Mutant plasminogen in hereditary angioedema is bypassing FXII/kallikrein to generate bradykinin

Hereditary Angioedema with Normal C1 Inhibitor: an Updated International Consensus Paper on Diagnosis, Pathophysiology, and Treatment

Hereditary angioedema (HAE) has been recognized for almost 150 years. The newest form of HAE, where C1 inhibitor levels are normal (HAE-nC1INH), was first described in 2000. Over the last two decades, new types of apparent non-mast cell-mediated angioedema with normal quantity and activity of C1INH have been described, in some cases with proven genetic pathogenic variants that co-segregate with angioedema expression within families. Like HAE due to C1INH deficiency, HAE-nC1INH patients are at risk of serious morbidity and mortality. Therefore, proactive management and treatment of HAE-nC1INH patients after an expert physician diagnosis is critically important. The underlying pathophysiology responsible for the angioedema has also been clarified in some of the HAE-nC1INH types. While several clinical guidelines and practice parameters including HAE-nC1INH have been published, we have made substantial progress in our understanding encompassing diagnostic criteria, pathophysiology, and treatment outcomes. HAE International (HAEi) and the US HAE Association (HAEA) convened a symposium of global HAE-nC1INH experts to synthesize our current knowledge in the area. Given the paucity of high-level evidence in HAE-nC1INH, all recommendations are based on expert opinion. This review and expert opinion on the best practice approach to diagnosing and treating HAE-nC1INH will support physicians to better manage patients with HAE-nC1INH.

Exploring the management of recurrent angioedema caused by different mechanisms

PURPOSE OF REVIEW

We aim to explore the most recent insights into the pathogenesis of recurrent angioedema caused by different mechanisms and then focus on the management and treatment approaches available.

RECENT FINDINGS

The recently developed DANCE consensus classification identifies five types of angioedema: mast cell-mediated (AE-MC), bradykinin-mediated, because of intrinsic vascular endothelium dysfunction (AE-VE), drug-induced (AE-DI), and due to unknown mechanisms (AE-UNK). These subtypes require different management with treatment choices targeting the main pathogenetic pathways involved in each form. For AE-MC and AE-BK, the therapeutic landscape has been significantly widened in recent years. Conversely, there is a lack of consensus for the hereditary forms because of newly discovered mutations ( factor 12 , plasminogen, kininogen-1 , myoferlin, angiopoietin-1 , heparan sulfate 3-O-sulfotransferase 6 ) and AE-UNK.

SUMMARY

Recurrent angioedema can present with or without wheals. Angioedema without wheals may be driven by bradykinin and/or mast cell mediators. The different forms respond to specific drugs and require a different management. For its potentially life-threatening and disfiguring features, angioedema should be promptly recognized and effectively treated. For this reason, enhancing awareness about various angioedema subtypes and their management provide a useful tool for the clinical practice.

[Berberine ameliorates coronary artery endothelial cell injury in Kawasaki disease through complement and coagulation cascades]

OBJECTIVES

To explore the role of berberine (BBR) in ameliorating coronary endothelial cell injury in Kawasaki disease (KD) by regulating the complement and coagulation cascade.

METHODS

Human coronary artery endothelial cells (HCAEC) were divided into a healthy control group, a KD group, and a BBR treatment group (n=3 for each group). The healthy control group and KD group were supplemented with 15% serum from healthy children and KD patients, respectively, while the BBR treatment group received 15% serum from KD patients followed by the addition of 20 mmol/L BBR. Differential protein expression was analyzed and identified using isobaric tags for relative and absolute quantitation technology and liquid chromatography-tandem mass spectrometry, followed by GO functional enrichment analysis and KEGG signaling pathway enrichment analysis of the differential proteins. Western blot was used to detect differential protein expression.

RESULTS

A total of 518 differential proteins were identified between the KD group and the healthy control group (300 upregulated proteins and 218 downregulated proteins). A total of 422 differential proteins were identified between the BBR treatment group and the KD group (221 upregulated proteins and 201 downregulated proteins). Bioinformatics analysis showed that compared to the healthy control group, the differential proteins in the KD group were enriched in the complement and coagulation cascade and ribosome biogenesis in eukaryotes. Compared to the KD group, the differential proteins in the BBR treatment group were also enriched in the complement and coagulation cascade and ribosome biogenesis in eukaryotes. Western blot results indicated that compared to the healthy control group, the expression of complement C1q subcomponent subunit C (C1QC), kininogen-1 (KNG1), complement C1s subcomponent (C1S), and C4b-binding protein alpha chain (C4BPA) was increased in the KD group (P<0.05). Compared to the KD group, the expression of KNG1, C1S, C1QC, and C4BPA was decreased in the BBR treatment group (P<0.05).

