Deletion of murine kininogen gene 1 (mKng1) causes loss of plasma kininogen and delays thrombosis

Common variants of large effect in F12, KNG1, and HRG are associated with activated partial thromboplastin time

Activated partial thromboplastin time (aPTT) is associated with risk of thrombosis and coagulation disorders. We conducted a genome-wide association study for aPTT and identified significant associations with SNPs in three coagulation cascade genes, F12 (rs2731672, combined p = 2.16 x 10(-30)), KNG1 (rs710446, combined p = 9.52 x 10(-22)), and HRG (rs9898, combined p = 1.34 x 10(-11)). These three SNPs explain approximately 18% of phenotypic variance in aPTT in the Lothian Birth Cohorts.

Cleaved high molecular weight kininogen inhibits tube formation of endothelial progenitor cells via suppression of matrix metalloproteinase 2

BACKGROUND AND OBJECTIVE

Endothelial progenitor cells (EPCs) contribute to postnatal neovascularization, thus promoting wide interest in their therapeutic potential in vascular injury and prevention of their dysfunction in cardiovascular diseases. Cleaved high molecular weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system (KKS), inhibits the functions of differentiated endothelial cells including in vitro and in vivo angiogenesis. In this study, our results provided the first evidence that HKa is able to target EPCs and inhibits their tube forming capacity.

METHODS AND RESULTS

We determined the effect of HKa on EPCs using a three-dimensional vasculogenesis assay. Upon stimulation with vascular endothelial growth factor (VEGF) alone, EPCs formed vacuoles and tubes, and differentiated into capillary-like networks. As detected by gelatinolytic activity assay, VEGF stimulated secretion and activation of matrix metallopeptidase 2 (MMP-2), but not MMP-9, in the conditioned medium of 3D culture of EPCs. Specific inhibition or gene ablation of MMP-2, but not MMP-9, blocked the vacuole and tube formation by EPCs. Thus, MMP-2 is selectively required for EPC vasculogenesis. In a concentration-dependent manner, HKa significantly inhibited tube formation by EPCs and the conversion of pro-MMP-2 to MMP-2. Moreover, HKa completely blocked the association between pro-MMP-2 and alphavbeta3 integrin, and its inhibition of MMP-2 activation was dependent on the presence of alphavbeta3 integrin. In a purified system, HKa did not directly inhibit MMP-2 activity.

CONCLUSIONS

HKa inhibits tube forming capacity of EPCs by suppression of MMP-2 activation, which may constitute a novel link between activation of the KKS and EPC dysfunction.

Upregulation of tissue factor in monocytes by cleaved high molecular weight kininogen is dependent on TNF-alpha and IL-1beta

Inflammatory bowel disease and arthritis are associated with contact activation that results in cleavage of kininogen to form high molecular weight kininogen (HKa) and bradykinin. We have previously demonstrated that HKa can stimulate inflammatory cytokine and chemokine secretion from human monocytes. We now show that HKa can upregulate tissue factor antigen and procoagulant activity on human monocytes as a function of time (1-4 h) and HKa concentration (75-900 nM). The amino acid sequence responsible to block HKa effects is G440-H455. The HKa receptor macrophage-1 (Mac-1; CD11b18) is the binding site as shown by inhibition by a monoclonal antibody to CD11b/18. Chemical inhibitors of JNK, ERK, and p38 signaling pathways block cell signaling, as does an inhibitor to the transcription factor NF-kappaB. A combination of monoclonal antibodies to TNF-alpha and IL-1beta but neither alone inhibited the HKa induction of tissue factor. These results suggest that HKa mimics LPS by triggering a paracrine pathway in monocytes that depends on TNF-alpha and IL-1beta. Antibodies to kininogen or peptidomimetics might be a useful and safe therapy in inflammatory diseases or sepsis involving cytokines.

