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Frontiers in Immunology 2023Dysregulated complement activation, increased protein citrullination, and production of autoantibodies against citrullinated proteins are hallmarks of rheumatoid...
BACKGROUND
Dysregulated complement activation, increased protein citrullination, and production of autoantibodies against citrullinated proteins are hallmarks of rheumatoid arthritis (RA). Citrullination is induced by immune cell-derived peptidyl-Arg deiminases (PADs), which are overactivated in the inflamed synovium. We characterized the effect of PAD2- and PAD4-induced citrullination on the ability of the plasma-derived serpin C1-inhibitor (C1-INH) to inhibit complement and contact system activation.
METHODS
Citrullination of the C1-INH was confirmed by ELISA and Western blotting using a biotinylated phenylglyoxal probe. C1-INH-mediated inhibition of complement activation was analyzed by C1-esterase activity assay. Downstream inhibition of complement was studied by C4b deposition on heat-aggregated IgGs by ELISA, using pooled normal human serum as a complement source. Inhibition of the contact system was investigated by chromogenic activity assays for factor XIIa, plasma kallikrein, and factor XIa. In addition, autoantibody reactivity to native and citrullinated C1-INH was measured by ELISA in 101 RA patient samples.
RESULTS
C1-INH was efficiently citrullinated by PAD2 and PAD4. Citrullinated C1-INH was not able to bind the serine protease C1s and inhibit its activity. Citrullination of the C1-INH abrogated its ability to dissociate the C1-complex and thus inhibit complement activation. Consequently, citrullinated C1-INH had a decreased capacity to inhibit C4b deposition the classical and lectin pathways. The inhibitory effect of C1-INH on the contact system components factor XIIa, plasma kallikrein, and factor XIa was also strongly reduced by citrullination. In RA patient samples, autoantibody binding to PAD2- and PAD4-citrullinated C1-INH was detected. Significantly more binding was observed in anti-citrullinated protein antibody (ACPA)-positive than in ACPA-negative samples.
CONCLUSION
Citrullination of the C1-INH by recombinant human PAD2 and PAD4 enzymes impaired its ability to inhibit the complement and contact systems . Citrullination seems to render C1-INH more immunogenic, and citrullinated C1-INH might thus be an additional target of the autoantibody response observed in RA patients.
Topics: Humans; Citrullination; Protein-Arginine Deiminases; Factor XIIa; Plasma Kallikrein; Factor XIa; Arthritis, Rheumatoid; Proteins; Autoantibodies
PubMed: 37426666
DOI: 10.3389/fimmu.2023.1203506 -
Journal of Thrombosis and Haemostasis :... Feb 2021Contact activation is triggered when blood is exposed to compounds or "surfaces" that promote conversion of the plasma zymogens factor XII (FXII) and prekallikrein to... (Review)
Review
Contact activation is triggered when blood is exposed to compounds or "surfaces" that promote conversion of the plasma zymogens factor XII (FXII) and prekallikrein to the active proteases FXIIa and kallikrein. FXIIa promotes blood coagulation by converting zymogen factor XI (FXI) to the protease FXIa. Contact activation appears to represent an enhancement of the propensity for FXII and prekallikrein to reciprocally activate each other by surface-independent limited proteolysis. The nature of the activities that perpetuate this process, and that trigger contact activation, are debated. FXII and prekallikrein, like most members of the chymotrypsin/trypsin protease family, are synthesized as single polypeptides that are presumed to be in an inactive state. Internal cleavage leads to conformational changes in the protease domain that convert the enzyme active site from a closed conformation to an open conformation accessible to substrates. We observed that FXII expresses a low level of activity as a single-chain zymogen that catalyzes prekallikrein activation in solution, as well as surface-dependent activation of prekallikrein, FXI, and FXII (autoactivation). Prekallikrein also expresses activity that promotes cleavage of kininogen to release bradykinin, and surface-dependent FXII activation. Modeling suggests that a glutamine residue at position 156 in the FXII and prekallikrein protease domains stabilizes an open active site conformation by forming hydrogen bonds with Asp194. The activity inherent in FXII and prekallikrein suggests a mechanism for sustaining reciprocal activation of the proteins and for initiating contact activation, and supports the premise that zymogens of some trypsin-like enzymes are active proteases.
