Modulation of inflammation by kininogen deficiency in a rat model of inflammatory arthritis

Identification of Aberrantly Expressed Genes during Aging in Rat Nucleus Pulposus Cells

Nucleus pulposus cells (NPCs) play a vital role in maintaining the homeostasis of the intervertebral disc (IVD). Previous studies have discovered that NPCs exhibited malfunction due to cellular senescence during disc aging and degeneration; this might be one of the key factors of IVD degeneration. Thus, we conducted this study in order to investigate the altered biofunction and the underlying genes and pathways of senescent NPCs. We isolated and identified NPCs from the tail discs of young (2 months) and old (24 months) SD rats and confirmed the senescent phenotype through SA-β-gal staining. CCK-8 assay, transwell assay, and cell scratch assay were adopted to detect the proliferous and migratory ability of two groups. Then, a rat Gene Chip Clariom™ S array was used to detect differentially expressed genes (DEGs). After rigorous bioinformatics analysis of the raw data, totally, 1038 differentially expressed genes with a fold change > 1.5 were identified out of 23189 probes. Among them, 617 were upregulated and 421 were downregulated. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted and revealed numerous number of enriched GO terms and signaling pathways associated with senescence of NPCs. A protein-protein interaction (PPI) network of the DEGs was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING) database and Cytoscape software. Module analysis was conducted for the PPI network using the MCODE plugin in Cytoscape. Hub genes were identified by the CytoHubba plugin in Cytoscape. Derived 5 hub genes and most significantly up- or downregulated genes were further verified by real-time PCR. The present study investigated underlying mechanisms in the senescence of NPCs on a genome-wide scale. The illumination of molecular mechanisms of NPCs senescence may assist the development of novel biological methods to treat degenerative disc diseases.

The Coagulation Factors Fibrinogen, Thrombin, and Factor XII in Inflammatory Disorders-A Systematic Review

Background

The interaction of coagulation factors has been shown to go beyond their traditional roles in hemostasis and to affect the development of inflammatory diseases. Key molecular players, such as fibrinogen, thrombin, or factor XII have been mechanistically and epidemiologically linked to inflammatory disorders like multiple sclerosis (MS), rheumatoid arthritis (RA), and colitis.

Objectives

To systematically review the evidence for a role of coagulation factors, especially factor XII, fibrinogen, and thrombin in inflammatory disorders like MS, RA, and bowel disorders.

Methods

A systematic literature search was done in the PubMed database to identify studies about coagulation factors in inflammatory diseases. Original articles and reviews investigating the role of the kallikrein–kinin and the coagulation system in mouse and humans were included.

Results

We identified 43 animal studies dealing with inflammatory disorders and factors of the kallikrein–kinin or the coagulation system. Different immunological influences are described and novel molecular mechanisms linking coagulation and inflammation are reported.

Conclusion

A number of studies have highlighted coagulation factors to tip the balance between hemostasis and thrombosis and between protection from infection and extensive inflammation. To optimize the treatment of chronic inflammatory disorders by these factors, further studies are necessary.

Factor XII-Driven Inflammatory Reactions with Implications for Anaphylaxis

Anaphylaxis is a life-threatening allergic reaction. It is triggered by the release of pro-inflammatory cytokines and mediators from mast cells and basophils in response to immunologic or non-immunologic mechanisms. Mediators that are released upon mast cell activation include the highly sulfated polysaccharide and inorganic polymer heparin and polyphosphate (polyP), respectively. Heparin and polyP supply a negative surface for factor XII (FXII) activation, a serine protease that drives contact system-mediated coagulation and inflammation. Activation of the FXII substrate plasma kallikrein leads to further activation of zymogen FXII and triggers the pro-inflammatory kallikrein-kinin system that results in the release of the mediator bradykinin (BK). The severity of anaphylaxis is correlated with the intensity of contact system activation, the magnitude of mast cell activation, and BK formation. The main inhibitor of the complement system, C1 esterase inhibitor, potently interferes with FXII activity, indicating a meaningful cross-link between complement and kallikrein-kinin systems. Deficiency in a functional C1 esterase inhibitor leads to a severe swelling disorder called hereditary angioedema (HAE). The significance of FXII in these disorders highlights the importance of studying how these processes are integrated and can be therapeutically targeted. In this review, we focus on how FXII integrates with inflammation and the complement system to cause anaphylaxis and HAE as well as highlight current diagnosis and treatments of BK-related diseases.

