ST2-deficient Mice Research Articles

Crosstalk between Interleukin-1 Receptor-Like 1 and Transforming Growth Factor-β Receptor Signaling Promotes Renal Fibrosis

IL-33, a member of the IL-1 family, acts as an alarmin in immune response. Epithelial-mesenchymal transition and transforming growth factor-β (TGF-β)–induced fibroblast activation are key events in the development of renal interstitial fibrosis. The current study found increased expression of IL-33 and interleukin-1 receptor-like 1 (IL1RL1, alias ST2), the receptor for IL-33, in human fibrotic renal tissues. In addition, IL-33– or ST2-deficient mice showed significantly reduced levels of fibronectin, α-smooth muscle actin, and vimentin, and increased E-cadherin levels. In HK-2 cells, IL-33 promotes the phosphorylation of the TGF-β receptor (TGF-βR), Smad2, and Smad3, and the production of extracellular matrix (ECM), with reduced expression of E-cadherin. Blocking TGF-βR signaling or suppressing ST2 expression impeded Smad2 and Smad3 phosphorylation, thereby reducing ECM production, suggesting that IL-33–induced ECM synthesis requires cooperation between the two pathways. Mechanistically, IL-33 treatment induced a proximate interaction between ST2 and TGF-βRs, activating downstream Smad2 and Smad3 for ECM production in renal epithelial cells. Collectively, this study identified a novel and essential role for IL-33 in promoting TGF-β signaling and ECM production in the development of renal fibrosis. Therefore, targeting IL-33/ST2 signaling may be an effective therapeutic strategy for renal fibrosis.

Staphylococcus aureus δ-toxin present on skin promotes the development of food allergy in a murine model.

Patients with food allergy often suffer from atopic dermatitis, in which Staphylococcus aureus colonization is frequently observed. Staphylococcus aureus δ-toxin activates mast cells and promotes T helper 2 type skin inflammation in the tape-stripped murine skin. However, the physiological effects of δ-toxin present on the steady-state skin remain unknown. We aimed to investigate whether δ-toxin present on the steady-state skin impacts the development of food allergy. The non-tape-stripped skins of wild-type, KitW-sh/W-sh, or ST2-deficient mice were treated with ovalbumin (OVA) with or without δ-toxin before intragastric administration of OVA. The frequency of diarrhea, numbers of jejunum or skin mast cells, and serum levels of OVA-specific IgE were measured. Conventional dendritic cell 2 (cDC2) in skin and lymph nodes (LN) were analyzed. The cytokine levels in the skin tissues or culture supernatants of δ-toxin-stimulated murine keratinocytes were measured. Anti-IL-1α antibody-pretreated mice were analyzed. Stimulation with δ-toxin induced the release of IL-1α, but not IL-33, in murine keratinocytes. Epicutaneous treatment with OVA and δ-toxin induced the local production of IL-1α. This treatment induced the translocation of OVA-loaded cDC2 from skin to draining LN and OVA-specific IgE production, independently of mast cells and ST2. This resulted in OVA-administered food allergic responses. In these models, pretreatment with anti-IL-1α antibody inhibited the cDC2 activation and OVA-specific IgE production, thereby dampening food allergic responses. Even without tape stripping, δ-toxin present on skin enhances epicutaneous sensitization to food allergen in an IL-1α-dependent manner, thereby promoting the development of food allergy.

Acquired resistance against skin penetration by Strongylodies rattiis dependent on IL-33 expressing APCs