Topics: Enzyme Precursors; Factor XI; Factor XII; Humans; Prekallikrein; Proteolysis
PubMed: 33107140
DOI: 10.1111/jth.15149 -
European Journal of Medicinal Chemistry Mar 2020Plasma kallikrein (PKal) belongs to the family of trypsin-like serine proteases. The expression of PKal is associated with multiple physiological systems or pathways... (Review)
Review
Plasma kallikrein (PKal) belongs to the family of trypsin-like serine proteases. The expression of PKal is associated with multiple physiological systems or pathways such as coagulation pathway, platelet aggregation process, kallikrein-kinin system, renin-angiotensin system and complement pathway. On the basis of PKal's multiple physiological functions, it has been considered as a potential target for several diseases including hereditary angioedema, microvascular complications of diabetes mellitus and cerebrovascular disease. Up to now, many PKal inhibitors have been identified and a few of them have reached clinical trials or market. This review summarizes the development of small molecule and peptide PKal inhibitors having different scaffolds and discusses their structure-activity relationship and selectivity. We hope this review facilitates a comprehensive understanding of the types of PKal inhibitors developed to tackle different manifestations of PKal-associated diseases.
Topics: Animals; Catalytic Domain; Drug Discovery; Enzyme Inhibitors; Humans; Molecular Structure; Plasma Kallikrein; Protein Binding; Structure-Activity Relationship
PubMed: 32066009
DOI: 10.1016/j.ejmech.2020.112137 -
World Journal of Stem Cells Sep 2014The tissue kallikrein-kinin system exerts a wide spectrum of biological activities in the cardiovascular, renal and central nervous systems. Tissue kallikrein-kinin... (Review)
Review
The tissue kallikrein-kinin system exerts a wide spectrum of biological activities in the cardiovascular, renal and central nervous systems. Tissue kallikrein-kinin modulates the proliferation, viability, mobility and functional activity of certain stem cell populations, namely mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs), mononuclear cell subsets and neural stem cells. Stimulation of these stem cells by tissue kallikrein-kinin may lead to protection against renal, cardiovascular and neural damage by inhibiting apoptosis, inflammation, fibrosis and oxidative stress and promoting neovascularization. Moreover, MSCs and EPCs genetically modified with tissue kallikrein are resistant to hypoxia- and oxidative stress-induced apoptosis, and offer enhanced protective actions in animal models of heart and kidney injury and hindlimb ischemia. In addition, activation of the plasma kallikrein-kinin system promotes EPC recruitment to the inflamed synovium of arthritic rats. Conversely, cleaved high molecular weight kininogen, a product of plasma kallikrein, reduces the viability and vasculogenic activity of EPCs. Therefore, kallikrein-kinin provides a new approach in enhancing the efficacy of stem cell therapy for human diseases.
PubMed: 25258666
DOI: 10.4252/wjsc.v6.i4.448 -
Expert Opinion on Biological Therapy Dec 2019: Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare yet still probably underdiagnosed clinical condition. Recurrent episodes of subcutaneous... (Review)
Review
: Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare yet still probably underdiagnosed clinical condition. Recurrent episodes of subcutaneous and sub-mucosal swelling may involve the skin, the gastrointestinal tract or even the upper airways, exposing the patients to the risk of death. With the aim of improving patients' quality of life, the therapeutic scenario has expanded over the years.: The focus of the present review is lanadelumab, a fully human, κ-light-chain, monoclonal immunoglobulin G1 against plasma kallikrein, currently approved for long-term prophylaxis of C1-INH-HAE attacks in the USA and Canada and designated as an orphan drug by the European Medicines Agency.: Lanadelumab is able to inhibit plasma kallikrein with high selectivity and affinity. The subsequent phases of drug development and the ongoing open-label trial have proven its safety and efficacy. It overcomes some of the limitations of other drugs available for long-term prophylaxis, given the easy route of administration, the simple administration schedule and the possibility to tailor the treatment to each patient. Further studies are needed to test its efficacy also in other types of angioedema for which a central role of plasma kallikrein is envisaged.