CONCLUSIONS

The complement and coagulation cascade may be involved in the regulation of BBR treatment for coronary injury in KD, and C1QC, KNG1, C1S, and C4BPA may serve as biomarkers for this treatment.

A clinical evaluation of patients with known mutations (plasminogen and factor XII) with a focus on prophylactic treatment

BACKGROUND

Hereditary angioedema with normal C1-inhibitor (HAE-nC1-INH) is a rare genetic disease. The symptoms can resemble other forms of hereditary angioedema (HAE), but the specific laboratory values are inconspicuous. The knowledge about treatment strategies in HAE-nC1-INH remains insufficient; most of the drugs are only licensed and approved for other types of HAE.

METHODS

An analysis of all patients with HAE-nC1-INH was carried out in a certified angioedema treatment center in southern Germany. Only patients with a confirmed HAE-nC1-INH mutation were included. The impact of disease was monitored with validated questionnaires.

RESULTS

Eighteen patients were included: two families with a factor XII mutation and seven families with a plasminogen mutation. All individuals received icatibant for on-demand therapy-efficient treatment response was reported. Three patients were severely affected, and prophylaxis was initiated with lanadelumab. According to the questionnaires, the clinical course and symptoms improved significantly under this prophylactic regime.

CONCLUSION

This is one of the first descriptions of the clinical outcomes as a response to prophylactic treatment with lanadelumab in HAE-nC1-INH patients with a known mutation. The therapeutic management of HAE-1 and HAE-2 should also be the basis of HAE-nC1-INH, including prophylaxis.

Targeting factor XIIa for therapeutic interference with hereditary angioedema

Hereditary angioedema (HAE) is a rare, potentially life-threatening genetic disorder characterized by recurrent attacks of swelling. Local vasodilation and vascular leakage are stimulated by the vasoactive peptide bradykinin, which is excessively produced due to dysregulation of the activated factor XII (FXIIa)-driven kallikrein-kinin system. There is a need for novel treatments for HAE that provide greater efficacy, improved quality of life, minimal adverse effects, and reduced treatment burden over current first-line therapies. FXIIa is emerging as an attractive therapeutic target for interference with HAE attacks. In this review, we draw on preclinical, experimental animal, and in vitro studies, providing an overview on targeting FXIIa as the basis for pharmacologic interference in HAE. We highlight that there is a range of FXIIa inhibitors in development for different therapeutic areas. Of these, garadacimab, an FXIIa-targeted inhibitory monoclonal antibody, is the most advanced and has shown potential as a novel long-term prophylactic treatment for patients with HAE in clinical trials. The evidence from these trials is summarized and discussed, and we propose areas for future research where targeting FXIIa may have therapeutic potential beyond HAE.

Angioedema After Use of Recombinant Tissue-Type Plasminogen Activators in Stroke

Angioedema without concomitant urticaria is a well-known complication of treatment with the recombinant tissue-type plasminogen activator (r-tPA) alteplase and its genetically modified variant tenecteplase. It is potentially lethal when causing airway obstruction and can require intubation. The latest guideline for the early management of patients with acute ischemic stroke from the American Heart Association/American Stroke Association advises to treat this complication initially by interfering with the histamine pathway. This article aims to clarify the pathophysiological mechanism of r-tPA-induced angioedema and provides several arguments that this condition is primarily bradykinin-mediated and hence should be treated initially by intervening with the bradykinin pathway. Second, other-less frequently reported-adverse symptoms after r-tPA therapy and their proposed pathophysiological mechanisms leading to specific treatment are described. This manuscript describes the need for an update of the section "3.5 IV alteplase" from the American Heart Association/American Stroke Association guideline to treat this r-tPA-induced angioedema adequately and prevent potentially fatal outcomes.

Contact System Activation and Bradykinin Generation in Angioedema: Laboratory Assessment and Biomarker Utilization

The role of contact system activation has been clearly established in the pathogenesis of hereditary angioedema due to C1 inhibitor deficiency (HAE-C1INH). C1 inhibitor (C1INH)-protease complexes, levels of functional C1INH, plasma kallikrein activation, and cleavage of high-molecular-weight kininogen have each been associated with disease activity. More recently, HAE with normal levels of C1INH (HAE-nl-C1INH) has been recognized. Six genetic mutations have been identified which are linked to HAE-nl-C1INH phenotypes. The majority of individuals with HAE-nl-C1INH fall into the unknown category. There is substantial evidence that bradykinin generation underlies the recurrent attacks of swelling in some of these cohorts.

Classification, Diagnosis, and Pathology of Angioedema Without Hives

A clear disease classification schema coupled with an understanding of the specific mechanisms involved in the different types of angioedema without hives informs the diagnostic assessment. The recommended approach involves several key steps. Foremost is the recognizing of the clinical clues which allow for the differentiation of mast cell-mediated disorders from bradykinin-mediated angioedema. Enhanced vascular permeability related to bradykinin is of critical importance to identify given the implications for disease morbidity and risk of mortality. The ability to efficiently categorize and diagnose all forms of angioedema results in improved patient outcomes.

