C1 Esterase Inhibitor Activity Research Articles

Clinical and laboratory spectrum of hereditary angioedema in a group of Egyptian children: a cross sectional study

BackgroundHereditary angioedema (HAE) is a hereditary illness represented by repeated bouts of submucosal or subcutaneous edema. Types of HAE includes; HAE with deficient C1-inhibitor (type 1), HAE with dysfunctional C1-inhibitor (type 2), and HAE with normal C1-inhibitor. Data on the epidemiology of HAE in Egypt are limited. Therefore, we aimed to characterize HAE in Egyptian children, identify the morbidity, and clarify HAE's different clinical and laboratory presentations.MethodsIn this cross-sectional study, we enrolled pediatric patients diagnosed with HAE according to the international hereditary angioedema WAO/EAACI guidelines. We gathered laboratory data on patients' mean serum C1 esterase inhibitor (C1-INH) level and activity, C4, and IgE levels.ResultsWe included 18 HAE patients (14 females and 4 males). They were between the ages of 6 and 18 years. The mean age upon confirmation of diagnosis was 8.4 ± 2.4 years. The mean time required to correctly diagnose HAE was 3.2 ± 1.8 years. We detected type I in 15 cases and type II in three cases. Eleven patients had a family member with HAE. In terms of previous misdiagnoses, 50% of patients were diagnosed with allergic angioedema. The median annual frequency of episodes was 17. The mean HAE attack time was 2.9 ± 1.5 days. Edema was most typically found in the face and abdomen. Trauma was the main triggering factor. We detected a significant direct relationship between severity of attack and C1-INH activity level.ConclusionsThis research adds a considerable clinical information about children with HAE. According to current results, there is a considerable underdiagnosis of HAE in Egypt. The detection and management of HAE can be improved by screening the relatives of HAE patients.

368: ANGIOEDEMA PREVENTING EXTUBATION IN A CASE OF ACQUIRED C-1 ESTERASE DEFICIENCY

Introduction: Acquired C1 esterase deficiency is a rare, life-threatening phenomenon that has been reported in association with lymphoproliferative and autoimmune disorders. Diagnosis is made based on the clinical presentation of angioedema and low C1 and C1q esterase inhibitor activity in a patient without a previous hereditary diagnosis. Treatment is aimed at addressing the underlying condition and plasma-derived C1 esterase inhibitor (C1-INH) concentrate, but clinical response can vary. Description: 75 year-old female with a past medical history of chronic lymphocytic leukemia (CLL) presented with spontaneous mouth and neck swelling unrelieved by antihistamines. Epinephrine and Solumedrol were administered, however the neck swelling worsened and the patient was intubated for airway protection. CT imaging of the neck revealed extensive subcutaneous neck edema. Attempts at extubation were limited by the patient’s persistent angioedema which was visualized by bronchoscopy. Glucocorticoids were ineffective as the patient had a reported allergy to Prednisone, therefore were further avoided. C1 esterase inhibitor (C1-INH) function was initially low at 7mg/dL, and repeat remained low at 10mg/dL with a C4 of .7mg/dL. C1q later returned low at < 1.2Eq/mL. The patient did not improve after treatment with plasma-derived C1-INH (Berinert). She eventually required tracheostomy placement, but had difficulty with subsequent downsizing due to persistent laryngeal edema with limited therapeutic options. Eventually, after 4 weeks, the patient was successfully decannulated. Discussion: There are no definitive guidelines for treatment of acquired C1 esterase deficiency, however therapies often follow the same course for hereditary forms including plasma-derived C1-INH. Often, these patients may not respond or require increased doses. If Berinert is ineffective, some immunologists and allergists have seen favorable outcomes and recommend treatment with the kallikrein inhibitor, ecallantide and the bradykinin B2 antagonist icatibant. To date, therapies targeted at prevention of angioedema in acquired cases have not been as successful as in hereditary forms, therefore, treatment is directed at the underlying condition, such as immunotherapy or chemotherapy for CLL.

