Uncovering a novel SERPING1 pathogenic variant: insights into the aggregation of C1-INH in hereditary angioedema.

BACKGROUND: Hereditary angioedema (HAE) is a rare autosomal dominant genetic disease characterized by recurrent edema and a potentially fatal risk. Despite its severity, there is a notable lack of effective methods for predicting and preventing HAE attacks. This study aims to thoroughly investigate the underlying pathological mechanisms of HAE and identify potential biomarkers that could aid in its prediction and prevention. RESULTS: In our investigation, we have discovered a novel pathogenic variant of the SERPING1 gene, specifically c.708T > G, in a Han family affected by HAE. Our observations indicate that this variant leads to an increase in the accumulation of C1-INH within the endoplasmic reticulum (ER), resulting in the upregulation of GRP75 protein expression. This cascade of events resulted in Ca2+ overload, disruption of mitochondrial structure and function, and eventually triggered apoptosis. Using siRNA to knock down GRP75 mitigates cellular calcium overload and mitochondrial damage induced by the SERPING1 mutation. CONCLUSION: Based on our findings, we propose that the detection of intracellular Ca2+ concentration could serve as a valuable biomarker for predicting acute attacks of HAE in patients. This discovery holds significant implications for the development of more targeted and effective strategies in the management of HAE.

PLAUR splicing pattern in hereditary angioedema patients' monocytes and macrophages.

BACKGROUND: The PLAUR gene encodes the urokinase-like plasminogen activator receptor (uPAR) and may undergo alternative splicing. Excluding cassette exons 3, 5 and 6 from the transcript results in truncated protein variants whose precise functions have not been elucidated yet. The PLAUR gene is one of several expressed in myeloid cells, where uPAR participates in different cellular processes, including the contact activation system and kallikrein-kinin system, which play an important role in hereditary angioedema (HAE) pathogenesis. A hypothesis about the PLAUR splicing pattern impact on HAE severity was tested. METHODS AND RESULTS: The RT-PCR quantified by capillary electrophoresis was used. Although no significant difference in alternative transcript frequency was observed between healthy volunteers and HAE patients, a significant increase in all cassette exon inclusion variants was revealed during monocyte-to-macrophage differentiation. CONCLUSIONS: PLAUR alternative splicing in monocytes and macrophages neither was different between HAE patients and healthy controls, nor reflected disease severity. However, the results showed an PLAUR splicing pattern was changing during monocyte-to-macrophage differentiation, but the significance of these changes is unknown and awaits future clarification.

A mechanism for hereditary angioedema caused by a lysine 311-to-glutamic acid substitution in plasminogen.

Patients with hereditary angioedema (HAE) experience episodes of bradykinin (BK)-induced swelling of skin and mucosal membranes. The most common cause is reduced plasma activity of C1 inhibitor, the main regulator of the proteases plasma kallikrein (PKa) and factor XIIa (FXIIa). Recently, patients with HAE were described with a Lys311 to glutamic acid substitution in plasminogen (Plg), the zymogen of the protease plasmin (Plm). Adding tissue plasminogen activator to plasma containing Plg-Glu311 vs plasma containing wild-type Plg (Plg-Lys311) results in greater BK generation. Similar results were obtained in plasma lacking prekallikrein or FXII (the zymogens of PKa and FXIIa) and in normal plasma treated with a PKa inhibitor, indicating Plg-Glu311 induces BK generation independently of PKa and FXIIa. Plm-Glu311 cleaves high and low molecular weight kininogens (HK and LK, respectively), releasing BK more efficiently than Plm-Lys311. Based on the plasma concentrations of HK and LK, the latter may be the source of most of the BK generated by Plm-Glu311. The lysine analog ε-aminocaproic acid blocks Plm-catalyzed BK generation. The Glu311 substitution introduces a lysine-binding site into the Plg kringle 3 domain, perhaps altering binding to kininogens. Plg residue 311 is glutamic acid in most mammals. Glu311 in patients with HAE, therefore, represents reversion to the ancestral condition. Substantial BK generation occurs during Plm-Glu311 cleavage of human HK, but not mouse HK. Furthermore, mouse Plm, which has Glu311, did not liberate BK from human kininogens more rapidly than human Plg-Lys311. This indicates Glu311 is pathogenic in the context of human Plm when human kininogens are the substrates.

