IL-33, an Alarmin of the IL-1 Family Involved in Allergic and Non Allergic Inflammation: Focus on the Mechanisms of Regulation of Its Activity

Interleukin-33 (IL-33) is a member of the interleukin-1 (IL-1) family that is expressed in the nuclei of endothelial and epithelial cells of barrier tissues, among others. It functions as an alarm signal that is released upon tissue or cellular injury. IL-33 plays a central role in the initiation and amplification of type 2 innate immune responses and allergic inflammation by activating various target cells expressing its ST2 receptor, including mast cells and type 2 innate lymphoid cells. Depending on the tissue environment, IL-33 plays a wide variety of roles in parasitic and viral host defense, tissue repair and homeostasis. IL-33 has evolved a variety of sophisticated regulatory mechanisms to control its activity, including nuclear sequestration and proteolytic processing. It is involved in many diseases, including allergic, inflammatory and infectious diseases, and is a promising therapeutic target for the treatment of severe asthma. In this review, I will summarize the literature around this fascinating pleiotropic cytokine. In the first part, I will describe the basics of IL-33, from the discovery of interleukin-33 to its function, including its expression, release and signaling pathway. The second part will be devoted to the regulation of IL-33 protein leading to its activation or inactivation.

The Paradigm Change of IL-33 in Vascular Biology

In this review, we focus on the actual understanding of the role of IL-33 in vascular biology in the context of the historical development since the description of IL-33 as a member of IL-1 superfamily and the ligand for ST2 receptor in 2005. We summarize recent data on the biology, structure and signaling of this dual-function factor with both nuclear and extracellular cytokine properties. We describe cellular sources of IL-33, particularly within vascular wall, changes in its expression in different cardio-vascular conditions and mechanisms of IL-33 release. Additionally, we summarize the regulators of IL-33 expression as well as the effects of IL-33 itself in cells of the vasculature and in monocytes/macrophages in vitro combined with the consequences of IL-33 modulation in models of vascular diseases in vivo. Described in murine atherosclerosis models as well as in macrophages as an atheroprotective cytokine, extracellular IL-33 induces proinflammatory, prothrombotic and proangiogenic activation of human endothelial cells, which are processes known to be involved in the development and progression of atherosclerosis. We, therefore, discuss that IL-33 can possess both protective and harmful effects in experimental models of vascular pathologies depending on experimental conditions, type and dose of administration or method of modulation.

Detrimental role of IL-33/ST2 pathway sustaining a chronic eosinophil-dependent Th2 inflammatory response, tissue damage and parasite burden during Toxocara canis infection in mice

Toxocariasis is a neglected disease that affects people around the world. Humans become infected by accidental ingestion of eggs containing Toxocara canis infective larvae, which upon reaching the intestine, hatch, penetrate the mucosa and migrate to various tissues such as liver, lungs and brain. Studies have indicated that Th2 response is the main immune defense mechanism against toxocariasis, however, there are still few studies related to this response, mainly the IL-33/ST2 pathway. Some studies have reported an increase in IL-33 during helminth infections, including T. canis. By binding to its ST2 receptor, IL-33 stimulating the Th2 polarized immune cell and cytokine responses. Thus, we aimed to investigate the role of the IL-33/ST2 pathway in the context of T. canis larval migration and the immunological and pathophysiological aspects of the infection in the liver, lungs and brain from Wild-Type (WT) BALB/c background and genetically deficient mice for the ST2 receptor (ST2-/-). The most important findings revealed that the IL-33/ST2 pathway is involved in eosinophilia, hepatic and cerebral parasitic burden, and induces the formation of granulomas related to tissue damage and pulmonary dysfunction. However, ST2-/- mice, the immune response was skewed to Th1/Th17 type than Th2, that enhanced the control of parasite burden related to IgG2a levels, tissue macrophages infiltration and reduced lung dysfunction. Collectively, our results demonstrate that the Th2 immune response triggered by IL-33/ST2 pathway mediates susceptibility to T. canis, related to parasitic burden, eosinophilia and granuloma formation in which consequently contributes to tissue inflammation and injury.

IL-33 / ST2 Signaling Promotes TF Expression by Regulating NF-κB Activation in Coronary Artery Endothelial Microparticles

IntroductionInterleukin (IL)-33 was previously shown to induce angiogenesis and inflammatory activation of endothelial Microparticles(EMPs). Tissue factor (TF) plays a central role in hemostasis and thrombosis.Material and methodsThe study analyzed the coronary blood of level of CD31+EMPs, TF protein and IL-33 protein in Acute Myocardial Infarction (AMI) and stable coronary artery disease (SCAD) patients. Human coronary artery endothelial cells (HCAECs) were treated with IL-33 to obtain EMPs. The TF activity of EMPs was tested by Thermo Fisher by adding the TF antibody. Furthermore, TF and Tissue Factor Pathway Inhibitor (TFPI) protein were tested by ELISA. Finally, NF-κB inhibitor dimethyl fumarate (DMF) and soluble extracellular domain of ST2 coupled to the Fc fragment of human IgG1 (sST2) were added to HCAECs which were treated with IL-33, and the TF protein level was also tested by ELISA.ResultsThe AMI patients had higher level of CD31+EMPs, TF protein and IL-33 protein than the SCAD patients in coronary artery. In AMI patients (N=27), the IL-33 protein positively correlated with CD31+EMPs (r=0.794, p<0.01). According to the ROC curve analysis, the AUC of CD31+EMPs, TF protein and IL-33 protein were 0.888, 0.962 and 0.778 respectively. In the cell culture, the TF activity and TF protein in EMPs increased gradually with time of intervention by the treatment of IL-33. IL-33 binding to the ST2 receptor promoted TF expression by regulating NF-κB activation in EMPs of HCAECs.ConclusionsActivated endothelial cells and EMPs they released simultaneously express TF, which is a risk factor for cardiovascular disease.

