IL-33 Reduces Saturated Fatty Acid Accumulation in Mouse Atherosclerotic Foci

The cellular and molecular mechanisms of atherosclerosis are still unclear. Type 2 innate lymphocytes (ILC2) exhibit anti-inflammatory properties and protect against atherosclerosis. This study aimed to elucidate the pathogenesis of atherosclerosis development using atherosclerosis model mice (ApoE KO mice) and mice deficient in IL-33 receptor ST2 (ApoEST2 DKO mice). Sixteen-week-old male ApoE KO and ApoEST2 DKO mice were subjected to an 8-week regimen of a high-fat, high-sucrose diet. Atherosclerotic foci were assessed histologically at the aortic valve ring. Chronic inflammation was assessed using flow cytometry and real-time polymerase chain reaction. In addition, saturated fatty acids (palmitic acid) and IL-33 were administered to human aortic endothelial cells (HAECs) to assess fatty acid metabolism. ApoEST2 DKO mice with attenuated ILC2 had significantly worse atherosclerosis than ApoE KO mice. The levels of saturated fatty acids, including palmitic acid, were significantly elevated in the arteries and serum of ApoEST2 DKO mice. Furthermore, on treating HAECs with saturated fatty acids with or without IL-33, the Oil Red O staining area significantly decreased in the IL-33-treated group compared to that in the non-treated group. IL-33 potentially prevented the accumulation of saturated fatty acids within atherosclerotic foci.

A novel type-2 innate lymphoid cell-based immunotherapy for cancer

Cell-based cancer immunotherapy has achieved significant advancements, providing a source of hope for cancer patients. Notwithstanding the considerable progress in cell-based immunotherapy, the persistently low response rates and the exorbitant costs associated with their implementation still present a formidable challenge in clinical settings. In the landscape of cell-based cancer immunotherapies, an uncharted territory involves Type 2 innate lymphoid cells (ILC2s) and interleukin-33 (IL-33) which promotes ILC2 functionality, recognized for their inherent ability to enhance immune responses. Recent discoveries regarding their role in actuating cytolytic T lymphocyte responses, including curbing tumor growth rates and hindering metastasis, have added a new dimension to our understanding of the IL-33/ILC2 axis. These recent insights may hold significant promise for ILC2 cell-based immunotherapy. Nevertheless, the prospect of adoptively transferring ILC2s to confer immune protection against tumors has yet to be investigated. The present study addresses this hypothesis, revealing that ILC2s isolated from the lungs of tumor-bearing mice, and tumor infiltrating ILC2s when adoptively transferred after tumor establishment at a ratio of one ILC2 per sixty tumor cells, leads to an influx of tumor infiltrating CD4+ and CD8+ T lymphocytes as well as tumor infiltrating eosinophils resulting in a remarkable reduction in tumor growth. Moreover, we find that post-adoptive transfer of ILC2s, the number of tumor infiltrating ILC2s is inversely proportional to tumor size. Finally, we find corollaries of the IL-33/ILC2 axis enhancing the infiltration of eosinophils in human prostate carcinomas patients' expressing high levels of IL-33 versus those expressing low levels of IL-33. Our results underscore the heightened efficacy of adoptively transferred ILC2s compared to alternative approaches, revealing an approximately one hundred fifty-fold superiority on a cell-per-cell basis over CAR T-cells in the specific targeting and elimination of tumors within the same experimental model. Overall, this study demonstrates the functional significance of ILC2s in cancer immunosurveillance and provides the proof of concept of the potential utility of ILC2 cell-based cancer immunotherapies.

Lack of S1PR2 in Macrophage Ameliorates Sepsis-associated Lung Injury through Inducing IL-33-mediated Type 2 Immunity

The function of type 2 immunity and mechanisms underlying the initiation of type 2 immunity after sepsis-induced lung injury remain unclear. Sphingosine-1-phosphate receptor 2 (S1PR2) has been demonstrated to modulate type 2 immunity in the context of asthma and pulmonary fibrosis. Thus, this study aims to investigate the role of type 2 immunity and whether and how S1PR2 regulates type 2 immunity in sepsis. Peripheral type 2 immune responses in patients with sepsis and healthy control subjects were assessed. The impact of S1PR2 on type 2 immunity in patients with sepsis and in a murine model of sepsis was further investigated. The type 2 innate immune responses were significantly increased in the circulation of patients 24 hours after sepsis, which was positively related to clinical complications and negatively correlated with S1PR2 mRNA expression. Animal studies showed that genetic deletion or pharmacological inhibition of S1PR2 induced type 2 innate immunity accumulation in the post-septic lungs. Mechanistically, S1PR2 deficiency promoted macrophage-derived interleukin (IL)-33 increase and the associated type 2 response in the lung. Furthermore, S1PR2-regulated IL-33 from macrophages mitigated lung injury after sepsis in mice. In conclusion, a lack of S1PR2 modulates the type 2 immune response by upregulating IL-33 release from macrophages and alleviates sepsis-induced lung injury. Targeting S1PR2 may have potential therapeutic value for sepsis treatment.

Dermatophagoides Pteronyssinus 1 (DerP1) May Trigger NLRP3-Mediated Corneal Epithelial Cell Pyroptosis by Elevating Interleukin-33 Expression Levels

PURPOSE

To characterize the in vivo effects of Dermatophagoides pteronyssinus 1 (DerP1) in mice and determine the underlying NLRP3 inflammasome-mediated pyroptosis signaling mechanisms in the human corneal epithelial cells (HCECs).

METHODS

DerP1 was used to induce allergic conjunctivitis in C57 mice. HCECs were sensitized with DerP1 in vitro to mimic their condition observed in allergic conjunctivitis in vivo. Transmission electron microscopy was used to evaluate pyroptosis in the HCECs, enzyme-linked immunosorbent assays to assess interleukin (IL)-33, IL-1β and IL-4 levels, flow cytometry to detect the proportion of Th2 cells, MTT assays to assess cell metabolic activity, immunofluorescence to evaluate the effects of DerP1 on functional HCEC phenotypes, and Western blot assays to detect the expression of NOD-like receptor family pyrin domain-containing 3 (NLRP3), gasdermin D (GSDMD), N-terminal fragment of GSDMD (GSDMD-N), pro-caspase-1, cleaved caspase-1, IL-1β, and IL-33. IL-33 expression in the HCECs was knocked down via lentivirus transfection.

RESULTS

In vivo, DerP1 promotes pyroptosis, production of Th2 inflammatory cytokines and IL-33, and NLRP3 activation in mouse corneas. In vitro, pyroptotic bodies were found in the HCECs after sensitization with DerP1. Various concentrations of DerP1 increased the expression levels of NLRP3, GSDMD, GSDMD-N, pro-caspase-1, cleaved caspase-1, and IL-1β in the HCECs, with the largest increase observed after exposure to 20 µM DerP1. In vitro, recombinant human IL-33 mediated the expression of pyroptotic biomarkers in the HCECs, whereas IL-33 silencing diminished 20 µM DerP1-induced increase in their expression levels.

CONCLUSIONS

DerP1 induces pyroptosis and allergic conjunctivitis, the expression of Th2 inflammatory cytokines, NLRP3 activation, and IL-33 in mouse corneas in our model. These effects would attribute to its activating NLRP3-GSDMD signaling pathway axis via enhancing IL-33 expression in HCECs.

Interleukin-33 Expression on Treatment Outcomes and Prognosis in Brazilian Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy

Interleukin-33 (IL-33), a member of the interleukin-1(IL-1) family of cytokines, remains poorly understood in the context of human breast cancer and its impact on treatment outcomes. This study aimed to elucidate IL-33 expression patterns within tumor samples from a cohort of Brazilian female breast cancer patients undergoing neoadjuvant chemotherapy while exploring its correlation with clinicopathological markers. In total, 68 samples were meticulously evaluated, with IL-33 expression quantified through a quantitative polymerase chain reaction. The findings revealed a substantial upregulation of IL-33 expression in breast cancer patient samples, specifically within the Triple-negative and Luminal A and B subtypes, when compared to controls (healthy breast tissues). Notably, the Luminal B subtype displayed a marked elevation in IL-33 expression relative to the Luminal A subtype (p < 0.05). Moreover, a progressive surge in IL-33 expression was discerned among Luminal subtype patients with TNM 4 staging criteria, further underscoring its significance (p < 0.005). Furthermore, chemotherapy-naïve patients of Luminal A and B subtypes exhibited heightened IL-33 expression (p < 0.05). Collectively, our findings propose that chemotherapy could potentially mitigate tumor aggressiveness by suppressing IL-33 expression in breast cancer, thus warranting consideration as a prognostic marker for gauging chemotherapy response and predicting disease progression in Luminal subtype patients. This study not only sheds light on the intricate roles of IL-33 in breast cancer but also offers valuable insights for future IL-33-related research endeavors within this context.

Serum alarmins and the risk of incident interstitial lung disease in rheumatoid arthritis

OBJECTIVES

To quantify associations of serum alarmins with risk of rheumatoid arthritis-associated interstitial lung disease (RA-ILD).

METHODS

Using serum collected at enrolment, three alarmins (interleukin [IL]-33, thymic stromal lymphopoietin [TSLP], and IL-25) were measured in a multicentre prospective RA cohort. ILD was classified using systematic medical record review. Cross-sectional associations of log-transformed (IL-33, TSLP) or quartile (IL-25) values with RA-ILD at enrolment (prevalent RA-ILD) were examined using logistic regression, while associations with incident RA-ILD developing after enrolment were examined using Cox proportional hazards. Covariates in multivariate models included age, sex, race, smoking status, RA disease activity score, and anti-cyclic citrullinated antibody positivity.