Factor XII(a) inhibitors: a review of the patent literature.

Introduction: Blood coagulation factor XII (FXII) is an emerging and potentially safe drug target, which dysregulation is associated with thrombosis, hereditary angioedema, and (neuro)inflammation. At the same time, FXII-deficiency is practically asymptomatic. Industrial and academic institutions have developed a number of potential therapeutic agents targeting either FXII zymogen or its active form FXIIa for the treatment of thrombotic and inflammatory conditions associated with the activity of this enzyme.Areas covered: A short overview of the FXII(a) structure and function, underlining its suitability as a drug target, is given. The article reviews patents reported over the last three decades on FXII(a)-targeting therapeutic agents. These agents include small molecules, proteins, peptides, oligonucleotides, siRNAs, and monoclonal antibodies.Expert opinion: The performed analysis of patents revealed that many FXII(a) inhibitors are in the early preclinical stage, while several already showed efficacy in vivo animal models of thrombosis, sepsis, hereditary angioedema, and multiple sclerosis. Two anti-FXIIa agents namely tick protein Ir-CPI and monoclonal antibody CSL312 are currently in human clinical trials. The results of these trials and further studies of FXII(a) pathophysiological functions will encourage the development of new FXII(a) inhibitors.

[Advances in the Pathogenesis of Hereditary Angioedema].

Hereditary angioedema(HAE)is a rare,hereditary disease characterized by recurrent subcutaneous and submucosal edema.Known genes associated with the pathogenesis of HAE include C1 esterase inhibitor gene,FⅫ gene,plasminogen gene,and angiopoietin 1 gene.Based on the known gene mutations,this review analyzes the effects of these mutations on the functions of protein products to figure out the possible pathogenic mechanism,so as to provide references for further investigations on the pathogenesis of HAE and seeking new prevention and treatment approaches.

Clinical presentation of hereditary angioedema.

Hereditary angioedema (HAE) is a rare, autosomal dominant disease caused by a deficiency in the C1-inhibitor protein. It is characterized by recurrent episodes of nonpruritic, nonpitting, subcutaneous or submucosal edema that typically involves the extremities or the gastrointestinal tract. However, the genitourinary tract, face, oropharynx, and/or larynx may be affected as well. Symptoms often begin in childhood, worsen at puberty, and persist throughout life, with unpredictable severity. Patients who are untreated may have frequent attacks, with intervals that can range from every few days to rare episodes. Minor trauma and stress are frequent precipitants of swelling episodes, but many attacks occur without clear triggers. HAE attacks may be preceded by a prodrome and/or be accompanied by erythema marginatum. The swelling typically worsens over the first 24 hours, before gradually subsiding over the subsequent 48 to 72 hours. Although oropharyngeal swelling is less frequent, more than half of patients have had at least one episode of laryngeal angioedema during their lifetime. Attacks may start in one location and spread to another before resolving. HAE attacks that involve the abdomen or oropharynx have been associated with significant morbidity and mortality. Abdominal attacks can cause severe abdominal pain, nausea, and vomiting. Bowel sounds are often diminished or silent, and guarding and rebound tenderness may be present on physical examination. These findings may lead to unnecessary abdominal imaging and procedures. Fluid shifts into the interstitial space or peritoneal cavity can cause clinically significant hypotension. Laryngeal edema poses the greatest risk for patients with HAE. Although prompt diagnosis and treatment improves outcomes, the variable presentation of HAE can make it difficult to diagnose.

Can the neutrophil-lymphocyte ratio predict type 1 hereditary angioedema attacks?

The neutrophil-lymphocyte ratio is a simple and easily used parameter for the assessment of inflammation. We aimed to determine the predictive potential of the neutrophil-lymphocyte ratio regarding episode occurrence in patients with hereditary angioedema. Sixty-six patients with Type 1 hereditary angioedema and 60 healthy controls were included in the study. The laboratory results of the patients in their episode-free periods were similar to those of the healthy controls. The median of neutrophil-lymphocyte ratio was higher during episodes when compared to normal periods (3.5 versus 2.0, p < .001). A significant positive correlation was present between the episode count and the neutrophil-lymphocyte ratio calculated during the episodes (r = 0.557, p < .001). We can conclude that the neutrophil-lymphocyte ratio, which is cheap and easy to calculate, can be used by clinicians as a predictive parameter for prediction of the episode count in patients with hereditary angioedema.