Genetic Association of Interleukin 33/ST2 Polymorphisms With Behcet’s Uveitis

Interleukin (IL)33, a member of the IL1 superfamily, functions as a nuclear factor and mediates biological effects by interacting with the ST2 receptor. Recent studies have described IL33 as an emerging pro-inflammatory cytokine in the immune system, and IL33/ST2 gene polymorphisms have been implicated in the pathogenesis of various immune diseases. However, the underlying mechanisms of IL33/ST2 in Behcet’s disease (BD) remain to be defined. Here, we investigated the association between IL33/ST2 gene polymorphisms and BD in 585 BD uveitis (BDU) patients and 834 healthy controls using Agena MassARRAY iPLEX platform. We found that rs3821204 was associated with the development of BDU. Moreover, the frequency of rs2210463 G allele was lower in patients with genital involvement. Association analysis revealed a much greater genetic difference between complete-type and incomplete-type BD groups, including three SNPs (rs7044343, rs1048274, and rs2210463). Our findings suggest that IL33/ST2 gene polymorphisms are involved in the pathogenesis of BDU. Different genetic backgrounds may exist in complete-type and incomplete-type BD patients.

Clinical cases of successful treatment CHF patients under the control of the soluble ST2-receptor concentrations

В статье приведены два клинических примера лечения пациентов после перенесенной острой декомпенсации сердечной недостаточности с использованием мониторирования концентрации нового биомаркера сердечной недостаточности (СН) — растворимого sST2-рецептора. Обсуждены преимущества этого биомаркера перед натрийуретическими пептидами, которые позволили достичь успеха в лечении пациентов с СН высокого риска In article presents 2 clinical cases of patient’s treatment after acute decompensated heart failure using concentration monitoring of a new biomarker of heart failure — soluble ST2-receptor. The advantages of this biomarker over natriuretic peptides, which allowed to achieve success in the treatment of patients with high risk HF, were discussed

IL-33 / ST2 Signaling Promotes TF Expression by Regulating NF-κB Activation in Coronary Artery Endothelial Microparticles of Acute Myocardial Infarction

Background: Interleukin (IL)-33 was previously shown to induce angiogenesis and inflammatory activation of endothelial cells derived Microparticles（EMPs）. Tissue factor (TF) plays a central role in hemostasis and thrombosis. Objective: The aim of this study was to investigate the effect of IL-33 on TF release of EMPs, which may be a new link between inflammation and coagulation. Methods: The study analyzed the coronary blood of level of CD31+EMPs, TF protein and IL-33 protein in acute myocardial infarction(AMI) and stable coronary artery disease(SCAD) patients. Human coronary artery endothelial cells (HCAECs) were treated with IL-33 to obtain MPs. The TF activity of EMPs was tested by thermo fisher by adding the TF antibody. Furthermore, TF and TFPI protein were tested by ELISA. Finally, NF-κB inhibitor dimethyl fumarate (DMF) and soluble extracellular domain of ST2 coupled to the Fc fragment of human IgG1 (sST2) were added HCAECs, which were treated with IL-33, then the TF protein level also was tested by ELISA. Results: The AMI patients have higher level of CD31+EMPs, TF protein and IL-33 protein than the SCAD patients in coronary blood. In AMI patients (N=27) , the IL-33 protein positively correlated with CD31+EMPs (r = 0.794, p < 0.01). According to the ROC curve analysis, the areas under the curve (AUC) of CD31+EMPs, TF protein and IL-33 protein were 0.888, 0.962 and 0.778. In the cell culture, the TF activity and TF protein in ECs-derived MPs increased gradually with time of intervention by the treatment of IL-33. IL-33 binding to the ST2 receptor promoted TF expression by regulating NF-κB activation in ECs-derived MPs of HCAECs. Conclusion: Activated endothelial cells and their released MPs simultaneously express TF, which is a risk factor for cardiovascular disease.

The Role of ST2 Receptor in the Regulation of Brucella abortus Oral Infection

The ST2 receptor plays an important role in the gut such as permeability regulation, epithelium regeneration, and promoting intestinal immune modulation. Here, we studied the role of ST2 receptor in a murine model of oral infection with Brucella abortus, its influence on gut homeostasis and control of bacterial replication. Balb/c (wild-type, WT) and ST2 deficient mice (ST2−/−) were infected by oral gavage and the results were obtained at 3 and 14 days post infection (dpi). Our results suggest that ST2−/− are more resistant to B. abortus infection, as a lower bacterial colony-forming unit (CFU) was detected in the livers and spleens of knockout mice, when compared to WT. Additionally, we observed an increase in intestinal permeability in WT-infected mice, compared to ST2−/− animals. Breakage of the intestinal epithelial barrier and bacterial dissemination might be associated with the presence of the ST2 receptor; since, in the knockout mice no change in intestinal permeability was observed after infection. Together with enhanced resistance to infection, ST2−/− produced greater levels of IFN-γ and TNF-α in the small intestine, compared to WT mice. Nevertheless, in the systemic model of infection ST2 plays no role in controlling Brucella replication in vivo. Our results suggest that the ST2 receptor is involved in the invasion process of B. abortus by the mucosa in the oral infection model.