RESULTS

Of 2,835 study participants, 115 participants (4.1%) had prevalent RA-ILD at baseline and an additional 146 (5.1%) developed incident ILD. There were no associations between serum alarmin concentrations and prevalent ILD in unadjusted or adjusted logistic regression models. In contrast, there was a significant inverse association between IL-33 concentration and the risk of developing incident RA-ILD in unadjusted (HR 0.73 per log-fold increase; 95% CI 0.57-0.95; p= 0.018) and adjusted (HR 0.77; 95% CI 0.59-1.00, p= 0.047) models. No significant associations of TSLP or IL-25 with incident ILD were observed.

CONCLUSIONS

In this study, we observed a significant inverse association between serum IL-33 concentration and the risk of developing incident RA-ILD, but no associations with prevalent ILD. Additional investigation is required to better understand the mechanisms driving this relationship and how serum alarmin IL-33 assessment might contribute to clinical risk stratification in patients with RA.

RORα overexpression reduced interleukin-33 expression and prevented mast cell degranulation and inflammation by inducing autophagy in allergic rhinitis

BACKGROUND

Retinoid acid receptor related orphan receptor α (RORα) is a nuclear receptor that along with other bioactive factors regulates cell proliferation, differentiation, and immunomodulation in vivo.

AIMS

The objective of this study was to explore the function and mechanism of RORα in allergic rhinitis (AR).

MATERIALS AND METHODS

Derp1 was used to construct an AR cell model in HNEpC cells, and RORα was overexpressed or silenced in the AR HNEpC cells. Next, LAD2 cells were co-cultured with the Derp1-treated HNEpC cells. Additionally, an AR mouse model was established using by OVA, and a RORα Adenovirus was delivered by nebulizing. Pathological tissue structures were evaluated by hematoxylin-eosin staining, and the levels of RORα, interleukin-33 (IL-33), and other proteins were analyzed immunohistochemistry, western blotting, and immunofluorescence staining. IL-33, IL-4, IL-5, and IL-13 levels were detected using enzyme-linked immunosorbent assay kits and cell migration was assessed by Transwell assays.

RESULTS

Our data showed that RORα was downregulated in the nasal mucosa tissues of AR patients. Derp1 treatment could cause a downregulation of RORα, upregulation of IL-33, the induction of NLRP3 inflammasomes, and cell migration in HNEpC cells. Furthermore, RORα overexpression dramatically attenuated IL-33 levels, NLRP3 inflammasome activity, and the migration of AR HNEpC cells induced with Derp1. Moreover, RORα in AR HNEpC cells could prevent mast cell (MC) degranulation and inflammation by accelerating autophagy, RORα overexpression inhibited MC degranulation and NLRP3-induced inflammation in the AR model mice. RORα overexpression reduced IL-33 expression in nasal epithelial cells, and also suppressed MC degranulation and inflammation by promoting autophagy.

CONCLUSION

RORα inhibits NLRP3 inflammasome in HNEpC, and attenuated mast cells degranulation and inflammation through autophagy in AR.

IL-33/ST2 Signaling in the Pathogenesis of Chronic Pain and Itch

Interleukin-33 (IL-33) is an inflammatory factor with an extensive range of biological effects and pleiotropic roles in diseases. Evidence suggests that IL-33 and its receptor ST2 play a pivotal role in chronic pain and itch at the level of primary sensory neurons, the spinal cord, and the brain. In this review, we outline an evolving understanding of the roles and mechanisms of IL-33 in chronic pathological pain, including inflammatory, neuropathic, and cancer, and chronic pruritus, such as allergic contact dermatitis, atopic dermatitis, and dry skin. Understanding the key roles of IL-33/ST2 signaling may provide exciting insights into the mechanisms of chronic pain and itch and lead to new clues for therapeutic approaches to the resolution of chronic pain and itch.

Inhibitory Effects of Simvastatin on IL-33-Induced MCP-1 via the Suppression of the JNK Pathway in Human Vascular Endothelial Cells

An alarmin, interleukin (IL)-33 is a danger signal that causes inflammation, inducing chemotactic proteins such as monocyte chemoattractant protein (MCP)-1 in various cells. As statins have pleiotropic actions including anti-inflammatory properties, we investigated the effects of simvastatin on IL-33-induced MCP-1 expression in human umbilical vein endothelial cells (HUVECs). HUVECs were stimulated with IL-33 in the presence or absence of simvastatin. Gene expression and protein secretion of MCP-1, phosphorylation of mitogen-activated protein kinase (MAPK), nuclear translocation of phosphorylated c-Jun, and human monocyte migration were investigated. Immunocytochemical staining and Western immunoblot analysis revealed that IL-33 augmented MCP-1 protein expression in HUVECs. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) showed that IL-33 significantly increased MCP-1 mRNA and protein secretion, which were suppressed by c-jun N-terminal kinase (JNK) inhibitor SP600125 and p38 MAPK inhibitor SB203580. Simvastatin inhibited IL-33-induced MCP-1 mRNA, protein secretion, phosphorylation of JNK and c-Jun. Additionally, the IL-33-induced nuclear translocation of phosphorylated c-Jun and THP-1 monocyte migration were also blocked by simvastatin. This study demonstrated that IL-33 induces MCP-1 expression via the JNK and p38 MAPK pathways in HUVECs, and that simvastatin inhibits MCP-1 production by selectively suppressing JNK. Simvastatin may inhibit the progression of IL-33-induced inflammation via suppressing JNK to prevent MCP-1 production.

Interleukin-33 as a Potential Therapeutic Target in Gastric Cancer Patients: Current Insights

Gastric cancer is a significant global health problem as it is the fifth most prevalent cancer worldwide and the fourth leading cause of cancer-related mortality. While cytotoxic chemotherapy remains the primary treatment for advanced GC, response rates are limited. Recent progresses, focused on molecular signalling within gastric cancer, have ignited new hope for potential therapeutic targets that may improve survival and/or reduce the toxic effects of traditional therapies. Carcinomas are generally initiated when critical regulatory genes get mutated, but the progression to malignancy is usually supported by the non-neoplastic cells that create a conducive environment for transformation and progression to occur. Interleukin 33 (IL-33) functions as a dual activity cytokine as it is also a nuclear factor. IL-33 is usually present in the nuclei of the cells. Upon tissue damage, it is released into the extracellular space and binds to its receptor, suppression of tumorigenicity 2 (ST2) L, which is expressed on the membranes of the target cells. IL-33 signalling activates the T Helper 2 (Th2) immune response among other responses. Although the studies on the role of IL-33 in gastric cancer are still in the early stages, they have revealed potentially important (though sometimes conflicting) functions or roles in cancer development and progression. The pro-tumorigenic roles include induction and the recruitment of tumor-associated immune cells, promoting metaplasia progression, and inducing stem cell like and EMT properties in gastric cancer cells. Therapeutic interventions to disrupt these functions may provide a unique strategy for gastric cancer prevention and treatment. This review aims to provide a summary of the role of IL-33 in GC, state its multiple functions in relation to GC, and show potential avenues for promising therapeutic investigation.

Interleukin-1 family cytokines in liver cell death: a new therapeutic target for liver diseases

INTRODUCTION

Liver cell death represents a basic biological process regulating the progression of liver diseases via distinct mechanisms. Accumulating evidence has uncovered participation of interleukin (IL)-1 family cytokines in liver cell death. Upon activation of cell death induced by hepatotoxic stimuli, IL1 family cytokines released by hepatic dead cells stimulate recruitment of immune cells, which in turn influence inflammation and subsequent liver injury, thus highlighting their potential as therapeutic targets in liver diseases. Enhancing our comprehension of mechanisms underlying IL1 family cytokine signaling in cell death responses could pave the way for novel therapeutic interventions aimed at addressing liver cell death-related liver pathologies.

AREAS COVERED

This review summarizes the recent findings reported in preclinical and clinical studies on mechanisms of liver cell death, alongside participation of IL1 family members consisting of IL1α, ILβ, IL18, and IL33 in liver cell death and their significant implications in liver diseases.

EXPERT OPINION

Discovery of new and innovative therapeutic approaches for liver diseases will need close cooperation between fundamental and clinical scientists to better understand the multi-step processes behind IL1 family cytokines' contributions to liver cell death.

Interleukin-33 increases type 2 innate lymphoid cell count and their activation in eosinophilic asthma

BACKGROUND

Interleukin-33 (IL-33) exacerbates asthma probably through type 2 innate lymphoid cells (ILC2s). Nevertheless, the association between eosinophilic asthma (EA) and ILC2s remains obscure, and the mechanisms by which IL-33 affects ILC2s are yet to be clarified.

METHODS

ILC2s were evaluated in peripheral blood mononuclear cells, induced sputum, and bronchoalveolar lavage fluid obtained from patients with EA. Confocal microscopy was performed to locate ILC2s in lung tissue and the mRNA expression of ILC2-related genes was also evaluated in the EA model. The proliferation of ILC2s isolated from humans and mice was assessed following IL-33 or anti-IL-33 stimulation.

