Molecular Dambusters: What Is Behind Hyperpermeability in Bradykinin-Mediated Angioedema?

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.

Delayed plasma kallikrein inhibition fosters post-stroke recovery by reducing thrombo-inflammation

Activation of the kallikrein-kinin system promotes vascular leakage, inflammation, and neurodegeneration in ischemic stroke. Inhibition of plasma kallikrein (PK) - a key component of the KKS - in the acute phase of ischemic stroke has been reported to reduce thrombosis, inflammation, and damage to the blood-brain barrier. However, the role of PK during the recovery phase after cerebral ischemia is unknown. To this end, we evaluated the effect of subacute PK inhibition starting from day 3 on the recovery process after transient middle artery occlusion (tMCAO). Our study demonstrated a protective effect of PK inhibition by reducing infarct volume and improving functional outcome at day 7 after tMCAO. In addition, we observed reduced thrombus formation in cerebral microvessels, fewer infiltrated immune cells, and an improvement in blood-brain barrier integrity. This protective effect was facilitated by promoting tight junction reintegration, reducing detrimental matrix metalloproteinases, and upregulating regenerative angiogenic markers. Our findings suggest that PK inhibition in the subacute phase might be a promising approach to accelerate the post-stroke recovery process.

Meta-analysis of ACE inhibitor-induced angioedema identifies novel risk locus

BACKGROUND

Angioedema is a rare but potentially life-threatening adverse drug reaction in patients receiving angiotensin-converting enzyme inhibitors (ACEis). Research suggests that susceptibility to ACEi-induced angioedema (ACEi-AE) involves both genetic and nongenetic risk factors. Genome- and exome-wide studies of ACEi-AE have identified the first genetic risk loci. However, understanding of the underlying pathophysiology remains limited.

OBJECTIVE

We sought to identify further genetic factors of ACEi-AE to eventually gain a deeper understanding of its pathophysiology.

METHODS

By combining data from 8 cohorts, a genome-wide association study meta-analysis was performed in more than 1000 European patients with ACEi-AE. Secondary bioinformatic analyses were conducted to fine-map associated loci, identify relevant genes and pathways, and assess the genetic overlap between ACEi-AE and other traits. Finally, an exploratory cross-ancestry analysis was performed to assess shared genetic factors in European and African-American patients with ACEi-AE.

RESULTS

Three genome-wide significant risk loci were identified. One of these, located on chromosome 20q11.22, has not been implicated previously in ACEi-AE. Integrative secondary analyses highlighted previously reported genes (BDKRB2 [bradykinin receptor B2] and F5 [coagulation factor 5]) as well as biologically plausible novel candidate genes (PROCR [protein C receptor] and EDEM2 [endoplasmic reticulum degradation enhancing alpha-mannosidase like protein 2]). Lead variants at the risk loci were found with similar effect sizes and directions in an African-American cohort.

CONCLUSIONS

The present results contributed to a deeper understanding of the pathophysiology of ACEi-AE by (1) providing further evidence for the involvement of bradykinin signaling and coagulation pathways and (2) suggesting, for the first time, the involvement of the fibrinolysis pathway in this adverse drug reaction. An exploratory cross-ancestry comparison implicated the relevance of the associated risk loci across diverse ancestries.

Kallikrein inhibitors for angioedema: the progress of preclinical and early phase studies

INTRODUCTION

Hereditary angioedema (HAE) is a rare genetic disorder characterized by recurrent edema and predominantly caused by the dysregulation of the kinin-kallikrein system.

AREAS COVERED

This manuscript presents the results of preclinical and early clinical trials of newer drugs targeting the dysregulated kinin-kallikrein system. ATN-249 is an oral drug that has shown promising results in preclinical and Phase I studies, and good tolerability in the prophylactic treatment of attacks. KVD900 is also an oral agent developed for the on-demand treatment of HAE attacks. It has shown positive results in Phase I/II studies, with rapid absorption. The third drug, IONIS-PKKRx, is an antisense oligonucleotide targeting plasma prekallikrein mRNA. It has shown a dose-dependent reduction of plasma prekallikrein levels and proenzyme activation in Phase I/II studies, and has shown promising results. STAR-0215 is a long acting anti-activated kallikrein monoclonal antibody. A Phase 1a single ascending dose trial evaluated its safety, pharmacokinetics, and pharmacodynamics. Lastly, NTLA-2002 is an investigational gene-editing therapy.