Biological therapy in hereditary angioedema: transformation of a rare disease.

Introduction: Hereditary angioedema, a disabling condition, with high mortality when untreated, is caused by C1 inhibitor deficiency and other regulatory disorders of bradykinin production or metabolism. This review covers the remarkable progress made in biological therapies for this rare disorder.Areas covered: Over the past 10 years, several evidence-based parenteral treatments have been licensed, including two plasma-derived C1 inhibitor replacement therapies and one recombinant C1 inhibitor replacement for acute treatment of angioedema attacks and synthetic peptides for inhibition of kallikrein or bradykinin B2 receptors, with oral small molecule treatments currently in clinical trial. Moreover, recent advances in prophylaxis by subcutaneous C1 inhibitor to restore near-normal plasma function or by humanized antibody inhibition of kallikrein have resulted in freedom from symptoms for a high proportion of those treated.Expert opinion: This plethora of treatment possibilities has come about as a result of recent scientific advances. Collaboration between patient groups, basic and clinical scientists, physicians, nurses, and the pharmaceutical industry has underpinned this translation of basic science into treatments and protocols. These in their turn have brought huge improvements in prognosis, quality of life and economic productivity to patients, their families, and the societies in which they live.

Evaluation of retinal microvascular perfusion in hereditary angioedema: a case-control study.

Evidence supports that hereditary angioedema (HAE) may be considered as a paroxysmal permeability disorder with defective but self-limiting endothelial barrier dysfunction. A potential subclinical abnormal vascular permeability at retinal capillaries could induce damage resulting in retinopathy. We aimed at exploring for the first time the presence of microangiopathy at retinal level from a highly selective cohort of patients with HAE due to C1 esterase inhibitor protein (C1INH) deficiency (type I). We conducted a pilot, prospective, case-control study including 20 type I HAE patients and 20 age-/sex-matched healthy controls (HC). All participants underwent standard ophthalmological examination including visual fields. Superficial and deep capillary plexi in the retina were analyzed by using new optical coherence tomography angiography (OCT-A). A total of 40 eyes from 20 HAE patients and 20 eyes from HC were evaluated. Perimetric indices of visual field were slightly worse in HAE than in controls. OCT-angiograms documented in HAE patients a lower retinal capillary density in both superficial and deep scans and a higher retinal thickness compared to healthy eyes. Our findings firstly documented subclinical abnormalities in retinal microvascular network in type I HAE patients that might be associated with early subtle functional changes. This preliminary evidence supports the hypothesis of a recurrent endothelial barrier failure at retinal level in HAE patients potentially resulting in chronic damage.

Hereditary angioedema: Looking for bradykinin production and triggers of vascular permeability.

Since the Osler's identification of the inherited nature of hereditary angioedema, a huge array of information was collected on pathogenetic mechanisms of the disease. Over the last years, information grew fast, and mutations in different genes, in addition to C1-inhibitor, were found to be causative. All types are inherited as autosomal-dominant traits with incomplete penetrance and little or no genotype-phenotype correlation. As a result, the clinical expression is characterized by a large heterogeneity. The acknowledgement of mechanisms leading to heterogeneity of the clinical phenotype is likely to provide important information not only for a better understanding of the pathogenesis but also for therapy. Regardless of which gene is mutated, similar pathways seem to play a pivotal role, triggering the up-regulation of contact activation system/kallikrein kinin system and giving rise to an unbalanced increase of bradykinin. However, notwithstanding the increase of bradykinin in bloodstream, the phenomenon is localized and no general vascular leakage and oedema is recognized. Thus, it is conceivable that there exist one or more localized factors that stimulate the production of bradykinin, which does not become a systemically event. Uncovering of these factors may shed lights on the missing part of the pathogenesis of hereditary angioedema. The present review, collecting information on pathogenesis from biochemical and genetics investigations, tries to provide a comprehensive view of the pathogenesis of hereditary angioedema. This can allow for a better understanding of the disease and lead to focused investigations that can further improve our knowledge.