RESULTS

The counts, activation, and mRNA expression of relevant genes in ILC2s were higher in PBMCs and airways of patients with EA. In addition, ILC2 cell counts correlated with Asthma control test, blood eosinophil count, Fractional exhaled nitric oxide level, and predicted eosinophilic airway inflammation. IL-33 induced stronger proliferation of ILC2s and increased their density around blood vessels in the lungs of mice with EA. Moreover, IL-33 treatment increased the counts and activation of ILC2s and lung inflammatory scores, whereas anti-IL-33 antibody significantly reversed these effects in EA mice. Finally, IL-33 enhanced PI3K and AKT protein expression in ILC2s, whereas inhibition of the PI3K/AKT pathway decreased IL-5 and IL-13 production by ILC2s in EA.

CONCLUSIONS

ILC2s, especially activated ILC2s, might be critical markers of EA. IL-33 can induce and activate ILC2s in the lungs via the PI3K/AKT pathway in EA. Thus, using anti-IL-33 antibody could be a part of an effective treatment strategy for EA.

Interleukin-33: Friend or Foe in Gastrointestinal Tract Cancers?

Accumulating evidence suggests that Interleukin-33 (IL-33), a member of the IL-1 family, has crucial roles in tissue homeostasis and repair, type 2 immunity, inflammation, and viral infection. IL-33 is a novel contributing factor in tumorigenesis and plays a critical role in regulating angiogenesis and cancer progression in a variety of human cancers. The partially unraveled role of IL-33/ST2 signaling in gastrointestinal tract cancers is being investigated through the analysis of patients' samples and by studies in murine and rat models. In this review, we discuss the basic biology and mechanisms of release of the IL-33 protein and its involvement in gastrointestinal cancer onset and progression.

Early activation and recruitment of invariant natural killer T cells during liver ischemia-reperfusion: the major role of the alarmin interleukin-33

Over the past thirty years, the complexity of the αβ-T cell compartment has been enriched by the identification of innate-like T cells (ITCs), which are composed mainly of invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells. Based on animal studies using ischemia-reperfusion (IR) models, a key role has been attributed to iNKT cells in close connection with the alarmin/cytokine interleukin (IL)-33, as early sensors of cell-stress in the initiation of acute sterile inflammation. Here we have investigated whether the new concept of a biological axis of circulating iNKT cells and IL-33 applies to humans, and may be extended to other ITC subsets, namely MAIT and γδ-T cells, in the acute sterile inflammation sequence occurring during liver transplant (LT). From a prospective biological collection of recipients, we reported that LT was accompanied by an early and preferential activation of iNKT cells, as attested by almost 40% of cells having acquired the expression of CD69 at the end of LT (i.e. 1-3 hours after portal reperfusion), as opposed to only 3-4% of conventional T cells. Early activation of iNKT cells was positively correlated with the systemic release of the alarmin IL-33 at graft reperfusion. Moreover, in a mouse model of hepatic IR, iNKT cells were activated in the periphery (spleen), and recruited in the liver in WT mice, as early as the first hour after reperfusion, whereas this phenomenon was virtually missing in IL-33-deficient mice. Although to a lesser degree than iNKT cells, MAIT and γδ-T cells also seemed targeted during LT, as attested by 30% and 10% of them acquiring CD69 expression, respectively. Like iNKT cells, and in clear contrast to γδ-T cells, activation of MAIT cells during LT was closely associated with both release of IL-33 immediately after graft reperfusion and severity of liver dysfunction occurring during the first three post-operative days. All in all, this study identifies iNKT and MAIT cells in connection with IL-33 as new key cellular factors and mechanisms of acute sterile inflammation in humans. Further investigations are required to confirm the implication of MAIT and iNKT cell subsets, and to precisely assess their functions, in the clinical course of sterile inflammation accompanying LT.

Hypoxia induces downregulation of the tumor-suppressive sST2 in colorectal cancer cells via the HIF-nuclear IL-33-GATA3 pathway

As a decoy receptor, soluble ST2 (sST2) interferes with the function of the inflammatory cytokine interleukin (IL)-33. Decreased sST2 expression in colorectal cancer (CRC) cells promotes tumor growth via IL-33-mediated bioprocesses in the tumor microenvironment. In this study, we discovered that hypoxia reduced sST2 expression in CRC cells and explored the associated molecular mechanisms, including the expression of key regulators of ST2 gene transcription in hypoxic CRC cells. In addition, the effect of the recovery of sST2 expression in hypoxic tumor regions on malignant progression was investigated using mouse CRC cells engineered to express sST2 in response to hypoxia. Our results indicated that hypoxia-dependent increases in nuclear IL-33 interfered with the transactivation activity of GATA3 for ST2 gene transcription. Most importantly, hypoxia-responsive sST2 restoration in hypoxic tumor regions corrected the inflammatory microenvironment and suppressed tumor growth and lung metastasis. These results indicate that strategies targeting sST2 in hypoxic tumor regions could be effective for treating malignant CRC.

Evaluation of interleukin-33 & sST2 levels in type-2 diabetic mellitus patients with or without metabolic syndrome

Background & objectives

Diabetes mellitus (DM) is characterized by increase in blood glucose levels due to defective insulin secretion or insulin sensitivity. Interleukins (ILs) are known to play an important role in the pathogenesis of DM. The aim of this study was to investigate the serum concentration of IL-33 and its receptor soluble ST2 (sST2) in patients with diabetes and draw a correlation between their serum levels and different standard glycaemic indices of patients affected with type-2 diabetes with or without metabolic syndrome.

Methods

Thirty type-2 diabetic individuals and 30 healthy controls were recruited for this study. Serum and plasma were separated by centrifugation of blood for quantitative measurement of IL-33, sST2 and other biochemical parameters.

Results

It was observed that serum IL-33 levels were significantly less and sST2 levels were significantly high in type-2 diabetic individuals as compared to healthy controls. A significant correlation between the serum IL-33 concentration and fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) levels were also found. Additionally, data also elucidated that serum levels of high-density lipoprotein, low-density lipoprotein or triglyceride in type-2 diabetics did not influence the serum levels of IL-33 and sST2, thereby excluding these factors as the major drivers of changes in serum IL-33 and sST2 concentration.

Interpretation & conclusions

This study demonstrated alteration in serum levels of IL-33 and sST2 in type-2 diabetic individuals. Further mechanistic studies, focusing on the progression of type-2 diabetes could elucidate the involvement of IL-33 in the cellular acquisition of insulin resistance as observed in type-2 diabetics.

Elevated levels of interleukin-33 are associated with asthma: A meta-analysis

BACKGROUND

Previous studies reported that patients with asthma showed higher levels of interleukin (IL)-33 in peripheral blood, compared to healthy control (HCs). However, we also noticed that there were no significant differences of IL-33 levels between controls and asthma patients in a recent study. We aim to conduct this meta-analysis and evaluate the feasibility of IL-33 in peripheral blood that may act as a promising biomarker in asthma.

METHODS

Articles published before December 2022 were searched in these databases (PubMed, Web of Science, EMBASE, and Google Scholar). We used STATA 12.0 software to compute the results.

RESULTS

The study showed that asthmatics showed higher IL-33 level in serum and plasma, compared to HCs (serum: standard mean difference [SMD] 2.06, 95% confidence interval [CI] 1.12-3.00, I²  = 98.4%, p < .001; plasma: SMD 3.67, 95% CI 2.32-5.03, I²  = 86.0%, p < .001). Subgroup analysis indicated that asthma adults showed higher IL-33 level in serum, compared to HCs, whereas no significant difference in IL-33 level in serum was showed between asthma children and HCs (adults: SMD 2.17, 95% CI 1.09-3.25; children: SMD 1.81, 95% CI -0.11 to 3.74). The study indicated that moderate and severe asthmatics showed higher IL-33 level in serum, compared to mild asthmatics (SMD 0.78, 95% CI 0.41-1.16, I²  = 66.2%, p = .011).

CONCLUSIONS

In conclusion, the main findings of present meta-analysis suggested that there was a significant correlation between IL-33 levels and the severity of asthma. Therefore, IL-33 levels of either serum or plasma may be regarded as a useful biomarker of asthma or the degree of disease.

Interleukin-33 Mediates Cardiomyopathy After Acute Kidney Injury by Signaling to Cardiomyocytes

BACKGROUND

Acute kidney injury (AKI) is a short-term life-threatening condition that, if survived, can lead to renal insufficiency and development of chronic kidney disease. The pathogenesis of AKI and chronic kidney disease involves direct effects on the heart and the development of hypertrophy and cardiomyopathy.

METHODS

We used mouse models of ischemia/reperfusion AKI and unilateral ureteral obstruction to investigate the role of IL-33 (interleukin-33) and its receptor-encoding gene Il1rl1 (also called ST2L [suppression of tumorigenicity 2]) in cardiac remodeling after AKI. Mice with cell type-specific genetic disruption of the IL-33/ST2L axis were used, and IL-33 monoclonal antibody, adeno-associated virus encoding IL-33 or ST2L, and recombinant IL-33, as well.

RESULTS

Mice deficient in Il33 were refractory to cardiomyopathy associated with 2 models of kidney injury. Treatment of mice with monoclonal IL-33 antibody also protected the heart after AKI. Moreover, overexpression of IL-33 or injection of recombinant IL-33 induced cardiac hypertrophy or cardiomyopathy, but not in mice lacking Il1rl1. AKI-induced cardiomyopathy was also reduced in mice with cardiac myocyte-specific deletion of Il1rl1 but not in endothelial cell- or fibroblast-specific deletion of Il1rl1. Last, overexpression of the ST2L receptor in cardiac myocytes recapitulated induction of cardiac hypertrophy.

