Bradykinin deficiency causes high blood pressure in mice

Bradykinin has a wide variety of physiological functions, including vasodilation and blood pressure reduction. However, the physiological roles of bradykinin are not fully understood. We used the CRISPR/Cas9 method to generate BKdelK1 and BKdelK2 mutant mice, targeting the BK portion of mouse kininogen1 and kininogen2 genes, respectively. The BKdelK1 and BKdelK2 mutant mice had about 50% reductions in plasma low molecular weight kininogen and trypsin-released BK, compared to wild mice. Both BKdelK1 and BKdelK2 mice had significantly elevated systolic blood pressure compared to WT mice. These results suggest that plasma LKNG is a source of KNG in the vascular kallikrein-kinin system and contributes to maintaining lower systolic blood pressure.

Inheritance Pattern of Hereditary Angioedema Indicates Mutation-Dependent Selective Effects During Early Embryonic Development

BACKGROUND

Hereditary angioedema (HAE) may be caused by a genetic deficiency of functional C1 inhibitor (C1-INH) or linked with mutations in the F12, PLG, and other genes in combination with normal C1-INH (HAEnCI). Although the types of hereditary angioedema due to deficiency of functional C1 inhibitor and HAEnCI are autosomal dominant inherited, there is the impression that in the types of HAEnCI more females carry disease-linked mutations.

OBJECTIVE

The aim of this study was to analyze the passing on of the HAE-specific mutations to the next generations in families with various types of HAE.

METHODS

Methods comprised pedigree analysis, Sanger sequencing analysis, biochemical analysis of parameters of the kallikrein-kinin system, and statistical analysis of the results. We analyzed a total of 1494 offspring of individuals carrying an HAE-linked mutation.

RESULTS

In HAE, less male and more female offspring of mutation carriers than expected for autosomal dominant inheritance inherited the familial mutation. In addition, there were less male offspring than expected in HAEnCI. This was independent of paternal or maternal inheritance.

CONCLUSION

We conclude that there is a sex- and mutation-dependent selection during early embryogenesis, possible around the time of implantation, favoring male wild-type and female mutant embryos. It also appears that 20% to 25% of male embryos carrying the HAE mutation are lost specific in HAEnCI. These findings point out that there is a potentially important role of the kallikrein-kinin system during early embryonic development.

Pathophysiology of Hereditary Angioedema (HAE) Beyond the SERPING1 Gene

Hereditary Angioedema (HAE) is an autosomal dominant disorder characterized clinically by recurrent episodes of swelling involving subcutaneous tissues, gastrointestinal tract, and oro-pharyngeal area. Gene mutations are the most common genetic cause of HAE and observed in more than 90% of patients. More than 700 mutation variants have been described so far. Patients with angioedema who have no mutations in the gene for C1-INH and normal levels and activity of this inhibitor are labelled: normal C1 inhibitor HAE. These include genetic mutations in factor 12 gene, plasminogen gene, angiopoietin gene, kininogen 1, and myoferlin genes. The clinical manifestations of patients with these mutations are similar to with patients with C1-INH gene mutations. However, a later age of onset, oro-pharyngeal involvement, and higher female preponderance have been reported in these rare subtypes of hereditary angioedema. With the advent and increased accessibility of whole-exome sequencing, it is expected that new genetic defects and novel pathophysiological pathways will be identified in families with HAE of unknown cause or normal C1-INH angioedema. This review covers some of the recent advances in the field of HAE. The review focuses on pathophysiology of HAE beyond the well-known C1-INH deficiency phenotypes, including various biomarkers that can serve the diagnosis and management of these rare disorders.

Kininogen supports inflammation and bacterial spreading during Streptococccus Pyogenes Sepsis

BACKGROUND

High-molecular-weight kininogen is a cofactor of the human contact system, an inflammatory response mechanism that is activated during sepsis. It has been shown that high-molecular-weight kininogen contributes to endotoxemia, but is not critical for local host defense during pneumonia by Gram-negative bacteria. However, some important pathogens, such as Streptococcus pyogenes, can cleave kininogen by contact system activation. Whether kininogen causally affects antibacterial host defense in S. pyogenes infection, remains unknown.

METHODS

Kininogen concentration was determined in course plasma samples from septic patients. mRNA expression and degradation of kininogen was determined in liver or plasma of septic mice. Kininogen was depleted in mice by treatment with selective kininogen directed antisense oligonucleotides (ASOs) or a scrambled control ASO for 3 weeks prior to infection. 24 h after infection, infection parameters were determined.

FINDINGS

Data from human and mice samples indicate that kininogen is a positive acute phase protein. Lower kininogen concentration in plasma correlate with a higher APACHE II score in septic patients. We show that ASO-mediated depletion of kininogen in mice indeed restrains streptococcal spreading, reduces levels of proinflammatory cytokines such as IL-1β and IFNγ, but increased intravascular tissue factor and fibrin deposition in kidneys of septic animals.

INTERPRETATION

Mechanistically, kininogen depletion results in reduced plasma kallikrein levels and, during sepsis, in increased intravascular tissue factor that may reinforce immunothrombosis, and thus reduce streptococcal spreading. These novel findings point to an anticoagulant and profibrinolytic role of kininogens during streptococcal sepsis.

FUNDING

Full details are provided in the Acknowledgements section.

