Commercial Immunodepleted Deficient Plasmas Contain Cleaved High Molecular Weight Kininogen (HK)

Abstract High molecular weight kininogen (HK) is known to bind specifically and saturably to Mac-1 with a Kd = 9–18 nM for neutrophils and to uPAR with a Kd =30 nM for endothelial cells. However, the functional results of HK interaction with Mac-1 or uPAR on leukocytes is not fully understood. Kallikrein cleavage of single chain HK to a two chain form (HKa) with release of bradykinin (BK) occurs in sepsis, arthritis, and inflammatory bowel disease. We hypothesized that HKa stimulates secretion of inflammatory cytokines. Mononuclear cells were isolated from normal subjects by a Histopaque density gradient. We have expressed kininogen domain 3 (D3) and a fragment of domain 3, coded for by exon 7, E7P (aaG235-Q292), in E. Coli as glutathione S-transferase (GST) fusion proteins. HK and HKa were purified proteins. GST was recombinant. All proteins contained <0.01 EU/ml endotoxin. For all experiments, 2 X 106/ml mononuclear cells/ml were preincubated with monoclonal antibodies, murine IgG (both at 1.8 mM) or HANKS buffer containing 0.15 M NaCl, pH 7.4 for 30 minutes at 37°C. HK, HKa, GST-D3, GST-E7P, GST-D5 or GST all at 600 nM were added. Centrifugation allowed separation of the mononuclear cell suspension into cells and supernatant. The latter was used for assay of interleukin-1β (IL-1β) by ELISA. HK and all fragments tested stimulated secretion of IL-1β of 84.8 to 306.3 pg/ml when incubated with mononuclear cells for 30 minutes at 37°C. Anti-Mac-1 antibody inhibited IL-1β secretion by HK 100%, by HKa 89%, by GST-D3 78%, by GST-E7P 94% and by GST-D5 98%. Anti-uPAR antibody inhibited IL-1β release by HK 88%, by HKa 77%, by GST-D3 95%, by GST-E7P 85%, and by GST-D5 76%. Inhibition by both receptor antibodies is consistent with their known complex formation. A monoclonal antibody (mAb) to HK D5 (C11C1) and a mAb to HK D3 (2B5) both inhibited IL-1β release by HK, HKa, GST-D5 and GST-D3 indicate that both D3 and D5 are important in cytokine release. Murine IgG gave 0% inhibition in all studies. These results indicate that kininogen may contribute to the pathogenesis of inflammatory diseases by releasing IL-1β from human blood mononuclear cells.

Abstract Human high molecular weight kininogen (HMWK), a single-chain protein with mol wt 120,000, is cleaved by human urinary kallikrein (HUK) to release kinin from within a disulfide loop and form a two-chain protein that retains all the procoagulant activity of the native molecule. Cleavage of HMWK by HUK is associated with a reduction in size to mol wt 115,000, as assessed by SDS-PAGE of unreduced protein, whereas the two chains of the reduced protein present together as a single broad band with mol wt 64,000. The 64,000 chain with procoagulant activity was chromatographically separated from the nonfunctional chain of similar size. The homogeneous procoagulant chain had an amino acid composition similar to that of smaller procoagulant (“light”) chains isolated by others upon cleavage of HMWK with plasma kallikrein and elicited an antiserum that was monospecific by Ouchterlony analysis and inhibited the procoagulant function of HMWK. Thus, the limited proteolysis of HMWK by HUK has permitted, for the first time, the isolation of a stable procoagulant chain that is equal in size to the nonfunctional chain. The common terminology of “heavy” and “light” chain for kinin-free kininogen obtained with plasma kallikrein reflects the continued degradation of the procoagulant carboxyterminal chain and is not appropriate for the initial two-chain product formed when kinin is released from HMWK. It is proposed that the initial cleavage products of HMWK be designated the A-chain, the B-fragment, and the C- chain, representing the amino-terminal chain, the released vasoactive peptide containing the bradykinin sequence, and the carboxy-terminal procoagulant chain, respectively. Thus, intact HMWK would contain, in sequence, A, B, and C regions.

In this study, we show that mice lacking high-molecular-weight kininogen (HK) were resistant to lipopolysaccharide (LPS)-induced mortality and had significantly reduced circulating LPS levels. Replenishment of HK-deficient mice with human HK recovered the LPS levels and rendered the mice susceptible to LPS-induced mortality. Binding of HK to LPS occurred through the O-polysaccharide/core oligosaccharide, consistent with the ability to bind LPS from K. pneumoniae, P. aeruginosa, S. minnesota, and different E. coli strains. Binding of LPS induced plasma HK cleavage to the two-chain form (HKa, containing a heavy chain [HC] and a light chain [LC]) and bradykinin. Both HKa and the LC, but not the HC, could disaggregate LPS. The light chain bound LPS with high affinity (Kd = 1.52 × 10−9 M) through a binding site in domain 5 (DHG15). A monoclonal antibody against D5 significantly reduced LPS-induced mortality and circulating LPS levels in wild-type mice. Thus, HK, as a major LPS carrier in circulation, plays an essential role in endotoxemia.