A critical role for plasma kallikrein in the pathogenesis of autoantibody-induced arthritis

The plasma kallikrein-kinin system (KKS) consists of serine proteases, prekallikrein (pKal) and factor XII (FXII), and a cofactor, high-MW kininogen (HK). Upon activation, activated pKal and FXII cleave HK to release bradykinin. Activation of this system has been noted in patients with rheumatoid arthritis, and its pathogenic role has been characterized in animal arthritic models. In this study, we generated 2 knockout mouse strains that lacked pKal and HK and determined the role of KKS in autoantibody-induced arthritis. In a K/BxN serum transfer-induced arthritis (STIA) model, mice that lacked HK, pKal, or bradykinin receptors displayed protective phenotypes in joint swelling, histologic changes in inflammation, and cytokine production; however, FXII-deficient mice developed normal arthritis. Inhibition of Kal ameliorated arthritis severity and incidence at early stage STIA and reduced the levels of major cytokines in joints. In addition to releasing bradykinin from HK, Kal directly activated monocytes to produce proinflammatory cytokines, up-regulated their C5aR and FcRIII expression, and released C5a. Immune complex increased pKal activity, which led to HK cleavage. The absence of HK is associated with a decrease in joint vasopermeability. Thus, we identify a critical role for Kal in autoantibody-induced arthritis with pleiotropic effects, which suggests that it is a new target for the inhibition of arthritis.-Yang, A., Zhou, J., Wang, B., Dai, J., Colman, R. W., Song, W., Wu, Y. A critical role for plasma kallikrein in the pathogenesis of autoantibody-induced arthritis.

The plasma contact system, a protease cascade at the nexus of inflammation, coagulation and immunity

The contact system is a potent procoagulant and proinflammatory plasma protease cascade that is initiated by binding ("contact")-induced, auto-activation of factor XII zymogen. Formed active serine protease FXIIa then cleaves plasma prekallikrein to kallikrein that in turn liberates the mediator bradykinin from its precursor high molecular weight kininogen. Bradykinin induces inflammation with implications for host defense and innate immunity. FXIIa also triggers the intrinsic pathway of coagulation that has been shown to critically contribute to thrombosis. Vice versa, FXII deficiency impairs thrombosis in animal models without inducing abnormal excessive bleeding. Recent work has established the FXIIa-driven contact system as promising target for anticoagulant and anti-inflammatory drugs. This review focuses on the biochemistry of the contact system, its regulation by endogenous and exogenous inhibitors, and roles in disease states. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Contact pathway of coagulation and inflammation

The contact system, also named as plasma kallikrein-kinin system, consists of three serine proteinases: coagulation factors XII (FXII) and XI (FXI), and plasma prekallikrein (PK), and the nonenzymatic cofactor high molecular weight kininogen (HK). This system has been investigated actively for more than 50 years. The components of this system and their interactions have been elucidated from in vitro experiments, which indicates that this system is prothrombotic by activating intrinsic pathway, and proinflammatory by producing bioactive peptide bradykinin. Although the activation of the contact system have been implicated in various types of human disease, in only a few instances is its role clearly defined. In the last 10 years, our understanding of the contact system, particularly its biology and (patho)physiology has greatly increased through investigations using gene-modified animal models. In this review we will describe a revitalized view of the contact system as a critical (patho)physiologic mediator of coagulation and inflammation.

A role for bradykinin in the development of anti-collagen antibody-induced arthritis

OBJECTIVES

Clinical and experimental observations have suggested that bradykinin, a major activation product of the plasma kallikrein-kinin system, is involved in the pathogenesis of arthritis, but the pathogenic role of bradykinin receptors remains inconclusive. In this study we examined whether bradykinin receptors are important in the pathogenesis of anti-collagen antibody-induced arthritis (CAIA) using double receptor-deficient (B1RB2R(-/-)) mice.