Definition, acronyms, nomenclature, and classification of angioedema (DANCE): AAAAI, ACAAI, ACARE, and APAAACI DANCE consensus

BACKGROUND

Angioedema (AE) manifests with intermittent, localized, self-limiting swelling of the subcutaneous and/or submucosal tissue. AE is heterogeneous, can be hereditary or acquired, may occur only once or be recurrent, may exhibit wheals or not, and may be due to mast cell mediators, bradykinin, or other mechanisms. Several different taxonomic systems are currently used, making it difficult to compare the results of studies, develop multicenter collaboration, and harmonize AE treatment.

OBJECTIVE

We developed a consensus on the definition, acronyms, nomenclature, and classification of AE (DANCE).

METHODS

The initiative involved 91 experts from 35 countries and was endorsed by 53 scientific and medical societies, and patient organizations. A consensus was reached by online discussion and voting using the Delphi process over a period of 16 months (June 2021 to November 2022).

RESULTS

The DANCE initiative resulted in an international consensus on the definition, classification, and terminology of AE. The new consensus classification features 5 types and endotypes of AE and a harmonized vocabulary of abbreviations/acronyms.

CONCLUSION

The DANCE classification complements current clinical guidelines and expert consensus recommendations on the diagnostic assessment and treatment of AE. DANCE does not replace current clinical guidelines, and expert consensus algorithms and should not be misconstrued in a way that affects reimbursement of medicines prescribed by physicians using sound clinical judgment. We anticipate that this new AE taxonomy and nomenclature will harmonize and facilitate AE research and clinical studies, thereby improving patient care.

A mechanism for hereditary angioedema caused by a methionine-379-to-lysine substitution in kininogens

ABSTRACT

Hereditary angioedema (HAE) is associated with episodic kinin-induced swelling of the skin and mucosal membranes. Most patients with HAE have low plasma C1-inhibitor activity, leading to increased generation of the protease plasma kallikrein (PKa) and excessive release of the nanopeptide bradykinin from high-molecular-weight kininogen (HK). However, disease-causing mutations in at least 10% of patients with HAE appear to involve genes for proteins other than C1-inhibitor. A point mutation in the Kng1 gene encoding HK and low-molecular weight kininogen (LK) was identified recently in a family with HAE. The mutation changes a methionine (Met379) to lysine (Lys379) in both proteins. Met379 is adjacent to the Lys380-Arg381 cleavage site at the N-terminus of the bradykinin peptide. Recombinant wild-type (Met379) and variant (Lys379) versions of HK and LK were expressed in HEK293 cells. PKa-catalyzed kinin release from HK and LK was not affected by the Lys379 substitutions. However, kinin release from HK-Lys379 and LK-Lys379 catalyzed by the fibrinolytic protease plasmin was substantially greater than from wild-type HK-Met379 and LK-Met379. Increased kinin release was evident when fibrinolysis was induced in plasma containing HK-Lys379 or LK-Lys379 compared with plasma containing wild-type HK or LK. Mass spectrometry revealed that the kinin released from wild-type and variant kininogens by PKa is bradykinin. Plasmin also released bradykinin from wild-type kininogens but cleaved HK-Lys379 and LK-Lys379 after Lys379 rather than Lys380, releasing the decapeptide Lys-bradykinin (kallidin). The Met379Lys substitutions make HK and LK better plasmin substrates, reinforcing the relationship between fibrinolysis and kinin generation.

Mechanisms involved in hereditary angioedema with normal C1-inhibitor activity

Patients with the inherited disorder hereditary angioedema (HAE) suffer from episodes of soft tissue swelling due to excessive bradykinin production. In most cases, dysregulation of the plasma kallikrein-kinin system due to deficiency of plasma C1 inhibitor is the underlying cause. However, at least 10% of HAE patients have normal plasma C1 inhibitor activity levels, indicating their syndrome is the result of other causes. Two mutations in plasma protease zymogens that appear causative for HAE with normal C1 inhibitor activity have been identified in multiple families. Both appear to alter protease activity in a gain-of-function manner. Lysine or arginine substitutions for threonine 309 in factor XII introduces a new protease cleavage site that results in formation of a truncated factor XII protein (Δ-factor XII) that accelerates kallikrein-kinin system activity. A glutamic acid substitution for lysine 311 in the fibrinolytic protein plasminogen creates a consensus binding site for lysine/arginine side chains. The plasmin form of the variant plasminogen cleaves plasma kininogens to release bradykinin directly, bypassing the kallikrein-kinin system. Here we review work on the mechanisms of action of the FXII-Lys/Arg309 and Plasminogen-Glu311 variants, and discuss the clinical implications of these mechanisms.