C1 Inhibitor Deficiency Results in Increased Activation of Coagulation and Enhanced Venous Thrombosis

Introduction: C1 esterase inhibitor (C1INH) is a broad acting serine protease inhibitor that functions as a major endogenous inhibitor of activated factor (F) XII, FXI and kallikrein of the contact system. Congenital deficiency for C1INH results in hereditary angioedema (HAE) that can cause potentially life-threatening episodes of bradykinin induced swelling. Patients with HAE have increased circulating markers of activation of coagulation, however, the effect of this procoagulant state on thrombosis remains unclear. Methods: Contact pathway triggered thrombin generation was assessed in citrated plasma from patients with HAE (n=19) or age and sex matched healthy controls (n=20) using calibrated automated thrombography. The association between HAE and risk of composite arterial thromboembolism (ATE) and composite venous thromboembolism (VTE) was analyzed in a registry-based study of HAE patients (n=239) and age and sex matched controls (n=2383) with data analyzed by conditional logistic regression. Markers of activation of coagulation were measured in the plasma of C1INH deficient mice or wildtype littermate controls. C1INH deficient mice or wildtype littermate controls were evaluated in the inferior vena cava stenosis model of venous thrombosis and the carotid artery ferric chloride model of arterial thrombosis. Hemostasis was assessed in C1INH deficient mice or wildtype littermate controls using a tail transection model. Results: Plasma from patients with HAE supported significantly increased intrinsic pathway-initiated thrombin generation compared to healthy controls reflected by significantly reduced lagtime and increased peak. Furthermore, the enhanced thrombin generation negatively correlated with residual plasma levels of C1INH activity. Given that enhanced plasma thrombin generation has been associated with an increased risk of VTE in the general population the association between HAE and VTE was further explored. HAE was found to be associated with a significantly increased risk of composite VTE (OR 3.57, 95% CI 2.16-5.81, P<0.0001) but not composite ATE (OR 1.20, 95% CI 0.81-2.09, P=0.278). Consistent with this finding the cumulative incidence of composite VTE, but not ATE, was significantly higher in patients with HAE compared to controls. C1INH deficient mice had significantly increased plasma levels of coagulation markers prothrombin fragment 1+2, thrombin-antithrombin complexes and D-dimer at baseline compared to wildtype littermate controls. In addition, C1INH deficient mice exhibited enhanced venous thrombus formation in the inferior vena cava stenosis model compared to wildtype littermate controls evidenced by increased thrombus weight. Interestingly, loss of C1INH had no effect on venous thrombus composition. Arterial thrombus formation in the carotid artery ferric chloride model was not significantly different between C1INH deficient mice and wildtype controls.Further, hemostasis, assessed using a tail transection model, did not differ significantly between C1INH deficient mice and wildtype littermate controls. Conclusions: Plasma from patients with HAE supported significantly increased contact pathway-initiated thrombin generation that was dependent on the degree of C1INH deficiency. HAE was found to be associated with a selective increase in the risk of composite VTE but not composite ATE. C1INH deficient mice had evidence of increased basal activation of coagulation consistent with impaired endogenous anticoagulant activity. Further, C1INH deficient mice exhibited increased venous thrombus formation but not arterial thrombus formation phenocopying findings in humans with HAE. This work strongly suggests that plasma C1INH is an important endogenous anticoagulant regulating basal activation of coagulation and providing selective protection against venous thrombus formation.

A Potentially Fatal Outcome of Oral Contraceptive Therapy: Estrogen-Triggered Hereditary Angioedema in an Adolescent

Hereditary angioedema (HAE) is characterized by recurrent angioedema attacks with no urticaria. This disease has a high mortality due to asphyxia. Level of complement component 4 (C4), C1 esterase inhibitor (C1-INH) level and function, and genetic mutations determine different endotypes of HAE. Clinical presentation and the triggers of vasogenic edema may change according to the endotypes. An adolescent girl with oligomenorrhea, obesity, hirsutism, and acanthosis nigricans was diagnosed with polycystic ovary syndrome and prescribed ethinyl estradiol and cyproterone acetate containing oral contraceptive (OC). On the sixteenth day of treatment, she developed angioedema of the face, neck, and chest leading to dyspnea. Adrenaline, antihistamine, and corticosteroid treatments were ineffective. In the family history, the patient’s mother and two cousins had a history of angioedema. C1-INH concentrate was administered with a diagnosis of HAE. C4 and C1-INH level and activity were normal. Genetic analysis identified a mutation in the factor 12 (F12) gene, and the diagnosis of F12-related HAE was made. OC treatment was discontinued. She has had no additional angioedema attacks in the follow-up period of two years. OC containing estrogen may induce the life-threatening first attack of F12-related HAE even in children. Recurring angioedema attacks in the family should be asked before prescribing estrogen-containing OC pills.