EXPERT OPINION

The targeted treatment of the dysregulated kinin-kallikrein system with specific inhibitors is promising for the prevention of angioedema attacks. Ongoing phase III studies will provide further insight into the efficacy and long-term safety of these novel therapies, potentially expanding treatment options for HAE treatment.

The Lectin Pathway of the Complement System-Activation, Regulation, Disease Connections and Interplay with Other (Proteolytic) Systems

The complement system is the other major proteolytic cascade in the blood of vertebrates besides the coagulation-fibrinolytic system. Among the three main activation routes of complement, the lectin pathway (LP) has been discovered the latest, and it is still the subject of intense research. Mannose-binding lectin (MBL), other collectins, and ficolins are collectively termed as the pattern recognition molecules (PRMs) of the LP, and they are responsible for targeting LP activation to molecular patterns, e.g., on bacteria. MBL-associated serine proteases (MASPs) are the effectors, while MBL-associated proteins (MAps) have regulatory functions. Two serine protease components, MASP-1 and MASP-2, trigger the LP activation, while the third component, MASP-3, is involved in the function of the alternative pathway (AP) of complement. Besides their functions within the complement system, certain LP components have secondary ("moonlighting") functions, e.g., in embryonic development. They also contribute to blood coagulation, and some might have tumor suppressing roles. Uncontrolled complement activation can contribute to the progression of many diseases (e.g., stroke, kidney diseases, thrombotic complications, and COVID-19). In most cases, the lectin pathway has also been implicated. In this review, we summarize the history of the lectin pathway, introduce their components, describe its activation and regulation, its roles within the complement cascade, its connections to blood coagulation, and its direct cellular effects. Special emphasis is placed on disease connections and the non-canonical functions of LP components.

What are the current anti-COVID-19 drugs? From traditional to smart molecular mechanisms

BACKGROUND

Coronavirus disease 19 (COVID-19) is the disease caused by SARS-CoV-2, a highly infectious member of the coronavirus family, which emerged in December 2019 in "Wuhan, China". It induces respiratory illness ranging from mild symptoms to severe disease. It was declared a "pandemic" by the World Health Organization (WHO) in March 2020. Since then, a vast number of clinical and experimental studies have been conducted to identify effective approaches for its prevention and treatment.

MAIN BODY

The pathophysiology of COVID-19 represents an unprecedented challenge; it triggers a strong immune response, which may be exacerbated by "a cytokine storm syndrome". It also induces thrombogenesis and may trigger multi-organ injury. Therefore, different drug classes have been proposed for its treatment and prevention, such as antivirals, anti-SARS-CoV-2 antibody agents (monoclonal antibodies, convalescent plasma, and immunoglobulins), anti-inflammatory drugs, immunomodulators, and anticoagulant drugs. To the best of our knowledge, this review is the first to present, discuss, and summarize the current knowledge about the different drug classes used for the treatment of COVID-19, with special emphasis on their targets, mechanisms of action, and important adverse effects and drug interactions. Additionally, we spotlight the latest "October 2023" important guidelines (NIH, IDSA, and NICE) and FDA approval or authorization regarding the use of these agents in the management of COVID-19.

CONCLUSION

Despite the wide array of therapeutic strategies introduced for the treatment of COVID-19, one of the most prominent therapeutic challenges is SARS-CoV-2 mutations and emerging new variants and subvariants. Currently, the anti-COVID-19 drug pipeline is continuously affording novel treatments to face this growing challenge.

A challenging case of bradykinin-mediated angioedema with airway obstruction: management and therapeutic strategies

Angioedema is a potentially life-threatening condition that can have an allergic origin, usually mediated by histamine or a non-allergic origin, mediated by bradykinin. The distinction between these origins may present a clinical challenge at first approach, especially in cases that appear as an emergency and the outcome is time dependent. The authors describe a rare case of bradykinin angioedema associated with airway obstruction and discuss the right approach and therapeutic options. A 46-year-old patient under ACE inhibitor, renin-angiotensin-aldosterone blocker and beta blocker presented with difficulty swallowing, shortness of breath and angioedema, associated with inspiratory stridor, incapacity of talking, plantar pruritus and vomits minutes after ingestion of shrimp. The symptoms did not respond to epinephrine, anti-histamines or steroids. The airway quickly became an emergency and the authors discuss the importance of airway obstruction management and having a multidisciplinary well-defined plan of approach with backup plans. Exuberant angioedema persisted leading to the suspicion of drug induced angioedema. Treatment with tranexamic acid 1g 6/6h and icatibant 30 mg 6/6h (3 doses) was started with resolution. In these cases, the rapid institution of the right pharmacological line will relate significantly to a better outcome. It is particularly important because, as their underlying physiopathologic mechanism differ, bradykinin mediated angioedema does not respond to drugs that histamine mediated angioedema does, like corticosteroids and antihistaminic. In severe and life-threatening cases icatibant and tranexamic acid have proven to be an effective therapy.

