Upregulation of cytokines and IL-17 in patients with hereditary angioedema

Increased thromboinflammatory load in hereditary angioedema

C1 inhibitor (C1Inh) is a serine protease inhibitor involved in the kallikrein-kinin system, the complement system, the coagulation system, and the fibrinolytic system. In addition to the plasma leakage observed in hereditary angioedema (HAE), C1Inh deficiency may also affect these systems, which are important for thrombosis and inflammation. The aim of this study was to investigate the thromboinflammatory load in C1Inh deficiency. We measured 27 cytokines including interleukins, chemokines, interferons, growth factors, and regulators using multiplex technology. Complement activation (C4d, C3bc, and sC5b-C9/TCC), haemostatic markers (β-thromboglobulin (β-TG), thrombin-antithrombin complexes (TAT), prothrombin fragment 1 + 2 (F1 + 2), active plasminogen activator inhibitor-1 (PAI-1), and the neutrophil activation marker myeloperoxidase (MPO) were measured by enzyme immunoassays. Plasma and serum samples were collected from 20 patients with HAE type 1 or 2 in clinical remission and compared with 20 healthy age- and sex-matched controls. Compared to healthy controls, HAE patients had significantly higher levels of tumour necrosis factor (TNF), interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-7, IL-9, IL-12, and IL-17A, chemokine ligand (CXCL) 8, chemokine ligand (CCL) 3, CCL4, IL-1 receptor antagonist (IL-1RA), granulocyte-macrophage colony-stimulating factor (GM-CSF), fibroblast growth factor (FGF) 2 and platelet-derived growth factor (PDGF)-BB. HAE patients also had higher levels of TAT and F1 + 2. Although granulocyte colony-stimulating factor (G-CSF), β-TG and PAI-1 were higher in HAE patients, the differences did not reach statistical significance after correction for multiple testing. In conclusion, C1Inh deficiency is associated with an increased baseline thromboinflammatory load. These findings may reflect that HAE patients are in a subclinical attack state outside of clinically apparent oedema attacks.

Biomarkers in Hereditary Angioedema

A biomarker is a defined characteristic measured as an indicator of normal, biologic, pathogenic processes, or biological responses to an exposure or intervention. Diagnostic biomarkers are used to detect a disease or a subtype of a disease; monitoring biomarkers are measured serially to assess a medical condition; response biomarkers are used to check biologic response following a medical intervention; predictive biomarkers are used to identify patients who are more likely to respond to a medical intervention; and prognostic biomarkers are used to assess the future likelihood of a clinical event. Although biomarkers have been extensively investigated and validated in many diseases and pathologies, very few are currently useful for the diagnosis, evaluation of disease activity, and treatment of hereditary angioedema (HAE). Pathophysiologic pathways involved in HAE reveal a plethora of molecules from the complement, coagulation, and fibrinolysis systems or from the vascular endothelium, which may serve as biomarkers. The most promising candidates, together with their laboratory readout systems, should be evaluated with regard to their analytical and clinical validity and utility. To be highly specific, such biomarkers should be linked to the pathomechanisms of HAE, particularly the bradykinin-generating cascade. Additionally, major advances in high-throughput omics-based technologies may facilitate the discovery of new candidate biomarkers in the future. This review will cover the existing as well as future potential biomarkers that will support the diagnosis, monitor disease activity, and can be used to assess the efficacy of new avenues of therapy of HAE and other forms of angioedema.

Neutrophils Are Dysregulated in Patients with Hereditary Angioedema Types I and II in a Symptom-Free Period