Abstract Interleukin 33 (IL-33) is an alarmin cytokine released from damaged epithelia that is essential for protection against gastrointestinal (GI) helminth (worm) infection, but whether IL-33 serves any role in cutaneous immunity against parasites remains unclear. While epithelial cells are considered the predominant source of IL-33, our recent work demonstrates that CD11c+ myeloid antigen presenting cells can express IL-33 to shape Type 2 immunity. We developed a percutaneous infection model using Strongylodies ratti, a rodent-specific GI helminth, to better understand mechanisms of host protection and the potential role for IL-33. Data show that C57BL/6 mice develop resistance to percutaneous infection upon secondary challenge, but IL-33 deficient mice lack this capacity. Surprisingly, mice with a selective IL-33 deficiency only in myeloid APC (CD11c Cre) also failed to develop secondary resistance to S. ratti, suggesting myeloid-derived IL-33 is essential for cutaneous immunity. Mechanistically, we find that loss of myeloid IL-33 impairs recruitment of gd T cells that express the IL-33 receptor ST2 and gene deficient mice that lack all gd T cells show defective protective immunity against S. ratti. Moreover, we propose that IL-33 drives a noncanonical Type 2 immunity, because mice lacking the Type 2 transcription factor STAT6 (Signal transducer and activator of transcription 6), have no defects in primary or secondary cutaneous immunity. Our work implies that myeloid APCs are a necessary source of IL-33 that drives acquired immunity against helminths, potentially through regulating gd T cell effector function(s). Ongoing studies seek to understand how myeloid APC derived IL-33 controls gd T cells to promote cutaneous immunity. NIH (R01 AI095289 and R01 GM083204) NSF GFRP

Full-length IL-33 augments pulmonary fibrosis in an ST2- and Th2-independent, non-transcriptomic fashion

Mature IL-33 (MIL33) acting through its receptor, ST2, is known to regulate fibrosis. The precursor, full-length IL-33 (FLIL33), may function differently from MIL33 and independently of ST2. Here we report that genetic deletion of either IL-33 or ST2 attenuates pulmonary fibrosis in the bleomycin model, as does Cre-induced IL-33 deficiency in response to either acute or chronic bleomycin challenge. However, adenovirus-mediated gene delivery of FLIL33, but not MIL33, to the lungs of either wild-type or ST2-deficient mice potentiates the profibrotic effect of bleomycin without inducing a Th2 phenotype. In cultured mouse lung cells, FLIL33 overexpression induces moderate and distinct transcriptomic changes compared with a robust response induced by MIL33, whereas ST2 deletion abrogates the effects of both IL-33 forms. Thus, FLIL33 may contribute to fibrosis in an ST2-independent, Th2-independent, non-transcriptomic fashion, suggesting that pharmacological targeting of both FLIL33 and MIL33 may prove efficacious in patients with pulmonary fibrosis.

Interleukin-33 protects mice against hindlimb ischemic injury by enhancing endothelial angiogenesis

Peripheral vascular disease usually leads to vascular injury and inflammatory reaction, and the main therapeutic measures are improving angiogenesis and restoring blood flow. Interleukin-33 (IL-33) is a pleiotropic cytokine implicated in immune responses and tissue repair. Here, we explore the effect of IL-33 in hindlimb ischemic injury and elucidate the potential mechanisms of action. The expression of IL-33 and its receptor ST2 were obviously elevated in ischemic hindlimb of mice underwent ligation surgery. Exogenous IL-33 apparently facilitated blood flow restoration in ischemic hindlimb, whereas ST2-deficient mice displayed severe defects in ischemic hindlimb repair. The activation of IL-33/ST2 signaling contributed to revascularization in ischemic hindlimb, which was related to modulation of proangiogenic function of endothelial cells. Further ex vivo and in vitro studies revealed that IL-33 clearly accelerated angiogenesis by Matrigel plug and tube formation assays. Mechanically, the angiogenic function of IL-33 is involved in regulation of Akt/eNOS pathway. All together, these findings imply that IL-33-mediated endothelial angiogenesis may represent a prospective effective therapy for hindlimb ischemic damage.

IL-33/ST2 Axis Protects Against Traumatic Brain Injury Through Enhancing the Function of Regulatory T Cells.

