Enhanced expression of factor XII (Hageman factor) in isolated livers of estrogen- and prolactin-treated rats

Estrogens and prolactin may raise the plasma titer of factor XII (Hageman factor) by enhancing gene expression at the level of transcription and RNA processing, protein synthesis, or secretion (or a combination of these). Alternatively, these hormones may protect factor XII or its transcripts from degradation. Because the liver is a major site of factor XII synthesis, we studied the expression and metabolism of factor XII in isolated livers of estrogen- and prolactin-treated rats. All rats were ovariectomized to reduce the effect of endogenous estrogen and prolactin on the expression of factor XII. When a phosphorus 32-labeled factor XII complementary DNA probe for Northern blot analysis was used, increased factor XII messenger RNA was found in poly (A) RNA prepared from livers of estrogen- and prolactin-treated rats relative to those of untreated rats. Simultaneously, enhanced release of immunoreactive factor XII was noted when isolated liver perfusion techniques were used. Cycloheximide, an inhibitor of protein synthesis, blocked the hepatic release of immunoreactive factor XII in both hormone-treated and untreated rats, suggesting that factor XII translation was directly affected. The biologic half-life of injected rat iodine 125-labeled factor XII in estradiol- and prolactin-treated rats was not significantly different from that in untreated rats. By inference from these data, the high plasma titer of factor XII observed in estrogen- and prolactin-treated rats is caused by enhanced hepatic expression at both transcriptional and translational levels, as well as by increased secretion of factor XII.

Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces

Human blood coagulation factor XI was activated by either autoactivation or thrombin. These reactions occurred only in the presence of negatively charged materials, such as dextran sulfate (approximately Mr 500,000), sulfatide, and heparin. During the activation, factor XI was cleaved at a single Arg-Ile bond by thrombin or factor XIa to produce an amino-terminal 50-kDa heavy chain and a carboxyl-terminal 35-kDa light chain. This activation pattern is identical to that produced by factor XIIa. The addition of a small amount of thrombin and sulfatide to factor XII-deficient plasma produced shorter clotting times than when these agents were added to factor XI/factor XII combined-deficient plasma. These results suggest that the activation of factor XI by thrombin and possibly the autoactivation of factor XI proceed in plasma to lead fibrin clot formation. These reactions may have a role on an appropriate negatively charged surface in normal hemostasis.

Zinc ions promote the binding of factor XII/factor XIIA to acidic phospholipids but have no effect on the binding of high-Mr kininogen

Binding of high-Mr kininogen and factor XII/factor XIIa to phospholipids coated on to polystyrene microtiter plates was investigated by ELISA. Both high-Mr kininogen and factor XII/factor XIIa bound specifically to the phospholipid surface. Binding was observed to negatively charged phospholipids only. The binding of high-Mr kininogen was not affected by the presence of zinc ions. At a surface concentration of 20% phosphatidylinositol phosphate in phosphatidylcholine a dissociation constant (kD) of 10 nM for the binding of high-Mr kininogen was calculated. The amount of bound purified alpha-factor XIIa could be increased 4-5-fold in the presence of zinc ions. The lowest zinc ion concentration giving maximal binding was 0.1 mM. The binding of alpha-factor XIIa was inhibited by high-Mr kininogen. Independent of the presence of zinc ions or high-Mr kininogen, a kD of 7.9 nM was calculated for alpha-factor XIIa binding. The binding of prekallikrein was dependent upon the presence and the concentration of high-Mr kininogen. In plasma containing aprotinin, the binding of high-Mr kininogen was apparently inhibited in the presence of zinc ions, which was a prerequisite for the binding of factor XII. This apparently inhibitory effect of zinc ions on the binding of high-Mr kininogen was probably due to the increased binding of factor XII, which displaced high-Mr kininogen.

