Some data on two purified kininogens from human plasma

The complex role of kininogens in hereditary angioedema

Human high molecular weight kininogen (HK) is the substrate from which bradykinin is released as a result of activation of the plasma “contact” system, a cascade that includes the intrinsic coagulation pathway, and a fibrinolytic pathway leading to the conversion of plasminogen to plasmin. Its distinction from low molecular weight kininogen (LK) was first made clear in studies of bovine plasma. While early studies did suggest two kininogens in human plasma also, their distinction became clear when plasma deficient in HK or both HK and LK were discovered. The light chain of HK is distinct and has the site of interaction with negatively charged surfaces (domain 5) plus a 6th domain that binds either prekallikrein or factor XI. HK is a cofactor for multiple enzymatic reactions that relate to the light chain binding properties. It augments the rate of conversion of prekallikrein to kallikrein and is essential for the activation of factor XI. It indirectly augments the “feedback” activation of factor XII by plasma kallikrein. Thus, HK deficiency has abnormalities of intrinsic coagulation and fibrinolysis akin to that of factor XII deficiency in addition to the inability to produce bradykinin by factor XII-dependent reactions. The contact cascade binds to vascular endothelial cells and HK is a critical binding factor with binding sites within domains 3 and 5. Prekallikrein (or factor XI) is attached to HK and is brought to the surface. The endothelial cell also secretes proteins that interact with the HK-prekallikrein complex resulting in kallikrein formation. These have been identified to be heat shock protein 90 (HSP 90) and prolylcarboxypeptidase. Cell release of urokinase plasminogen activator stimulates fibrinolysis. There are now 6 types of HAE with normal C1 inhibitors. One of them has a mutated kininogen but the mechanism for overproduction (presumed) of bradykinin has not yet been determined. A second has a mutation involving sulfation of proteoglycans which may lead to augmented bradykinin formation employing the cell surface reactions noted above.

Polyphosphate: a link between platelets, coagulation and inflammation

Inorganic polyphosphate (polyP) is abundant in biological organisms. PolyP is a major component of dense granules of human platelets and is secreted upon platelet activation. Studies from our lab and others have shown that polyP is a potent modulator of the blood clotting cascade, acting as a pro-hemostatic, prothrombotic and proinflammatory agent depending on its polymer size and location. PolyP may represent at least one of the long-sought (patho)physiologic activators of the contact pathway of blood clotting, and its actions may also help to explain previously unexplained abilities of activated platelets to enhance plasma clotting reactions. PolyP may have utility as a hemostatic agent to control bleeding, and conversely, polyP antagonists might have utility as antithrombotic/anti-inflammatory agents with reduced bleeding side effects. The detailed molecular mechanisms by which polyP modulates blood clotting reactions still remain to be elucidated.

Interaction of high-molecular-weight kininogen with endothelial cell binding proteins suPAR, gC1qR and cytokeratin 1 determined by surface plasmon resonance (BiaCore)

The physiologic activation of the plasma kallikrein-kinin system requires the assembly of its constituents on a cell membrane. High- molecular-weight kininogen (HK) and cleaved HK (HKa) both interact with at least three endothelial cell binding proteins: urokinase plasminogen activator receptor (uPAR), globular C1q receptor (gC1qR,) and cytokeratin 1 (CK1). The affinity of HK and HKa for endothelial cells are KD=7-52 nM. The contribution of each protein is unknown. We examined the direct binding of HK and HKa to the soluble extracellular form of uPAR (suPAR), gC1qR and CK1 using surface plasmon resonance. Each binding protein linked to a CM-5 chip and the association, dissociation and KD (equilibrium constant) were measured. The interaction of HK and HKa with each binding protein was zinc-dependent. The affinity for HK and HKa was gC1qR>CK1>suPAR, indicating that gC1qR is dominant for binding. The affinity for HKa compared to HK was the same for gC1qR, 2.6-fold tighter for CK1 but 53-fold tighter for suPAR. Complex between binding proteins was only observed between gC1qR and CK1 indicating that a binary CK1-gC1qR complex can form independently of kininogen. Although suPAR has the weakest affinity of the three binding proteins, it is the only one that distinguished between HK and HKa. This finding indicates that uPAR may be a key membrane binding protein for differential binding and signalling between the cleaved and uncleaved forms of kininogen. The role of CK1 and gC1qR may be to initially bind HK to the membrane surface before productive cleavage to HKa.