Neutrophils impact on processes preceding the formation of bradykinin, a major swelling mediator in hereditary angioedema (HAE), yet their potential role in HAE pathogenesis has not been sufficiently studied. We assessed the relative mRNA expression of 10 genes related to neutrophil activation using RNA extracted from the peripheral blood neutrophils of 23 HAE patients in a symptom-free period and 39 healthy donors. Increased relative mRNA expression levels of CD274, IL1B, IL1RN, IL8, MMP9, and TLR4, together with a lack in their mutual correlations detected in HAE patients compared to healthy controls, suggested a preactivated state and dysregulation of patients' neutrophils. Patients' neutrophil-alerted state was further supported by increased CD11b, decreased CD16 plasma membrane deposition, and increased relative CD274⁺ and CD87⁺ neutrophil counts, but not by increased neutrophil elastase or myeloperoxidase plasma levels. As CD274 mediates inhibitory signals to different immune cells, neutrophils were cocultured with T-cells/PBMC. The decrease in CD25⁺ and IFN-γ ⁺ T-cell/PBMC ratio in patients indicated the patients' neutrophil suppressive functions. In summary, the results showed neutrophils' alerted state and dysregulation at the transcript level in patients with HAE types I and II even in a symptom-free period, which might make them more susceptible to edema formation. Neutrophils' T-cell suppressive capacity in HAE patients needs to be further investigated.

The complex alteration in the network of IL-17-type cytokines in patients with hereditary angioedema

Hereditary angioedema (HAE) is a rare autosomic-dominant disorder characterized by a deficiency of C1 esterase inhibitor which causes episodic swellings of subcutaneous tissues, bowel walls and upper airways that are disabling and potentially life-threatening. We evaluated n = 17 patients with confirmed HAE diagnosis during attack and remission state and n = 19 healthy subjects. The samples were tested for a panel of IL (Interleukin)-17-type cytokines (IL-1β, IL-6, IL-10, granulocyte-macrophage colony stimulating factor (GM-CSF), IL-17, IL-21, IL-22, IL-23) and transforming growth factor-beta (TGF-β) subtypes. Data indicate that there are variations of cytokine levels in HAE subjects comparing the condition during the crisis respect to the value in the remission phase, in particular type 17 signature cytokines are increased, whereas IL-23 is unmodified and TGF-β3 is significantly reduced. When comparing healthy and HAE subjects in the remission state, we found a significant difference for IL-17, GM-CSF, IL-21, TGF-β1 and TGF-β2 cytokines. These results confirm and extend our previous findings indicating that in HAE there is operating an inflammatory activation process, which involves also T helper 17 (Th17) cytokines and TGF-β isoforms, associated with localized angioedema attacks and characterized by elevated bradykinin levels.

"Nuts and Bolts" of Laboratory Evaluation of Angioedema

Angioedema, as a distinct disease entity, often becomes a clinical challenge for physicians, because it may cause a life-threatening condition, whereas prompt and accurate laboratory diagnostics may not be available. Although the bedside diagnosis needs to be established based on clinical symptoms and signs, family history, and the therapeutic response, later, laboratory tests are available. Currently, only for five out of the nine different types of angioedema can be diagnosed by laboratory testing, and these occur only in a minority of the patient population. Hereditary angioedema with C1-inhibitor (C1-INH) deficiency type I can be diagnosed by the low C1-INH function and concentration, whereas in type II, C1-INH function is low, but its concentration is normal or even elevated. C1q concentration is normal in both forms. Acquired angioedema with C1-INH deficiency type I is characterized by the low C1-INH function and concentration; however, C1q concentration is also low, and autoantibodies against C1-INH cannot be detected. Complement profile of acquired angioedema with C1-INH deficiency type II is similar to that of type I, but in this form, autoantibodies against C1-INH are present. Hereditary angioedema due to a mutation of the coagulation factor XII can be diagnosed exclusively by mutation analysis of FXII gene. Diagnostic metrics are not available for idiopathic histaminergic acquired angioedema, idiopathic non-histaminergic acquired angioedema, acquired angioedema related to angiotensin-converting enzyme inhibitor, and hereditary angioedema of unknown origin; these angioedemas can be diagnosed by medical and family history, clinical symptoms, and therapeutic response and by excluding the forms previously described. Several potential biomarkers of angioedema are used to date only in research. In the future, they could be utilized into the clinical practice to improve the differential diagnosis, therapy, as well as the prognosis of angioedema.