Contact activation factors in plasma from pregnant women--increased level of an association between factor XII and kallikrein

The plasma levels of FXII, prekallikrein (PK), and high- and low molecular weight kininogens (HK and LK) were studied in pregnant women in the last trimester and in non-pregnant controls. FXIIa and plasma kallikrein were assayed in acetone-treated citrated plasma (CPLa) with the tetrapeptide S-2222 as substrate, using soybean trypsin inhibitor and corn inhibitor to exclude kallikrein and FXIIa respectively. No difference in PK-level could be registered for the two kinds of plasma, but the level of FXII had increased to about 150% in the pregnancy plasma. No difference in HK-level was observed, whereas the LK-level was significantly higher in pregnancy plasma, about 250% and 160% in rocket immunoassay and bioassay respectively. In fractions from gel filtration of plasma acetone-activated in the presence of benzamidine (BPLa), kallikrein was assayed as S-2302 amidase, HK and LK were measured in rocket immunoassay, and HK and FXII were studied in PAGE immunoblot experiments. In contrast to previous results obtained upon gel filtration of CPLa, not only kallikrein and HK, but in addition also FXII now appeared together in the same fractions and as two separate peaks. One peak eluting in early fractions (gel mol. wt. 300-400 KD), and one late eluting peak of proteins adsorbed to the gel material. The first peak was notably marked in pregnancy plasma. The results provide support for the assumption of an association in plasma between the three contact activation factors studied.

Mechanism of the participation of the contact system in the Vroman effect. Review and summary

The contact system comprises three zymogens (factor XII, factor XI, and prekallikrein) and the non-enzymatic activation cofactor, high-molecular-weight kininogen (HK). When blood comes into contact with negatively charged surfaces, a small amount of factor XII is adsorbed and activated which, in turn, generates kallikrein from prekallikrein. Kallikrein amplifies the activation of the contact system by producing additional factor XIIa molecules as well as by activating the cofactor, HK, to HKa. HKa, while complexed with either prekallikrein or factor XI, can penetrate a barrier of fibrinogen and adsorb to the surface, where it optimally positions these zymogens for activation by adjacent factor XIIa molecules. Factor XIa can then degrade the light chain of HKa, producing the inactive cofactor HKi, which no longer has the ability to adsorb to a surface or support coagulation. The Vroman effect refers to the 'conversion' of fibrinogen from plasma on a negatively charged surface. Fibrinogen is detectable within seconds after normal plasma contacts the surface but, within minutes, is undetectable. On the other hand, HK, although not initially detectable on the surface, is found at later times when fibrinogen is no longer visible. However, in plasma lacking factor XII or HK, fibrinogen remains detectable at times when it is undetectable in normal plasma. The phenomenon of the Vroman effect is explained by the mechanism of surface-dependent activation of factor XII, which both directly and indirectly (through the formation of kallikrein) generates HKa from HK. HKa (but not HK) displaces fibrinogen from the surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibrinolytic studies in 13 unrelated families with factor XII deficiency

BACKGROUND AND METHODS

We report the results of extensive "in vitro" fibrinolytic studies in 18 homozygous and 14 obligatory heterozygous subjects belonging to 13 unrelated families with factor XII deficiency. All homozygotes had unmeasurable factor XII activity (XII:C) and antigen (XII:Ag). None had bleeding symptoms, whereas a myocardial infarction occurred in one of them at age 51. In heterozygotes XII:C and XII:Ag were 55.9 +/- 14.1% and 52.1 +/- 16.4% (corresponding figures in 40 normals 100.6 +/- 18.3% and 101.5 +/- 29.7%). Total intrinsic fibrinolytic activity was assayed on fibrin plates in the dextran sulfate euglobulin fraction of plasma from resting subjects, to which flufenamate was added to inhibit blood plasminogen activator inhibitors.

RESULTS

Fibrinolytic activity was reduced in all homozygotes (40 +/- 12 BAU/ml) in comparison to heterozygotes (103 +/- 12 BAU/ml) and normals (98 +/- 20 BAU/ml). The addition of purified activated beta-XII led to a complete restoration of fibrinolysis in homozygotes. The addition of anti-urokinase antibodies completely suppressed the reduced intrinsic fibrinolytic activity in homozygotes (4 +/- 7 BAU/ml), whereas a reduction to about 50% was evident in heterozygotes and normals.

