Comparing Pathways of Bradykinin Formation in Whole Blood From Healthy Volunteers and Patients With Hereditary Angioedema Due to C1 Inhibitor Deficiency

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.

Bradykinin release following trauma and hemorrhagic shock causes pulmonary alveolar leak in a rodent model

BACKGROUND

Hemorrhage accounts for 40% of the preventable death following severe injury. Activation of systemic coagulation produces bradykinin (BK), which may cause leak from the plasma to the extravascular space and to the tissues, which is part of the complex pathophysiology of trauma-induced end-organ injury. We hypothesize that BK, released during activation of coagulation in severe injury, induces pulmonary alveolar leak.

METHODS

Isolated neutrophils (PMNs) were pretreated with a specific BK receptor B2 antagonist HOE-140/icatibant and BK priming of the PMN oxidase was completed. Rats underwent tissue injury/hemorrhagic shock (TI/HS), TI/icatibant/HS, and controls (no injury). Evans blue dye was instilled, and the percentage leak from the plasma to the lung was calculated from the bronchoalveolar lavage fluid (BALF). CINC-1 and total protein were measured in the BALF, and myeloperoxidase was quantified in lung tissue.

RESULTS

The BK receptor B2 antagonist HOE140/icatibant inhibited (85.0 ± 5.3%) BK priming of the PMN oxidase ( p < 0.05). The TI/HS model caused activation of coagulation by increasing plasma thrombin-antithrombin complexes ( p < 0.05). Versus controls, the TI/HS rats had significant pulmonary alveolar leak: 1.46 ± 0.21% versus 0.36 ± 0.10% ( p = 0.001) and increased total protein and CINC-1 in the BALF ( p < 0.05). Icatibant given after the TI significantly inhibited lung leak and the increase in CINC-1 in the BALF from TI/icatibant/HS rats versus TI/HS ( p < 0.002 and p < 0.05) but not the total protein. There was no PMN sequestration in the lungs. Conclusions: This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

CONCLUSION

This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

LEVEL OF EVIDENCE

Original Article, Basic Science.

Picomolar Sensitivity Analysis of Multiple Bradykinin-Related Peptides in the Blood Plasma of Patients With Hereditary Angioedema in Remission: A Pilot Study

Background

Hereditary angioedema (HAE) is a rare autosomal dominant disease; the most well understood forms concern the haplodeficiency of C1 esterase inhibitor (C1INH) and a gain of function mutation of factor XII (FXII). The acute forms of these conditions are mediated by an excessive bradykinin (BK) formation by plasma kallikrein.

Methods

A validated LC-MS/MS platform of picomolar sensitivity developed for the analysis of eleven bradykinin-related peptides was applied to the plasma of HAE-C1INH and HAE-FXII sampled during remission.

Results

In HAE-C1INH plasma, the concentrations of the relatively stable BK1−5 fragment (mean ± S.E.M.: 12.0 ± 4.2 pmol/L), of BK2−9 (0.7 ± 0.2 pmol/L) and of the sums of BK and its tested fragments (18.0 ± 6.4 pmol/L) are significantly greater than those recorded in the plasma of healthy volunteers (1.9 ± 0.6, 0.03 ± 0.03 and 4.3 ± 0.8 pmol/L, respectively), consistent with the previous evidence of permanent plasma kallikrein activity in this disease. Kinin levels in the plasma of HAE-FXII patients did not differ from controls, suggesting that triggering factors for contact system activation are not active during remission.

Conclusion

BK1−5, BK2−9 and the sum of BK and its fragments determined by the sensitive LC-MS/MS technique are proposed as potential biomarkers of HAE-C1INH in remission while this was not applicable to HAE-FXII patients.