Hereditary Angioedema Attacks: Local Swelling at Multiple Sites

Hereditary angioedema (HAE) patients experience recurrent local swelling in various parts of the body including painful swelling of the intestine and life-threatening laryngeal oedema. Most HAE literature is about attacks located in one anatomical site, though it is mentioned that HAE attacks may also involve multiple anatomical sites simultaneously. A detailed description of such multi-location attacks is currently lacking. This study investigated the occurrence, severity and clinical course of HAE attacks with multiple anatomical locations. HAE patients included in a clinical database of recombinant human C1-inhibitor (rhC1INH) studies were evaluated. Visual analog scale scores filled out by the patients for various symptoms at various locations and investigator symptoms scores during the attack were analysed. Data of 219 eligible attacks in 119 patients was analysed. Thirty-three patients (28%) had symptoms at multiple locations in anatomically unrelated regions at the same time during their first attack. Up to five simultaneously affected locations were reported. The observation that severe HAE attacks often affect multiple sites in the body suggests that HAE symptoms result from a systemic rather than from a local process as is currently believed.

Neutrophil activation during attacks in patients with hereditary angioedema due to C1-inhibitor deficiency

BACKGROUND

Earlier studies have shown that the absolute number of neutrophil granulocytes (NGs) may increase during attack of hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE). Whether NGs undergo activation during attack has not yet been investigated. However, as neutrophil elastase (NE) can cleave and inactivate C1-INH which may contribute to the dysregulation of the kallikrein-kinin system and hence, to edema formation. Our aim was to investigate the possible activation of NGs during attacks.

METHODS

We studied blood samples obtained from 26 patients with C1-INH-HAE during symptom-free periods and during attacks, along with samples from 26 healthy volunteers. NG count (NGC), NE, myeloperoxidase (MPO), pentraxin 3 (PTX3), CRP, C5a, factor H, IL-8, and TNF-α levels were measured.

RESULTS

NGC was higher during attacks than during symptom-free periods (p = 0.0132), and the same was observed for NE (p = 0.0026), MPO (p = 0.0008), and PTX3 levels (p = 0.0409). There was a strong positive correlation between NE and MPO levels during attacks (p < 0.0001, R = 0.709). Furthermore, IL-8 (p = 0.0061) and TNF-α (p = 0.0186) levels were also elevated during attacks, compared with symptom-free periods. By contrast, C5a and factor H levels were similar in samples obtained during attacks or in symptom-free periods.

CONCLUSION

Increased NGC was associated with elevated NE and MPO levels - this suggests neutrophil activation during attacks. The strong positive correlation between NE and MPO levels, together with the elevated PTX3 concentration, may indicate the expression of neutrophil extracellular traps. All these processes may contribute to the activation of kallikrein-kinin system, which leads to the onset of an edematous episode.

C-reactive protein levels in hereditary angioedema

Hereditary angioedema (HAE) patients experience recurrent episodes of angioedema attacks that can be painful, disfiguring and even life-threatening. The disorder results from a mutation in the gene that controls the synthesis of C1-inhibitor (C1INH). C1INH is a major regulator of activation of the contact system. It is often assumed that attacks results from uncontrolled local activation of the contact system with subsequent formation of bradykinin. To evaluate the involvement of inflammatory reactions in HAE, we analysed C-reactive protein (CRP) levels. HAE patients included in a clinical database of recombinant human C1-inhibitor (rhC1INH) studies were evaluated. For the current study we analysed CRP levels when patients were asymptomatic, during a clinical attack and in a follow-up period, and correlated these with the clinical manifestations of the attack. Data from 68 HAE patients were analysed and included CRP levels on 273 occasions. While asymptomatic, 20% of the patients analysed had increased CRP. At the onset of the attack (P = 0·049) and during the next 24 h CRP rose significantly (P = 0·002) in patients with an abdominal location, and post-attack levels were significantly higher in these patients than in patients with attacks at other locations (P = 0·034). In conclusion, CRP levels are elevated in a substantial proportion of asymptomatic HAE patients. Levels of CRP increase significantly during an abdominal attack. These data suggest low-grade systemic inflammatory reactions in HAE patients as well as a triggering event for attacks that starts prior to symptom onset.