Traumatic brain injury (TBI) is a devastating condition due to its long-term sequelae on neurological functions. Inflammatory responses after TBI are critical for injury expansion and repair. Recent research in central nervous system (CNS) disorders reveals the importance of IL-33 and its receptor (ST2) as an alarmin system to initiate immune responses. This study explored the role of IL-33/ST2 signaling in TBI. TBI was induced in adult male C57BL/6J mice using a controlled cortical impact (CCI) model. We found that the expression of IL-33 increased in the injured brain and blood, and ST2 was elevated in the circulating and infiltrating regulatory T cells (Tregs) early after TBI. ST2 deficient mice exhibited reduced Treg numbers in the blood and brain 5 days after TBI. The brain lesion size was enlarged in ST2 knockout mice, which was accompanied by deteriorated sensorimotor function 5 days after TBI. In contrast, post-TBI treatment with IL-33 (2 μg/30 g body weight, intranasal) for 3 days significantly reduced brain lesion size and improved neurological functions 5 days after TBI. Meanwhile, IL-33 treatment increased ST2 expression in circulating and brain infiltrating Tregs. To further explore the involvement of Tregs in IL-33/ST2-mediated neuroprotection, Tregs were depleted by CD25 antibody injection. The absence of Tregs significantly reduced the protective effect of IL-33 after TBI. In vitro study confirmed that IL-33 (50 ng/ml) increased the production of IL-10 and TGFβ from activated Tregs and boosted the inhibitory effect of Tregs on T effector cell proliferation. Taken together, this study suggests that the activation of IL-33/ST2 signaling reduces brain lesion size and alleviates functional deficits after TBI at least partially through regulating the Treg response. IL-33 may represent a new immune therapeutic strategy to improve TBI outcomes.

Excessive activation of IL-33/ST2 in cancer-associated fibroblasts promotes invasion and metastasis in ovarian cancer.

Ovarian cancer is highly prevalent and has high mortality rates due to metastasis and relapse. The cross communication between cancer-associated fibroblasts (CAFs) and cancer-associated macrophages (CAMs) in the ovarian tumor microenvironment leads to cancer cell invasion and metastasis. However, the role of overproduction of IL-33/ST2 in the CAFs of ovarian cancer is still unclear. The expression of IL-33, ST2, apoptosis-related proteins and epithelial-mesenchymal transition (EMT) markers was measured by western blotting. Primary normal fibroblasts and CAFs from ovarian cancerous tissue were isolated and cultured in vitro, and the medium was used to stimulate blood-derived monocytes. Flow cytometry analysis was used to detect the frequency of M2-like macrophages in blood-derived monocytes from patients with ovarian cancer. Cell invasion were evaluated using Transwell assays. A xenograft model was used to study tumor growth in ST2-knockout and wild-type NOD-SCID mice. The results demonstrated higher expression of IL-33 and ST2 in carcinoma tissues compared with in para-carcinoma tissues, and there was a survival improvement associated with elevated IL-33. IL-33 and culture supernatants from CAFs, rather than normal ovarian fibroblasts, led to a higher expression of M2 macrophage marker genes in human blood-derived monocytes. Invasion and migration were aggravated in COC1 cells co-cultured with CAF-induced CAMs, and the EMT marker genes were upregulated. It was reported that EMT marker genes were downregulated and tumor volumes were significantly reduced in ST2-deficient mice. Overall, the IL-33/ST2 axis in ovarian cancer might integrate IL-33-expressing CAFs with M2 type-like CAMs, which aggravated invasion and metastasis by promoting EMT.

GRK2 regulates group 2 innate lymphoid cell mobilization in sepsis

BackgroundSepsis induces group 2 innate lymphoid cell (ILC2) expansion in the lung. However, the origin of these lung-recruited ILC2 and the mechanism of ILC2 expansion are unclear. This study aims to determine the origin of lung-recruited ILC2 and its underlying mechanism in sepsis.MethodsSepsis was induced by cecal ligation and puncture (CLP) model in wild-type, IL-33-deficient and ST2-deficient mice. The frequency, cell number and C-X-C chemokine receptor 4 (CXCR4) expression of ILC2 in bone marrow (BM), blood and lung were measured by flow cytometry. In the in vitro studies, purified ILC2 progenitor (ILC2p) were challenged with IL-33 or G protein-coupled receptor kinase 2 (GRK2) inhibitor, the CXCR4 expression and GRK2 activity were detected by confocal microscopy or flow cytometry.ResultsWe show that IL-33 acts through its receptor, ST2, on BM ILC2p to induce GRK2 expression and subsequent downregulation of cell surface expression of CXCR4, which results in decreasing retention of ILC2p in the BM and promoting expansion of ILC2 in the lung. Importantly, we demonstrate that reduced IL-33 level in aging mice contributes to impaired ILC2 mobilization from BM and accumulation in the lung following sepsis.ConclusionThis study identifies a novel pathway in regulating ILC2p mobilization and expansion during sepsis and indicates BM as the main source of ILC2 in the lung following sepsis.