An anti-cell adhesion globulin was purified from human plasma by heparin-affinity chromatography. The purified globulin inhibited spreading of osteosarcoma and melanoma cells on vitronectin, and of endothelial cells, platelets, and mononuclear blood cells on vitronectin or fibrinogen. It did not inhibit cell spreading on fibronectin. The protein had the strongest antiadhesive effect when preadsorbed onto the otherwise adhesive surfaces. Amino acid sequence analysis revealed that the globulin is cleaved (kinin-free) high molecular weight kininogen (HKa). Globulin fractions from normal plasma immunodepleted of high molecular weight kininogen (HK) or from an individual deficient of HK lacked adhesive activity. Uncleaved single-chain HK preadsorbed at neutral pH, HKa preadsorbed at pH greater than 8.0, and HKa degraded further to release its histidine-rich domain had little anti-adhesive activity. These results indicate that the cationic histidine-rich domain is critical for anti-adhesive activity and is somehow mobilized upon cleavage. Vitronectin was not displaced from the surface by HKa. Thus, cleavage of HK by kallikrein results in both release of bradykinin, a potent vasoactive and growth-promoting peptide, and formation of a potent anti-adhesive protein.

Abstract Abstract 3305 Background and objective: High molecular weight kininogen (HK) is an abundant plasma protein that serves as an important component of the intrinsic pathway of coagulation. HK normally circulates as in the single chain form, but may be cleaved by plasma kallikrein to release the nonapeptide bradykinin, resulting in the formation cleaved high molecular weight kininogen (HKa) that consists of a heavy and light chain linked by a single disulfide bond. Conformational changes occurring after kallikrein cleavage result in increased exposure of histidine and glycine-rich regions with kininogen domain 5 that impart HKa with unique properties, including the ability to inhibit angiogenesis by causing selective apoptosis of proliferating endothelial cells. However, the receptors that mediate the antiangiogenic activity of HKa remain controversial, and the signaling pathways that lead to apoptosis have not been defined. Previous studies suggested possible involvement of SRC family kinases (SFK) in this process, and the purpose of this work was to further define the activation of SFKs and their downstream targets during HKa-induced endothelial cell apoptosis. Results: We first assessed the activation of SFKs in proliferating endothelial cells stimulated with bFGF before and after incubation with HKa (6–20 nM). SFKs are maintained in an inactive state through tyrosine phosphorylation of their C-terminal region mediated by the negative regulator C-terminal Src kinase (Csk). Exposure of endothelial cells to HKa caused downregulation of Csk in a dose-dependent manner within 60 minutes. In parallel, we observed a significant increase in expression of the proapoptotic SFK Lck in endothelial cells exposed to HKa, though expression of other SFKs including Lyn, Fyn, Src, Hck and Blk were not significantly altered. Increased expression of Lck was associated with activation of p53 and increased expression of the pro-apoptotic Bcl-2 family members Bax and Bak. Endothelial cell lysates prepared within 60 minutes of exposure to HKa demonstrated significant increases in the activity of caspases 3 and 7, as well as depletion of DNA fragmentation factors (DFF) 45 and 35, which cleave and inactivate DFF40, a major endonuclease involved in apoptosis. In parallel studies, endothelial cells depleted of Lck by treatment with Lck siRNA displayed loss of p53 phosphorylation, caspase 3 and 7 activity, and expression of Bax and Bad with no effects on the expression of Bad and Bid. Conclusion: These findings demonstrate a critical role for Csk in regulation of SFK activation and endothelial homeostasis, and demonstrate that downregulation of Csk by HKa leads to activation of a Lck-dependent, p53-mediated apoptotic pathway. Increasing the expression of Lck may represent a novel mechanism for regulation of aberrant angiogenesis. Disclosures: No relevant conflicts of interest to declare.

SummaryThe plasma of a 68-year-old man with cross reacting material (CRM)-positive prekallikrein (PK) deficiency was studied. PK clotting activity was <0.01 U/ml, and PK antigen was 0.1 U/ml. No circulating anticoagulant against PK was detectable. The abnormal PK molecule, denoted as prekallikrein Zürich, was partially characterized by immunological and functional studies on the propositus’ plasma. Immunobiotting analysis showed the abnormal PK being a single chain molecule of the same M r (80 kDa) as normal PK. Dextran sulfate activation of the propositus’ plasma did not lead to proteolytic cleavage of the variant PK molecule, in contrast to dextran sulfate activation of a mixture of 1 volume normal plasma and 9 volumes CRM-negative PK deficient plasma. Agarose gel electrophoresis followed by immunoblotting demonstrated that PK Zürich was complexed with high molecular weight kininogen similarly to PK in normal plasma. Incubation of the propositus’ plasma with purified β-FXIIa resulted in impaired cleavage of PK Zürich when compared with PK hydrolysis in a mixture of 10% normal plasma and 90% CRM-negative PK deficient plasma. Moreover, proteolytically cleaved PK Zürich showed no enzymatic activity against factor XII and high molecular weight kininogen.These studies show that the functional defect of prekallikrein Zürich is due to an impaired cleavage by activated factor XII and probably the lack of enzymatic activity of the cleaved variant molecule.