Cleaved high molecular weight kininogen inhibits tube formation of endothelial progenitor cells via suppression of matrix metalloproteinase 2

BACKGROUND AND OBJECTIVE

Endothelial progenitor cells (EPCs) contribute to postnatal neovascularization, thus promoting wide interest in their therapeutic potential in vascular injury and prevention of their dysfunction in cardiovascular diseases. Cleaved high molecular weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system (KKS), inhibits the functions of differentiated endothelial cells including in vitro and in vivo angiogenesis. In this study, our results provided the first evidence that HKa is able to target EPCs and inhibits their tube forming capacity.

METHODS AND RESULTS

We determined the effect of HKa on EPCs using a three-dimensional vasculogenesis assay. Upon stimulation with vascular endothelial growth factor (VEGF) alone, EPCs formed vacuoles and tubes, and differentiated into capillary-like networks. As detected by gelatinolytic activity assay, VEGF stimulated secretion and activation of matrix metallopeptidase 2 (MMP-2), but not MMP-9, in the conditioned medium of 3D culture of EPCs. Specific inhibition or gene ablation of MMP-2, but not MMP-9, blocked the vacuole and tube formation by EPCs. Thus, MMP-2 is selectively required for EPC vasculogenesis. In a concentration-dependent manner, HKa significantly inhibited tube formation by EPCs and the conversion of pro-MMP-2 to MMP-2. Moreover, HKa completely blocked the association between pro-MMP-2 and alphavbeta3 integrin, and its inhibition of MMP-2 activation was dependent on the presence of alphavbeta3 integrin. In a purified system, HKa did not directly inhibit MMP-2 activity.

CONCLUSIONS

HKa inhibits tube forming capacity of EPCs by suppression of MMP-2 activation, which may constitute a novel link between activation of the KKS and EPC dysfunction.

Thrombosis in flowing blood

In this issue of Blood, van der Meijden and colleagues report on the mechanisms by which collagen exposure in flow-dependent circulation contributes to thrombus formation.

Contact activation of kallikrein-kinin system by superparamagnetic iron oxide nanoparticles in vitro and in vivo

Previously we reported that plasma kallikrein and high molecular weight kininogen attach to the surface of dextran-coated superparamagnetic iron oxide nanoparticles (SPION) through the incompletely covered iron oxide core (Simberg et al., Biomaterials, 2009). Here we show that SPION also activate kallikrein-kinin system in vitro and in vivo. The serine protease activity of kallikrein was stably associated with SPION and could be detected on the nanoparticles even after extensive washing steps. The enzymatic activity was not detectable in kininogen-deficient and Factor XII-deficient plasma. The enzymatic activation could be blocked by precoating SPION with histidine-rich Domain 5 (D5) of kininogen. Importantly, the kallikrein activity was detectable in plasma of SPION-injected, but not of D5/SPION-injected mice. Tumor-targeted SPION when injected into kininogen-deficient and control mice, produced high levels of vascular clotting in tumors, suggesting that kallikrein activation is not responsible for the nanoparticle-induced thrombosis. These data could help in understanding the toxicity of nanomaterials and could be used in designing nanoparticles with controlled enzymatic activity.

The kinin B(1) receptor and inflammation: new therapeutic target for cardiovascular disease

The kinin B(1) receptor plays an important role in mediating the inflammatory effects of the kallikrein-kinin pathway. The recent development of orally available non-peptidic antagonists and genetically modified mice deficient in B(1) receptor expression have demonstrated that the receptor plays a pivotal role in the cellular, particularly neutrophil, recruitment associated with an acute inflammatory response. These tools have also enabled elucidation of the pathways involved in mediating this effect and have highlighted a major role for chemokines, particularly CXCL5 and CCL2. Neutrophil recruitment is involved in the pathogenesis of renal disease and has very recently been implicated in the early stages of atherosclerosis. In this review we discuss the most recent evidence linking the B(1) receptor with the pathogenesis of these two inflammatory cardiovascular diseases and highlight the therapeutic potential of the kinin B(1) receptor in these disease states.