IL-33/ST2 axis deficiency exacerbates neutrophil-dominant allergic airway inflammation.

ObjectiveThe IL‐33/ST2 axis has been extensively investigated in type 2 eosinophilic inflammation. Here, we aimed to investigate the role of the IL‐33/ST2 axis in neutrophil‐dominant allergic airway inflammation.MethodsHouse‐dust mite (HDM) extract and lipopolysaccharide (LPS) were administered to establish a murine model of neutrophil‐dominant allergic airway inflammation. The formation of neutrophilic extracellular traps (NETs) in the lung tissues was demonstrated by immunofluorescence imaging. Mature IL‐33 in bronchoalveolar lavage fluid (BALF) was detected by Western blotting. The neutrophilic chemokine KC produced by bone marrow‐derived macrophages (BMDMs) or primary alveolar epithelial cells was measured with a commercial ELISA kit.ResultsIn the present study, we observed neutrophilic inflammation and tight junction damage in the lungs of mice sensitised with HDM and LPS. Furthermore, sensitisation with HDM and LPS resulted in the formation of NETs, accompanied by increased levels of mature IL‐33 in the BALF. Moreover, LPS damaged the epithelial tight junction protein occludin directly or indirectly by inducing NET formation. Surprisingly, IL‐33 deficiency augmented neutrophilia and epithelial barrier injury in the lungs of mice after sensitisation with HDM and LPS. Similarly, the absence of ST2 exacerbated the neutrophilic inflammatory response, decreased the expression of occludin and exacerbated the severity of neutrophil‐dominant allergic airway inflammation in an HDM/LPS‐induced mouse model. Mechanistically, BMDMs and alveolar epithelial cells from IL‐33‐ or ST2‐deficient mice tended to produce higher levels of the neutrophilic chemokine KC.ConclusionsThese results demonstrated that the IL‐33/ST2 axis may play a protective role in neutrophil‐dominant allergic airway inflammation.

IL-33-ST2 axis regulates myeloid cell differentiation and activation enabling effective club cell regeneration

Evidence points to an indispensable function of macrophages in tissue regeneration, yet the underlying molecular mechanisms remain elusive. Here we demonstrate a protective function for the IL-33-ST2 axis in bronchial epithelial repair, and implicate ST2 in myeloid cell differentiation. ST2 deficiency in mice leads to reduced lung myeloid cell infiltration, abnormal alternatively activated macrophage (AAM) function, and impaired epithelial repair post naphthalene-induced injury. Reconstitution of wild type (WT) AAMs to ST2-deficient mice completely restores bronchial re-epithelialization. Central to this mechanism is the direct effect of IL-33-ST2 signaling on monocyte/macrophage differentiation, self-renewal and repairing ability, as evidenced by the downregulation of key pathways regulating myeloid cell cycle, maturation and regenerative function of the epithelial niche in ST2−/− mice. Thus, the IL-33-ST2 axis controls epithelial niche regeneration by activating a large multi-cellular circuit, including monocyte differentiation into competent repairing AAMs, as well as group-2 innate lymphoid cell (ILC2)-mediated AAM activation.

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.

Pulmonary IL-33 orchestrates innate immune cells to mediate respiratory syncytial virus-evoked airway hyperreactivity and eosinophilia.

Respiratory syncytial virus (RSV) infection is epidemiologically linked to asthma. During RSV infection, IL-33 is elevated and promotes immune cell activation, leading to the development of asthma. However, which immune cells are responsible for triggering airway hyperreactivity (AHR), inflammation and eosinophilia remained to be clarified. We aimed to elucidate the individual roles of IL-33-activated innate immune cells, including ILC2s and ST2+ myeloid cells, in RSV infection-triggered pathophysiology. The role of IL-33/ILC2 axis in RSV-induced AHR inflammation and eosinophilia were evaluated in the IL-33-deficient and YetCre-13 Rosa-DTA mice. Myeloid-specific, IL-33-deficient or ST2-deficient mice were employed to examine the role of IL-33 and ST2 signaling in myeloid cells. We found that IL-33-activated ILC2s were crucial for the development of AHR and airway inflammation, during RSV infection. ILC2-derived IL-13 was sufficient for RSV-driven AHR, since reconstitution of wild-type ILC2 rescued RSV-driven AHR in IL-13-deficient mice. Meanwhile, myeloid cell-derived IL-33 was required for airway inflammation, ST2+ myeloid cells contributed to exacerbation of airway inflammation, suggesting the importance of IL-33 signaling in these cells. Local and peripheral eosinophilia is linked to both ILC2 and myeloid IL-33 signaling. This study highlights the importance of IL-33-activated ILC2s in mediating RSV-triggered AHR and eosinophilia. In addition, IL-33 signaling in myeloid cells is crucial for airway inflammation.