SARS-CoV-2 Spike Protein Destabilizes Microvascular Homeostasis

SARS-CoV-2 infection can cause compromised respiratory function and thrombotic events. SARS-CoV-2 binds to and mediates downregulation of angiotensin converting enzyme 2 (ACE2) on cells that it infects. Theoretically, diminished enzymatic activity of ACE2 may result in increased concentrations of pro-inflammatory molecules, angiotensin II, and Bradykinin, contributing to SARS-CoV-2 pathology. Using immunofluorescence microscopy of lung tissues from uninfected, and SARS-CoV-2 infected individuals, we find evidence that ACE2 is highly expressed in human pulmonary alveolar epithelial cells and significantly reduced along the alveolar lining of SARS-CoV-2 infected lungs. Ex vivo analyses of primary human cells, indicated that ACE2 is readily detected in pulmonary alveolar epithelial and aortic endothelial cells. Exposure of these cells to spike protein of SARS-CoV-2 was sufficient to reduce ACE2 expression. Moreover, exposure of endothelial cells to spike protein-induced dysfunction, caspase activation, and apoptosis. Exposure of endothelial cells to bradykinin caused calcium signaling and endothelial dysfunction (increased expression of von Willibrand Factor and decreased expression of Krüppel-like Factor 2) but did not adversely affect viability in primary human aortic endothelial cells. Computer-assisted analyses of molecules with potential to bind bradykinin receptor B2 (BKRB2), suggested a potential role for aspirin as a BK antagonist. When tested in our in vitro model, we found evidence that aspirin can blunt cell signaling and endothelial dysfunction caused by bradykinin in these cells. Interference with interactions of spike protein or bradykinin with endothelial cells may serve as an important strategy to stabilize microvascular homeostasis in COVID-19 disease.

IMPORTANCE SARS-CoV-2 causes complex effects on microvascular homeostasis that potentially contribute to organ dysfunction and coagulopathies. SARS-CoV-2 binds to, and causes downregulation of angiotensin converting enzyme 2 (ACE2) on cells that it infects. It is thought that reduced ACE2 enzymatic activity can contribute to inflammation and pathology in the lung. Our studies add to this understanding by providing evidence that spike protein alone can mediate adverse effects on vascular cells. Understanding these mechanisms of pathogenesis may provide rationale for interventions that could limit microvascular events associated with SARS-CoV-2 infection.

Subclinical Signs of Retinal Involvement in Hereditary Angioedema

To explore retinal abnormalities using spectral domain optical coherence tomography (SD-OCT) and OCT-angiography (OCT-A) in a highly selective cohort of patients with type I hereditary angioedema (HAE). This prospective case-control study included 40 type I HAE patients and 40 age-/sex-matched healthy subjects (HC). All participants underwent SD-OCT-scanning of retinal posterior pole (PP), peripapillary retinal nerve fiber layer (pRNFL), and optic nerve head (ONH). Superficial/deep capillary density was analyzed by OCT-A. A total of 80 eyes from 40 HAE and 40 eyes from HC were evaluated. The pRNFL was thicker in HAE than in HC in nasal superior (p < 0.0001) and temporal quadrants (p = 0.0005 left, p = 0.003 right). The ONH thickness in HAE patients was greater than in HC in the nasal (p = 0.008 left, p = 0.01 right), temporal (p = 0.0005 left, p = 0.003 right), temporal inferior (p = 0.007 left, p = 0.0008 right), and global (p = 0.005 left, p = 0.007 right) scans. Compared to HC, HAE showed a lower capillary density in both superficial (p = 0.001 left, p = 0.006 right) and deep (p = 0.008 left, p = 0.004 right) whole images, and superficial (p = 0.03 left) and deep parafoveal (p = 0.007 left, p = 0.005 right) areas. Our findings documented subclinical retinal abnormalities in type I HAE, supporting a potential role of the retinal assessment by SD-OCT/OCT-A as a useful tool in the comprehensive care of HAE patients.