Abstract 110: C1 Esterase Inhibitor Functions As An Anticoagulant In Human And Murine Venous Thrombosis

Factor (F) XII and FXI play a central role in venous thrombus formation in preclinical disease models and contributes to venous thromboembolism (VTE) in humans. Agents targeting FXIa have been developed and effectively prevent VTE in humans. C1 esterase inhibitor (C1INH) is a serine protease inhibitor that inhibits several proteases, including FXII and FXI. In this study, we investigated the anticoagulant activity of C1INH in humans and mice. First, plasma C1INH levels were determined in a population-based nested case-control study consisting of 405 VTE patients and 829 age- and sex-matched controls derived from the Tromsø Study. Participants with plasma C1INH levels in the highest quartile had a significantly lower risk of VTE (odds ratio [OR] of 0.68, confidence interval 0.49-0.96, P&lt;0.05), unprovoked VTE (OR 0.59, confidence interval 0.39-0.89) and pulmonary embolism (OR 0.57, confidence interval 0.34-0.92) compared to participants with C1INH levels in the lowest quartile after adjustment for age and sex. Secondly, plasma-based thrombin generation studies were conducted to assess the anticoagulant function of C1INH. Supplementation of normal human pooled plasma with exogenous human purified C1INH (0.2 and 0.4mg/ml) significantly inhibited thrombin generation initiated with silica (P&lt;0.05) and significantly prolonged the activated partial thromboplastin assay clotting time (P&lt;0.001). Thirdly, administration of a clinically approved human purified C1INH product to mice significantly reduced thrombus weight (P&lt;0.05) in the murine inferior vena cava stenosis model of venous thrombosis. Studies with C1 inhibitor deficient mice and substrate selective C1INH variants are currently ongoing. Our results indicate that C1INH serves as an endogenous anticoagulant with higher plasma levels of C1INH associated with a decreased future risk of VTE. Further, exogenous C1INH effectively inhibits thrombin generation in vitro and venous thrombus formation in a mouse model. Our findings suggest that C1INH may prevent thrombosis caused by activation of the intrinsic coagulation pathway.

The Genetics of Hereditary Angioedema: A Review.

Hereditary angioedema is a rare inherited disorder characterized by recurrent episodes of the accumulation of fluids outside of the blood vessels, causing rapid swelling of tissues in the hands, feet, limbs, face, intestinal tract, or airway. Mutations in SERPING1, the gene that encodes C1-INH (C1 esterase inhibitor), are responsible for the majority of cases of hereditary angioedema. C1 esterase inhibitor (C1-INH) is a major regulator of critical enzymes that are implicated in the cascades of bradykinin generation, which increases the vascular permeability and allows the flow of fluids into the extracellular space and results in angioedema. Moreover, a dominantly inherited disease has been described that has a similar clinical picture to C1-INH-HAE (Hereditary angioedema due to C1 inhibitor deficiency), but with normal C1-INH level and activity. This new type of HAE has no mutation in the SERPING1 gene and it is classified as nC1-INH-HAE (HAE with normal C1-INH). Currently mutations in six different genes have been identified as causing nC1-INH-HAE: factor XII (F12), plasminogen (PLG), angiopoietin 1 (ANGPT1), Kininogen 1 (KNG1), Myoferlin (MYOF), and heparan sulfate (HS)-glucosamine 3-O-sulfotransferase 6 (HS3ST6). In this review we aim to summarize the recent advances in genetic characterization of angioedema and possible future prospects in the identification of new genetic defects in HAE. We also provide an overview of diagnostic applications of genetic biomarkers using NGS technologies (Next Generation Sequencing).