The interleukin-33 receptor contributes to pulmonary responses to ozone in male mice: role of the microbiome

BackgroundInterleukin-33 is released in the airways following acute ozone exposure and has the ability to cause airway hyperresponsiveness, a defining feature of asthma. Ozone causes greater airway hyperresponsiveness in male than female mice. Moreover, sex differences in the gut microbiome account for sex differences in this response to ozone. The purpose of this study was to determine whether there were sex differences in the role of interleukin-33 in ozone-induced airway hyperresponsiveness and to examine the role of the microbiome in these events.MethodsWildtype mice and mice genetically deficient in ST2, the interleukin-33 receptor, were housed from weaning with either other mice of the same genotype and sex, or with mice of the same sex but opposite genotype. At 15 weeks of age, fecal pellets were harvested for 16S rRNA sequencing and the mice were then exposed to air or ozone. Airway responsiveness was measured and a bronchoalveolar lavage was performed 24 h after exposure.ResultsIn same-housed mice, ozone-induced airway hyperresponsiveness was greater in male than female wildtype mice. ST2 deficiency reduced ozone-induced airway hyperresponsiveness in male but not female mice and abolished sex differences in the response to ozone. However, sex differences in the role of interleukin-33 were unrelated to type 2 cytokine release: ozone-induced increases in bronchoalveolar lavage interleukin-5 were greater in females than males and ST2 deficiency virtually abolished interleukin-5 in both sexes. Since gut microbiota contribute to sex differences in ozone-induced airway hyperresponsiveness, we examined the role of the microbiome in these ST2-dependent sex differences. To do so, we cohoused wildtype and ST2 deficient mice, a situation that allows for transfer of microbiota among cage-mates. Cohousing altered the gut microbial community structure, as indicated by 16S rRNA gene sequencing of fecal DNA and reversed the effect of ST2 deficiency on pulmonary responses to ozone in male mice.ConclusionsThe data indicate that the interleukin-33 /ST2 pathway contributes to ozone-induced airway hyperresponsiveness in male mice and suggest that the role of interleukin-33 is mediated at the level of the gut microbiome.

Blockade of IL-33R/ST2 Signaling Attenuates Toxoplasma gondii Ileitis Depending on IL-22 Expression.

Oral T. gondii infection (30 cysts of 76K strain) induces acute lethal ileitis in sensitive C57BL/6 (B6) mice with increased expression of IL-33 and its receptor ST2 in the ileum. Here we show that IL-33 is involved in ileitis, since absence of IL-33R/ST2 attenuated neutrophilic inflammation and Th1 cytokines upon T. gondii infection with enhanced survival. Blockade of ST2 by neutralizing ST2 antibody in B6 mice conferred partial protection, while rmIL-33 aggravated ileitis. Since IL-22 expression further increased in absence of ST2, we blocked IL-22 by neutralizing antibody, which abrogated protection from acute ileitis in ST2 deficient mice. In conclusion, severe lethal ileitis induced by oral T. gondii infection is attenuated by blockade of ST2 signaling and may be mediated in part by endogenous IL-22.

ST2 regulates bone loss in a site-dependent and estrogen-dependent manner.