CONCLUSIONS

These results indicate that IL-33 released from the kidney during AKI underlies cardiorenal syndrome by directly signaling to cardiac myocytes, suggesting that antagonism of IL-33/ST2 axis would be cardioprotective in patients with kidney disease.

The alarmin interleukin-33 promotes the expansion and preserves the stemness of Tcf-1+ CD8+ T cells in chronic viral infection

T cell factor 1 (Tcf-1) expressing CD8⁺ T cells exhibit stem-like self-renewing capacity, rendering them key for immune defense against chronic viral infection and cancer. Yet, the signals that promote the formation and maintenance of these stem-like CD8⁺ T cells (CD8⁺SL) remain poorly defined. Studying CD8⁺ T cell differentiation in mice with chronic viral infection, we identified the alarmin interleukin-33 (IL-33) as pivotal for the expansion and stem-like functioning of CD8⁺SL as well as for virus control. IL-33 receptor (ST2)-deficient CD8⁺ T cells exhibited biased end differentiation and premature loss of Tcf-1. ST2-deficient CD8⁺SL responses were restored by blockade of type I interferon signaling, suggesting that IL-33 balances IFN-I effects to control CD8⁺SL formation in chronic infection. IL-33 signals broadly augmented chromatin accessibility in CD8⁺SL and determined these cells' re-expansion potential. Our study identifies the IL-33-ST2 axis as an important CD8⁺SL-promoting pathway in the context of chronic viral infection.

A CpG-Oligodeoxynucleotide Suppresses Th2/Th17 Inflammation by Inhibiting IL-33/ST2 Signaling in Mice from a Model of Adoptive Dendritic Cell Transfer of Smoke-Induced Asthma

Tobacco smoke exposure is a major environmental risk factor that facilitates the development and progression of asthma. Our previous study showed that CpG oligodeoxynucleotide (CpG-ODN) inhibits thymic stromal lymphopoietin (TSLP)-dendritic cells (DCs) to reduce Th2/Th17-related inflammatory response in smoke-related asthma. However, the mechanism underlying CpG-ODN -downregulated TSLP remains unclear. A combined house dust mite (HDM)/cigarette smoke extract (CSE) model was used to assess the effects of CpG-ODN on airway inflammation, Th2/Th17 immune response, and amount of IL-33/ST2 and TSLP in mice with smoke-related asthma induced by adoptive transfer of bone-marrow-derived dendritic cells (BMDCs) and in the cultured human bronchial epithelium (HBE) cells administered anti-ST2, HDM, and/or CSE. In vivo, compared to the HDM alone model, the combined HDM/CSE model had aggravated inflammatory responses, while CpG-ODN attenuated airway inflammation, airway collagen deposition, and goblet cell hyperplasia and reduced the levels of IL-33/ST2, TSLP, and Th2/Th17-cytokines in the combined model. In vitro, IL-33/ST2 pathway activation promoted TSLP production in HBE cells, which could be inhibited by CpG-ODN. CpG-ODN administration alleviated Th2/Th17 inflammatory response, decreased the infiltration of inflammatory cells into the airway, and improved the remodeling of smoke-related asthma. The underlying mechanism may be that CpG-ODN inhibits the TSLP-DCs pathway by downregulating the IL-33/ST2 axis.

Alarmins and MicroRNAs, a New Axis in the Genesis of Respiratory Diseases: Possible Therapeutic Implications

It is well ascertained that airway inflammation has a key role in the genesis of numerous respiratory pathologies, including asthma, chronic obstructive pulmonary disease, and acute respiratory distress syndrome. Pulmonary tissue inflammation and anti-inflammatory responses implicate an intricate relationship between local and infiltrating immune cells and structural pulmonary cells. Alarmins are endogenic proteins discharged after cell injury in the extracellular microenvironment. The purpose of our review is to highlight the alterations in respiratory diseases involving some alarmins, such as high mobility group box 1 (HMGB1) and interleukin (IL)-33, and their inter-relationships and relationships with genetic non-coding material, such as microRNAs. The role played by these alarmins in some pathophysiological processes confirms the existence of an axis composed of HMGB1 and IL-33. These alarmins have been implicated in ferroptosis, the onset of type 2 inflammation and airway alterations. Moreover, both factors can act on non-coding genetic material capable of modifying respiratory function. Finally, we present an outline of alarmins and RNA-based therapeutics that have been proposed to treat respiratory pathologies.

Prognostic value of interleukin-33, sST2, myeloperoxidase, and matrix metalloproteinase-9 in acute aortic dissection

Background and purpose

Acute aortic dissection (AAD) is a life-threatening cardiovascular emergency. Both neutrophil granzyme and interleukin (IL)-33/ST2 systems have proven to be effective diagnostic markers for AAD. This study aimed to investigate the relationship between plasma IL-33, soluble suppression of tumorigenesis-2 (sST2), myeloperoxidase (MPO), and matrix metalloproteinase (MMP)-9 levels at admission and all-cause mortality in patients with AAD.

Methods

A total of 155 patients with AAD were enrolled from the Prospective Evaluation of Acute Chest Pain (PEACP) study. Plasma concentrations of IL-33, sST2, and MMP-9 were measured using an enzyme-linked immunosorbent assay, and MPO was detected using a chemiluminescence immunoassay. Aortic anatomical parameters were measured using CT radiography. The primary endpoint was all-cause mortality rate.

Results

The median age of the patients was 55 years, and 96 (61.9%) were diagnosed with type A-AAD. After adjusting for confounding factors, the highest tertiles of IL-33, sST2, MPO, and MMP-9 had hazard risks of 0.870 (95% CI: 0.412-1.836, P = 0.714), 3.769 (95% CI: 1.504-9.446, P = 0.005), 4.689 (95% CI: 1.985-11.076, P < 0.001), and 4.748 (95% CI: 1.763-12.784, P = 0.002), respectively, compared to the lowest tertile. Pearson's correlation analysis revealed a significant correlation between these markers (P < 0.001). Moreover, sST2, MPO, and MMP-9 levels had a significant positive correlation with aortic diameter and pseudolumen area (P < 0.001).

Conclusion

The biomarkers sST2, MPO, and MMP-9 were independently associated with mortality in patients with AAD. The significant correlation between these biomarkers suggests a pathogenic role for the IL-33/ST2/neutrophil granzyme system in patients with AAD.

Acute rotavirus infection causes significant activation of the IL-33/IL-13 axis

AIM

Overactivation of the IL-33/IL-13 axis is the main step in initializing allergic inflammation and promoting allergic diseases. Data on viral pathogens as risk factors for subsequent allergic disease are contradictory. The strongest associations have been made between upper respiratory tract virus infections and asthma. Intestinal viral infections also activate IL-33 and IL-13 as part of the innate antiviral response. The aim of this study was to test whether there are differences in IL-13 and IL-33 concentrations in pediatric patients with acute rotavirus- and norovirus infections and healthy controls.

MATERIAL AND METHODS

Forty children with acute rotavirus, 27 with acute norovirus intestinal infections and 17 control children were enrolled in this study. Blood IL-33 and IL-13 detection was performed with enzyme-linked immunosorbent assays (ELISAs).

RESULTS

Acute rotavirus infection caused a significant elevation in IL-33 and IL-13 compared to acute norovirus infection (63.85 pg/ml vs. 0, P = 0.0026, and 94.24 pg/ml vs. 0.88 pg/ml, P = 0.0003, respectively) and healthy controls (63.85 pg/ml vs. 9.89 pg/ ml, P = 0.0018, and 94.24 pg/ml vs. 0.14 pg/ml, P &lt; 0.0001, respectively). There was no significant difference in IL-33 and IL-13 concentrations between the acute norovirus group and healthy controls (0 vs. 9.89 pg/ml, P = 0.8276 and 0.88 pg/ml vs. 0.14 pg/ml, P = 0.1652, respectively).

CONCLUSION

Acute rotavirus infection causes a significant elevation in IL-33 and IL-13, compared to norovirus and healthy control children.

Astegolimab or Efmarodocokin Alfa in Patients With Severe COVID-19 Pneumonia: A Randomized, Phase 2 Trial

OBJECTIVES

Severe cases of COVID-19 pneumonia can lead to acute respiratory distress syndrome (ARDS). Release of interleukin (IL)-33, an epithelial-derived alarmin, and IL-33/ST2 pathway activation are linked with ARDS development in other viral infections. IL-22, a cytokine that modulates innate immunity through multiple regenerative and protective mechanisms in lung epithelial cells, is reduced in patients with ARDS. This study aimed to evaluate safety and efficacy of astegolimab, a human immunoglobulin G2 monoclonal antibody that selectively inhibits the IL-33 receptor, ST2, or efmarodocokin alfa, a human IL-22 fusion protein that activates IL-22 signaling, for treatment of severe COVID-19 pneumonia.

DESIGN

Phase 2, double-blind, placebo-controlled study (COVID-astegolimab-IL).

SETTING

Hospitals.

PATIENTS

Hospitalized adults with severe COVID-19 pneumonia.

INTERVENTIONS

Patients were randomized to receive IV astegolimab, efmarodocokin alfa, or placebo, plus standard of care. The primary endpoint was time to recovery, defined as time to a score of 1 or 2 on a 7-category ordinal scale by day 28.