A robust multiplexed assay to quantify C1-inhibitor, C1q, and C4 proteins for in vitro diagnosis of hereditary angioedema from dried blood spot

Hereditary angioedema (HAE) is a rare genetic disease caused by deficiency or dysfunction of C1 esterase inhibitor (C1-INH). Plasma C1-INH activity and concentrations of C1-INH and complement components 1q and 4 (C1q, C4) are critical to the HAE diagnosis. We describe a novel multiplexed assay to simultaneously measure C1-INH, C1q, and C4 levels in dried blood spot (DBS) of HAE patients. The blood proteins were extracted from 3 mm punches of DBS samples and were subsequently digested by trypsin. The signature peptide derived from each protein was quantified by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Analyte-depleted blood was generated as a surrogate matrix for the preparation of calibration curves to overcome the interference of endogenous proteins, and the assay reproducibility was further monitored by assessing the signal of plasma transferrin as a house-keeping protein. The assay was fully validated following regulatory guideline, with a quantification range of 12.5–800 μg/mL for C1-INH and C4 and 3.13–200 μg/mL for C1q. The precision and accuracy ranged from 3.3%–9.8% and -8.2%–12.6%, respectively. All the patient samples exhibited C1-INH levels lower than normal range except the Type II patient and the C4 and C1q concentrations were as expected. Results from the DBS-based LC–MS assay were highly correlated with the ELISA data measured in plasma of the same subjects. The method described here offers unique advantages such as less invasive sampling, minimal blood processing, and easy transportation and sample storage, allowing, for the first time, C1-INH, C4, and C1q levels to be simultaneously determined in a drop of dried blood.

Perioperative Management of Patients With Hereditary Angioedema With Special Considerations for Cardiopulmonary Bypass.

Hereditary angioedema (HAE) is a rare autosomal dominant disorder mostly due to the deficiency of C1-esterase inhibitor (C1-INH). Reduced C1-INH activity below ~38% disrupts homeostasis of bradykinin (BK) formation by increasing kallikrein activation and causes recurrent angioedema attacks affecting the face, extremities, genitals, bowels, oropharynx, and larynx. HAE symptoms can be debilitating and potentially life-threatening. The recent clinical developments of biological and pharmacological agents have immensely improved acute and long-term care of patients with moderate-to-severe HAE. The therapies are given as on-demand and/or prophylaxis, and self-administration is highly recommended and performed with some agents via intravenous or subcutaneous route. Perioperative clinicians need to be familiar with the symptoms and diagnosis of HAE as well as available therapies because of the potential need for airway management, sedation, or anesthesia for various medical and surgical procedures and postoperative care. Cardiovascular surgery using cardiopulmonary bypass is a unique condition in which heparinized blood comes into direct contact with an artificial surface while pulmonary circulation, a major reserve of angiotensin-converting enzyme (ACE), becomes excluded. These changes result in systemic kallikrein activation and BK formation even in non-HAE patients. The objectives of this review are (1) to review pathophysiology of HAE and laboratory testing, (2) to summarize pertinent pharmacological data on the prophylactic and on-demand treatment strategies, and (3) to discuss available clinical data for perioperative management in cardiovascular surgery.

Features of diagnostics and clinical approaches to case management of patients with hereditary angioedema without C1 esterase inhibitor deficiency. Analysis of the clinical case

This article describes the clinical, biochemical and genetic features of hereditary angioedema (HAE) with normal level and functional activity of C1 esterase inhibitor. The discussion includes pathogenesis, diagnostics and case management of patients with hereditary angioedema without C1 esterase inhibitor deficiency. The materials of few scientific sources about patients with HAE without C1 esterase inhibitor deficiency in stages and our own clinical case (the female patient of fertile age with a confirmed mutation associated with factor XII (Hageman) deficiency) was given. The article describes the current state of the issue of the algorithm of primary diagnostics and differential diagnostics of HAE without C1 esterase inhibitor deficiency based on international and Russian data. It has been suggested that the new understanding of pathogenesis and treatment of patients with HAE without C1 esterase inhibitor deficiency is encouraging and becoming accessible to the medical society.