A method for the quantitative assay of native single chain and kallikrein cleaved two-chain high molecular weight kininogen (HMWK) in plasma has been developed. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of whole plasma is followed by electroblotting of the electropherogram to nitrocellulose membranes and detection of the inmobilized HMWK with its physiologic ligands, plasma prekallikrein or factor XI. Using 1251-prekallikrein or 125I-F.XI overlay nitrocellulose bound HMWK can be visualized by autoradiography.Using unreduced SDS-PAGE cleaved two-chain HMWK (Mr 107,000 and 95,000) is electrophoretically separated from uncleaved single chain HMWK (Mr 150,000). Counting the radioactivity of the nitrocellulose pieces corresponding to cleaved HMWK permits its quantitative measurement by comparison with standards consisting of decreasing amounts of fully dextran sulfate activated normal human plasma. Single chain HMWK is similarly assayed using reduced SDS-PAGE and unactivated normal human plasma standards.This technique is highly specific and sensitive to ˜ 50 ng of either cleaved or uncleaved HMWK. Varying concentrations of cleaved HMWK were found in plasmas from patients suffering from various systemic inflanmatory conditions. Higher levels of in vivo cleaved HMWK were observed during acute attacks of hereditary angioedema due to Cl-inhibitor deficiency.This technique may be useful for the assessment of the degree of in vitro or in vivo activation of the contact system of plasma.

How single-chain urokinase (ScuPA) mediates angiogenesis is incompletely understood. ScuPA (≥4 nM) induces phosphorylated (p)ERK1/2 (MAPK44 and MAPK42) and pAkt (Ser473) in umbilical vein and dermal microvascular endothelial cells. Activation of pERK1/2 by ScuPA is blocked by PD-98059 or U-0126, and pAkt (Ser473) activation is inhibited by wortmannin or LY-294002. ScuPA (32 nM) or protease-inhibited two-chain urokinase stimulates pERK1/2 to the same extent, indicating that signaling is not dependent on enzymatic activity. ScuPA induces pERK1/2, but not pAkt (Ser473), in SIN1−/−cells, indicating that the two pathways are not identical. Peptides from domain 2 of the urokinase plasminogen activator receptor (uPAR) or domain 5 of high-molecular-weight kininogen compete with ScuPA for the induction of pERK1/2 and pAkt (Ser473). A peptide of the integrin-binding site on uPAR, a β1-integrin peptide that binds uPAR, antibody 6S6 to β1-integrin, tyrosine kinase inhibitors AG-1478 or PP3, and small interfering RNA knockdown of VEFG receptor 2, but not HER1–HER4, blocked ScuPA-induced pERK1/2 and pAkt (Ser473). ScuPA-induced endothelial cell proliferation was blocked by inhibitors of pERK1/2 and pAkt (Ser473), antibody 6S6, and uPAR or kininogen peptides. ScuPA initiated aortic sprouts and Matrigel plug angiogenesis in normal, but not uPAR-deficient, mouse aortae or mice, respectively, but these were blocked by PD-98059, LY-294002, AG-1478, or cleaved high-molecular-weight kininogen. In summary, this investigation indicates a novel, a nonproteolytic signaling pathway initiated by zymogen ScuPA and mediated by domain 2 of uPAR, β1-integrins, and VEGF receptor 2 leading to angiogenesis. Kininogens or peptides from it downregulate this pathway.

Proteolytic cleavage and activation of isolated, single chain, zymogen Hageman factor was observed in the presence of kaolin alone. The rate of cleavage of kaolin-bound Hageman factor was enhanced 50-fold by the presence of prekallikrein and high molecular weight kininogen. The two-chain 82,000 dalton form of activated Hageman factor (α-HF(a)) also cleaved kaolin- bound single-chain Hageman factor in a dose-dependent manner, yielding fragments of 28,000 and, 50,000 dahons under reducing conditions. Cleavage of kaolin-bound single-chain Hageman factor was not inhibited by preincubation with diisopropylfluorophosphate (12 mM) for 10 min, but long-term incubation of Hageman factor with diisopropylfluorophosphate (up to 48 h) resulted in inhibition of cleavage of kaolin-bound Hageman factor to an extent proportional to the inhibition of procoagulant Hageman factor activity. Hageman factor cleavage was maximal when the kaolin concentration was {approximately} 10-fold greater than the Hageman factor concentration (wt:wt), and was partially inhibited by high molecular weight kininogen. Kaolin-bound Hageman factor cleaved clotting factor XI in an amount which correlated with the extent of cleavage of the Hageman factor. These findings are compatible with the concept that single-chain Hageman factor and α- HF(a), are both capable of cleaving and activating kaolin-bound Hageman factor and that a close molecular association of kaolin-bound Hageman factor molecules is required for this reaction.