MEASUREMENTS AND MAIN RESULTS

The study randomized 396 patients. Median time to recovery was 11 days (hazard ratio [HR], 1.01 d; p = 0.93) and 10 days (HR, 1.15 d; p = 0.38) for astegolimab and efmarodocokin alfa, respectively, versus 10 days for placebo. Key secondary endpoints (improved recovery, mortality, or prevention of worsening) showed no treatment benefits. No new safety signals were observed and adverse events were similar across treatment arms. Biomarkers demonstrated that both drugs were pharmacologically active.

CONCLUSIONS

Treatment with astegolimab or efmarodocokin alfa did not improve time to recovery in patients with severe COVID-19 pneumonia.

Protein and mRNA expression of interleukin-33 in periodontally diseased and healthy individuals and impact of nonsurgical periodontal therapy in salivary IL-33 levels

Background

Interleukin (IL)-33 is a member of IL-1 beta family of cytokines having a pivotal role in bone destruction. However, its role in periodontal disease is not clearly established. The objective of the present study was to evaluate salivary and gingival IL-33 expression in periodontally healthy and diseased individuals. The change in salivary IL-33 after nonsurgical therapy was also analyzed.

Materials and Methods

Salivary IL-33 concentration was estimated using enzyme-linked immunosorbent assay in periodontally healthy and diseased individuals (30 in each group). Re-evaluation was done in periodontitis patients after 6 weeks of nonsurgical therapy. Further, the messenger ribonucleic acid expression of IL-33 in healthy and diseased gingival tissues was also examined using reverse transcriptase-polymerase chain reaction and correlated with IL-1 beta messenger ribonucleic acid.

Results

Salivary IL-33 concentration in periodontitis patients was 1.65 fold higher than healthy controls (P < 0.0001), and 16% reduction was noticed after nonsurgical treatment. Salivary IL-33 concentration could be used to differentiate periodontitis from health at a cutoff value of 543.16 ng/mL with 93.33% sensitivity and 90% specificity (area under the curve 0.92). Upregulated gingival expression of IL-33 was also noted in periodontitis patients, and it was positively correlated with IL-1 beta (r = 0.7).

Conclusion

The study reconfirms the role of IL-33 in periodontal disease, proposed a threshold value of differentiating healthy and periodontitis patients, and suggests IL-33 as a potential diagnostic biomarker for periodontal disease and to evaluate the response to periodontal therapy.

Patterns of Interstitial Lung Disease in Egyptian Patients with Systemic Sclerosis: Relation to Disease Parameters

BACKGROUND

Pulmonary involvement is the most common leading cause of morbidity and mortality associated with systemic sclerosis. Therefore, identifying the various patterns of pulmonary affection is crucial in the clinical management of these patients. In the current study, we aim to investigate the patterns of interstitial lung disease (ILD) associated with SSc patients (SSc- ILD) and their relation to serologic markers and clinical parameters.

METHODS

A cross-sectional study was undertaken on thirty-four adult SSc patients who met the 2013 ACR/EULAR criteria for SSc and Forty healthy controls of matched age and sex. The patients were subjected to history taking, clinical examination, skin assessment using the modified Rodnan Skin Score (mRSS), chest x-ray (CXR), pulmonary function test (PFTs), and high resolution computed tomography of the chest (HRCT). Routine laboratory tests were conducted in addition to immunologic tests and an enzyme-linked immunosorbent assay (ELISA) to determine the IL-33 level.

RESULTS

ILD was found in 23 SSc patients (67.6%); 20 patients had diffuse type while 3 patients had limited type. Non-specific interstitial pneumonia (NSIP) was found in 56.5%, usual interstitial pneumonia (UIP) was found in 21.7%, pleuroparenchymal fibroelastosis (PPFE) was found in 8.7%, and organizing pneumonia (OP) with the mixed pattern was found in 13% of SSc patients. Additionally, the mean IL-33 level in SSc patients was 98±12.7 compared to 66.2±10.6 in the control group (p < 0.001), with ILD patients having a significantly higher level (101.7±13.4) than those without (90.4±6.2), and a strong positive correlation with mRSS.

CONCLUSION

Even in asymptomatic patients with SSc, ILD is prevalent, with NSIP being the most common pattern. IL-33 could be considered a potential biomarker for predicting the presence of ILD in SSc patients.

Adiponectin and Interleukin-33: Possible Early Markers of Metabolic Syndrome

Adiponectin is one of the most important molecules in the body's compensatory response to the development of insulin resistance. By trying to maintain insulin sensitivity, increase insulin secretion and prevent inflammation, adiponectin tries to maintain glucose homeostasis. Interleukin-33, which belongs to the group of alarmins, also promotes insulin secretion. Interleukin-33 might be either pro-inflammatory or anti-inflammatory depending on the disease and the model. However, interleukin-33 has shown various protective effects in CVD, obesity and diabetes. The aim of our study was to investigate the association between adiponectin and interleukin-33 in patients with metabolic syndrome. As expected, all patients with metabolic syndrome had worse parameters that represent the hallmark of metabolic syndrome compared to the control group. In the subgroup of patients with low adiponectin, we observed less pronounced characteristics of metabolic syndrome simultaneously with significantly higher values of interleukin-33 compared to the subgroup of patients with high adiponectin. Our findings suggested that adiponectin might be an early marker of metabolic syndrome that emerges before anthropomorphic, biochemical and clinical parameters. We also suggest that both interleukin-33 and adiponectin may be used to predict the inflammatory status in the early stage of metabolic syndrome.

Cerebrospinal fluid levels of sortilin-1, lipocalin-2, autotaxin, decorin and interleukin-33 in patients with idiopathic intracranial hypertension

BACKGROUND

Idiopathic intracranial hypertension (IIH) is characterized by increased cerebrospinal fluid (CSF) pressure of unknown cause. It has been suggested that the inflammatory process plays a role in the pathophysiology of the disease. Sortilin-1, lipocalin-2, autotaxin, decorin, and interleukin-33 (IL-33) are among the factors involved in inflammatory processes.

OBJECTIVE

To investigate the CSF levels of sortilin-1, lipocalin-2, autotaxin, decorin, and IL-33 in patients with IIH.

METHODS

A total of 24 IIH patients and 21 healthy controls were included in the study. Demographic characteristics of the patients and of the control group as well as CSF pressures were evaluated. Sortilin-1, lipocalin-2, autotaxin, decorin and IL-33 levels in the CSF were measured.

RESULTS

The CSF levels lipocalin-2, sortilin-1, autotaxin, IL-33 and CSF pressure were significantly higher in the patients group compared with the control group (p < 0.001). Decorin levels were reduced in patients (p < 0.05). There was no correlation between the autotaxin and IL-33 levels and age, gender, CSF pressure, and body mass index. The results of our study showed that inflammatory activation plays an important role in the development of the pathophysiology of IIH. In addition, the fact that the markers used in our study have never been studied in the etiopathogenesis of IIH is important in explaining the molecular mechanism of this disease.

CONCLUSION

Studies are needed to evaluate the role of these cytokines in the pathophysiology of the disease. It is necessary to evaluate the effects of these molecules on this process.

Louki Zupa decoction attenuates the airway inflammation in acute asthma mice induced by ovalbumin through IL-33/ST2-NF-κB/GSK3β/mTOR signalling pathway

CONTEXT

Asthma is a common respiratory system disease. Louki Zupa decoction (LKZP), a traditional Chinese medicine, presents a promising efficacy against lung diseases.

OBJECTIVE

To investigate the pathogenic mechanism of asthma and reveal the intervention mechanism of LKZP.

MATERIALS AND METHODS

Forty-eight female Balb/c mice were randomly divided into 6 groups: normal control group (NC), ovalbumin (OVA)/saline asthma model group, OVA/LL group, OVA/LM group, OVA/LH group and OVA/DEX group (n = 8 per group). The asthmatic mice were modelled through intraperitoneal injecting and neutralizing OVA. LKZP decoction was administrated by gavage at the challenge stage for seven consecutive days (2.1, 4.2 and 8.4 g/kg/day). We investigated the change in lung function, airway inflammation, mucus secretion and TH-1/TH-2-related cytokines. We further verify the activated status of the IL-33/ST2/NF-κB/GSK3β/mTOR signalling pathway.

RESULTS

LKZP was proved to improve asthmatic symptoms, as evidenced by the down-regulated airway resistance by 36%, 58% and 53% (p < 0.01, p < 0.001 vs. OVA/saline group), up-regulated lung compliance by 102%, 114% and 111%, decreased airway inflammation and mucus secretion by 33%, 40% and 33% (p < 0.001 vs. OVA/saline group). Moreover, the content of cytokines in BALF related to airway allergy (such as IgE) and T helper 1/T helper 2 cells (like IL-2, IL-4, IL-5, IL-13, TNF-α and IFN-γ), were also markedly reduced by 13-65% on LKZP intervention groups compared with model group. Mechanistic research revealed that the IL-33/ST2-NF-κB/GSK3β/mTOR signalling pathway was activated in the OVA/saline group and LKZP significantly down-regulated this pathway.

DISCUSSION AND CONCLUSION

LKZP improves lung function, airway inflammation, mucus secretion and correct immune imbalance by intervening with the IL-33/ST2-NF-κB/GSK3β/mTOR signalling pathway, presenting a promising therapeutic choice for asthma.