METHODS

CAIA was induced in B1RB2R(+/+) and B1RB2R(-/-) mice by injection of an anti-collagen antibody cocktail on day 0 and lipopolysaccharide on day 3. Severity of disease was evaluated by measurement of joint diameter and histological analysis. The expression of proinflammatory cytokines in joint tissue and peripheral mononuclear cells was determined by ELISA and real-time RT-PCR.

RESULTS

The absent expression of B1R and B2R mRNA in B1RB2R(-/-) mice was confirmed by RT-PCR. Although B1RB2R(+/+) mice developed severe CAIA, the severity of the disease was significantly attenuated in B1RB2R(-/-) mice. In B1RB2R(+/+) mice bearing CAIA, both B1R and B2R mRNA levels were increased in joint tissue and peripheral mononuclear cells. Compared with B1RB2R(+/+) mice, the production of IL-1β and IL-6 in joint tissue and their mRNA expression in peripheral mononuclear cells were remarkably reduced in B1RB2R(-/-) mice.

CONCLUSION

These observations provide genetic evidence that bradykinin plays an important role in the pathogenesis of CAIA. B1R, whose expression is induced in inflamed joint tissue and peripheral inflammatory cells, is important in the development of CAIA.

Role of plasma kallikrein-kinin system activation in synovial recruitment of endothelial progenitor cells in experimental arthritis

OBJECTIVE

To examine whether activation of the plasma kallikrein-kinin system (KKS) mediates synovial recruitment of endothelial progenitor cells (EPCs) in arthritis.

METHODS

EPCs were isolated from Lewis rat bone marrow, and expression of progenitor cell-lineage markers and functional properties were characterized. EPCs were injected intravenously into Lewis rats with arthritis, and their recruitment and formation of de novo blood vessels in inflamed synovium were evaluated. The role of plasma KKS was examined using a plasma kallikrein inhibitor (EPI-KAL2) and an antikallikrein antibody (13G11). A transendothelial migration assay was used to determine the role of bradykinin and its receptor in EPC mobilization.

RESULTS

EPCs from Lewis rats exhibited a strong capacity to form tubes and vacuoles and expressed increased levels of bradykinin type 2 receptor (B2R) and progenitor cell markers CD34 and Sca-1. In Lewis rats with arthritis, EPCs were recruited into inflamed synovium at the acute phase of disease and formed de novo blood vessels. Inhibition of plasma kallikrein by EPI-KAL2 and 13G11 significantly suppressed synovial recruitment of EPCs and hyperproliferation of synovial cells. Bradykinin stimulated transendothelial migration of EPCs in a concentration-dependent manner. This was mediated by B2R, as demonstrated by the finding that knockdown of B2R with silencing RNA completely blocked bradykinin-stimulated transendothelial migration. Moreover, bradykinin selectively up-regulated expression of the homing receptor CXCR4 in EPCs.

CONCLUSION

These observations demonstrate a novel role of plasma KKS activation in the synovial recruitment of EPCs in arthritis, acting via kallikrein activation and B2R-dependent mechanisms. B2R might be involved in the mobilization of EPCs via up-regulation of CXCR4.

High molecular weight kininogen activates B2 receptor signaling pathway in human vascular endothelial cells

The nonenzymatic cofactor high molecular weight kininogen (HK) is a precursor of bradykinin (BK). The production of BK from HK by plasma kallikrein has been implicated in the pathogenesis of inflammation and vascular injury. However, the functional role of HK in the absence of prekallikrein (PK), the proenzyme of plasma kallikrein, on vascular endothelial cells is not fully defined. In addition, no clinical abnormality is seen in PK-deficient patients. Therefore, an investigation into the effect of HK, in the absence of PK, on human pulmonary artery endothelial cell (HPAEC) function was performed. HK caused a marked and dose-dependent increase in the intracellular calcium [Ca(2+)](i) level in HPAEC. Gd(3+) and verapamil potentiated the HK-induced increase in [Ca(2+)](i). HK-induced Ca(2+) increase stimulated endothelial nitric oxide (NO) and prostacyclin (PGI(2)) production. The inhibitors of B(2) receptor-dependent signaling pathway impaired HK-mediated signal transduction in HPAEC. HK had no effect on endothelial permeability at physiological concentration. This study demonstrated that HK regulates endothelial cell function. HK could play an important role in maintaining normal endothelial function and blood flow and serve as a cardioprotective peptide.