In Vitro Modeling of Bradykinin-Mediated Angioedema States

Kinins (peptides related to bradykinin, BK) are formed from circulating substrates, the kininogens, by the action of two proteases, the kallikreins. The only clinical application of a BK receptor ligand, the B₂ receptor antagonist icatibant, is the treatment of the rare hereditary angioedema (HAE) caused by the deficiency of C1-esterase inhibitor (C1-INH). Less common forms of HAE (genetic variants of factor XII, plasminogen, kininogen) are presumably mediated by increased BK formation. Acquired forms of BK-mediated angioedema, such as that associated with angiotensin-I converting enzyme (ACE) inhibition, are also known. Antibody-based analytical techniques are briefly reviewed, and support that kinins are extremely short-lived, prominently cleared by ACE. Despite evidence of continuous activation of the kallikrein–kinin system in HAE, patients are not symptomatic most of the time and their blood or plasma obtained during remission does not generate excessive immunoreactive BK (iBK), suggesting effective homeostatic mechanisms. HAE-C1-INH and HAE-FXII plasmas are both hyperresponsive to fibrinolysis activation. On another hand, we suggested a role for the alternate tissue kallikrein–kinin system in patients with a plasminogen mutation. The role of the BK B₁ receptor is still uncertain in angioedema states. iBK profiles under in vitro stimulation provide fresh insight into the physiopathology of angioedema.

Measurement of Bradykinin Formation and Degradation in Blood Plasma: Relevance for Acquired Angioedema Associated With Angiotensin Converting Enzyme Inhibition and for Hereditary Angioedema Due to Factor XII or Plasminogen Gene Variants

Bradykinin (BK)-mediated angioedema (AE) states are rare acquired or hereditary conditions involving localized edema of the subcutaneous and submucosal tissues. Citrated plasma from healthy volunteers or patients with hereditary angioedema (HAE) with normal level of C1-inhibitor (C1-INH) was used to investigate pathways of BK formation and breakdown relevant to AE physiopathology. The half-life of BK (100 nM) added to normal plasma was 34 s, a value that was increased ~12-fold when the angiotensin converting enzyme (ACE) inhibitor enalaprilat (130 nM) was added (enzyme immunoassay measurements). The BK half-life was similarly increased ~5-fold following 2 daily oral doses of enalapril maleate in healthy volunteers, finding of possible relevance for the most common form of drug-associated AE. We also addressed the kinetics of immunoreactive BK (iBK) formation and decline, spontaneous or under three standardized stimuli: tissue kallikrein (KLK-1), the particulate material Kontact-APTT™ and tissue plasminogen activator (tPA). Relative to controls, iBK production was rapid (10–20 min) and very intense in response to tPA in plasma of female heterozygotes for variants in gene F12 coding for factor XII (FXII) (p.Thr328Lys, 9 patients; p.Thr328Arg, one). An increased response to Kontact-APTT™ and an early tPA-induced cleavage of anomalous FXII (immunoblots) were also observed. Biotechnological inhibitors showed that the early response to tPA was dependent on plasmin, FXIIa and plasma kallikrein. Results from post-menopausal and pre-menopausal women with HAE-FXII were indistinguishable. The iBK production profiles in seven patients with the plasminogen p.Lys330Glu variant (HAE-PLG) did not significantly differ from those of controls, except for an unexpected, rapid and lanadelumab-resistant potentiation of KLK-1 effect. This enzyme did not cleave plasminogen or factor XII, suggesting a possible idiosyncratic interaction of the plasminogen pathogenic variant with KLK-1 activity. KLK-1 abounds in salivary glands and human saliva, hypothetically correlating with the clinical presentation of HAE-PLG that includes the swelling of the tongue, lips and contiguous throat tissues. Samples from HAE patients with normal C1-INH levels and F12 gene did not produce excessive iBK in response to stimuli. The ex vivo approach provides physiopathological insight into AE states and supports the heterogeneous physiopathology of HAE with normal C1-INH.