IL-33 induces NF-κB activation in ILC2 that can be suppressed by in vivo and ex vivo 17β-estradiol

Asthmatic women tend to develop severe airway disease in their reproductive years, and 30%-40% of asthmatic women have peri-menstrual worsening of asthma symptoms. This indicates that fluctuations in ovarian hormones are involved in advancement of asthmatic disease and exacerbation of symptoms. Group 2 innate lymphoid cells, or ILC2, are readily detected in allergic conditions, such as rhinosinusitis, in individuals that develop nasal polyps do to allergen exposures, and in allergic asthma. ILC2 are airway localized immune cells activated by IL-33, an innate cytokine that perpetuates allergic inflammation by driving the production of IL-5 and IL-13. We have previously shown that ILC2 are highly activated in naïve and ovalbumin (OVA) challenged, female BALB/c mice in comparison to male mice following stimulation with IL-33. Here, we investigated the effect of steady-state ovarian hormones on ILC2 and the NF-κB signaling pathway following OVA sensitization and challenge. We found that estrogen-treated ovariectomized mice (OVX-E2) that had been challenged with OVA had reduced IL-5 and IL-13 production by lung ILC2 as compared to lung ILC2 isolated from intact male and female sham-operated controls that had been treated with OVA. ILC2 were isolated from untreated animals and co-cultured ex vivo with and without estrogen plus IL-33. Those estrogen-treated ILC2 similarly produced less IL-5 and IL-13 in comparison to untreated, and had reduced NF-κB activation. Single-cell RNA sequencing showed that 120 genes were differentially expressed in male and female ILC2, and Nfkb1 was found among top-ranked regulatory interactions. Together, these results provide new insight into the suppressive effect of estrogen on ILC2 which may be protective in female asthmatics. Understanding further how estrogen modulates ILC2 may provide therapeutic targets for the treatment of allergic diseases.

Quercetin Ameliorates Renal Injury and Pyroptosis in Lupus Nephritis through Inhibiting IL-33/ST2 Pathway In Vitro and In Vivo

Lupus nephritis (LN) is a common and serious symptom in patients with systemic lupus erythematosus (SLE). Tubular interstitial fibrosis is a common underlying mechanism in the development of lupus nephritis to end-stage renal failure (ESRD). Quercetin is widely proven to prevent tissue fibrosis. Therefore, the purpose of this study is to investigate the beneficial effects of quercetin on the inhibition of fibrosis and inflammation pathways in in vitro and in vivo lupus nephritis models. In the current study, MRL/lpr mice as animal models, and HK-2 human renal tubular epithelial cells were stimulated by interleukin-33 (IL-33) to mimic the cellular model of lupus nephritis. Immunohistochemical staining, immunoblotting assay, immunofluorescence staining, and quantitative real-time polymerase chain reaction assay were used. The in vivo results showed that quercetin improved the renal function and inhibited both fibrosis- and inflammation-related markers in MRL/lpr mice animal models. The in vitro results indicated that quercetin ameliorated the accumulation of fibrosis- and inflammation-related proteins in IL-33-induced HK-2 cells and improved renal cell pyroptosis via the IL33/ST2 pathway. Overall, quercetin can improve LN-related renal fibrosis and inflammation, which may offer an effective potential therapeutic strategy for lupus nephritis.

Interleukin-33 regulates the functional state of microglia

Microglia, the most prominent resident immune cells, exhibit multiple functional states beyond their immunomodulatory roles. Non-immune functions such as synaptic reorganization, removal of cellular debris, and deposition of abnormal substances are mediated by phagocytosis of normal or enhanced microglia. Activation or migration of microglia occurs when environmental cues are altered. In response to pathological factors, microglia change into various phenotypes, preventing or exacerbating tissue damage. Interleukin-33 (IL-33) is an important cytokine that regulates innate immunity, and microglia are thought to be its target cells. Here, we outline the role of IL-33 in the expression of microglial functions such as phagocytosis, migration, activation, and inflammatory responses. We focus on microglial properties and diverse functional states in health and disease, including the different effects of IL-33 perturbation on microglia in vivo and in vitro. We also highlight several well-established mechanisms of microglial function mediated by IL-33, which may be initiators and regulators of microglial function and require elucidation and expansion of the underlying mechanisms.

Clusters Based on Immune Markers in a Lithuanian Asthma Cohort Study

OBJECTIVE

Asthma is divided into various distinct phenotypes on the basis of clinical characteristics, physiological findings, and triggers, and phenotyping is usually performed in a hypothesis-driven univariate manner. However, phenotyping can also be performed using computer algorithms to evaluate hypotheses-free relationships among many clinical and biological characteristics. We aimed to identify asthma phenotypes based on multiple demographic, clinical, and immunological characteristics.

METHODS

Cluster analysis in R v3.5.0 was performed using asthma patient data. A total of 170 adult patients with asthma (diagnosed according to the GINA recommendations) were recruited to the study. All patients completed questionnaires about their smoking history and underwent physical examination, spirometry, skin-prick test, blood sample collection to evaluate peripheral blood cell counts and serum IgE, periostin, and interleukin (IL)-33 levels, as well as body mass index measurements. Data normality was checked with histograms and QQ plots. Hierarchical clustering was performed using Ward's linkage with Ward's clustering criterion. The optimal number of clusters was validated using the Dunn criterion as well as by comparing different clustering algorithms using the clValid package.

RESULTS

Three clusters characterizing asthma phenotypes were identified: (1) early-onset, highly atopic, and eosinophilic asthma associated with male sex and high levels of IL-33 and periostin; (2) late-onset, eosinophilic asthma associated with female sex and low levels of IL-33 and periostin; and (3) late-onset, obese, neutrophilic asthma associated with female sex, persistent airway obstruction, and very low IL-33 and periostin levels.

The role of IL-33/ST2 signaling in the tumor microenvironment and Treg immunotherapy

Interleukin (IL)-33 is a tissue-derived nuclear cytokine belonging to the IL-1 family. Stimulation-2 (ST2) is the only known IL-33 receptor. ST2 signals mostly on immune cells found within tissues, such as regulatory T cells (Treg cells), CD8+ T cells, and natural killer (NK) cells. Therefore, the IL-33/ST2 signaling pathway is important in the immune system. IL-33 deficiency impairs Treg cell function. ST2 signaling is also increased in active Treg cells, providing a new approach for Treg-related immunotherapy. The IL-33/ST2 signaling pathway regulates multiple immune-related cells by activating various intracellular kinases and factors in the tumor microenvironment (TME). Here, we review the latest studies on the role of the IL-33/ST2 signaling pathway in TME and Treg immunotherapy.

Transcriptomic Regulation of Macrophages by Matrix-Bound Nanovesicle-Associated Interleukin-33

The innate immune response, particularly the phenotype of responding macrophages, has significant clinical implications in the remodeling outcome following implantation of biomaterials and engineered tissues. In general, facilitation of an anti-inflammatory (M2-like) phenotype is associated with tissue repair and favorable outcomes, whereas pro-inflammatory (M1-like) activation can contribute to chronic inflammation and a classic foreign body response. Biologic scaffolds composed of extracellular matrix (ECM) and, more recently, matrix-bound nanovesicles (MBV) embedded within the ECM are known to direct macrophages toward an anti-inflammatory phenotype and stimulate a constructive remodeling outcome. The mechanisms of MBV-mediated macrophage activation are not fully understood, but interleukin-33 (IL-33) within the MBV appears critical for M2-like activation. Previous work has shown that IL-33 is encapsulated within the lumen of MBV and stimulates phenotypical changes in macrophages independent of its canonical surface receptor stimulation-2 (ST2). In the present study, we used next-generation RNA sequencing to determine the gene signature of macrophages following exposure to MBV with and without intraluminal IL-33. MBV-associated IL-33 instructed an anti-inflammatory phenotype in both wild-type and st2-/- macrophages by upregulating M2-like and downregulating M1-like genes. The repertoire of genes regulated by ST2-independent IL-33 signaling were broadly related to the inflammatory response and crosstalk between cells of both the innate and adaptive immune systems. These results signify the importance of the MBV intraluminal protein IL-33 in stimulating a pro-remodeling M2-like phenotype in macrophages and provides guidance for the designing of next-generation biomaterials and tissue engineering strategies. Impact statement The phenotype of responding macrophages is predictive of the downstream remodeling response to an implanted biomaterial. The clinical impact of macrophage phenotype has motivated studies to investigate the factors that regulate macrophage activation. Matrix-bound nanovesicles (MBV) embedded within the extracellular matrix direct macrophages toward an anti-inflammatory (M2)-like phenotype that is indicative of a favorable remodeling response. Although the mechanisms of MBV-mediated macrophage activation are not fully understood, the intraluminal protein interleukin-33 (IL-33) is clearly a contributing signaling molecule. The present study identifies those genes regulated by MBV-associated IL-33 that promote a pro-remodeling M2-like macrophage activation state and can guide future therapies in regenerative medicine.