Features of diagnostics and clinical approaches to case management of patients with hereditary angioedema without C1 esterase inhibitor deficiency. Analysis of the clinical case

This article describes the clinical, biochemical and genetic features of hereditary angioedema (HAE) with normal level and functional activity of C1 esterase inhibitor. The discussion includes pathogenesis, diagnostics and case management of patients with hereditary angioedema without C1 esterase inhibitor deficiency. The materials of few scientific sources about patients with HAE without C1 esterase inhibitor deficiency in stages and our own clinical case (the female patient of fertile age with a confirmed mutation associated with factor XII (Hageman) deficiency) was given. The article describes the current state of the issue of the algorithm of primary diagnostics and differential diagnostics of HAE without C1 esterase inhibitor deficiency based on international and Russian data. It has been suggested that the new understanding of pathogenesis and treatment of patients with HAE without C1 esterase inhibitor deficiency is encouraging and becoming accessible to the medical society.

A novel functional C1 inhibitor activity assay in dried blood spot for diagnosis of Hereditary angioedema

BackgroundHereditary angioedema (HAE) is a rare genetic disease caused by deficiency or dysfunction of C1 esterase inhibitor (C1-INH). Timely and accurate diagnosis is an ongoing challenge. Measurement of plasma C1-INH activity is currently the critical standard test. We describe a novel and highly robust point-of-care assay to quantify C1-INH activity in dried blood spot (DBS). MethodsC1-INH was extracted from 3 mm punches of DBS samples and incubated with excess amount of C1 esterase (C1s). The mixture was subsequentially incubated with C1s substrate, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation of the enzyme reaction product. ResultsThe assay was validated within a quantification range from 100 to 1500 mU/mL. The intra-day precision and accuracy ranged from 4.0% to 11.6% and −11.1% to −2.1%, and the inter-day precision and accuracy were 8.1–13.1% and −10.3% to 0.9%, respectively. Normal C1-INH activity (n = 103) ranged from 311 to 1090 mU/mL, whereas 23 out of 24 HAE patients exhibited C1-INH activity lower than 100 mU/mL. ConclusionDBS specimen collection for measurement of functional C1-INH activity in a physician’s office is straightforward and not limited by logistic considerations and therefore, appropriate for the diagnosis of HAE in high throughput diagnostic laboratories.

A Case of Prolonged Angioedema After Cardiac Surgery

Angioedema (AE) is a transient capillary leak syndrome, caused by either histamine or bradykinin, that presents as an acute nonpitting swelling of the skin, subcutaneous tissues, and mucous membranes of the face, lips, tongue, upper airways, and gastrointestinal tract, with or without a rash. A lack of response to antihistamines, steroids, and epinephrine suggests a bradykinin-mediated AE. Bradykinin-AE may be inherited, acquired, or drug related. Mechanism of increased bradykinin can include decreased C1-esterase inhibitor (C1-INH) levels or activity, increased bradykinin production, or decreased bradykinin breakdown, the latter occurring during angiotensin converting enzyme inhibitor (ACEi). A 65-year-old woman had coronary artery bypass grafting, which was complicated by prolonged bradykinin-AE owing to ACEi, requiring prolonged endotracheal tube intubation. Treatment with a C1-esterase inhibitor (Berinert) on postoperative day 7 resulted in a dramatic improvement in airway edema and tongue swelling within 7 hours, and the patient was subsequently extubated. The case is unusual because of the prolonged course of AE and the benefit of late administration of C1-INH concentrate.

C1 Esterase Inhibitor Activity Is Reduced in the Acute Phase Following Burn Injury: A Prospective Observational Study

Hereditary angioedema has been attributed to an inherited deficiency of C1 esterase inhibitor that increases vascular permeability. The role of C1 esterase inhibitor in burn patients has not been described previously. In this study, we attempted to identify the relationship between serial changes of C1 esterase inhibitor activity and the clinical course in major burn patients. This study was a single-center, prospective, observational study. C1 esterase inhibitor activity values were serially examined in major burn patients admitted into the burn center from April 2014 to December 2016. Inclusion criteria were age ≥16 years old and %TBSA burned ≥20%. This study included 38 patients with major burn. C1 esterase inhibitor activity after burn dropped acutely on days 1 and 2 but increased immediately until days 3 to 5, after which it continued to gradually increase to above the reference value. C1 esterase inhibitor activity on admission showed significant inverse correlation with the volume of infusion per body weight required in the first 24 hours after injury and %TBSA burned (r = -0.405, P = 0.01; r = -0.375, P = 0.02, respectively). C1 esterase inhibitor activity on admission was significantly lower in the nonsurvivors than in the survivors during the 28-day evaluation period (59% vs 90%, P = 0.01). These findings suggest that C1 esterase inhibitor may play a critical role in regulating vascular permeability in the acute phase following the burn injury.

