levels of tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), plasminogen activator inhibitor-2 (PAI-2), plasmin-alpha(2) antiplasmin (PAP), D-dimers and markers of endothelial dysfunction were measured with Doppler ultrasound at 23 weeks. Those with BN had decreased PAP and D-dimer levels, and raised PAI-1 and thrombomodulin levels. Mothers with BN and PET/FGR had significantly increased t-PA levels and reduced PAI-2 levels. BN at 23 weeks of gestation is associated with increased PAI-1 levels. Within the BN group, mothers who developed PET/FGR had increased t-PA levels and decreased PAI-2 levels, although there was no net change in fibrinolysis as measured by D-dimer levels. No single fibrinolytic marker is helpful in determining pregnancy outcome in those with BN, but t-PA and PAI-2 are worthy of study in a multifactorial algorithm.

ASSOCIATION BETWEEN THE SEVERITY OF SEPSIS AND THE CHANGES IN HEMOSTATIC MOLECULAR MARKERS AND VASCULAR ENDOTHELIAL DAMAGE MARKERS

It is well known that disorders of coagulation and fibrinolysis play a major role in the development of organ dysfunction during sepsis. Furthermore, the importance of the early initiation of anticoagulation therapy for severe cases has been emphasized based on the success of recent clinical trials. The purpose of this study is to search for useful markers for predicting organ dysfunction. Plasma samples were prospectively collected from 78 patients within 48 h after the onset of sepsis. Hemostatic markers and endothelial damage markers were compared between the patients with and without organ dysfunction. The WBC and platelet counts were not different between the groups. In contrast, fibrin/fibrinogen degradation products, D-dimer, thrombin-antithrombin complex, plasmin alpha2-antiplasmin complex, soluble fibrin, and total plasminogen activator inhibitor-1 were significantly higher, and the antithrombin activity and protein C levels were lower in the patients with organ dysfunction. Thus, the changes in the hemostatic molecular markers were associated with organ dysfunction from an early stage of sepsis, and antithrombin and protein C activities were found to be the most reliable markers.

The prognostic value of the soluble urokinase-type plasminogen activator receptor (s-uPAR) in plasma of breast cancer patients with and without metastatic disease

Elevated levels of soluble uPAR (s-uPAR) and other fibrinolytic parameters functionally related to the urokinase-type plasminogen activator system might indicate the presence of cancer cells. In 25 breast cancer patients with metastases s-uPAR was significantly increased compared with 25 patients without metastases and with 25 healthy controls: 420 pg mL-1 vs. 145 pg mL-1 (P = 0.005) and 190 pg mL-1 (P = 0.003). Plasmin-alpha2-antiplasmin (PAP) complexes and d-dimers were significantly increased in breast cancer patients with metastases compared with patients without metastases and with healthy controls. The levels of plasminogen activator inhibitor (PAI)-1 activity, uPA antigen and factor (F)XIIa did not significantly differ between the patient groups and healthy controls. PAP complexes (529 microg L-1 vs. 420 microg L-1; P = 0.03), d-dimers (278.5 ng mL-1 vs. 79.0 ng mL-1; P = 0.005) and FXIIa (1.64 ng mL-1 vs. 1.19 ng mL-1; P = 0.01) were significantly higher in patients with metastases not surviving compared with patients with metastases surviving the 3-year follow-up period. Plasma s-uPAR levels in the patients with metastases did not discriminate between patients surviving and patients not surviving after 3-year follow-up. No significant differences in s-uPAR or any of the other parameters were found in the five patients developing metastases during follow-up. A single value of s-uPAR is of limited value in the follow-up of breast cancer patients with and without metastatic disease and does not predict survival or future metastases.

Postoperative reduction of fibrinolysis as a prognostic factor of fatal outcome.