CONCLUSIONS

Our data confirm that reduced "in vitro" intrinsic fibrinolytic activity is a common finding in homozygous factor XII deficiency and that two independent mechanisms, one factor XII-dependent and urokinase-independent and the other factor XII-independent and urokinase-dependent, are responsible for the generation of intrinsic fibrinolysis in human plasma.

A new Italian family with severe prekallikrein deficiency. Desmopressin-induced fibrinolysis and coagulation changes in homozygous and heterozygous members

In this paper we report the case of a new Italian family with severe cross-reacting material prekallikrein deficiency (CRM-). The proposita is a 22-year-old woman referred for evaluating an extremely prolonged activated partial thromboplastin time (APTT) detected during a routine screening. No clearcut bleeding history was reported. Prekallikrein antigen and activity were not measurable. The other contact-phase factors were within the normal range. Using an electromechanical coagulometer, six different commercial reagents yielded a markedly prolonged APTT (ratio greater than 2). By prolonging the incubation time up to 10 min, APTT was normalized only with reagents employing ellagic acid as activator. On the contrary, APTT remained markedly prolonged using particulate activators (i.e. micronized silica and celite). No differences were observed using either rabbit or bovine brain cephalin. APTT was also performed on a laser automated ACL instrument; in this case reagents using ellagic acid yielded only moderately prolonged APTT values (ratio 1.3 vs 1.4). The intrinsic fibrinolytic activity, as assessed by blood activator inventory test, was found to be moderately reduced (about 50% of normal) in the proposita, whereas normal values were measured in the heterozygous relatives. After infusion of 0.3 micrograms/kg 1-desamino-8-D-arginine vasopressin (DDAVP), kallikrein levels did not change in the proposita and her heterozygous relatives. A normal release of tissue-plasminogen activator, as assessed by fibrin-plate assay, was observed in all family members including the proposita.

Activation of human Hageman factor by Pseudomonas aeruginosa elastase in the presence or absence of negatively charged substance in vitro

Human Hageman factor, a plasma proteinase zymogen, was activated in vitro under a near physiological condition (pH 7.8, ionic strength I = 0.14, 37 degrees C) by Pseudomonas aeruginosa elastase, which is a zinc-dependent tissue destructive neutral proteinase. This activation was completely inhibited by a specific inhibitor of the elastase, HONHCOCH(CH2C6H5)CO-Ala-Gly-NH2, at a concentration as low as 10 microM. In this activation Hagemen factor was cleaved, in a limited fashion, liberating two fragments with apparent molecular masses of 40 and 30 kDa, respectively. The appearance of the latter seemed to correspond chronologically to the generation of activated Hageman factor. Kinetic parameters of the enzymatic activation were kcat = 5.8 x 10(-3) s-1, Km = 4.3 x 10(-7) M and kcat/Km = 1.4 x 10(4) M-1 x s-1. This Km value is close to the plasma concentration of Hageman factor. Another zinc-dependent proteinase, P. aeruginosa alkaline proteinase, showed a negligible Hageman factor activation. In the presence of a negatively charged soluble substance, dextran sulfate (0.3-3 micrograms/ml), the activation rate by the elastase increased several fold, with the kinetic parameters of kcat = 13.9 x 10(-3) s-1, Km = 1.6 x 10(-7) M and kcat/Km = 8.5 x 10(4) M-1 x s-1. These results suggested a participation of the Hageman factor-dependent system in the inflammatory response to pseudomonal infections, due to the initiation of the system by the bacterial elastase.

Hepatocytes express blood coagulation factor XII (Hageman factor)

The liver synthesizes blood coagulation factor XII (Hageman factor). The specific cell that expresses factor XII, however, has not been previously identified. We used primary rat hepatocytes cultured in serum-free medium to study the transcription, de novo synthesis, and secretion of factor XII. A 32P-labeled human factor XII complementary DNA probe was used for RNA blot hybridization. A single band of hybridization at 2.4 kilobases appeared in blots of polyadenylated RNA derived from 24-hour hepatocyte cultures. This corresponds to the known size of factor XII-processed primary transcript (messenger RNA). Cultured hepatocytes secreted labeled factor XII when tritiated leucine was added to the medium, indicating that the hepatocytes used 3H-leucine to synthesize factor XII de novo. In these hepatocyte cultures immunoreactive factor XII levels progressively increased in 24 hours and factor XII clotting activity increased in parallel. Cycloheximide inhibited the accumulation of both immunoreactive and coagulant factor XII. Secreted factor XII from the rat hepatocytes comigrated with authentic rat plasma factor XII at 80,000 molecular weight in a Western immunoblot. These data indicate that cultured hepatocytes transcribe, synthesize, and secrete authentic factor XII.