Interleukin-33 (IL-33) and its receptor, ST2, are implicated in bone remodeling. The lack of estrogen after menopause results in an accelerated bone loss. Here we investigated the role of ST2 in the bone loss induced by estrogen deficiency. ST2-deficient mice (ST2-/- ) and their littermates (wildtype [WT]) were ovariectomized (OVX), while ovary-intact mice were used as controls. Bone sites were analyzed by microcomputed tomography, histomorphometry, and quantitative real-time polymerase chain reaction (qPCR). Deletion of IL-33 or ST2 resulted in a similar bone loss in the femur and maxilla. Ovariectomy in WT mice caused bone loss in the same areas. The lack of ST2 in OVX mice did not alter bone remodeling in the femur but prevented bone loss in the maxilla. Consistently, ovariectomy increased the IL-33 messenger RNA (mRNA) levels in the maxilla but not in the femur. Under mechanical stimulation, ovariectomy and ST2 deletion independently increased bone remodeling induced by orthodontic tooth movement, which was also associated with a greater number of osteoclasts and a reduced number of osteoblasts in the maxillary bone. ST2-/- OVX mice, however, displayed twice as many osteoblasts as that of WT OVX mice. Ovariectomy and ST2 deletion differently altered the cytokine mRNA levels in the maxilla. Remarkably, interleukin-10 expression was decreased in both WT OVX and ST2-/- mice, and this reduction was completely restored in ST2-/- OVX mice. The results demonstrate that estrogen and IL33/ST2 independently protect against bone loss. However, the ovariectomy-induced bone loss is IL-33/ST2-dependent in the maxilla but not in the femur, indicating a bimodal and site-specific role of ST2 in bone remodeling.

The IL-33 Receptor ST2 Regulates Pulmonary Inflammation and Fibrosis to Bleomycin.

Idiopathic pulmonary fibrosis is a progressive, devastating, and yet untreatable fibrotic disease of unknown origin. Interleukin-33 (IL-33), an IL-1 family member acts as an alarmin with pro-inflammatory properties when released after stress or cell death. Here, we investigated the role of IL-33 in the bleomycin (BLM)-induced inflammation and fibrosis model using mice IL-33 receptor [chain suppression of tumorigenicity 2 (ST2)] mice compared with C57BL/6 wild-type mice. Unexpectedly, 24 h post-BLM treatment ST2-deficient mice displayed augmented inflammatory cell recruitment, in particular by neutrophils, together with enhanced levels of chemokines and remodeling factors in the bronchoalveolar space and/or the lungs. At 11 days, lung remodeling and fibrosis were decreased with reduced M2 macrophages in the lung associated with M2-like cytokine profile in ST2-deficient mice, while lung cellular inflammation was decreased but with fluid retention (edema) increased. In vivo magnetic resonance imaging (MRI) analysis demonstrates a rapid development of edema detectable at day 7, which was increased in the absence of ST2. Our results demonstrate that acute neutrophilic pulmonary inflammation leads to the development of an IL-33/ST2-dependent lung fibrosis associated with the production of M2-like polarization. In addition, non-invasive MRI revealed enhanced inflammation with lung edema during the development of pulmonary inflammation and fibrosis in absence of ST2.

IL33 signaling contributes to diesel exhaust particles-induced asthma exacerbations by promoting innate and adaptive type 2 and type 17 responses

Abstract Rationale Exposure to traffic pollution, notably diesel exhaust particles (DEP), promote asthma exacerbations and a mixed Th2/Th17 response. The contribution of TSLP and IL33, generated by sressed lung epithelial cells, to DEP-induced asthma exacerbations remains poorly understood. Method We used TSLP receptor deficient mice, mice lacking the IL33 receptor (ST2) and Balb/c control mice and exposed them 9 times over a 3-week period to saline, house dust mite extract (HDM; 10ug) and/or DEP (100ug). Seven weeks later some mice received a single HDM challenge to assess memory responses. Airway hyper-responsiveness (AHR), BALF inflammation and lung T-cells and ILC subsets were assessed after primary and recall responses. Results DEP co-exposure with HDM exacerbates HDM-induced AHR and Th2 responses. AHR was similar between TSLPR deficient mice and control mice exposed to HDM+DEP. In contrast, AHR was significantly decreased in ST2-deficient mice compared to wild type mice. The impact of ST2 deficiency on lung accumulation of ILC2 and Th2 cells was modest. Following HDM+DEP co-exposures, decreases in ILC3, γδ T-cells and Th17 cells were observed in the lungs of ST2 deficient mice compared to control mice. The in vivo HDM recall response recapitulated the impaired AHR associated with decreases in IL17A secreting cells observed after the primary response in HDM+DEP exposed ST2 deficient mice. Finally, a decrease in lung levels of pathogenic IL5/IL13/IL17A producing CD4+ T-cells was observed after the primary and recall responses. Conclusions IL33 but not TSLP contributes to DEP-induced asthma exacerbations by affecting the accumulation of innate and adaptive type 2 and type 17 cells, notably pathogenic Th2/Th17 cells.