For the resection of an esophagus carcinoma a mortality rate of 2 to 30% was described. It is still unclear whether an abdominothoracic or transhiatal intervention is superior regarding the outcome. To investigate the prognostic value of fibrinolytic markers, plasmin-alpha2-antiplasmin (PAP) and D-dimer (DD) values were determined daily in the early postoperative period for 11 days. In addition, the course of PAP and DD concentrations was compared with the method of esophagectomy. Of the 28 patients enclosed in the study, 5 died between day 10 and day 34 owing to adult respiratory distress syndrome and septicemia. The PAP and DD concentrations increased in survivors after surgery until day 5 and day 7, respectively. The concentrations were twofold and 10-fold higher than the upper reference level. In contrast, four of five nonsurvivors showed an inadequate increase in PAP concentrations within the reference range, whereas the course of DD was inconspicuous. The sensitivity and specificity of PAP and DD in respect to a fatal outcome was calculated by receiver operating characteristic analysis based on all results: sensitivity 76% (PAP-cut off value 760 microg/L) and 49% (DD 6 mg/L), specificity 77% and 72%, respectively. The biochemical markers showed no significant differences between the abdominothoracic and transhiatal esophagectomy. In the abdominothoracic intervention, lower PAP and higher DD concentrations were observed. The results showed that the PAP concentrations could detect a fatal outcome within the first 5 days after surgery.

Plasmin-independent gelatinase B (matrix metalloproteinase-9) release by monocytes under the influence of urokinase.

It is shown that the release of matrix metalloproteinase-9 (gelatinase B) by THP-1 and U937 cells into conditioned media is increased under the action of recombinant single-chain urokinase. This effect is not accompanied by proteolytic activation of gelatinase B and is related to release of a pro-form of the enzyme. The action of urokinase on monocytes is time-dependent and becomes significant 12-24 h after the beginning of cell incubation. The dependence of the effect on the concentration of urokinase is characterized by half-maximum at about 20 nM and saturation at about 200 nM. The urokinase-induced gelatinase B release is not dependent on the action of plasmin because plasmin inhibitors aprotinin and alpha2-antiplasmin do not abolish this action. Additionally, tissue type plasminogen activator does not induce gelatinase B release by monocytes as observed under the action of urokinase. Nevertheless, the catalytic activity of urokinase participates in the development of the observed effect because it is significantly depressed by the natural urokinase inhibitor PAI-1. The effect of urokinase is completely abolished by actinomycin D and cycloheximide, indicating the participation of transcription and translation processes in its development.

The imbalance between coagulation and fibrinolysis is related to the severity of the illness and the prognosis in sepsis.

ObjectivesThe coagulation and fibrinolytic system appears to be activated by the septic process independently, leading to the syndrome of disseminated intravascular coagulation(DIC). In this study, we investigated the changes within the hemostatic system related to the severity of the illness and the prognosis in patients with sepsis.MethodsPlasma thrombin-antithrombin III (TAT) and plasmin-α2-antiplasmin (PAP) complexes were measured using ELISA methods in 32 patients with sepsis and 20 controls and were analyzed according to the APACHE III scores and survival of the patients.ResultsPlasma TAT and PAP in patients with sepsis were significantly higher than controls. Nonsurvivors showed greater levels of TAT(21.7±22.3ng/mL) and lower levels of PAP(628.4±378.1ng/mL) than survivors (TAT: 11.1±11.2ng/mL; PAP: 857.1±364.1ng/mL). The imbalance between coagulation and fibrinolysis described as TAT/PAP ratio was closely related with APACHE III scores in patients with sepsis(r=0.47) and the TAT/PAP ratio in nonsurvivors was significantly higher compared with survivors(34.4±21.4 vs. 14.4±13.8).ConclusionIn sepsis, both coagulation and the fibrinolysis system are activated and the imbalance between coagulation and fibrinolysis predisposes to the hypercoagulation state and is closely related to the severity of the disease and the prognosis.

Diagnostic value of hemostatic parameters in bone marrow transplant-associated thrombotic microangiopathy.

We investigated hemostatic parameters in a prospective study of 16 patients who received bone marrow transplants (BMT). We found a significant rise in the levels of fibrinogen, plasmin-alpha2 antiplasmin inhibitor complex, tissue-plasminogen activator.plasminogen activator inhibitor complex (t-PA.PAI), von Willebrand factor antigen, and thrombomodulin on day 14 after transplant compared with values before transplant. Protein C and thrombin-antithrombin III levels did not change significantly. No significant changes in prothrombin time ratio, activated partial thromboplastin time, or protein S were detected. Patients who had grades II-IV graft-versus-host disease (GVHD) (n = 6) showed a significantly higher level of t-PA.PAI on day 14 compared with those with grades 0-I GVHD (n = 10) (P = 0.0062). Three patients with grades II-IV GVHD developed thrombotic microangiopathy (TMA) on days 19, 19 and 62. In these patients, we noted significantly lower levels of fibrinogen (P = 0.0383), and significantly higher levels of t-PA.PAI (P = 0.0008) and thrombomodulin (P = 0.0001) on day 14 compared with those patients who did not develop TMA. These results suggest that prothrombotic states and endothelial damage may be caused by the conditioning regimen and/or acute GVHD during BMT; thrombomodulin values on day 14 post BMT may be useful in surveillance for TMA because of endothelial cell injury.