A hereditary angioedema screening in two villages, based on an index case, and identification of a novel mutation, "1033G>T", at the SERPING1 gene.

IntroductionHereditary angioedema (HAE) may be fatal and diagnosis can be delayed up to 10 years. We aimed to screen HAE in two villages based on an index case of HAE and to investigate for the mutation of the C1 esterase inhibitor (C1-INH) gene.Material and methodsA total of 124 people were screened in two villages. The frequency and severity of symptoms were scored. C4, C1-INH levels and C1-INH activity were measured. We investigated for mutations of the C1-INH gene.ResultsThirty-five cases of type I HAE and 7 cases of type II HAE were determined. Thirty-one (73.8%) patients diagnosed with HAE were 18 years old or younger. There was a positive correlation between C4 levels, C1-INH levels (p < 0.0001, r = 0.81), and C1-INH activity levels (p < 0.0001, r = 0.631) and between the age at diagnosis and severity score (p < 0.0001, r = 0.651). A positive correlation was found between the age at first symptom onset and C4 levels (p = 0.002, r = 0.774), and C1-INH levels (p = 0.006, r = 0.714). A marginally significant negative correlation was found between C1-INH activity levels and severity scores (p = 0.1, r = –0.515). We identified a novel heterozygous 1033G>T missense variant of the C1-INH gene, SERPING1, in patients with type I HAE.ConclusionsThere are long delay periods in the diagnosis of HAE and when the index case is present, family screening may be very important and even life-saving, in particular, in paediatric patients without symptoms. Furthermore, the present study provides evidence to link a novel mutation, c.1033G>T, to the development of HAE in a large HAE family from Turkey.

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.

Calibrated kallikrein generation in human plasma

ObjectivesThe physiological role of the contact system remains inconclusive. No obvious clinical complications have been observed for factor XII (FXII), prekallikrein (PK), or high molecular weight kininogen deficiencies even though the contact system in vitro is associated with coagulation, fibrinolysis, and inflammation. A global generation assay measuring the initial phase of the contact system could be a valuable tool for studies of its physiological role. Design and methodsWe investigated whether such a method could be developed using the principle of the Calibrated Automated Thrombin generation method as a template. ResultsA suitable kallikrein specific fluorogenic substrate was identified (KM=0.91mM, kcat=19s−1), and kallikrein generation could be measured in undiluted plasma when silica was added as activator. Disturbing effects, including substrate depletion and the inner-filter effect, however, affected the signal. These problems were corrected for by external calibration with α2-macroglobulin-kallikrein complexes. Selectivity studies of the substrate, experiments with FXII and PK depleted plasmas, and plasma with high or low complement C1-esterase inhibitor activity indicated that the obtained and calibrated signal predominantly was related to FXII-dependent kallikrein activity. ConclusionsThe findings described show that establishment of a kallikrein generation method is possible. Potentially, this setup could be used for clinical studies of the contact system.

Plasmin is a natural trigger for bradykinin production in patients with hereditary angioedema with factor XII mutations

Patients with angioedema experience unpredictable attacks of tissue swelling in which bradykinin is implicated. Several distinct mutations in Factor XII (FXII) are associated with hereditary angioedema (HAE) in the presence of normal C1 esterase inhibitor activity (FXII-HAE). The underlying disease mechanisms are unclear, which complicates diagnosis and treatment. We sought to identify the natural trigger for FXII activation, which causes uncontrolled bradykinin production in patients with FXII-HAE. We generated recombinant variants of FXII, representing health and disease, and studied their behavior in functional studies. We investigated bradykinin-forming pathways in blood plasma with newly developed nanobody-based analytic methods. We here report that FXII-HAE mutations collectively introduce new sites that are sensitive to enzymatic cleavage by plasmin. These FXII mutants rapidly activate after cleavage by plasmin, escape from inhibition through C1 esterase inhibitor, and elicit excessive bradykinin formation.Furthermore, our findings indicate that plasmin modulates disease activity in patients with FXII-HAE. Finally, we show that soluble lysine analogs attenuate this mechanism, explaining their therapeutic value in patients with HAE. Our findings indicate a new pathway for bradykinin formation in patients with HAE, in which FXII is cleaved and activated by plasmin. This should lead to the identification of new markers for diagnosis and targets for treatment.