Polyphosphate and omptins: novel bacterial procoagulant agents

Derangement of the blood clotting system contributes strongly to multiple organ failure in severe sepsis. In this review, we examine two microbial modulators of the clotting system: polyphosphates and omptins. Polyphosphates are linear polymers of inorganic phosphate that are abundant in the acidocalcisomes of prokaryotes and unicellular organisms as well as in the dense granules of human platelets. Polyphosphates modulate haemostasis by: (1) triggering clotting via the contact pathway; (2) accelerating the activation of coagulation factor V (a key cofactor in blood clotting) and (3) causing fibrin to form clots whose fibrils are thicker and more resistant to fibrinolysis. While polyphosphates are found in all prokaryotes, omptins have a more limited distribution among certain Gram-negative species. Omptins are outer membrane aspartyl proteases which were recently found to proteolytically inactivate tissue factor pathway inhibitor (TFPI), the main inhibitor of the initiation phase of blood clotting. Omptin activity against TFPI requires lipopolysaccharide without O-antigen (rough LPS) such as is found on the surface of Yersinia pestis, the etiologic agent of plague. Interestingly, expression of Pla, the Yersinia pestis omptin, has a demonstrated virulence role in converting plasminogen into the fibrinolytic enzyme plasmin, which would seemingly antagonize any procoagulant effect of TFPI inactivation. However, since the rate of TFPI inactivation is much higher than the rate of plasminogen activation, we suggest that Pla may have a dual function in supporting the bubonic form of plague which is unique to Yersinia pestis.

High-molecular-weight kininogen fragments stimulate the secretion of cytokines and chemokines through uPAR, Mac-1, and gC1qR in monocytes

OBJECTIVE

Plasma high-molecular-weight kininogen (HK) is cleaved in inflammatory diseases by kallikrein to HKa with release of bradykinin (BK). We postulated a direct link between HKa and cytokine/chemokine release.

METHODS AND RESULTS

HKa, but not BK, releases cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and chemokines IL-8 and MCP-1 from isolated human mononuclear cells. At a concentration of 600 nM, glutathione-S-transferase (GST) fusion proteins of kininogen domain 3 (D3), a fragment of domain 3, E7P (aaG255-Q292), HK domain 5 (D5), the D5 recombinant peptides HG (aa K420-D474) and HGK (aa H475-S626) stimulated secretion of IL-1beta from mononuclear cells. Monoclonal antibodies (MAbs) specific for D5 or specific for D3 blocked release of IL-1beta by HKa, supporting the importance of both domains. Antibodies to HK receptors on leukocytes including Mac-1, LFA-1, uPAR, and C1qR inhibited IL-1beta secretion induced by tKa 98%, 89%, 85%, and 62%, respectively. Fractionation of mononuclear cells identified the responsible cell, a blood monocyte. Inhibitors of signaling pathways NFkB, JNK, and p38 but not extracellular signal-regulated kinase (ERK) decreased cytokine release from mononuclear cells. HKa increased the synthesis of IL-1beta as deduced by an increase of IL-1beta mRNA at 1 to 2 hours.

CONCLUSIONS

HKa domains 3 and 5 may contribute to the pathogenesis of inflammatory diseases by releasing IL-1beta from human monocytes using intracellular signaling pathways initiated by uPAR, beta2 integrins and gC1qR.

Isolation and characterization of rat plasma glandular kallikrein

A method has been developed to purify glandular kallikrein present in rat plasma by using Sepharose-Aprotinin affinity chromatography and elution of the enzyme with p-aminobenzamidine. The isolated enzyme liberated kinins from kininogen II of low molecular weight (sp. act. 14 ng kinins/min X mg) and p-nitroaniline (pNA) from the substrate S-2266 (sp. act. 1.23 nmoles pNA/min X mg); it was inhibited by aprotinin, benzamidine and rat urinary antikallikrein antibody but not by ovomucoid. In polyacrylamide gel electrophoresis, the enzymatic activities of the preparation were associated with two light protein bands of molecular weights equal to that of urinary kallikrein (35,000 daltons). Using this method, the recovery of [125I]kallikrein added to the plasma was 82-88%. The concentration of the enzyme in normal rat plasma was equivalent to 6.1 +/- 2.1 (S.D.) ng kallikrein/ml. The mean value found in nephrectomized rats was 20.0 +/- 6.3 (S.D.) ng kallikrein/ml. This increment was highly significant (P less than 0.001). Our results confirm the presence of glandular kallikrein in plasma which had been detected by other methods; they also demonstrate that the material purified from plasma is enzymatically active, suggesting that kallikrein may play a biological role in the control of blood circulation.