Plasminflammation-An Emerging Pathway to Bradykinin Production

Plasminogen activation is essential for fibrinolysis—the breakdown of fibrin polymers in blood clots. Besides this important function, plasminogen activation participates in a wide variety of inflammatory conditions. One of these conditions is hereditary angioedema (HAE), a rare disease with characteristic attacks of aggressive tissue swelling due to unregulated production and activity of the inflammatory mediator bradykinin. Plasmin was already implicated in this disease decades ago, but a series of recent discoveries have made it clear that plasmin actively contributes to this pathology. Collective evidence points toward an axis in which the plasminogen activation system and the contact system (which produces bradykinin) are mechanistically coupled. This is amongst others supported by findings in subtypes of HAE that are caused by gain-of-function mutations in the genes that respectively encode factor XII or plasminogen, as well as clinical experience with the antifibrinolytic agents in HAE. The concept of a link between plasminogen activation and the contact system helps us to explain the inflammatory side effects of fibrinolytic therapy, presenting as angioedema or tissue edema. Furthermore, these observations motivate the development and characterization of therapeutic agents that disconnect plasminogen activation from bradykinin production.

Increased fibrinolysis-induced bradykinin formation in hereditary angioedema confirmed using stored plasma and biotechnological inhibitors

Objective

We recently investigated the pathways of immunoreactive bradykinin (iBK) formation in fresh blood of normal volunteers and of patients with hereditary angioedema due to C1-esterase inhibitor deficiency (HAE-1/-2). Herein, we adapted the techniques to small volumes (200 μl) of previously frozen citrated plasma and further analyzed the mechanisms of iBK formation with additional biotechnological inhibitors.

Results

Measurable iBK formation was observed under stimulation with tissue kallikrein (KLK-1, 10 nM), the particulate material Kontact-APTT (concentration reduced to 2% v/v) or recombinant tissue plasminogen activator (tPA, 169 nM), with little background in unstimulated plasma incubated for up to 2 h. Plasma samples from HAE-1/-2 patients responded earlier to tPA than those from controls, as previously reported with whole blood. Lanadelumab inhibited iBK formation induced by Kontact-APTT and tPA. A highly specific plasmin inhibitor, DX-1000, abolished tPA-induced iBK formation in plasma but had no effect against Kontact-APTT, confirming the role of fibrinolysis in tPA-induced kinin formation. The anti-lanadelumab neutralizing antibody M293-D02 reversed the inhibitory effects of lanadelumab. Frozen plasma is a suitable material for measuring iBK formation kinetics, with possible applications such as investigating the effect of rare disease states on the kallikrein–kinin system and monitoring the effect of HAE prophylactic treatments.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4335-8) contains supplementary material, which is available to authorized users.

Genetic Variation of Kallikrein-Kinin System and Related Genes in Patients With Hereditary Angioedema

Hereditary angioedema (HAE) is an autosomal dominant disease caused by C1-INH deficiency due to mutations in SERPING1 (C1-INH-HAE) in most of the cases, or by specific mutations in factor XII gene, F12 (F12-HAE). Identification of polymorphisms in the genes encoding proteins from key pathways driving HAE can help to understand how genetic diversity contributes to its phenotypic variability. Here, 15 genes related to the Kallikrein-Kinin System (KKS) were analyzed by next generation sequencing in 59 patients with C1-INH-HAE or F12-HAE from Brazil, Denmark and Spain, and 19 healthy relatives in a total of 31 families. We identified 211 variants, from which 23 occurred only in Danish subjects and 79 were found only in Brazilian individuals, resulting in 109/211 variations in common between European and Brazilian population in the HAE families analyzed. BDKRB2 and CPM presented a large number of variants in untranslated regions, 46/49 and 19/24, respectively; whereas ACE (n = 26), SERPING1 (n = 26), CPM (n = 24), and NOS3 (n = 16) genes presented the higher number of variants directly affecting amino acid sequence. Despite the large amount of variants identified, the lack of association between genotype and phenotype indicates that the modulation of HAE symptom requires a more complex regulation, probably involving pathways beyond the KKS, epigenetics and environmental factors. Considering the new HAE types recently described, molecules involved in the regulation of vasculature and in plasminogen activation become promising targets for future genetic studies.