Interactions of C1(-)-inhibitors from normal persons and patients with type II hereditary angioneurotic edema with purified activated Hageman factor (factor XIIa)

Activated high molecular weight Hageman factor (75 Kd) and Hageman factor carboxy-terminal fragments both formed complexes with purified C1(-)-inhibitor, but the Hageman factor fragments appeared to have a higher affinity for the C1(-)-inhibitor than activated Hageman factor. Therefore, the clot-promoting activity of activated Hageman factor might be relatively unimpaired if Hageman factor fragments are also present. Normal C1(-)-inhibitor was cleaved by Hageman factor fragments. Clot-promoting activity was not generated in Hageman factor by exposure to Hageman factor fragments, nor was Hageman factor cleaved by Hageman factor fragments. When Hageman factor was cleaved by streptokinase-activated plasminogen, a 40 Kd fragment was released. In contrast to their interactions with other proteinases, which are blocked by normal C1(-)-inhibitor, Type II C1(-)-inhibitors from plasmas of affected members of eight different kindred with this form of hereditary angioneurotic edema all inhibited the specific coagulant activity of activated Hageman factor to some degree. They did not all form complexes with activated Hageman factor that were stable during sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

A new index for collagen induced platelet aggregation

In this paper, we propose a new index of platelet aggregation for optical aggregometry, the "R" value. This represents the rate of change in the half time for platelet aggregation (T1/2) induced by collagen with changes in the platelet concentration and expresses the degree of platelet sensitivity to collagen. The "R" value has been shown to reflect the aggregability of platelets due to activation of the contact factors. The "R" values were significantly different in the acute and chronic phases of occlusive arterial disease, while ordinary platelet aggregation parameters did not change. A decrease in the "R" value appears to indicate a platelet hyperfunction and hypercoagulable state, in other words a prethrombotic state.

Pseudomonas elastase acts as a virulence factor in burned hosts by Hageman factor-dependent activation of the host kinin cascade

Purified Pseudomonas elastase injected subcutaneously into the skin of an Evans blue dye-injected (intravenously) guinea pig caused dye leakage similar to that observed when histamine or bradykinin was injected in the same animal. The histamine-induced dye leakage was ablated in antihistamine-treated guinea pigs, but elastase- and bradykinin-induced dye leakages were not. Local injections of specific inhibitors of the host Hageman factor-dependent bradykinin-generating pathway given immediately prior to elastase injection reduced dye leakage in a dose-related manner. Elastase-related dye release was enhanced when angiotension-converting enzyme inhibitor, a substance which prevents host enzymes from breaking down bradykinin, was injected prior to elastase injection. We conclude that Pseudomonas elastase generates bradykinin in the infected host via a Hageman factor-dependent pathway.

Coagulation factor XII (Hageman factor) Washington D.C.: inactive factor XIIa results from Cys-571----Ser substitution

Structural studies on a congenital abnormal coagulation factor XII (Hageman factor), factor XII Washington D.C., have been performed to identify the defect responsible for its lack of procoagulant activity. Amino acid sequence analysis of a tryptic peptide isolated from the abnormal factor XII indicated that Cys-571 (equivalent to Cys-220 in the chymotrypsin numbering system) had been replaced by serine. No other substitutions in the active-site triad--namely, His-393, Asp-442, and Ser-544--were found. We propose that the Cys-571----Ser replacement found in this factor XII variant destroys the formation of the disulfide linkage between Cys-540 and Cys-571, giving rise to an altered conformation of the active-site serine residue or the secondary substrate-binding site and, thus, leads to the loss of enzyme activity.