Topics: Angioedemas, Hereditary; Antibodies, Monoclonal, Humanized; Humans; Immunoglobulin G; Plasma Kallikrein; Quality of Life
PubMed: 31657963
DOI: 10.1080/14712598.2019.1685490 -
Journal of Investigational Allergology... 2016Angioedema is defined as local, noninflammatory, self-limiting edema that is circumscribed owing to increased leakage of plasma from the capillaries located in the deep... (Review)
Review
Angioedema is defined as local, noninflammatory, self-limiting edema that is circumscribed owing to increased leakage of plasma from the capillaries located in the deep layers of the skin and the mucosae. Two mediators, histamine and bradykinin, account for most cases of angioedema. Angioedema can occur with wheals as a manifestation of urticaria, and this form is frequently allergic. In the present review, we discuss nonallergic angioedema without wheals, which can be divided into 3 acquired and 4 hereditary forms. Histamine is the mediator in acquired angioedema of unknown etiology (idiopathic histaminergic acquired angioedema), whereas in other forms the main mediator is bradykinin. Angioedema can be caused by C1-inhibitor deficiency (C1-INH-hereditary angioedema and C1-INH-acquired angioedema), mutations in coagulation factor XII (FXII-hereditary angioedema), and treatment with angiotensin-converting enzyme inhibitors (ACEI-acquired angioedema). Etiology remains unclear in acquired angioedema (idiopathic nonhistaminergic acquired angioedema) and in 1 type of hereditary angioedema (hereditary angioedema of unknown origin). Several treatments are licensed for hereditary C1-INH deficiency. Plasma-derived and recombinant C1-INHs, the bradykinin receptor blocker icatibant, and the plasma kallikrein inhibitor ecallantide have been approved for on-demand treatment to reverse angioedema symptoms. Attenuated androgen and plasma-derived C1-INH are approved for prophylaxis.
Topics: Angioedema; Angiotensin-Converting Enzyme Inhibitors; Bradykinin; Complement C1 Inhibitor Protein; Humans
PubMed: 27470642
DOI: 10.18176/jiaci.0087 -
F1000Research 2016The complement system, which consists of three independent but interacting pathways, constitutes a powerful arm of innate immunity. Its major function is to recognize... (Review)
Review
The complement system, which consists of three independent but interacting pathways, constitutes a powerful arm of innate immunity. Its major function is to recognize and destroy pathogenic microorganisms as well as eliminate modified self-antigens. Although it is a fine-tuned system with innate capacity to discriminate self from non-self as well as danger from non-danger signals, an unwarranted activation can nonetheless occur and cause tissue destruction. To prevent such activation, specific regulators present both in plasma and on the cell surface tightly control it. Data accumulated over the past four decades have also shown that the complement system is capable of not only cross-talk with the activation cascades of plasma--i.e. blood coagulation, contact activation, and the kinin/kallikrein system--but also serving as a bridge between innate and adaptive immunity. It is for these reasons that the various activation steps of the complement system have been recently targeted for therapy to treat diseases in which the role of complement is beyond doubt. This trend will certainly continue for years to come, especially as novel concepts guiding the field into areas never contemplated before are continuing to be discovered.
PubMed: 27990282
DOI: 10.12688/f1000research.10065.1 -
ACS Medicinal Chemistry Letters Feb 2023The invention in this patent application relates to ()-spiro[benzo[][1,3]oxazine-4,3'-pyrrolidin]-2(1)-one derivatives, represented generally by formula 1. These...
The invention in this patent application relates to ()-spiro[benzo[][1,3]oxazine-4,3'-pyrrolidin]-2(1)-one derivatives, represented generally by formula 1. These compounds are selective plasma kallikrein inhibitors and may potentially be beneficial in the treatment of several diseases and disorders, including hereditary angioedema, uveitis, posterior uveitis, wet age-related macular degeneration, diabetic macular edema, diabetic retinopathy, and retinal vein occlusion.