Decreased adhesion to endothelium leads to elevated neutrophil granulocyte count in hereditary angioedema patients

As many aspects of hereditary angioedema (HAE) due to C1-inhibitor (C1-INH) deficiency (C1-INH-HAE) cannot be explained with elevated bradykinin level alone, it has recently become clear that other factors also play an important role in the pathogenesis. One of these factors could be elevated neutrophil granulocyte (NG) counts, which are associated with increased NG activation in C1-INH-HAE patients; however, their origin has not been elucidated so far. Here, we aimed to investigate whether the excess of NGs is due to disturbed maturation, biased circulating/marginated pool equilibrium or decreased elimination. We enrolled 20 attack-free C1-INH-HAE patients together with 21 healthy controls and collected blood samples. We compared cell surface maturation markers, adhesion molecules, cytokine receptors, and Ca2+-mobilization of NG by flow cytometry, activation markers by ELISA, and NG/endothelial cell adhesion by automated pipetting system. Cell-surface markers showed normal maturation of NGs in C1-INH-HAE patients. Adhesion of NGs to endothelial cells pretreated with lipopolysaccharide or phorbol 12-myristate 13-acetate was significantly weaker in samples from C1-INH-HAE patients and bradykinin had no effect on the adhesion. NGs from C1-INH-HAE patients were in an activated state when assessed by soluble activation markers without any stimulation. Our data support that the maturation of NGs in C1-INH-HAE patients is normal, whereas adhesion properties of patient-derived NGs to the endothelium are reduced compared to those from healthy controls, indicating a bias between the circulating and marginated pools of NGs in patients. Bradykinin may not be responsible for reduced adhesion properties of NGs.

Patient-rated angioedema severity using a novel photo-aid for predicting non-mast cell mediator-induced angioedema diagnosis

Background

Patients with non-mast cell mediator-induced angioedema (NM-AE) usually experience a diagnostic delay. Therefore, a clinical tool for predicting NM-AE diagnosis is essential.

Objective

To identify clinical predictors related to a confirmed diagnosis of NM-AE.

Methods

Participants with a history of recurrent AE with unknown causes were enrolled. They were classified into mast cell mediator-induced AE (M-AE) and NM-AE according to the response to anti-mast cell mediator therapy. All participants were asked to rate their worst AE ever experienced (% Photomax) from 0 to 100% using a novel photo aid. Clinical characteristics were recorded and analyzed by univariable and multivariable analysis.

Results

Thirty-five participants were included, 25 with NM-AE and 10 with M-AE. AE located at extremities, face, and genitalia and positive family history were significantly associated with NM-AE. The AE severity in the NM-AE group was significantly higher than in the M-AE group, with the mean % Photomax of 82.4 ± 20.3 vs 47.5 ± 25.6 (p < 0.001), respectively. Univariable analysis showed that the % Photomax (every 10% increase), feet AE and hands AE were predictive of being NM-AE with the area under the receiver operating characteristic curve (AuROC) of 0.87 (95% CI 0.75, 0.99), 0.85 (95% CI 0.72, 0.98), and 0.84 (0.69, 0.99), respectively. Multivariable analysis showed that the combination of hands AE and % Photomax enhanced diagnostic accuracy (AuROC 0.94, 95% CI 0.86, 1.0) and constituted the prototype formula for calculating the diagnostic probability.

Conclusion

Patient-rated angioedema severity using a novel photo aid combined with hands AE had a high probability of diagnosing NM-AE.

CU06-1004 alleviates vascular hyperpermeability in a murine model of hereditary angioedema by protecting the endothelium

BACKGROUND

Over-release of the vasoactive peptide bradykinin (BK) due to mutation in the SERPING1 gene is the leading cause of hereditary angioedema (HAE). BK directly activates endothelial cells and increases vascular permeability by disrupting the endothelial barrier, leading to angioedema affecting face, lips, extremities, gastrointestinal tract, and larynx. Although various pharmacological treatment options for HAE became available during the last decade, they are presently limited and pose a major economic burden on patients. To identify additional therapeutic options for HAE, we evaluated the effect of CU06-1004, an endothelial dysfunction blocker, on BK-induced vascular hyperpermeability and the HAE murine model.