The Role of Interleukin-33 in Pathogenesis of Bronchial Asthma. New Experimental Data.

Interleukin-33 (IL-33) belongs to the IL-1 cytokine family and plays an important role in modulating immune system by inducing Th2 immune response via the ST2 membrane receptor. Epithelial cells are the major producers of IL-33. However, IL-33 is also secreted by other cells, e.g., bone marrow cells, dendritic cells, macrophages, and mast cells. IL-33 targets a broad range of cell types bearing the ST2 surface receptor. Many ST2-positive cells, such as Th2 cells, mast cells, basophils, and eosinophils, are involved in the development of allergic bronchial asthma (BA). This suggests that IL-33 directly participates in BA pathogenesis. Currently, the role of IL-33 in pathogenesis of inflammatory disorders, including BA, has been extensively investigated using clinical samples collected from patients, as well as asthma animal models. In particular, numerous studies on blocking IL-33 and its receptor by monoclonal antibodies in asthma mouse model have been performed over the last several years; IL-33- and ST2-deficient transgenic mice have also been generated. In this review, we summarized and analyzed the data on the role of IL-33 in BA pathogenesis and the prospects for creating new treatments for BA.

IL-33 signalling in liver immune cells enhances drug-induced liver injury and inflammation.

The aim of this study was to investigate the contribution of IL-33/ST2 axis in the onset and progression of acute liver injury using a mice model of drug-induced liver injury (DILI). DILI was induced by overdose administration of acetaminophen (APAP) by oral gavage in wild-type BALB/c, ST2-deficient mice and in different bone marrow chimeras. Neutrophils were depleted by anti-Ly6G and macrophages with clodronate liposomes (CLL). Blood and liver were collected for biochemical, immunologic and genetic analyses. Mice were imaged by confocal intravital microscopy and liver non-parenchymal cells and hepatocytes were isolated for flow cytometry, genetic and immunofluorescence studies. Acetaminophen overdose caused a massive necrosis and accumulation of immune cells within the liver, concomitantly with IL-33 and chemokine release. Liver non-parenchymal cells were the major sensors for IL-33, and amongst them, neutrophils were the major players in amplification of the inflammatory response triggered by IL-33/ST2 signalling pathway. Blockage of IL-33/ST2 axis reduces APAP-mediated organ injury by dampening liver chemokine release and activation of resident and infiltrating liver non-parenchymal cells.

IL-33 restricts tumor growth and inhibits pulmonary metastasis in melanoma-bearing mice through eosinophils

ABSTRACT The alarmin IL-33 is an IL-1 family member that stimulates pleiotropic immune reactions depending on the target tissue and microenvironmental factors. In this study, we have investigated the role of IL-33/ST2 axis in antitumor response to melanoma. Injection of IL-33 in mice-bearing subcutaneous B16.F10 melanoma resulted in significant tumor growth delay. This effect was associated with intratumoral accumulation of CD8+ T cells and eosinophils, decrease of immunosuppressive myeloid cells, and a mixed Th1/Th2 cytokine expression pattern with local and systemic activation of CD8+ T and NK cells. Moreover, intranasal administration of IL-33 determined ST2-dependent eosinophil recruitment in the lung that prevented the onset of pulmonary metastasis after intravenous injection of melanoma cells. Accordingly, ST2-deficient mice developed pulmonary metastasis at higher extent than wild-type counterparts, associated with lower eosinophil frequencies in the lung. Of note, depletion of eosinophils by in vivo treatment with anti-Siglec-F antibody abolished the ability of IL-33 to both restrict primary tumor growth and metastasis formation. Finally, we show that IL-33 is able to activate eosinophils resulting in efficient killing of target melanoma cells, suggesting a direct antitumor activity of eosinophils following IL-33 treatment. Our results advocate for an eosinophil-mediated antitumoral function of IL-33 against melanoma, thus opening perspectives for novel cancer immunotherapy strategies.