Activation of plasma kinin system correlates with severe coagulation disorders in patients with ovarian hyperstimulation syndrome

The aim of this study was to evaluate status of plasma kinin system in patients with ovarian hyperstimulation syndrome (OHSS), in order to investigate whether activation of the plasma kinin system correlates with increased blood coagulability. In the first part of the study, concentrations of plasma prekallikrein (PK) in OHSS cycles (n = 13) were monitored from the day of human chorionic gonadotrophin (HCG) administration to the mid-luteal phase, and were compared with those of control cycles (n = 17). The average value of PK in OHSS cycles began to decrease on day 8, and by day 10 was significantly lower than that of control cycles (86 +/- 6 versus 106 +/- 4%, P <0.01). The time course of changes in PK concentration correlated well with the clinical condition of OHSS patients. In the second part of the study, we obtained data from 26 patients who were hospitalized because of severe OHSS, to investigate the correlation between PK and other haemostatic markers. OHSS patients with severe PK reduction (<80% normal, n = 9) demonstrated significantly higher values of plasma thrombin-antithrombin III and plasmin-alpha2 antiplasmin, and more severe haemoconcentration, compared to those OHSS patients who had no reduction in PK (n = 17). In conclusion, our data suggest that activation of the plasma kinin system occurs specifically and occasionally in OHSS patients, and is associated with increased blood coagulability. Thus, when an OHSS patient demonstrates a low value of plasma PK, more careful management is required to prevent thromboembolic complications.

Effects of Heparin Therapy on Fibrinolysis in Patients with Pulmonary Embolism

Previous investigations suggested that heparin administration to humans enhances the tissue type plasminogen activator (tPA) levels in blood, but it remains uncertain whether this effect induces fibrinolysis. We studied the effect of therapeutic levels of heparinization on plasma markers for fibrinolysis in patients suspected of pulmonary embolism (PE). Blood samples were taken from 49 consecutive patients; 28 had confirmed PE, 21 had PE excluded. On admission, the plasma levels of plasmin-alpha 2antiplasmin complexes and D-dimer were significantly higher in the patient group with PE compared to those in whom PE was excluded. After heparinization the tPA levels increased in both groups, showing that this effect was not dependent on the initial level of activity of fibrinolysis. In spite of this increment in tPA levels, the concentrations of plasmin-alpha 2antiplasmin complexes and D-dimer decreased. In conclusion, although heparinization in patients with or without pulmonary embolism does lead to elevated tPA:Ag levels, this is not accompanied by enhanced fibrinolysis.

Inhibition of Factor XII in Septic Baboons Attenuates the Activation of Complement and Fibrinolytic Systems and Reduces the Release of Interleukin-6 and Neutrophil Elastase

In previous studies, we have shown that administration of monoclonal antibody (MoAb) C6B7 against human factor XII to baboons challenged with a lethal dose of Escherichia coli abrogates activation of the contact system and modulates secondary hypotension. To evaluate the contribution of activated contact proteases to the appearance of other inflammatory mediators in this experimental model of sepsis, we studied the effect of administration of MoAb C6B7 on activation of complement and fibrinolytic cascades, stimulation of neutrophil degranulation, and release of the proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). Activation of the complement system, as reflected by circulating C3b/c and C4b/c levels, was significantly reduced in five animals that had received MoAb C6B7 before a lethal dose of E coli as compared with five control animals that had been given a lethal challenge only. Inhibition of contact activation also modulated the fibrinolytic response, since the release of tissue-type plasminogen activator (t-PA) and the appearance of plasmin-alpha2-antiplasmin (PAP) complexes into the circulation was significantly attenuated upon pretreatment with anti-factor XII MoAb. In contrast, plasma levels of plasminogen activator inhibitor (PAI) were modestly enhanced in the treatment group. Degranulation of neutrophils, as assessed by circulating elastase-alpha1-protease inhibitor complexes, and release of IL-6 but not of TNF-alpha was decreased in anti-factor XII-treated animals. Observed differences in the inflammatory response between treatment and control groups were not likely due to different challenges, since the number of E coli that had been infused, as well as circulating levels of endotoxin after the challenge, were similar for both groups. These data suggest that activation of the contact system modulates directly or indirectly various mediator systems involved in the inflammatory response during severe sepsis in nonhuman primates.