METHODS

To investigate the effect of CU06-1004 on BK-induced vascular hyperpermeability in vivo, we pre-administrated WT mice with the drug and then induced vascular leakage through intravenous injection of BK and observed vascular alternation. Then, SERPING1 deficient mice were used for a HAE murine model. For an in vitro model, the HUVEC monolayer was pre-treated with CU06-1004 and then stimulated with BK.

RESULTS

Bradykinin disrupted the endothelial barrier and formed interendothelial cell gaps, leading to hyperpermeability in vivo and in vitro. However, CU06-1004 treatment protected the endothelial barrier by suppressing Src and myosin light chain activation via BK and alleviated hyperpermeability.

CONCLUSION

Our study shows that CU06-1004 oral administration significantly reduced vascular hyperpermeability in the HAE murine model by protecting the endothelial barrier function against BK stimulation. Therefore, protecting endothelium against BK with CU06-1004 could serve as a potential prophylactic/therapeutic approach for HAE patients.

Treatment of hereditary angioedema—single or multiple pathways to the rescue

Hereditary angioedema (HAE) is a rare disease caused by mutations in the SERPING1 gene. This results in deficient or dysfunctional C1 esterase inhibitor (C1-INH) and affects multiple proteases involved in the complement, contact-system, coagulation, and fibrinolytic pathways. Current options for the treatment and prevention of HAE attacks include treating all affected pathways via direct C1-INH replacement therapy; or specifically targeting components of the contact activation system, in particular by blocking the bradykinin B₂ receptor (B2R) or inhibiting plasma kallikrein, to prevent bradykinin generation. Intravenously administered plasma-derived C1-INH (pdC1-INH) and recombinant human C1-INH have demonstrated efficacy and safety for treatment of HAE attacks, although time to onset of symptom relief varied among trials, specific agents, and dosing regimens. Data from retrospective and observational analyses support that short-term prophylaxis with intravenous C1-INH products can help prevent HAE attacks in patients undergoing medical or dental procedures. Long-term prophylaxis with intravenous or subcutaneous pdC1-INH significantly decreased the HAE attack rate vs. placebo, although breakthrough attacks were observed. Pathway-specific therapies for the management of HAE include the B2R antagonist icatibant and plasma kallikrein inhibitors ecallantide, lanadelumab, and berotralstat. Icatibant, administered for treatment of angioedema attacks, reduced B2R-mediated vascular permeability and, compared with placebo, reduced the time to initial symptom improvement. Plasma kallikrein inhibitors, such as ecallantide, block the binding site of kallikrein to prevent cleavage of high molecular weight kininogen and subsequent bradykinin generation. Ecallantide was shown to be efficacious for HAE attacks and is licensed for this indication in the United States, but the labeling recommends that only health care providers administer treatment because of the risk of anaphylaxis. In addition to C1-INH replacement therapy, the plasma kallikrein inhibitors lanadelumab and berotralstat are recommended as first-line options for long-term prophylaxis and have demonstrated marked reductions in HAE attack rates. Investigational therapies, including the activated factor XII inhibitor garadacimab and an antisense oligonucleotide targeting plasma prekallikrein messenger RNA (donidalorsen), have shown promise as long-term prophylaxis. Given the requirement of lifelong management for HAE, further research is needed to determine how best to individualize optimal treatments for each patient.

BRAF increases endothelial cell stiffness through reorganization of the actin cytoskeleton

The dynamics of the actin cytoskeleton and its connection to endothelial cell-cell junctions determine the barrier function of endothelial cells. The proper regulation of barrier opening/closing is necessary for the normal function of vessels, and its dysregulation can result in chronic and acute inflammation leading to edema formation. By using atomic force microscopy, we show here that thrombin-induced permeability of human umbilical vein endothelial cells, associated with actin stress fiber formation, stiffens the cell center. The depletion of the MEK/ERK kinase BRAF reduces thrombin-induced permeability prevents stress fiber formation and cell stiffening. The peripheral actin ring becomes stabilized by phosphorylated myosin light chain, while cofilin is excluded from the cell periphery. All these changes can be reverted by the inhibition of ROCK, but not of the MEK/ERK module. We propose that the balance between the binding of cofilin and myosin to F-actin in the cell periphery, which is regulated by the activity of ROCK, determines the local dynamics of actin reorganization, ultimately driving or preventing stress fiber formation.