Contact phase of blood coagulation is not activated in edema of high altitude

To examine whether bradykinin generated by the activation of the contact phase of blood coagulation is involved in the pathogenesis of edema occurring after acute exposure to high altitude, 15 mountaineers were examined at 490 m and 1, 3, and 5 days after arrival at 4,559 m. The clotting activity levels of factor XII, factor XI, plasma prekallikrein, and high-molecular-weight kininogen (HMWK) were measured, and plasma kallikrein-induced proteolytic cleavage of HMWK was assessed by ligand blotting by use of radiolabeled factor XI. After an ascent on foot from 1,170 to 4,559 m in 3 days, three subjects developed high-altitude pulmonary edema, and four subjects presented facial edema. There was no evidence for activation of the contact system in any subject as demonstrated by the lack of proteolytic cleavage of HMWK at high altitude. The absence of contact system activation was further supported by stable plasma levels of the individual factors of contact activation. Therefore, we conclude that bradykinin generated by plasma kallikrein-induced cleavage of HMWK is not involved in the pathogenesis of edema due to acute exposure to high altitude.

Activation of the contact system of coagulation by a monoclonal antibody directed against a neodeterminant in the heavy chain region of human coagulation factor XII (Hageman factor)

We studied the characteristics of two monoclonal antibodies (mAbs), F1 and F3, against human coagulation factor XII (Hageman factor). Experiments with trypsin-digested 125I-factor XII revealed that the epitope for mAb F1 is located in the NH2-terminal Mr 40,100 portion of factor XII, whereas that for mAb F3 resides in the COOH-terminal Mr 30,000 portion of this protein. Factor XII in fresh plasma (single-chain factor XII) bound approximately 190 times less to mAb F1 than factor XII in dextran sulfate-activated plasma (cleaved factor XII). However, no difference in accessibility of the epitope for mAb F1 was observed between cleaved and single-chain factor XII when bound to glass. mAb F3 appeared to bind to both single-chain and cleaved factor XII in plasma as well as when bound to glass. Neither mAb F1, nor F3 affected the amidolytic activity of factor XIIa, whereas both mAb F1 and F3 inhibited factor XII-coagulant activity to about 15 and 70%, respectively, at a molar ratio of mAb to factor XII of 20 to 1. mAb F1, as well as F(ab')2 and F(ab') fragments of this antibody induced activation of the contact system in plasma, as reflected by the generation of factor XIIa. C1 inhibitor and kallikrein. C1 inhibitor complexes. Activation was induced neither upon incubation with mAb F3, nor with that of control mAbs. mAb F1-induced contact activation required the presence of factor XII, prekallikrein, and high molecular weight kininogen and, in contrast to activation by negatively charged surfaces, was not inhibited by the presence of Polybrene. Based on these results we propose that a conformational change in factor XII is a key event in the activation process of this molecule. This conformational change can be induced by binding of factor XII to a surface as well as by proteolytic cleavage. As mAb F1 can also induce this conformational change, this antibody may provide a unique tool in studies of the activation of factor XII.

Interaction of type 1 plasminogen activator inhibitor with the enzymes of the contact activation system

The interaction between type 1 plasminogen activator inhibitor (PAI-1), a serine protease inhibitor, and the three serine proteases generated during contact activation of plasma was studied using functional and immunologic approaches. Incubation of Factor XIIa, Factor XIa, and plasma kallikrein with either purified PAI-1 or platelet-derived PAI-1 resulted in the formation of sodium dodecyl sulfate-stable complexes as revealed by immunoblotting techniques. Functional assays indicated that Factor XIa and, to a lesser extent, Factor XIIa and plasma kallikrein neutralized the ability of purified PAI-1 to bind to immobilized tissue-type plasminogen activator (t-PA). Immunoblotting demonstrated that these enzymes also neutralized the ability of PAI-1 to form complexes with fluid-phase t-PA. Clot lysis assays employing purified proteins and 125I-fibrinogen were used to investigate the profibrinolytic effect of these contact activation enzymes. At enzyme concentrations that did not result in direct activation of plasminogen, only Factor XIa was capable of stimulating the lysis of clots supplemented with both t-PA and PAI-1. As a consequence of their interactions with PAI-1, the amidolytic activity of Factor XIIa, Factor XIa, and plasma kallikrein was neutralized by this inhibitor in a time-dependent and concentration-dependent manner. Minimum values estimated for the apparent second-order rate constant of inhibition were 1.6 x 10(4), 2.1 x 10(5), and 6.0 x 10(4) M-1 s-1 for Factor XIIa, Factor XIa, and plasma kallikrein, respectively. These data define new reactions between coagulation and fibrinolysis proteins and suggest that a major mechanism for stimulation of the intrinsic fibrinolytic pathway may involve neutralization of PAI-1 by Factor XIa.