Protocols to Assess Coagulation Following In Vitro Infection with Hemorrhagic Fever Viruses

During the course of infection with a hemorrhagic fever virus (HFV), the checks and balances associated with normal coagulation are perturbed resulting in hemorrhage in severe cases and, in some patients, disseminated intravascular coagulopathy (DIC). While many HFVs have animal models that permit the analyses of systemic coagulopathy, animal infection models do not exist for all HFVs and moreover do not always recapitulate the pathology observed in human tissues. Furthermore, molecular analyses of how coagulation is affected are not always straightforward or practical when using ex-vivo animal-derived samples, thus reinforcing the importance of cell culture studies. This chapter highlights procedures utilizing human umbilical vein endothelial cells (HUVECs) as a model system to evaluate components of the intrinsic (prekallikrein (PK), factor XII (FXII), kininogen, and bradykinin (BK)) and extrinsic (Tissue Factor (TF)) systems. Specifically, protocols are included for the generation of a coculture blood vessel model, plating and infection of HUVEC monolayers and assays designed to measure activation of PK and FXII, cleavage of kininogen, and to measure the expression of TF mRNA and protein.

Complement, Kinins, and Hereditary Angioedema: Mechanisms of Plasma Instability when C1 Inhibitor is Absent

Plasma of patients with types I and II hereditary angioedema is unstable if incubated in a plastic (i.e., inert) vessel at 37 °C manifested by progressively increasing formation of bradykinin. There is also a persistent low level of C4 in 95 % of patients even when they are symptomatic. These phenomena are due to the properties of the C1r subcomponent of C1, factor XII, and the bimolecular complex of prekallikrein with high molecular weight kininogen (HK). Purified C1r auto-activates in physiologic buffers, activates C1s, which in turn depletes C4. This occurs when C1 inhibitor is deficient. The complex of prekallikrein-HK acquires an inducible active site not present in prekallikrein which in Tris-type buffers cleaves HK stoichiometrically to release bradykinin, or in phosphate buffer auto-activates to generate kallikrein and bradykinin. Thus immunologic depletion of C1 inhibitor from factor XII-deficient plasma (phosphate is the natural buffer) auto-activates on incubation to release bradykinin. Normal C1 inhibitor prevents this from occurring. During attacks of angioedema, if factor XII auto-activates on surfaces, the initial factor XIIa formed converts prekallikrein to kallikrein, and kallikrein cleaves HK to release bradykinin. Kallikrein also rapidly activates most remaining factor XII to factor XIIa. Additional cleavages convert factor XIIa to factor XIIf and factor XIIf activates C1r enzymatically so that C4 levels approach zero, and C2 is depleted. There is also a possibility that kallikrein is generated first as a result of activation of the prekallikrein-HK complex by heat shock protein 90 released from endothelial cells, followed by kallikrein activation of factor XII.

Pharmacological Activities and Hydrolysis by Peptidases of [Phospho-Ser(6)]-Bradykinin (pS(6)-BK)

Phosphorylated kininogen and some of its fragments containing serine phosphorylated bradykinin ([pS(6)]-Bk) were identified in human serum and plasma by a phosphoproteomic approach. We report the kininogenase ability of human tissue and plasma kallikreins and tryptase to generate [pS(6)]-Bk or Lys-[pS(6)]-Bk having as substrate the synthetic human kininogen fluorescent fragment Abz-MISLMKRPPGF[pS(386)]PFRSSRI-NH2. The pharmacological assays of [pS(6)]-Bk showed it as a full B2 bradykinin receptor agonist in smooth muscle, it produces a portal liver hypertensive response in rat and mouse paw edema that lasts longer than Bk. The rat hypotensive response to infusions of Bk is greater than that of [pS(6)]Bk, both if injected through femoral vein or aorta. [pS(6)]-Bk was more resistant than Bk to kininase digestion performed with angiotensin converting enzyme, neprilysin, thimet oligopeptidase, aminopeptidase P and carboxypeptidase M. (1)H-NMR experiments indicated that [pS(6)]-Bk has lower flexibility, with the pS(6)-P(7) bond restricted to the trans conformation, and can explain [pS(6)]-Bk resistance to hydrolysis. In conclusion, [pS(6)]-Bk presenting lower activity than Bk, with longer lasting effects and being slowly released by kininogenases from synthetic Abz-MISLMKRPPGF[pS(386)]PFRSSRI-NH2, suggests that phosphorylation of the kininogens can be an efficient kallikrein-kinin system regulator.

Cleaved high molecular weight kininogen stimulates JNK/FOXO4/MnSOD pathway for induction of endothelial progenitor cell senescence

OBJECTIVE

Recently we have reported that cleaved high molecular weight kininogen (HKa) accelerates the onset of endothelial progenitor cells (EPCs) senescence by induction of reactive oxygen species (ROS). However, the mechanisms by which HKa induces production of ROS remain unknown. In this study, we have shown that HKa induces EPC senescence via stimulation of c-Jun N-terminal kinases (JNK)-related pathway.

METHODS AND RESULTS

Treatment of human EPCs with HKa for 72h stimulated JNK phosphorylation at Thr183/Tyr185, and FOXO4 phosphorylation at Thr451, Concomitantly, upregulated the expression of MnSOD at protein and mRNA levels in a concentration-dependent manner. HKa increased intracellular level of H2O2, without affecting the expression of catalase. To narrow down the functional domain of HKa, recombinant proteins of human HK heavy chain (HC, 19-380aa) and light chain (LC, 390-644aa) were generated. HC, but not LC, increased senescence of EPCs and intracellular ROS levels, to a similar extent with HKa. Moreover, HC at 50 nM increased FOXO4 phosphorylation at Thr451 and the protein level of MnSOD in EPCs.

CONCLUSION

These results demonstrate that HKa accelerates the onset of EPC senescence by stimulating JNK/FOXO4/MnSOD pathway, its effect is mediated by the HC.