A narrative review on sacubitril/valsartan and ventricular arrhythmias

Sacubitril/valsartan, the first angiotensin receptor neprilysin inhibitor approved by the Food and Drug Administration for marketing, has been shown to reduce the risk of cardiovascular death or heart failure hospitalization and improve symptoms in patients with chronic heart failure with a reduced ejection fraction. However, some researchers have also found that sacubitril/valsartan has an antiarrhythmic effect. The mechanism by which sacubitril/valsartan reduces the mortality associated with malignant ventricular arrhythmias is not precise. Many studies have concluded that ventricular arrhythmia is associated with a reduction in myocardial fibrosis. This article reviews the current understanding of the effects of sacubitril/valsartan on the reduction of ventricular arrhythmia and explains its possible mechanisms. The results of this study suggest that sacubitril/valsartan reduces the occurrence of appropriate implantable cardioverter-defibrillator shocks. Meanwhile, sacubitril/valsartan may reduce the occurrence of ventricular arrhythmias by affecting 3 pathways of B-type natriuretic peptide, Angiotensin II, and Bradykinin. The conclusion of this study is that sacubitril/valsartan reduces the number of implantable cardioverter-defibrillator shocks and ventricular arrhythmias in heart failure with reduced ejection fraction patients.

An update on factor XII-driven vascular inflammation

The plasma protein factor XII (FXII) is the liver-derived zymogen of the serine protease FXIIa that initiates an array of proteolytic cascades. Zymogen activation, enzymatic FXIIa activity and functions are regulated by interactions with cell receptors, negatively charged surfaces, other serine proteases, and serpin inhibitors, which bind to distinct protein domains and regions in FXII(a). FXII exerts mitogenic activity, while FXIIa initiates the pro-inflammatory kallikrein-kinin pathway and the pro-thrombotic intrinsic coagulation pathway, respectively. Growing evidence indicates that FXIIa-mediated thrombo-inflammation plays a crucial role in various pathological states besides classical thrombosis, such as endothelial dysfunction. Consistently, increased FXIIa levels are associated with hypercholesterolemia and hypertriglyceridemia. In contrast, FXII deficiency protects from thrombosis but is otherwise not associated with prolonged bleeding or other adverse clinical manifestations. Here, we review current concepts for FXII(a)-driven vascular inflammation focusing on endothelial hyperpermeability, receptor signaling, atherosclerosis and immune cell activation.

Guhong Injection Protects Against Apoptosis in Cerebral Ischemia by Maintaining Cerebral Microvasculature and Mitochondrial Integrity Through the PI3K/AKT Pathway

Guhong injection (GHI) can be used for the treatment of ischemic stroke. We investigated the antiapoptotic activity of GHI, its ability to repair the cerebral microvessels and mitochondria, and the PI3K/AKT signaling pathway of GHI against cerebral ischemia. Western blot and immunohistochemical analyses were used to determine the expression of cleaved caspase-3, B-cell lymphoma-2 (Bcl-2), cytochrome c (Cyt-c), basic fibroblast growth factor (BFGF), vascular endothelial growth factor (VEGF), transforming growth factor-β1 (TGF-β1), and proteins in the PI3K/AKT signaling pathway. Transmission electron microscopy and scanning electron microscopy were used to evaluate the structures of the cerebral microvasculature and cells. Hoechst 33342 staining was used to evaluate the nuclear morphology. FITC-AV/PI double staining was used to measure the antiapoptotic effects. The fluorescent dye JC-1 was used to measure mitochondrial membrane potential. The enzyme-linked immunosorbent assay (ELISA) was used to detect the activities of matrix metalloproteinase-9 (MMP-9). Biochemical assay kits were used to detect the activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA). Compared with the middle cerebral artery occlusion (MCAO) group, there was decreased infarct volume and significantly improved neurological deficits in the GHI group. In addition, the expression of Bcl-2 was significantly upregulated, while the expression of Cyt-c, Bax, and cleaved caspase-3 was notably downregulated. GHI administration attenuated the pathological change and morphology of the cerebral microvasculature, and immunohistochemical staining indicated that the expressions of BFGF, VEGF, and TGF-β1 were significantly increased. The cell morphology, cell viability, cell nuclei characteristics, and mitochondrial morphology normalized following GHI treatment, which decreased the release of Cyt-c and the mitochondrial membrane potential. The levels of LDH, MMP-9, and MDA decreased, while SOD increased. Moreover, GHI administration inhibited the activation of the PI3K/AKT signaling pathway in rat brain microvascular endothelial cells (rBMECs) following oxygen/glucose deprivation (OGD) injury. Therefore, our results show that GHI administration resulted in antiapoptosis of cerebral cells and repair of cerebral microvessels and mitochondria via the PI3K/AKT signaling pathway.