The role of plasma high molecular weight kininogen in experimental intestinal and systemic inflammation

Anti-HK antibody reveals critical roles of a 20-residue HK region for Aβ-induced plasma contact system activation

Alzheimer's disease (AD) is a neurodegenerative disorder and the leading cause of dementia. Vascular abnormalities and neuroinflammation play roles in AD pathogenesis. Plasma contact activation, which leads to fibrin clot formation and bradykinin release, is elevated in many AD patients, likely due to the ability of AD's pathogenic peptide β-amyloid (Aβ) to induce its activation. Since overactivation of this system may be deleterious to AD patients, the development of inhibitors could be beneficial. Here, we show that 3E8, an antibody against a 20-amino acid region of high molecular weight kininogen's (HK) domain 6, inhibits Aβ-induced intrinsic coagulation. Mechanistically, 3E8 inhibits contact system activation by blocking the binding of prekallikrein (PK) and factor XI (FXI) to HK, thereby preventing their activation and the continued activation of factor XII (FXII). The 3E8 antibody can also disassemble HK/PK and HK/FXI complexes in normal human plasma in the absence of a contact system activator due to its strong binding affinity for HK, indicating its prophylactic ability. Furthermore, the binding of Aβ to both FXII and HK is critical for Aβ-mediated contact system activation. These results suggest that a 20-amino acid region of HK's domain 6 plays a critical role in Aβ-induced contact system activation, and this region may provide an effective strategy to inhibit or prevent contact system activation in related disorders.

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.

Plasma vascular non-inflammatory molecule 3 is associated with gastrointestinal acute graft-versus-host disease in mice

Background

Gastrointestinal acute graft-versus-host disease (GI aGVHD) is a lethal complication following allogeneic hematopoietic stem cell transplantation (HSCT). However, it is still very difficult to make a diagnosis of GI aGVHD in practice. To date, no consensus plasma biomarker of GI aGVHD can be used to help make a diagnosis. Here, we attempted to identify GI aGVHD associated plasma proteins in murine model, which can help make a diagnosis of GI aGVHD.

Methods

We used 8-plex isobaric tags for relative and absolute quantitation (8-plex iTRAQ) to screen out proteins in plasma samples taken from murine models before and after allogeneic HSCT. Next mRNA expressions were validated by quantitative real-time polymerase chain reaction in mouse intestinal epithelial samples.

Results

We found that five proteins were increased at least 2-fold in the allogeneic group at day 7 compared with days 0, 3 and 15 (after Cyclosporin A treatment) and the syngeneic group at day 7. These 5 proteins were VNN3, ZNF746, C4BP, KNG1 and FETUB, and they were consistent with results from negative labeling with 8-plex iTRAQ. Furthermore, increase in mRNA level of VNN3 was confirmed in murine intestinal epithelial samples with aGVHD.

Conclusions

Our results demonstrate that plasma VNN3 protein is associated with GI aGVHD in murine model.

Electronic supplementary material

The online version of this article (10.1186/s12950-017-0178-z) contains supplementary material, which is available to authorized users.

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.

An initial characterization of the serum phosphoproteome

Phosphorylation is a dynamic post-translational protein modification that is the basis of a general mechanism for maintaining and regulating protein structure and function, and of course underpins key cellular processes through signal transduction. In the last several years, many studies of large-scale profiling of phosphoproteins and mapping phosphorylation sites from cultured human cells or tissues by mass spectrometry technique have been published; however, there is little information on general (or global) phosphoproteomic characterization and description of the content of phosphoprotein analytes within the circulation. Circulating phosphoproteins and phosphopeptides could represent important disease biomarkers because of their well-known importance in cellular function, and these analytes frequently are mutated and activated in human diseases such as cancer. Here, we report an initial attempt to characterize the phosphoprotein content of serum. To accomplish this, we developed a method in which phosphopeptides are enriched from digested serum proteins and analyzed by LC-MS/MS using LTQ-Orbitrap (CID) and LTQ-ETD mass spectrometers. With this approach, we identified approximately 100 unique phosphopeptides with stringent filtering criteria and a lower than 1% false discovery rate.

Factor VII-activating protease in patients with acute deep venous thrombosis

Factor VII-activating protease (FSAP) is involved in haemostasis and inflammation. FSAP cleaves single chain urokinase-type plasminogen activator (scu-PA). The 1601GA genotype of the 1601G/A polymorphism in the FSAP gene leads to the expression of a FSAP variant with reduced ability to activate scu-PA, without affecting the ability to activate coagulation Factor VII (FVII). Previous studies have investigated the association of the 1601GA genotype with incidence and progression of carotid stenosis and deep venous thrombosis (DVT). The present study is the first to evaluate the potential association between the FSAP phenotype and DVT. We studied the association between the 1601G/A polymorphism, FSAP activity, FSAP antigen, Factor VIIa (FVIIa), prothrombin fragment 1+2 (F1+2), and C-reactive protein (CRP) in plasmas of 170 patients suspected for DVT. FSAP genotypes were equally distributed in patients with (n=64) and without DVT (n=106), (P=0.94). The 1601GA genotype was associated with significant reduction of FSAP activity (P<0.001) and FSAP antigen levels (P=0.04). Patients with DVT showed significantly higher FSAP activity (P=0.008), FSAP antigen (P=0.003), and F1+2 levels (P<0.001) than patients without DVT. The association between the FSAP measures and DVT disappeared when adjusted for CRP levels. F1+2 correlated positively to FSAP antigen (P=0.01), while FVIIa-levels were comparable in patients with and without DVT. We conclude that even though FSAP measures are significantly increased in patients with acute DVT, alterations in the scu-PA activating properties of FSAP are presumably not markedly involved in the development of acute DVT, and that the association between FSAP and DVT disappears after adjustment for CRP.

The contact system--a novel branch of innate immunity generating antibacterial peptides

Activation of the contact system has two classical consequences: initiation of the intrinsic pathway of coagulation, and cleavage of high molecular weight kininogen (HK) leading to the release of bradykinin, a potent proinflammatory peptide. In human plasma, activation of the contact system at the surface of significant bacterial pathogens was found to result in further HK processing and bacterial killing. A fragment comprising the D3 domain of HK is generated, and within this fragment a sequence of 26 amino acids is mainly responsible for the antibacterial activity. A synthetic peptide covering this sequence kills several bacterial species, also at physiological salt concentration, as effectively as the classical human antibacterial peptide LL-37. Moreover, in an animal model of infection, inhibition of the contact system promotes bacterial dissemination and growth. These data identify a novel and important role for the contact system in the defence against invasive bacterial infection.