Radioimmunoassays of human high and low molecular weight kininogens in plasmas and platelets

Radioimmunoassays of human high molecular weight kininogen (HMWK) and low molecular weight kininogen (LMWK) were developed using antibodies directed against the light and the heavy chains of kallikrein-cleaved HMWK. With the anti-light chain antibodies, the radioimmunoassay was specific for HMWK with a detection limit of 0.4 ng. The anti-heavy chain antibodies were used to quantify the concentration of total kininogen antigens. In four different plasmas with a congenital deficiency in HMWK procoagulant activity, there was no detectable antigen in two cases and trace amounts, less than 1 micrograms/ml in the other plasmas (normal concentration: 72 +/- 6 micrograms/ml). In the absence of HMWK, the radioimmunoassay performed with the anti-heavy chain antibodies was specific for LMWK. The amount of LMWK was different in each of these patients' plasmas, ranging from no detectable antigen, i.e. less than 0.15 micrograms/ml, to a normal content. Antigens immunologically indistinguishable from plasma kininogens were detected in lysates of five times washed platelets. HMWK antigen concentration was 3.17 +/- 0.87 micrograms per 10(11) platelets (mean value in 11 donors). LMWK was also present in platelet lysates and the relative concentration versus HMWK was the same as in plasma.

Purification of single-chain human low-molecular-weight kininogen and demonstration of its cleavage by human urinary kallikrein

Human low-molecular-weight kininogen (LMWK) was purified to apparent physical and functional homogeneity by a six-step procedure consisting of ion-exchange chromatography, reverse ammonium sulfate gradient solubilization, hydrophobic chromatography on phenyl-Sepharose, gel filtration, and removal of contaminating proteins by their affinity for Affi-Gel blue and zinc. The recovery averaged 15.6% (n = 4). Purified LMWK presented as a single stained band on alkaline polyacrylamide gel electrophoresis which corresponded to the region of function in eluates from a duplicate gel. The apparent homogeneity was also observed in sodium dodecyl sulfate (SDS)-gel electrophoresis, where the protein presented as a single band of Mr = 65,000 without reduction and 68,000 with reduction. A mole of substrate released 0.8 mol of kinin in 5 min when cleaved by human urinary kallikrein (HUK), and 0.9 mol after 30 min. Cleavage of the single-chain LMWK released kinin from within a disulfide loop as indicated by the SDS-gel electrophoresis of reduced and unreduced kinin-free LMWK. The heavy chain exhibited an Mr = 62,000, which is similar to the Mr of the amino-terminal chain of human HMWK and is consistent with their antigenic relatedness. In contrast to the Mr = 64,000 procoagulant chain of human HMWK, the small (less than 10,000) carboxy-terminal chain of LMWK has no procoagulant activity and may serve only to protect the kinin moiety in the intact substrate.

Rodent kinin-forming enzyme systems--I. Purification and characterization of plasma kininogen

Low molecular weight (LMW) kininogen was purified 70-fold with a 16% yield from fresh rat plasma by DEAE-Sephadex chromatography, ammonium sulfate precipitation, Sephadex G-200 gel filtration, SP-Sephadex chromatography, CM-cellulose chromatography, and Sephadex G-200 gel filtration. Ferguson plots of polyacrylamide gel electrophoretic patterns revealed four bands with relative molecular weights of 64,000, 123,500, 252,436 and 357,900 (ratio of 1:2:4:6). Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis provided a single protein band with a molecular weight of 72,000, suggesting that the four kininogen bands had been caused by the aggregation of a single oligomeric protein. The purified LMW rat kininogen Fraction B (3.9 micrograms bradykinin/mg) was used to elicit an antiserum in the rabbit. Monospecificity of the antiserum was demonstrated by immunoelectrophoresis (Laurell rocket and Grabar methods) and, thus, the homogeneity of the kininogen was also. The purified kininogen (both Fractions A and B) formed kinin with human urinary kallikrein, rat urinary kallikrein and hog pancreatic kallikrein. Murphy-Sturm lymphosarcoma acid protease also formed kinin when incubated with the kininogen at pH 3.0. The isoelectric point for both fractions was at pH 4.3. Amino acid analyses showed the two kininogen fractions to be rich in acidic amino acids and to have a total carbohydrate content of 8.5% consisting of galactose (1.2 to 1.5%), mannose (1.9 to 2.1%), N-acetylglucosamine (4.3 to 5.1%), N-acetylgalactosamine (0.3%), and sialic acid (0.68%).

A convenient large-scale preparation of high molecular weight kininogen from human plasma

Human high molecular weight (HMW) kininogen was purified by chromatography on DEAE-Sephadex A-50 and CM-Sephadex C-50, followed by gel filtration on Sephadex G-50. From 5 l fresh human plasma approximately 120 mg HMW kininogen was obtained. The yield was 40%. The preparation had a specific activity of 14 microgram bradykinin equivalent/A280 unit. Upon polyacrylamide disc gel electrophoresis HMW kininogen was separated into two close bands, whereas only one band with an apparent Mr of 120 000 was obtained in sodium dodecyl sulfate electrophoresis. Both protein fractions separated in disc gel electrophoresis released kinins upon incubation with kallikreins. The purified HMW kininogen had an isoelectric point of 4.65 when measured by isoelectric focusing. The amino acid composition of the purified HMW kininogen is given. The amino terminus of the molecule is blocked. In oligomerization studies adducts with molecular weights up to 810 000 were obtained. HMW kininogen gave a single precipitin arc in immunoelectrophoresis with antiserum directed against HMW kininogen.