Time course of clotting and fibrinolytic markers in acute upper gastrointestinal bleeding

One hundred consecutive patients with acute upper gastrointestinal bleeding were investigated. Blood coagulation and fibrinolytic activity were monitored by levels of plasma thrombin-antithrombin III (TAT) complex and plasmin-alpha 2-antiplasmin (PAP) complex in samples obtained from patients at admission with haematemesis and/or melana and in samples obtained from patients the first day after admission. Blood was transfused according to a restrictive policy. Median plasma TAT complex was significantly elevated both at admission and on the first day after admission compared with a reference group. Plasma PAP complex levels were normal at admission but decreased on the first day after admission. This decrease was independent of blood transfusion. The results indicate hypercoagulability at admission among patients with upper gastrointestinal haemorrhage reinforced by the development of a hypofibrinolytic state during the first day after admission. Restricted blood transfusion was not associated with any detectable change in blood coagulation or fibrinolysis in these patients.

Alpha-2-macroglobulin functions as an inhibitor of fibrinolytic, clotting, and neutrophilic proteinases in sepsis: studies using a baboon model.

Alpha-2-macroglobulin (alpha 2M) may function as a proteinase inhibitor in vivo. Levels of this protein are decreased in sepsis, but the reason these levels are low is unknown. Therefore, we analyzed the behavior of alpha 2M in a baboon model for sepsis. Upon challenge with a lethal (4 baboons) or a sublethal (10 baboons) dose of Escherichia coli, levels of inactivated alpha 2M (i alpha 2M) steadily increased, the changes being more pronounced in the animals that received the lethal dose. The rise in i alpha 2M significantly correlated with the increase of thrombin-antithrombin III, plasmin-alpha 2-antiplasmin, and, to a lesser extent, with that of elastase-alpha 1-antitrypsin complexes, raising the question of involvement of fibrinolytic, clotting, and neutrophilic proteinases in the inactivation of alpha 2M. Experiments with chromogenic substrates confirmed that thrombin, plasmin, elastase, and cathepsin G indeed had formed complexes with alpha 2M. Changes in alpha 2M similar to those observed in the animals that received E. coli occurred in baboons challenged with Staphylococcus aureus, indicating that alpha 2M formed complexes with the proteinases just mentioned in gram-positive sepsis as well. We conclude that alpha 2M in this baboon model for sepsis is inactivated by formation of complexes with proteinases, derived from activated neutrophils and from fibrinolytic and coagulation cascades. We suggest that similar mechanisms may account for the decreased alpha 2M levels in clinical sepsis.

The structure and expression of the genes for T-kininogen in the rat.

T-kininogen plays an important role in the acute phase response to trauma in the rat as a possible source of kinins and as a cysteine proteinase inhibitor. Two T-kininogens are expressed by rat liver from two separate genes. T-kininogen expression in liver during the acute phase response is regulated at the level of transcription. The similarity in T- and K-kininogen gene structure suggests divergent evolution from a common gene ancestor.

Thrombin Vs. Plasmin generation in disseminated lntravascular coagulation associated with various underlying disorders

In order to assess the thrombin and plasmin generation in vivo in disseminated intravascular coagulation (DIC), plasma levels of thrombin-antithrombin III (ATIII) complex (TAT) and plasmin-alpha 2-antiplasmin (a2AP) complex (PAP) were measured together with standard coagulation and fibrinolytic parameters in 80 patients with DIC. Both TAT and PAP were markedly elevated in patients with DIC. When plotted by the underlying disease categories, differences in the magnitude of the elevations of these complexes were recognized among groups. Patients with acute promyelocytic leukemia (APL) had the highest PAP, the lowest TAT/PAP ratio, low a2AP, and low fibrinogen, indicating that the most excessive fibrinolysis can occur in APL. Similar profiles, although less marked, were observed in patients with other leukemias and vascular diseases. Patients with sepsis showed the highest TAT/PAP ratio and the lowest PAP with no decrease in a2AP or fibrinogen, demonstrating a relatively impaired fibrinolysis. Patients with cancer had a relatively high TAT and high TAT/PAP ratio. In addition, both TAT and PAP were markedly elevated in patients with shock. From these, it was suggested that, although laboratory manifestations in DIC are extremely variable from patient to patient, underlying disorders are, at least in part, responsible for the observed variations. Recognition of this variable activation of coagulation and fibrinolysis would be helpful for the proper management of patients with DIC.