Cleaved high-molecular-weight kininogen accelerates the onset of endothelial progenitor cell senescence by induction of reactive oxygen species

OBJECTIVE

Cleaved high-molecular-weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system, inhibits endothelial cell functions. We questioned whether HKa affects the function of endothelial progenitor cells (EPCs) and accelerates their senescence.

METHODS AND RESULTS

Treatment with HKa for 2 weeks markedly inhibited the formation of large colonies and proliferation of EPCs on collagen surfaces, whereas HKa did not affect collagen-mediated EPC adhesion and survival. Concomitantly, treated EPCs displayed flattened and giant cell morphological changes and formation of intracellular vacuoles. As determined by acidic β-galactosidase staining, HKa increased senescent EPCs by 2- and >3-fold after culture for 1 and 2 weeks, respectively. In addition, HKa suppressed the telomerase activity of EPCs. HKa concentration-dependently increased the generation of intracellular reactive oxygen species (ROS) and markedly upregulated p38 kinase phosphorylation and prosenescence molecule p16(INK4a) expression. SB203580, a p38 inhibitor, attenuated the level of HKa-enhanced p16(INK4a) expression. Either quenching of ROS or inhibition of p38 kinase prevented HKa-induced EPC senescence.

CONCLUSIONS

HKa accelerates the onset of EPC senescence by activating the ROS-p38 kinase-p16(INK4a) signaling cascade. This novel activity of HKa points out the likelihood of HKa serving as an endogenous inducer of EPC senescence.

Chondroitin sulfate and abnormal contact system in rheumatoid arthritis

Rheumatoid arthritis (RA) is a heterogeneous autoimmune disease that affects 1% of the population worldwide. In the K/BxN mouse model of RA, autoantibodies specific for glucose-6-phosphate isomerase (GPI) from these mice can transfer joint-specific inflammation to normal mice. The binding of GPI/autoantibody to the cartilage surface is a prerequisite for autoantibody-induced joint-specific inflammation in the mouse model. Chondroitin sulfate (CS) on cartilage surface is the long sought high-affinity receptor for GPI. The binding affinity and structural differences between mouse paw/ankle CS and knee/elbow CS correlate with the distal to proximal disease severity in these joints. The data presented in this chapter indicate that autoantigen/autoantibodies in blood circulation activate contact system to produce vasodilators to allow immune complex, protein aggregates, and other plasma proteins to get into the joints. Cartilage surface CS binds and retains autoantigen/autoantibodies. The CS/autoantigen/autoantibody complexes could induce C3a and C5a production through contact system activation. C3a and C5a trigger degranulation of mast cells, which further recruit plasma contact system and complement proteins, immune cells, and immune activation factors to facilitate joint-specific tissue destruction. Therefore, either reducing autoantibody production or inhibiting autoantibody-induced contact system activation might be effective in RA prevention.

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.

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

High-molecular-weight kininogen (HK) plays an important role in the assembly of the plasma kallikrein-kinin system. While the human genome contains a single copy of the kininogen gene, 3 copies exist in the rat (1 encoding K-kininogen and 2 encoding T-kininogen). Here, we confirm that the mouse genome contains 2 homologous kininogen genes, mKng1 and mKng2, and demonstrate that these genes are expressed in a tissue-specific manner. To determine the roles of these genes in murine development and physiology, we disrupted mKng1, which is expressed primarily in the liver. mKng1(-/-) mice were viable, but lacked plasma HK and low-molecular-weight kininogen (LK), as well as DeltamHK-D5, a novel kininogen isoform that lacks kininogen domain 5. Moreover, despite normal tail vein bleeding times, mKng1(-/-) mice displayed a significantly prolonged time to carotid artery occlusion following Rose Bengal administration and laser-induced arterial injury. These results suggest that a single gene, mKng1, is responsible for production of plasma kininogen, and that plasma HK contributes to induced arterial thrombosis in mice.