Purification of a high molecular weight kininogen from rat plasma

A high molecular weight kininogen has been isolated from rat plasma and purified. At each preparative step the kininogen concentration and purity were monitored by assay on the perfused isolated rat uterus in terms of bradykinin equivalents formed per mg protein following incubation of the plasma fractions with rodent acid protease for 24 hours at 37 degrees and pH 4.0. Kinin formation by crystalline trypsin and human pancreatic kallikrein also was compared. Citrated rat plasma first was precipitated with 43% ammonium sulfate. The kininogen fractions then were subjected to a series of gel filtration ion exchange chromatographic columns that included G-200 Sephadex, G-200: G-100 Sephadex interconnected columns, DEAE-A50 Sephadex, and hydroxylapatite. The kininogen fractions finally were subjected to preparative polyacrylamide gel electrophoresis, resulting in a final purification of 92.9-fold compared to the initial rat plasma. A single major kininogen protein band and a minor band of protein impurity were obtained on disc gel electrophoresis. Only the pancreatic kallikrein did not form kinin from this purified kininogen. The apparent molecular weight was estimated by SDS polyacrylamide gel technique to be 110,000.

Kinin-forming enzyme in human skin: the purification and characterization of a kinin-forming enzyme

A kinin-forming-enzyme in human skin extract was further purified by successive column chromatography on DEAE-cellulose, Hydroxylapatite-cellulose and Sepharose-4B. By these procedures, 2.7 mg of purified enzyme was obtained from 10 gm of original skin. The purified material was homogeneous as ascertained by cellulose acetate membrane electrophoresis, sodium dodecyl sulfate polyacrylamide gel disc electrophoresis and ultracentrifugation. It had an S20,w value of 4.3 and an apparent molecular weight of 104,000 as measured by gel filtration on Sephadex G-200. The purified enzyme was comparatively heat-stable, but was unstable below pH values of 5 and above pH 9. It possessed arginine or lysine esterolytic activity, but not tyrosine or tryptophane esterolytic activity and denatured proteolytic activity. This enzyme was not affected by metal ion, cystein, glutathion or rho-chloromercuribenzoate, but was strongly inhibited by alpha-N-rho-tosyl-L-lysine chloromethyl ketone or soybean-trypsin inhibitor. It was also inhibited by alpha 1-antitrypsin, but not by alpha 2-macroglobulin. This enzyme was confirmed to be immunologically distinct from human plasma, urinary or pancreas kallikrein.

Rapid purification of human high molecular weight kininogen

Human high molecular weight kininogen was isolated by a rapid procedure, using anion exchange chromatography on QAE-Sephadex, ammonium sulfate precipitation and cation exchange chromatography on CM-Sephadex. The poor recovery and relatively low specific activity observed in earlier experiments was found to be due to a contaminant, presumably enzymatic, capable of releasing kinin from the kininogen. The "spontaneous" kinin release was blocked by soy bean trypsin inhibitor and by C1-inactivator. The isolated kininogen was stable at different temperatures, did not contain free kinin and was a good substrate for plasma kallikrein and plasmin.

The effect of water, sodium overloading and diuretics upon urinary kallikrein

The effects of acute administration of either water or 2% NaCl solution via a stomach tube and injections of diurecits, furosemide (5, 10 mg) and acetazoleamide (5, 20 mg per rat), in adult rats upon urinary kallikrein (Kal), Na and K, were studied. Hyperhydration with water (5% b.w.) produced in 121% increase and 2% NaCl overloading (5% b.w.) 275% increase in urinary Kal within 120 min after gavage, when compared with the excretion of non hyperhydrated rats. Furosemide 5 mg in hyperhydrated animals produced in the same period an excretion of 645 +/- 52 ng BR of Kal, which is 147% higher to that excreted by the hyperhydrated controls. The same dose of furosemide in 2% NaCl loaded rats, produced an excretion of Kal equivalent to 1333 +/- 72 ng BR which is 180% greater than in controls similarly loaded. Acetazoleamide 20 mg and furosemide 5 mg produced similar excretions of Kal even though natriuresis is greater tna kalliuresis is lesser in furosemide injected rats. Evaluation of total kidney Kal has shown that a single (10 mg) or a series of furosemide injections (8 days 5 mg + 1 day 10 mg), brings about a significant (p is less than 0.001) decrease in renal Kal, but the increase of Kal excreted in the urine (120 min) is 3.5 times more (under a single injection) and 42 times more (under 9 injections) than the amount which disappears from the kidneys. Apparently furosemide not only stimulates Kal excretion, but also Kal synthesis in the kidney. The results support the concept that the Kal system would be involved in excretory functions dealing both with sodium and water excretion.