Mapping of a putative surface-binding site of human coagulation factor XII

We have localized the binding epitope(s) of two murine monoclonal antibodies (B7C9 and P5-2-1) that were shown previously to inhibit the activation of human coagulation factor XII by negatively charged surfaces. A factor XII cDNA expression library in lambda gt11 was screened with antibody B7C9, and 16 immunoreactive bacteriophage were isolated. Fusion proteins from each of the recombinant phage were reactive with both monoclonal antibodies. Two of the phage cDNA inserts were found to code for amino acid residues -6-+31 and +1-+47 of factor XII, respectively, thereby defining the limits of the antigenic peptide to amino acids +1-+31. Each of the remaining 14 recombinant phage contained longer factor XII cDNA inserts that included sequences coding for the amino-terminal 31 amino acid residues. These results were confirmed by direct binding of antibody B7C9 to synthetic peptides containing amino acids 1-14 and 1-28 of factor XII. Further experiments with a set of nested peptides also indicated that amino acid residues 1-4 were essential but not sufficient for binding of B7C9 to the peptides. Hydrophobicity analysis of the amino-terminal region of plasma factor XII revealed a highly hydrophilic region between amino acid residues 5 and 15 that contained positively charged lysine residues at positions 8, 11, and 13. We conclude that a major epitope(s) recognized by monoclonal antibodies B7C9 and P5-2-1 is present in the amino-terminal 28 amino acids of factor XII. It is proposed that binding of these antibodies to factor XII blocks interaction of the positively charged region between residues 5 and 15 with negatively charged surfaces, thereby inhibiting activation.

Significance of various anticoagulation therapies during use of a left ventricular assist device

A multicomparative study to establish adequate anticoagulation therapy for left ventricular assist devices was undertaken by administrating various anticoagulants: heparin, a prostacyclin analogue combined with a protease inhibitor; thromboxane A2 synthetase inhibitor; or a protease inhibitor alone. Our investigation suggested that combined administration of prostacyclin analogue and protease inhibitor (FUT-175) is ideal anticoagulation therapy from the point of blood coagulation and fibrinolysis. Currently, however, sole administration of FUT-175 is adequate anticoagulation therapy during clinical use of left ventricular assist devices.

Characterization of blood microemboli associated with ex vivo left ventricular assist devices in a bovine model

An ex vivo left ventricular assist device (LVAD) model was used in calves to study the production of blood microemboli (BME) and to evaluate possible correlations between constant-pressure filtration (CPF) measurements of flow-resistant BME, light-scattering microemboli detection (LSMD), observable thrombus accumulation, and hematologic markers. Aortic LVAD cannulae were implanted through the chest wall in two calves, and each calf received a series of LVADs, each operating 1-4 days. Blood samples from the LVADs underwent CPF through 20 mu pore filters at 20 mm Hg to produce estimates of occlusive BME concentration. Laser (He-Ne) light was directed through the outflow cannula, and the differentially-scattered light was detected for computer estimation of microemboli size, volume, and frequency. Blood chemistry and coagulation parameters were also analyzed. Removed LVADs were examined with polar coordinate mapping of accumulated perivalvular thrombi. One ventricle produced significantly greater CPF results, LSMD results, and Factor XII levels. During the use of that ventricle, the CPF results increased slowly with time after LVAD connection, while the LSMD results and Factor XII levels increased immediately after connection, followed by a later decrease. This contrast is explainable in terms of the dynamic development of BME strength. The calf model appears useful for the study of thrombogenesis, and the CPF and LSMD methods of BME analysis complement each other, and other measurements.