Novel roles for factor XII-driven plasma contact activation system

PURPOSE OF REVIEW

Blood coagulation is a tightly regulated process, involving vascular endothelium, platelets, and plasma coagulation factors. Formation of fibrin involves a series of sequential proteolytic reactions, initiated by the 'extrinsic' and 'intrinsic' pathway of coagulation. As hereditary deficiency of factor XII, the protease that triggers the intrinsic pathway and the kallikrein-kinin system, is not associated with a bleeding disorder or other disease states, the physiological role of factor XII is unknown.

RECENT FINDINGS

Patient studies, genetically altered mouse models, and plasma assays analyzed functions of the factor XII-driven contact activation system for coagulation and inflammation. This review focuses on articles, which report phenotypization of animals deficient in the contact system proteins factor XII, factor XI and high-molecular-weight kininogen, as well as novel links between factor XII and edema formation, discovery of new in-vivo activators of factor XII, and functions of the factor XII downstream protease factor XI.

SUMMARY

Recent studies improved understanding of the factor XII-driven contact system in hemostasis, thrombosis, and inflammation. Studies in mouse models revealed that deficiency in contact system proteins protects from arterial thrombus formation, but does not affect hemostasis. Targeting contact system proteins offers new opportunities for safe anticoagulation associated with minimal bleeding risk. Furthermore, targeting factor XII activity provides an opportunity to treat edema formation.

The elusive physiologic role of Factor XII

Physiologic hemostasis upon injury involves many plasma proteins in a well-regulated cascade of proteolytic reactions to form a clot. Deficiency of blood coagulation Factors VIII, IX, or XI is associated with hemophilia. Factor XII (FXII) autoactivates by contact with a variety of artificial or biologic negatively charged surfaces (contact activation), resulting in blood coagulation and activation of the inflammatory kallikrein-kinin and complement systems. However, surprisingly, individuals deficient in FXII rarely suffer from bleeding disorders. Most biologic surfaces that activate FXII become expressed in disease states. Investigators have long searched for physiologic activators of FXII and its role in vivo. In this issue of the JCI, Maas et al. show that misfolded protein aggregates produced during systemic amyloidosis allow for plasma FXIIa and prekallikrein activation and increased formation of kallikrein-C1 inhibitor complexes, without Factor XIa activation and coagulation (see the related article beginning on page 3208). This study describes a novel biologic surface for FXII activation and activity, which initiates inflammatory events independent of hemostasis.

Misfolded proteins activate factor XII in humans, leading to kallikrein formation without initiating coagulation

When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.

Genomic analyses of Haemonchus contortus infection in sheep: abomasal fistulation and two Haemonchus strains do not substantially confound host gene expression in microarrays

To determine whether fistulation and differing strains of Haemonchus contortus complicate genome analysis of the host response to infection, two pilot experiments examined parasite development and gene expression in the abomasal mucosa of parasitised sheep. No significant differentially-expressed genes were detected in a comparison between ivermectin-susceptible McMaster and ivermectin-resistant CAVR strains of H. contortus. This demonstrated that the sheep response was not significantly altered by the ivermectin-resistance status of the parasite. However, sheep infected with McMaster strain had a significantly lower proportion of larvae and a higher mean FEC at post-mortem than sheep infected with CAVR, suggesting that McMaster larvae advance to patency faster than CAVR larvae. Abomasal fistulation resulted in significant upregulation of three genes and significant downregulation of two genes. Fistulated sheep had significantly lower FEC than the other groups but the proportion of larvae at post-mortem was not significantly different to other groups infected with the same strain (CAVR). Hence fistulation does not alter establishment of the CAVR isolate, but may slow its progression to patency. The observation that different H. contortus strains and abomasal fistulation induced minimal changes in mucosal gene expression validated the design of a subsequent experiment (manuscript in preparation) where sequential biopsies taken during infection were analysed by microarray to describe the molecular responses which inhibit larval establishment.