Hereditary Angioedema: Insights into inflammation and allergy.

Hereditary Angioedema (HAE) is a rare autosomal recessive bradykinin (BK)-mediated disease characterized by local episodes of non-pitting swelling. Initially considered a complement-mediated disease, novel pathogenic mechanisms uncovered in the last decade have revealed new HAE-associated genes and tight physiological relationships among complement, contact, coagulation, fibrinolysis and inflammation. Uncontrolled production of BK due to inefficient regulation of the plasma contact system, increased activity of contact and coagulation factors or a deficient regulation of BK receptor-triggered intracellular signalling are on the basis of HAE pathology. In this new scenario, HAE can result from different mechanisms that may generate distinct clinical phenotypes of the disease. This review focuses in the recent advances and unsolved challenges in our comprehension of this ever increasingly complex pathology.

A review of kallikrein inhibitor lanadelumab in hereditary angioedema.

Hereditary angioedema with C1 esterase inhibitor deficiency is a rare disorder characterized by unpredictable swelling of the face, larynx and gastrointestinal tract. Kallikreins are serine proteases that cleave kininogens to produce bradykinin leading to inflammation. A new prophylactic drug is lanadelumab (DX-2930, SHP-643), a recombinant, fully human IgG1 monoclonal antibody kallikrein inhibitor. Pharmacokinetics show a half-life of 14 days with a dose-dependent effect. Completed trials for lanadelumab include two Phase III studies with updated efficacy in preventing angioedema in hereditary angioedema patients. Ongoing data show the safety of the targeted therapy along with less frequent administration requirements. Information on long-term safety is still needed, as well as, further studies on the correlation of subcutaneous administered dosing requirements and severity of side effects.

Angioedema due to acquired C1-inhibitor deficiency: spectrum and treatment with C1-inhibitor concentrate.

BACKGROUND: Acquired angioedema due to C1-inhibitor (C1-INH) deficiency (AAE-C1-INH) is a serious condition that may result in life-threatening asphyxiation due to laryngeal edema. It is associated with malignant B-cell lymphoma and other disorders. The purpose of this study was to describe the characteristics and associated disorders of patients with AAE-C1-INH and assess the efficacy of plasma-derived C1-INH concentrate (pdC1-INH) in the treatment of AAE-C1-INH. Forty-four patients with AAE-C1-INH from the Angioedema Outpatient Service of Mainz were assessed for associated disorders. In 32 of these patients, the duration of swelling attacks was measured before and after treatment with pdC1-INH (Berinert® (CSL Behring, Marburg, Germany)). The time between injection and complete resolution of symptoms and treatment effectiveness was provided by the patients. RESULTS: The following underlying disorders were present: monoclonal gammopathy of undetermined significance (47.7%), non-Hodgkin lymphoma (27.3%), anti-C1-INH autoantibodies alone (11.4%), and other conditions (4.5%). In 9.1% patients, no associated disorder could be found. AAE-C1-INH led to the detection of lymphoma in 75% of patients with the malignancy. Treatment with pdC1-INH shortened attacks by an average (SD) 54.4 (± 32.8) hours (P < 0.0001). The earlier the attack was treated, the shorter the time between injection and resolution of symptoms (P = 0.0149). A total of 3553 (97.7%) of the 3636 attacks were effectively treated with pdC1-INH as assessed by the patient. The mean (SD) dose per-attack was 787 (± 442) U. pdC1-INH was effective in 1246 (93.8%) of 1329 attacks in 8 patients with anti-C1-INH autoantibodies and in 344 (99.4%) of 346 attacks in 6 patients without autoantibodies. The average (SD) dose per effectively treated attack was 1238.4 (± 578.2) U in patients with anti-C1-INH autoantibodies and 510.2 (± 69.1) U in patients without autoantibodies. CONCLUSIONS: pdC1-INH is highly effective in treating AAE-C1-INH patients and is also effective in the vast majority of attacks in patients with anti-C1-INH autoantibodies. It is fast-acting and reduces attack duration.