Trifuhalol A Suppresses Allergic Inflammation through Dual Inhibition of TAK1 and MK2 Mediated by IgE and IL-33

The activation and degranulation of immune cells play a pivotal role in allergic inflammation, a pathological condition that includes anaphylaxis, pruritus, and allergic march-related diseases. In this study, trifuhalol A, a phlorotannin isolated from Agarum cribrosum, inhibited the degranulation of immune cells and the biosynthesis of IL-33 and IgE in differentiated B cells and keratinocytes, respectively. Additionally, trifuhalol A suppressed the IL-33 and IgE-mediated activation of RBL-2H3 cells through the regulation of the TAK1 and MK2 pathways. Hence, the effect of trifuhalol A on allergic inflammation was evaluated using a Compound 48/80-induced systemic anaphylaxis mouse model and a house dust mite (HDM)-induced atopic dermatitis (AD) mouse model. Trifuhalol A alleviated anaphylactic death and pruritus, which appeared as an early-phase reaction to allergic inflammation in the Compound 48/80-induced systemic anaphylaxis model. In addition, trifuhalol A improved symptoms such as itching, edema, erythema, and hyperkeratinization in HDM-induced AD mice as a late-phase reaction. Moreover, the expression of IL-33 and thymic stromal lymphopoietin, inflammatory cytokines secreted from activated keratinocytes, was significantly reduced by trifuhalol A administration, resulting in the reduced infiltration of immune cells into the skin and a reduction in the blood levels of IgE and IL-4. In summarizing the above results, these results confirm that trifuhalol A is a potential therapeutic candidate for the regulation of allergic inflammation.

Interleukin-33 regulates the endoplasmic reticulum stress of human myometrium via an influx of calcium during initiation of labor

Background:

Inflammation is currently recognized as one of the major causes of premature delivery. As a member of the interleukin-1β (IL-1β) family, interleukin-33 (IL-33) has been shown to be involved in normal pregnancy as well as a variety of pregnancy-related disorder. This study aims to investigate the potential function of IL-33 in uterine smooth muscle cells during labor.

Methods:

Myometrium samples from term pregnant (≥37 weeks gestation) women were either frozen or cells were isolated and cultured. Immunohistochemistry and western blotting were used to assess the distribution of IL-33. Cultured cells were incubated with lipopolysaccharide (LPS) to mimic inflammation as well as in the presence of 4μ8C (IRE1 inhibitor III) to block endoplasmic reticulum (ER) stress and BAPTA-AM, a calcium chelator.

Results:

LPS reduced the expression of nuclear IL-33 in a time-limited manner and induced ER stress. However, knockdown of IL-33 increased LPS-induced calcium concentration, ER stress and phosphorylation of nuclear factor kappa-B (NF-κB), and P38 mitogen-activated protein kinase (P38 MAPK). In addition, siRNA IL-33 further stimulates LPS enhanced cyclooxygenase-2 (COX-2) expression via NF-κB and p38 pathways. IL-33 expression was decreased in the nucleus with the onset of labor. LPS-induced ER stress and increased expression of the labor-associated gene, COX-2, as well as IL-6 and IL-8 in cultured myometrial cells. IL-33 also increased COX-2 expression, but after it was knocked down, the stimulating effect of LPS on calcium was enhanced. 4μ8C also inhibited the expression of COX-2 markedly. The expression of calcium channels on the membrane and intracellular free calcium ion were both increased which was accompanied by phosphorylated NF-κB and p38.

Conclusions:

These data suggest that IL-33 may be involved in the initiation of labor by leading to stress of the ER via an influx of calcium ions in human uterine smooth muscle cells.

Funding:

This study was supported by grants from the National Natural Science Foundation of China (No. 81300507).

Rapamycin Dampens Inflammatory Properties of Bone Marrow ILC2s in IL-33-Induced Eosinophilic Airway Inflammation

The alarmin cytokine interleukin (IL)-33 plays an important proinflammatory role in type 2 immunity and can act on type 2 innate lymphoid cells (ILC2s) and type 2 T helper (T_H2) cells in eosinophilic inflammation and asthma. The mechanistic target of rapamycin (mTOR) signaling pathway drives immune responses in several inflammatory diseases, but its role in regulating bone marrow responses to IL-33 is unclear. The aim of this study was to determine the role of the mTORC1 signaling pathway in IL-33-induced bone marrow ILC2 responses and its impact on IL-33-induced eosinophilia. Wild-type mice were intranasally exposed to IL-33 only or in combination with the mTORC1 inhibitor, rapamycin, intraperitoneally. Four groups were included in the study: saline-treated (PBS)+PBS, rapamycin+PBS, PBS+IL-33 and rapamycin+IL-33. Bronchoalveolar lavage fluid (BALF), serum and bone marrow cells were collected and analyzed by differential cell count, enzyme-linked immunosorbent assay and flow cytometry. IL-33 induced phosphorylation of the mTORC1 protein rpS6 in bone marrow ILC2s both ex vivo and in vivo. The observed mTOR signal was reduced by rapamycin treatment, indicating the sensitivity of bone marrow ILC2s to mTORC1 inhibition. IL-5 production by ILC2s was reduced in cultures treated with rapamycin before stimulation with IL-33 compared to IL-33 only. Bone marrow and airway eosinophils were reduced in mice given rapamycin before IL-33-exposure compared to mice given IL-33 only. Bone marrow ILC2s responded to IL-33 in vivo with increased mTORC1 activity and rapamycin treatment successfully decreased IL-33-induced eosinophilic inflammation, possibly by inhibition of IL-5-producing bone marrow ILC2s. These findings highlight the importance of investigating specific cells and proinflammatory pathways as potential drivers of inflammatory diseases, including asthma.

Very-low-density lipoprotein receptor-enhanced lipid metabolism in pancreatic stellate cells promotes pancreatic fibrosis

Lipoprotein disorder is a common feature of chronic pancreatitis (CP); however, the relationship between lipoprotein disorder and pancreatic fibrotic environment is unclear. Here, we investigated the occurrence and mechanism of pancreatic stellate cell (PSC) activation by lipoprotein metabolites and the subsequent regulation of type 2 immune responses, as well as the driving force of fibrotic aggressiveness in CP. Single-cell RNA sequencing revealed the heterogeneity of PSCs and identified very-low-density lipoprotein receptor (VLDLR)⁺ PSCs that were characterized by a higher lipid metabolism. VLDLR promoted intracellular lipid accumulation, followed by interleukin-33 (IL-33) expression and release in PSCs. PSC-derived IL-33 strongly induced pancreatic group 2 innate lymphoid cells (ILC2s) to trigger a type 2 immune response accompanied by the activation of PSCs, eventually leading to fibrosis during pancreatitis. Our findings indicate that VLDLR-enhanced lipoprotein metabolism in PSCs promotes pancreatic fibrosis and highlight a dominant role of IL-33 in this pro-fibrotic cascade.

Association of Interleukin-33 with Recurrent Pregnancy Loss in Egyptian Women

Background

A successful pregnancy requires a distinct and complex immunological state. Cytokines appear to be critical for the establishment of a tolerogenic environment towards the semi-allogenic foetus during the foeto-maternal interphase, and a shift from a Th1- to a Th2-cytokine profile may be crucial. An imbalance of cytokines can be a significant factor in recurrent pregnancy loss (RPL). Interleukin-33 (IL-33) is a member of the IL- 1 cytokine family, involved in both the innate and adaptive immune responses coordinating immune cell function for a broad range of physiological and pathological processes, including the regulation of pregnancy outcome.

Objectives

The aim of this study was to investigate a possible association between IL-33 and RPL in Egyptian women.

Methods

The study was conducted on 66 Egyptian females recruited from Ain Shams University Specialized Hospital and 66 matched healthy non-pregnant females of typical childbearing age without a history of RPL. Serum IL-33 was measured in all subjects using a sandwich ELISA technique.

Results

Serum IL-33 levels were significantly higher in patients with RPL than in the healthy control group. In addition, in the patient group, there was a positive correlation between serum IL-33 level and both age and number of miscarriages and a negative correlation between serum IL-33 level and the number of deliveries.

Conclusion

In Egyptian women, serum levels of IL-33 are associated with RPL, thus IL-33 level could be a predictive biomarker for RPL in early pregnancy.

Schizophrenia and Alarmins

Schizophrenia, consisting of a group of severe psychiatric disorders with a complex etiology, is a leading cause of disability globally. Due to the lack of objective indicators, accurate diagnosis and selection of effective treatments for schizophrenia remain challenging. The association between schizophrenia and alarmins levels has been proposed for many years, but without solid evidence. Alarmins are prestored molecules that do not require processing and can be released upon cell death or damage, making them an ideal candidate for an early initiator of inflammation. Immunological biomarkers seem to be related to disease progression and treatment effectiveness. Several studies suggest strong associations among the high-mobility group box 1 protein (HMGB1), interleukin-1α, interleukin-33, S100B, heat-shock proteins, and uric acid with schizophrenic disorders. The purpose of this review is to discuss the evidence of central and peripheral immune findings in schizophrenia, their potential causes, and the effects of immunomodulatory therapies on symptoms and outline potential applications of these markers in managing the illness. Although there are currently no effective markers for diagnosing or predicting treatment effects in patients with schizophrenia, we believe that screening immune-inflammatory biomarkers that are closely related to the pathological mechanism of schizophrenia can be used for early clinical identification, diagnosis, and treatment of schizophrenia, which may lead to more effective treatment options for people with schizophrenia.

Interaction Between CD34+ Fibrocytes and Airway Smooth Muscle Promotes IL-8 Production and Akt/PRAS40/mTOR Signaling in Asthma

Background

The circulating progenitor cells of fibroblasts (fibrocytes) have been shown to infiltrate the airway smooth muscle compartment of asthma patients; however, the pathological significance of this discovery has yet to be elucidated. This study established a co-culture model of airway smooth muscle cells (ASMCs) and fibrocytes from asthmatic or normal subjects to evaluate innate cytokine production, corticosteroid responses, and signaling in ASMCs.