PubMed: 36793429
DOI: 10.1021/acsmedchemlett.2c00526 -
Cellular Signalling Nov 2018Factor XII (FXII) is a protease that is mainly produced in the liver and circulates in plasma as a single chain zymogen. Following contact with negatively charged... (Review)
Review
Factor XII (FXII) is a protease that is mainly produced in the liver and circulates in plasma as a single chain zymogen. Following contact with negatively charged surfaces, FXII is converted into the two-chain active form, FXIIa. FXIIa initiates the intrinsic blood coagulation pathway via activation of factor XI. Furthermore, it converts plasma prekallikrein to kallikrein (PK), which reciprocally activates FXII and liberates bradykinin from high molecular weight kininogen. In addition, FXIIa initiates fibrinolysis via PK-mediated urokinase activation and activates the classical complement pathway. Even though the main function of FXII seems to relate to the activation of the intrinsic coagulation pathway and the kallikrein-kinin system, a growing body of evidence suggests that FXII may also directly regulate cellular responses. In this regard, it has been found that FXII/FXIIa induces the expression of inflammatory mediators, promotes cell proliferation, and enhances the migration of neutrophils and lung fibroblasts. In addition, it has been reported that genetic ablation of FXII protects against neuroinflammation, reduces the formation of atherosclerotic lesions in Apoe mice, improves wound healing, and inhibits postnatal angiogenesis. Although the aforementioned effects can be partially explained by the downstream products of FXII activation, the ability of FXII/FXIIa to directly regulate cellular responses has recently emerged as an alternative hypothesis. These direct cellular reactions to FXII/FXIIa will be discussed in the review.
Topics: Animals; Atherosclerosis; Blood Coagulation; Bradykinin; Cell Movement; Cell Proliferation; Complement Pathway, Classical; Factor XI; Factor XII; Fibrinolysis; Fibroblasts; Humans; Inflammation; Kininogen, High-Molecular-Weight; Mice; Neutrophils; Plasma Kallikrein; Prekallikrein; Wound Healing
PubMed: 30118759
DOI: 10.1016/j.cellsig.2018.08.006 -
Translational Stroke Research Apr 2022Plasma kallikrein (PKa) has been implicated in contributing to hemorrhage following thrombolytic therapy; however, its role in spontaneous intracerebral hemorrhage is...
Plasma kallikrein (PKa) has been implicated in contributing to hemorrhage following thrombolytic therapy; however, its role in spontaneous intracerebral hemorrhage is currently not available. This report investigates the role of PKa on hemorrhage and hypertension in stroke-prone spontaneously hypertensive rats (SHRSP). SHRSP were fed with a high salt-containing stroke-prone diet to increase blood pressure and induce intracerebral hemorrhage. The roles of PKa on blood pressure, hemorrhage, and survival in SHRSP were examined in rats receiving a PKa inhibitor or plasma prekallikrein antisense oligonucleotide (PK ASO) compared with rats receiving control ASO. Effects on PKa on the proteolytic cleavage of atrial natriuretic peptide (ANP) were analyzed by tandem mass spectrometry. We show that SHRSP on high-salt diet displayed increased levels of PKa activity compared with control rats. Cleaved kininogen was increased in plasma during stroke compared to SHRSP without stroke. Systemic administration of a PKa inhibitor or PK ASO to SHRSP reduced hemorrhage and blood pressure, and improved neurological function and survival compared with SHRSP receiving control ASO. Since PKa inhibition was associated with reduced blood pressure in hypertensive rats, we investigated the effects of PKa on the cleavage of ANP. Incubation of PKa with ANP resulted in the generation fragment ANP, which displayed reduced effects on blood pressure lowering compared with full length ANP. PKa contributes to increased blood pressure in SHRSP, which is associated with hemorrhage and reduced survival. PKa-mediated cleavage of ANP reduces its blood pressure lowering effects and thereby may contribute to hypertension-induced intracerebral hemorrhage.
Topics: Animals; Atrial Natriuretic Factor; Blood Pressure; Cerebral Hemorrhage; Hypertension; Plasma Kallikrein; Rats; Rats, Inbred SHR; Stroke
PubMed: 34241810
DOI: 10.1007/s12975-021-00929-x