Activation of hageman factor and prekallikrein and generation of kinin by various microbial proteinases

Activation of the Hageman factor-kallikrein-kinin system by serratial 56-kDa proteinase was previously demonstrated (Matsumoto, K., Yamamoto, T., Kamata, T., and Maeda, H. (1984) J. Biochem. (Tokyo) 96, 739-749; Kamata, R., Yamamoto, T., Matsumoto, K., and Maeda, H. (1985) Infect. Immun. 48, 747-753). To investigate whether the activation of the system is specific for 56-kDa proteinase or is found similarly with other microbial proteinases, 11 proteinases of microbial origins were studied; the 56-kDa proteinase was the control. For in vitro studies, activation of guinea pig Hageman factor and prekallikrein was examined in purified systems as well as in plasma as a zymogen source. Specific antibodies and inhibitors confirmed the activation steps of the cascade. In the in vivo study the enhancement of vascular permeability in guinea pig skin and its sensitivity to inhibitors of activated Hageman factor, plasma kallikrein, or a kininase were examined. The results from the in vivo experiments were consistent with those in vitro. Taking all the data together, we classified the 11 microbial proteinases into three groups as follows: 1) Serratia marcescens 56-, 60-, and 73-kDa proteinases, Pseudomonas aeruginosa alkaline proteinase and elastase, and Aspergillus melleus proteinase (this group activated Hageman factor but not prekallikrein); 2) Vibrio vulnificus proteinase, subtilisin from Bacillus subtilis, and thermolysin from Bacillus stearothermophilus (this group activated both Hageman factor and prekallikrein); 3) Streptomyces caespitosus proteinase and V8 proteinase from Staphylococcus aureus (this group activated neither Hageman factor nor prekallikrein, but generated kinin from high molecular weight kininogen directly).

Release of elastase from purified human lung mast cells and basophils. Identification as a Hageman factor cleaving enzyme

Elastase, a serine protease, is capable of inducing severe lung destruction in experimental animal models. We now report that this proteinase exists preformed in neutrophil-free sonicates of purified human lung mast cells (greater than 98% purity) and in circulating peripheral blood basophils (greater than 97% purity). The elastase levels in both cell types (41-174 ng/10(6) cells) represents approximately 3-20% of those found in human neutrophils; both cell types released their elastase following anti-IgE and ionophore A23187 challenge. The apparent molecular size of the mast cell enzyme on Sephadex G-100 gel filtration, as well as its inhibition profile, was identical to that of purified human neutrophil elastase. This mast cell elastase is identical to our previously reported mast cell-derived Hageman factor cleaving activity. Mast cell-, basophil-, and neutrophil-derived elastases cleave Hageman factor into fragments of 52,000 and 28,000 Da; cleavage by all three enzymes is inhibited by preincubation with polyclonal antibodies directed against human neutrophil elastase.

Plasminogen activators in dextran sulfate-activated euglobulin fractions: a molecular analysis of factor XII- and prekallikrein-dependent fibrinolysis

To elucidate the mechanism by which activation of the contact system of blood coagulation leads to expression of fibrinolytic activity, we have determined the molecular characteristics of the plasminogen activators present in dextran sulfate-treated euglobulin fractions by electrophoretic-zymographic analysis and specific immunoadsorption. In addition to free and protease inhibitor-bound tissue-type plasminogen activator (t-PA), dextran sulfate precipitates of euglobulins contained the complex formed between plasma kallikrein and C1-inhibitor, an indicator of prekallikrein activation. These precipitates also contained substantial fibrinolytic activity related to urinary-type plasminogen activator (u-PA). Autoradiographic analysis was then used to evaluate the cleavage of 125I-single-chain u-PA (prourokinase) in dextran sulfate euglobulins as well as after exposure to kallikrein or beta-factor XIIa. This analysis supported the conclusion that plasma kallikrein-mediated cleavage and activation of single-chain u-PA is the mechanism operative for the development of lytic activity in euglobulin precipitates following activation of the contact system.