Methods

CD34⁺ fibrocytes were purified from peripheral blood of asthmatic (Global Initiative for Asthma treatment step 4–5) and normal subjects and cultured for 5∼7 days. In a transwell plate, ASMCs were co-cultured with fibrocytes at a ratio of 2:1, ASMCs were cultured alone (control condition), and fibrocytes were cultured alone for 48 h. Measurements were obtained of interleukin-8 (IL-8), IL-6, IL-17, thymic stromal lymphopoietin, and IL-33 levels in the supernatant and IL-33 levels in the cell lysate of the co-culture. Screening for intracellular signaling in the ASMCs after stimulation was performed using condition medium from the patients’ co-culture (PtCM) or IL-8. mRNA and western blot analysis were used to analyze AKT/mTOR signaling in ASMCs stimulated via treatment with PtCM or IL-8.

Results

Compared with ASMCs cultured alone, IL-8 levels in the supernatant and IL-33 levels in the ASMCs lysate were significantly higher in samples co-cultured from asthmatics, but not in those co-cultured from normal subjects. Corticosteroid-induced suppression of IL-8 production was less pronounced in ASMCs co-cultured with fibrocytes from asthma patients than in ASMCs co-cultured from normal subjects. ASMCs stimulated using PtCM and IL-8 presented elevating activated AKT substrate PRAS40. Treatment with IL-8 and PtCM increased mRNA expression of mTOR and P70S6 kinases in ASMCs. Treatment with IL-8 and PtCM also significantly increased phosphorylation of AKT and mTOR subtract S6 ribosomal protein in ASMCs.

Conclusion

The interaction between ASMCs and fibrocytes from asthmatic patients was shown to increase IL-8 and IL-33 production and promote AKT/mTOR signaling in ASMCs. IL-8 production in the co-culture from asthmatic patients was less affected by corticosteroid than was that in the co-culture from normal subjects. Our results elucidate the novel role of fibrocytes and ASMCs in the pathogenesis of asthma.

IL-33 and IL-10 Serum Levels Increase in MCI Patients Following Homotaurine Treatment

Homotaurine is a potential therapeutic compound for treatment of Alzheimer’s disease (AD), but its efficacy is still under investigation. Emerging data have shown that other than neuroprotective, homotaurine is endowed with anti-inflammatory activities, though with still unclear underlying mechanisms. Inflammation plays a critical role in the pathogenesis of AD and we previously suggested that homotaurine supplementation in patients with amnestic mild cognitive impairment (MCI) plays beneficial effects associated to a decrease in the circulating levels of the pro-inflammatory cytokine IL-18. Here we report that MCI patients supplemented with homotaurine for 12 months show elevated serum levels of IL-10 and IL-33, as compared to baseline, in addition to the described IL-18 decrease. Furthermore, we observed a significant positive correlation between IL-10 and IL-33 levels after treatment but not at the baseline, underlining the effectiveness of the compound in modulating both cytokines in an inter-related fashion and in regulating the pro/anti-inflammation balance. Furthermore, the elevation of both IL-10 and IL-33 is significantly associated with an improvement of episodic memory of treated patients, as measured by the Delayed Verbal Ray Test. In conclusion, our results confirm that homotaurine treatment exerts an overall anti-inflammatory action in MCI patients, based not only on the down-regulation of pro-inflammatory IL-18, but also on up-regulation of the anti-inflammatory IL-33 and IL-10 cytokines, which in turn are associated with an amelioration of patient’s cognitive functions. Future studies should be addressed to investigate the molecular mechanisms of homotaurine anti-inflammatory activity and its therapeutic exploitation in early AD.

Eosinophilic fasciitis induced by a game of drumming probably via type 2 innate immunity

We report a case of eosinophilic fasciitis triggered by strenuous physical activity, which did not relapse during the follow-up period. We ascertained that interleukin-33 (IL-33) was released from the vascular endothelial cells after intense exercise, inducing type 2 innate lymphocytes (ILC2) and causing fasciitis. A healthy woman experienced itching on both limbs a few hours after a game of drumming. Her hand, knee joints, and legs gradually swelled up with groove signs along the superficial veins. White blood cell and eosinophil counts were significantly elevated. Magnetic resonance imaging revealed a high signal at the fascia on both lower limbs. Histopathological findings of the left lower limb tissue specimen showed edematous fascia with eosinophils. No relapse of eosinophilic fasciitis was observed after finishing treatment with prednisolone. Immunological staining for IL-4, IL-5, IL-33, tumor necrosis factor-α, and interferon-γ was performed on the fascial tissue. Both IL-4 and IL-5 were stained on the lymphocytes at the muscle and fascia levels; however, CD3 and CD4 were unstained in these cells, suggesting that those cells were ILC2. Tumor necrosis factor-α and interferon-γ were unstained. Vascular endothelial cells in the fascia strongly expressed IL-33. Eosinophilic fasciitis may be associated with type 2 immunity triggered by IL-33 in the current case.

Evaluation of serum interleukin-33 and soluble suppression of tumorigenicity 2 (sST2) receptors in patients with and without periodontal disease

Context

: Interleukin-33 and its receptor soluble suppression of tumorigenicity 2.

(

sST2) play an important role in inflammation and its role in periodontal disease is yet unclear. The role of both IL-33 and sST2 together in periodontal disease as biomarkers has never been studied.

Aim

: To assess the levels of IL-33 and sST2 in serum samples of patients with periodontitis and healthy subjects.

Methods

: A total of 71 subjects (30 healthy subjects and 41 patients with periodontal disease) were included in the cross-sectional study. Community Periodontal Index (CPI) was used to assess periodontal health by utilizing a mouth mirror and a CPI probe. Venous blood was collected and serum was separated. Serum levels of IL-33 and sST2 were determined by the enzyme-linked immunosorbent assay (ELISA) assay.

Statistical Analysis

Graph Pad Prism 5 was used for statistical analysis. Mann Whitney test was applied to compare the two groups.

Results

: The level of IL-33 was not found to be elevated among healthy subjects and sST2 was found elevated among patients with periodontal disease. The serum concentration of IL-33 was found at 472 ± 114 pg/ml and 282 ± 77 pg/ml among healthy subjects and patients with periodontal disease respectively. Significantly higher values of sST2 at 28 ± 2 ng/ml were found among periodontal patients as compared to healthy subjects with values of 18 ± 1 ng/ml. No significant differences were noted between mild to moderate and severe periodontitis for IL-33 and sST2 between the two groups.

Conclusion

This study shows alteration in serum levels of IL-33 and sST2 in periodontitis patients. IL-33 and sST2 may be potential inflammatory markers of periodontitis. Further studies are required on a large sample size for better understanding. This pilot study is the first to assess the serum levels of both IL-33 and sST2 together among patients with and without periodontal disease.

Overexpression of Interleukin-33 in Recombinant Rabies Virus Enhances Innate and Humoral Immune Responses through Activation of Dendritic Cell-Germinal Center Reactions

Rabies is a zoonotic infectious disease caused by rabies virus (RABV), and its mortality rate is as high as 100%. Globally, an average of 60,000 people die from rabies each year. The most effective method to prevent and limit rabies is vaccination, but it is currently expensive and inefficient, consisting of a 3-dose series of injections and requiring to be immunized annually. Therefore, it is urgent to develop a single dose of long-acting rabies vaccine. In this study, recombinant rabies virus (rRABV) overexpressing interleukin-33 (IL-33) was constructed and designated as rLBNSE-IL33, and its effect was evaluated in a mouse model. The results showed that rLBNSE-IL33 could enhance the quick production of RABV-induced immune antibodies as early as three days post immunization (dpi) through the activation of dendritic cells (DCs), a component of the innate immune system. Furthermore, rLBNSE-IL33 induced high-level virus-neutralizing antibodies (VNA) production that persisted for 8 weeks by regulating the T cell-dependent germinal center (GC) reaction, thus resulting in better protection against rabies. Our data suggest the IL-33 is a novel adjuvant that could be used to enhance innate and humoral immune responses by activating the DC-GC reaction, and thus, rLBNSE-IL33 could be developed as a safe and effective vaccine for animals.

Could Interleukin-33 (IL-33) Govern the Outcome of an Equine Influenza Virus Infection? Learning from Other Species

Influenza A viruses (IAVs) are important respiratory pathogens of horses and humans. Infected individuals develop typical respiratory disorders associated with the death of airway epithelial cells (AECs) in infected areas. Virulence and risk of secondary bacterial infections vary among IAV strains. The IAV non-structural proteins, NS1, PB1-F2, and PA-X are important virulence factors controlling AEC death and host immune responses to viral and bacterial infection. Polymorphism in these proteins impacts their function. Evidence from human and mouse studies indicates that upon IAV infection, the manner of AEC death impacts disease severity. Indeed, while apoptosis is considered anti-inflammatory, necrosis is thought to cause pulmonary damage with the release of damage-associated molecular patterns (DAMPs), such as interleukin-33 (IL-33). IL-33 is a potent inflammatory mediator released by necrotic cells, playing a crucial role in anti-viral and anti-bacterial immunity. Here, we discuss studies in human and murine models which investigate how viral determinants and host immune responses control AEC death and subsequent lung IL-33 release, impacting IAV disease severity. Confirming such data in horses and improving our understanding of early immunologic responses initiated by AEC death during IAV infection will better inform the development of novel therapeutic or vaccine strategies designed to protect life-long lung health in horses and humans, following a One Health approach.

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.