Angiopoietin-1 haploinsufficiency affects the endothelial barrier and causes hereditary angioedema.

BACKGROUND: Different mutations of the angiopoietin-1 gene (ANGPT1) have been associated with the occurrence of hereditary angioedema (HAE). OBJECTIVE: The purpose of the study is to clarify whether the ANGPT1 A119S variant plays its role via haploinsufficiency or a dominant negative effect. METHODS: The ability of ANGPT1 A119S variant to affect the endothelial barrier function was assessed by immunocytochemistry. Inter-endothelial gap formation molecules primarily responsible for cell-cell adhesions of HUVECs, vascular endothelial (VE)-cadherin and ß-catenin, and reorganization of the F-actin cytoskeletal were evaluated. RESULTS: In in vitro conditions mimicking the heterozygous state, the p.A119S variant significantly reduced the capability to bind its natural receptor (80.7% of normal), less than the homozygous condition (59.1%). After stimulation of VEGF or bradykinin, the addiction to equimolar amounts of wtANGPT1 and ANGPT1 p.A119S clearly reduced the expression of VE-cadherin on the endothelial cell surface (31% and 24% respectively). Likewise, cell surface expression of ß-catenin was reduced and severe gap formation between adjacent HUVECs developed. In cultured cells, ß-catenin expression was mostly observed along the cell surface. Treatment with equimolar amounts of wtANGPT1 and ANGPT1 p.A119S failed to restore the reorganization of the F-actin cytoskeletal elements. ANGPT1 p.A119S variant in homozygous condition further diminished VE-cadherin and ß-catenin expression and failed to reduce stress fibre formation significantly affecting the endothelial barrier functionality. CONCLUSIONS AND CLINICAL RELEVANCE: Present data show that in a heterozygous state the p.A119S substitution results in a pathogenic loss of function of the protein due to a mechanism of haploinsufficiency. The ANGPT1 reduced ability to counteract the increment of endothelial permeability produced by inducers, such as VEGF and bradykinin, stimulate vascular leakage and reorganization of the F-actin cytoskeletal elements. As a result, a partial impairment of the ANGPT1 functionality, like when dominant mutations occur, represents a pathophysiological cause of HAE.

Lanadelumab for the Prophylactic Treatment of Hereditary Angioedema with C1 Inhibitor Deficiency: A Review of Preclinical and Phase I Studies.

Hereditary angioedema (HAE) with C1 esterase inhibitor (C1-INH) deficiency (C1-INH-HAE) is a rare disease characterized by diminished levels or dysfunctional activity of C1-INH, leading to dysregulated plasma kallikrein activity within the kallikrein-kinin pathway. Symptoms manifest as painful, potentially life-threatening swelling of subcutaneous tissues throughout the body and/or submucosal edema in the upper airway or gastrointestinal tract. Attacks recur with unpredictable frequency, intensity, and duration, placing a heavy burden on patients' daily lives. Despite improved availability of medications for on-demand treatment during attacks and prophylaxis of future attacks, unmet needs remain. Lanadelumab, a fully human monoclonal antibody, may help address some of the limitations of existing prophylactic options (e.g., the need for intravenous administration or frequent dosing). Preclinical studies demonstrate that it is highly potent and specifically inhibits plasma kallikrein, and findings from phase Ia and Ib studies suggest this agent is well tolerated and provides sustained inhibition of plasma kallikrein, allowing for less frequent dosing. The phase III HELP Study (NCT02586805) evaluating the efficacy and safety of lanadelumab in preventing HAE attacks has been completed, and its open-label extension (NCT02741596) is ongoing. Lanadelumab is now approved in the USA and Canada for prophylaxis to prevent attacks of HAE in patients aged ≥ 12 years. This review provides an overview of the discovery and clinical development of lanadelumab, from preclinical through phase Ib studies, characterizing its safety/tolerability, efficacy, and pharmacokinetic and pharmacodynamic profiles. It also highlights how this agent may positively impact clinical care of patients with C1-INH-HAE.