A monoclonal antibody specific for Lys-plasminogen. Application to the study of the activation pathways of plasminogen in vivo.

Human plasminogen, a glycoprotein with NH2-terminal Glu, is rapidly converted by traces of plasmin to proteolytic derivatives with NH2-terminal Met 68, Lys 77, or Val 78 ("Lys-plasminogen"), which are much more readily activated to plasmin than is Glu-plasminogen. It has, therefore, been proposed that physiological activation of Glu-plasminogen occurs mainly via Lys-plasminogen intermediates (Wiman, B., and Wallén, P. (1973) Eur. J. Biochem. 36, 25-31). In the present study we have characterized a murine monoclonal antibody (LPm1) directed against an epitope exposed in Lys-plasminogen but not in Glu-plasminogen. The antibody was secreted by a hybridoma obtained by fusion of mouse myeloma cells (P3X63-Ag8-6.5.3) with spleen cells of a mouse immunized with purified Lys-plasmin-alpha 2-antiplasmin complex. Coupling of the alpha-amino groups of Lys-plasminogen with phenylisothiocyanate resulted in complete loss of immunoreactivity for LPm1, which was, however, fully restored by cleavage of the derivatized NH2-terminal amino acid. After a second cycle, immunoreactivity was not restored, indicating that the LPm1 antibody-binding site depends on the presence of Lys 77 and/or Val 78 as NH2-terminal amino acids. The immunoreactivity of Lys-plasminogen with LPm1 is abolished by reduction of the protein, suggesting that conversion of Glu-plasminogen to Lys-plasminogen is associated with a conformational alteration exposing the epitope for the LPm1 monoclonal antibody. In order to investigate the pathways of plasminogen activation in vivo, total plasmin-alpha 2-antiplasmin and Lys-plasmin-alpha 2-antiplasmin complexes were measured with sandwich-type micro enzyme-linked immunosorbent assays. Therefore, microtiter plates were coated with monoclonal antibodies against alpha 2-antiplasmin, and bound antigen was quantitated with horseradish peroxidase-conjugated LPm1 or a monoclonal antibody reacting equally well with Glu-plasmin as with Lys-plasmin. In 25 healthy subjects the plasmin-alpha 2-antiplasmin levels in plasma were undetectable (less than 0.1 nM). Infusion of tissue-type plasminogen activator in patients with thromboembolic disease resulted in generation of high concentrations of Glu-plasmin-alpha 2-antiplasmin complex (620 +/- 150 nM, n = 7) whereas neither Lys-plasmin-alpha 2-antiplasmin complex nor Lys-plasminogen were consistently detected. It is, therefore, concluded that activation of the fibrinolytic system in vivo occurs by direct cleavage of the Arg 560-Val 561 bond in Glu-plasminogen and not via formation of the Lys-plasminogen intermediates.

Relationship between preoperative status of the fibrinolytic system and occurrence of deep vein thrombosis after major abdominal surgery

This study comprised 50 patients subjected to major abdominal surgery, of which 13 developed deep vein thrombosis (DVT) according to the 125I-fibrinogen test. Plasma was sampled preoperatively, for the specific analysis of tissue plasminogen activator (t-PA) before and during venous occlusion. The recently described fast t-PA inhibitor and plasmin alpha2-antiplasmin complex (PAP) were also measured. The result of the laboratory analyses were correlated to the development of DVT. From the data obtained it is concluded that the evaluation of t-PA release during venous occlusion is a poor predictive factor for the occurrence of DVT after major abdominal surgery. The level of the t-PA inhibitor appears to be raised in these patients, but the values obtained in this material were not related to the development of postoperative DVT. Patients with elevated PAP levels, as shown previously, have a lesser tendency to develop postoperative DVT.