The alterations of mouse plasma proteins during septic development

A fundamental issue for sepsis therapy is to control the development of inflammation at an early stage. With cecal ligation and puncture (CLP) surgery, the mouse model has clearly shown the septic signs triggered by chronic insult. To monitor the plasma proteomic responses to sepsis, the mouse blood was collected at intervals after sham and CLP surgery followed by the sample treatment to remove high abundance serum albumin. The treated mouse plasma proteins were well resolved by two-dimensional electrophoresis (2-DE). The image analysis revealed that these 2-DE spots observed from the sham and the CLP samples 4 h after surgery were comparable, whereas more than 30 different spots appeared on the 2-DE gels between the sham and CLP mouse plasma 24 h after surgery, indicating that some plasma proteins responded to the inflammatory development. These differential spots were verified by MALDI-TOF/TOF MS, resulting in 13 unique sepsis-responsive proteins. More importantly, most of them exhibited multiple spots as difference on the 2-DE gels. Furthermore, these isospots were incubated with PNGase F to eliminate N-linked oligosaccharides on proteins and then evaluated by Western blot as well as mass spectrometry. The results of PNGase F digestion suggested that most sepsis-associated proteins remained in N-glycosylation status but changed their N-glycans during septic development.

Antithrombotic activity of kininogen is mediated by inhibitory effects of domain 3 during arterial injury in vivo

High-molecular-weight kininogen (HK) and its domain 3 (D3) exhibit anticoagulant properties and inhibit platelet activation at low thrombin concentration in vitro. We hypothesized that the rapid occlusive thrombosis in HK-deficient (HKd) rats following endothelial injury of the aorta results from enhanced platelet aggregation by thrombin. The effects of D3 (G235-M357) or D3-derived peptides on thrombosis in vivo were tested. D3 and its exon 7C terminal peptide (E7CP, K270-Q292), expressed as glutathione S-transferase (GST) fusion proteins (GST-D3, GST-E7CP), or GST alone, as well as cleaved HK (HKa) or synthetic peptide E7CP, were infused intravenously 10 min before endothelial injury. Blood flow was reduced down to 10% of baseline flow within 28 +/- 5.2 min by a platelet-fibrin thrombus in GST-treated HKd rats compared with >240 min in GST-treated normal HK rats (wild type). GST-D3, GST-E7CP, HKa, or E7CP infusion prolonged the flow time to 233, >240, 223, and >240 min, respectively, in HKd rats. When GST-E7CP was infused 10 min after the injury, blood flow was maintained for >240 min. Thrombin-antithrombin concentrations were elevated by injury in HKd rats receiving GST from 35 to 55 microg/l and decreased with GST-E7CP, HKa, or E7CP reconstitution to 40, 15, and 9 microg/l, respectively. We conclude that HKd rats are prothrombotic and that HKa, kininogen D3, and its fragment E7CP modulate arterial thrombosis after endothelial injury.

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.

Genetically altered animal models in the kallikrein-kinin system

Transgenic and gene-targeting technologies allowing the generation of genetically altered animal models have greatly advanced our understanding of the function of specific genes. This is also true for the kallikrein-kinin system (KKS), in which some, but not yet all, components have been functionally characterized using such techniques. The first genetically altered animal model for a KKS component was supplied by nature, the brown Norway rat carrying an inactivating mutation in the kininogen gene. Mice deficient in tissue kallikrein, B1 and B2 receptors, some kinin-degrading enzymes, and factor XII followed, together with transgenic rat and mouse strains overexpressing tissue kallikrein, B1 and B2 receptors, and degrading enzymes. There are still no animal models with genetic alterations in plasma kallikrein, kininases I and some other degrading enzymes. The models have confirmed an important role of the KKS in cardiovascular pathology, inflammation, and pain, and have partially elucidated the distinct function of the two receptors. This created the basis for rational decisions concerning the putative use of kinin receptor agonists and antagonists in therapeutic applications. However, a more thorough analysis of the existing models and the generation of new, more sophisticated transgenic models will be necessary to clarify the still elusive issue as to where and by which mechanisms the kinins exert their actions.