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

Multiple pathways have been proposed to generate bradykinin (BK)-related peptides from blood. We applied various forms of activation to fresh blood obtained from 10 healthy subjects or 10 patients with hereditary angioedema (HAE-1 or -2 only) to investigate kinin formation. An enzyme immunoassay for BK was applied to extracts of citrated blood incubated at 37°C under gentle agitation for 0-2 h in the presence of activators and/or inhibitory agents. Biologically active kinins in extracts were corroborated by c-Fos accumulation in HEK 293a cells that express either recombinant human B2 or B1 receptors (B2R, B1R). Biological evidence of HAE diagnostic and blood cell activation was also obtained. The angiotensin converting enzyme inhibitor enalaprilat, without any effect per se, increased immunoreactive BK (iBK) concentration under active stimulation of blood. Tissue kallikrein (KLK-1) and Kontact-APTT, a particulate material that activates the contact system, rapidly (5 min) and intensely (>100 ng/mL) induced similar iBK generation in the blood of control or HAE subjects. Tissue plasminogen activator (tPA) slowly (≥1 h) induced iBK generation in control blood, but more rapidly and intensely so in that of HAE patients. Effects of biotechnological inhibitors indicate that tPA recruits factor XIIa (FXIIa) and plasma kallikrein to generate iBK. KLK-1, independent of the contact system, is the only stimulus leading to an inconsistent B1R stimulation. Stimulating neutrophils or platelets did not generate iBK. In the HAE patients observed during remission, iBK formation capability coupled to B2R stimulation appears largely intact. However, a selective hypersensitivity to tPA in the blood of HAE patients suggests a role of plasmin-activated FXIIa in the development of attacks. Proposed pathways of kinin formation dependent on blood cell activation were not corroborated.

Severity of hereditary angioedema, prevalence, and diagnostic considerations.

Hereditary angioedema (HAE) is a rare disorder, characterized by intermittent attacks of swelling in any part of the body, without the presence of hives. This lifelong disease typically presents in the first 2 decades of life, and is commonly associated with a deficiency in functional C1 esterase inhibitor (C1-INH) activity. C1-INH levels may be decreased or normal, with an accompanied decrease in functionality, depending on the type of HAE present. The frequency and severity of attacks are highly variable among patients with HAE, but can have a significant impact on a patient's quality of life, and may be fatal if not properly managed. Early diagnosis of the disease can lead to the development of an individualized treatment plan to assist with prevention and management of angiodema attacks. Delays in diagnosis remain, as healthcare professionals often fail to include HAE in the differential diagnosis when patients present with attacks, and patients therefore often go undiagnosed or are misdiagnosed for several years before a diagnosis of HAE is made. It is important for providers to recognize the most common clinical features of HAE and how to evaluate patients to effectively diagnose, prevent, and treat future attacks.

Long-term prophylaxis therapy in patients with hereditary angioedema with C1 inhibitor deficiency.

OBJECTIVE: To review the criteria for long-term prophylaxis therapy in patients with hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE), describe how these criteria have evolved over time, and anticipate how criteria may change in the future with the availability of new C1-INH-HAE treatment options. DATA SOURCES: Treatment guidelines, consensus statements, and expert reviews. STUDY SELECTIONS: Manuscripts that described long-term prophylaxis therapy in patients with C1-INH-HAE were selected. RESULTS: Historically, patients with C1-INH-HAE were considered to be candidates for long-term prophylaxis therapy if they had at least 1 attack per month, had at least 5 days of disability per month because of C1-INH-HAE, or did not sufficiently respond to on-demand treatment. More recently, guidelines and reviews state that thresholds of number of attacks or days of disability are arbitrary and that treatment plans should be individualized to the patient's needs. Furthermore, all patients should have a comprehensive management plan that is reviewed periodically and should have at least 2 doses of on-demand treatment available. Prophylaxis therapy should be discussed as a potential treatment option for each patient; however, the decision for its use will depend on the patient's individual needs and the course of their symptoms. CONCLUSION: The criteria for long-term prophylaxis therapy in C1-INH-HAE have changed with the recognition that treatments should be individualized to the patient's needs and with the availability of new medications that have more favorable benefit-risk profiles, are easier to use, and improve patients' quality of life.