Recombinant replacement therapy for hereditary angioedema due to C1 inhibitor deficiency.

Hereditary angioedema is a rare genetic condition transmitted as an autosomal dominant trait and characterized most commonly by the production of either inadequate or nonfunctioning C1 esterase inhibitor (C1-INH), a blood protein that regulates proteases in the complement, fibrinolytic and contact systems. Patients with hereditary angioedema suffer from episodic, unpredictable manifestations of edema affecting multiple anatomical locations, including the GI tract, facial tissue, the upper airway, oropharynx, urogenital region and/or the arms and legs. A rational approach to treatment is replacement of C1-INH protein, to normalize the levels of C1-INH activity and halt the progression of the biochemical activation processes underlying the edema formation. Ruconest is a highly purified recombinant human C1-INH. This article will focus on the results of ten clinical studies demonstrating the efficacy and safety of Ruconest(®) (Pharming Group NV, Leiden, the Netherlands), which is now approved for use in Europe, Israel and the USA.

Amniotic fluid embolism: pathophysiology and new strategies for management.

The registry program of amniotic fluid embolism (AFE) in Japan started in 2003. More than 400 hundred clinical diagnosed amniotic fluid embolism has been accumulated. Those data showed that there were two etiologies of AFE: the fetal materials create physical obstructions in the maternal microvessels in various organs, such as the lung; and (ii) the liquids cause an anaphylactoid reaction that leads to pulmonary vasospasm and activation of platelets, white blood cells and/or complements. The clinical findings showed that AFE was characterized mainly by cardiopulmonary collapse, the other involves the presence of disseminated intravascular coagulation (DIC) and atonic bleeding. Zinc coproporphyrin-1, sialyl Tn antigen (STN), complement C3, C4 and interleukin-8 have been used as serum markers of AFE. The levels of zinc coproporphyrin-1 and STN were increased in cardiopulmonary collapse type AFE, and a marked reduction of C3 and C4 was observed in DIC type AFE. At the primary medical institution, initial treatments for shock airway management, vascular management, fluid replacement, administration of anti-DIC therapy such as antithrombin, and administration of fresh frozen plasma should be provided. C1 esterase inhibitor activity in AFE cases was significantly lower than those of normal pregnant women. C1 esterase inhibitor may be a promising candidate of treatment of AFE.

C1 Esterase Inhibitor Activity in Amniotic Fluid Embolism*

Amniotic fluid embolism exhibits activation of the complement system and the kallikrein-kinin and coagulofibrinolytic systems. C1 esterase inhibitor is a major inhibitor of C1 esterase and can inhibit plasma kallikrein and also factors XIIa and XIa. Its activity has been shown to be significantly lower in pregnancy and labor than in the nonpregnant state. The purpose of this study was to determine C1 esterase inhibitor activity levels in amniotic fluid embolism. Retrospective study. A single university-based center. One hundred six cases with amniotic fluid embolism in a total of 194 singleton pregnant women between January 2010 and December 2011. None. One hundred six cases of amniotic fluid embolism had applied to the Japan amniotic fluid embolism registration center in Hamamatsu University School of Medicine between January 2010 and December 2011. In amniotic fluid embolism cases, 85 cases were nonfatal and 21 cases were fatal. Eighty-eight women who delivered without amniotic fluid embolism were regarded as a control. C1 esterase inhibitor activity levels were significantly lower in amniotic fluid embolism patients (30.0% ± 1.8%) than in control women (62.0% ± 2.0%) (p < 0.0001). C1 esterase inhibitor activity levels in fatal amniotic fluid embolism cases (22.5% ± 3.4%) were significantly lower than those in nonfatal amniotic fluid embolism cases (32.0% ± 2.1%) (p < 0.05). These results demonstrated that low C1 esterase inhibitor activity levels were closely associated with the pathogenesis of amniotic fluid embolism suggesting that C1 esterase inhibitor activity levels have potential as a prognosis factor of amniotic fluid embolism.