Floxed Il1rl2 Locus with mCherry Reporter Element Reveals Distinct Expression Patterns of the IL-36 Receptor in Barrier Tissues.

IL-36 cytokines are emerging as beneficial in immunity against pathogens and cancers but can also be detrimental when dysregulated in autoimmune and autoinflammatory conditions. Interest in targeting IL-36 activity for therapeutic purposes is rapidly growing, yet many unknowns about the functions of these cytokines remain. Thus, the availability of robust research tools is essential for both fundamental basic science and pre-clinical studies to fully access outcomes of any manipulation of the system. For this purpose, a floxed Il1rl2, the gene encoding the IL-36 receptor, mouse strain was developed to facilitate the generation of conditional knockout mice. The targeted locus was engineered to contain an inverted mCherry reporter sequence that upon Cre-mediated recombination will be flipped and expressed under the control of the endogenous Il1rl2 promoter. This feature can be used to confirm knockout in individual cells but also as a reporter to determine which cells express the IL-36 receptor IL-1RL2. The locus was confirmed to function as intended and further used to demonstrate the expression of IL-1RL2 in barrier tissues. Il1rl2 expression was detected in leukocytes in all barrier tissues. Interestingly, strong expression was observed in epithelial cells at locations in direct contact with the environment such as the skin, oral mucosa, the esophagus, and the upper airways, but almost absent from epithelial cells at more inward facing sites, including lung alveoli, the small intestine, and the colon. These findings suggest specialized functions of IL-1RL2 in outward facing epithelial tissues and cells. The generated mouse model should prove valuable in defining such functions and may also facilitate basic and translational research.

Interleukin-33 ameliorates perioperative neurocognitive disorders by modulating microglial state.

Perioperative neurocognitive disorders (PND) are cognitive dysfunctions that usually occur in elderly patients after anesthesia and surgery. Microglial overactivation is a key underlying mechanism. Interleukin-33 (IL-33) is a member of the IL-1 family that orchestrates microglial function. In the present study, we explored how IL-33, which regulates microglia, contributes to cognitive improvement in a male mouse model of PND. An exploratory laparotomy was performed to establish a PND model. The expression levels of IL-33 and its receptor ST2 were evaluated using Western blot. IL-33/ST2 secretion, microglial density, morphology, phagocytosis of synapse, and proliferation, and dystrophic microglia were assessed using immunofluorescence. Synaptic plasticity was measured using Golgi staining and long-term potentiation. The Morris water maze and open field test were used to evaluate cognitive function and anxiety. Hippocampal expression of IL-33 and ST2 were elevated on postoperative day 3. We confirmed that IL-33 was secreted by astrocytes and neurons, whereas ST2 mainly colocalized with microglia. IL-33 treatment induced microgliosis after anesthesia and surgery. These microglia had larger soma sizes and shorter and fragmented branches. Compared to the Surgery group, IL-33 treatment reduced the synaptic phagocytosis of microglia and increased microglial proliferation and dystrophic microglia. IL-33 treatment also reversed the impaired synaptic plasticity and cognitive function caused by anesthesia and surgery. In conclusion, these results indicate that IL-33 plays a key role in regulating microglial state and synaptic phagocytosis in a PND mouse model. IL-33 treatment has a therapeutic potential for improving cognitive dysfunction in PND.

IL-33 controls IL-22-dependent antibacterial defense by modulating the microbiota.

IL-22 plays a critical role in defending against mucosal infections, but how IL-22 production is regulated is incompletely understood. Here, we show that mice lacking IL-33 or its receptor ST2 (IL-1RL1) were more resistant to Streptococcus pneumoniae lung infection than wild-type animals and that single-nucleotide polymorphisms in IL33 and IL1RL1 were associated with pneumococcal pneumonia in humans. The effect of IL-33 on S. pneumoniae infection was mediated by negative regulation of IL-22 production in innate lymphoid cells (ILCs) but independent of ILC2s as well as IL-4 and IL-13 signaling. Moreover, IL-33's influence on IL-22-dependent antibacterial defense was dependent on housing conditions of the mice and mediated by IL-33's modulatory effect on the gut microbiota. Collectively, we provide insight into the bidirectional crosstalk between the innate immune system and the microbiota. We conclude that both genetic and environmental factors influence the gut microbiota, thereby impacting the efficacy of antibacterial immune defense and susceptibility to pneumonia.

IL-33-ST2 signaling in fibro-adipogenic progenitors alleviates immobilization-induced muscle atrophy in mice.

BACKGROUND: The regenerative and adaptive capacity of skeletal muscles reduces with age, leading to severe disability and frailty in the elderly. Therefore, development of effective therapeutic interventions for muscle wasting is important both medically and socioeconomically. In the present study, we aimed to elucidate the potential contribution of fibro-adipogenic progenitors (FAPs), which are mesenchymal stem cells in skeletal muscles, to immobilization-induced muscle atrophy. METHODS: Young (2-3 months), adult (12-14 months), and aged (20-22 months) mice were used for analysis. Muscle atrophy was induced by immobilizing the hind limbs with a steel wire. FAPs were isolated from the hind limbs on days 0, 3, and 14 after immobilization for transcriptome analysis. The expression of ST2 and IL-33 in FAPs was evaluated by flow cytometry and immunostaining, respectively. To examine the role of IL-33-ST2 signaling in vivo, we intraperitoneally administered recombinant IL-33 or soluble ST2 (sST2) twice a week throughout the 2-week immobilization period. After 2-week immobilization, the tibialis anterior muscles were harvested and the cross-sectional area of muscle fibers was evaluated. RESULTS: The number of FAPs increased with the progression of muscle atrophy after immobilization in all age-groups. Transcriptome analysis of FAPs collected before and after immobilization revealed that Il33 and Il1rl1 transcripts, which encode the IL-33 receptor ST2, were transiently induced in young mice and, to a lesser extent, in aged mice. The number of FAPs positive for ST2 increased after immobilization in young mice. The number of ST2-positive FAPs also increased after immobilization in aged mice, but the difference from the baseline was not statistically significant. Immunostaining for IL-33 in the muscle sections revealed a significant increase in the number of FAPs expressing IL-33 after immobilization. Administration of recombinant IL-33 suppressed immobilization-induced muscle atrophy in aged mice but not in young mice. CONCLUSIONS: Our data reveal a previously unknown protective role of IL-33-ST2 signaling against immobilization-induced muscle atrophy in FAPs and suggest that IL-33-ST2 signaling is a potential new therapeutic target for alleviating disuse muscle atrophy, particularly in older adults.

The ST2+ Treg/amphiregulin axis protects from immune-mediated hepatitis.

Introduction: The alarmin IL-33 has been implicated in the pathology of immune-mediated liver diseases. IL-33 activates regulatory T cells (Tregs) and type 2 innate lymphoid cells (ILC2s) expressing the IL-33 receptor ST2. We have previously shown that endogenous IL-33/ST2 signaling activates ILC2s that aggravate liver injury in murine immune-mediated hepatitis. However, treatment of mice with exogenous IL-33 before induction of hepatitis ameliorated disease severity. Since IL-33 induces expression of amphiregulin (AREG) crucial for Treg function, we investigated the immunoregulatory role of the ST2+ Treg/AREG axis in immune-mediated hepatitis. Methods: C57BL/6, ST2-deficient (Il1rl1-/-) and Areg-/- mice received concanavalin A to induce immune-mediated hepatitis. Foxp3Cre+ x ST2fl/fl mice were pre-treated with IL-33 before induction of immune-mediated hepatitis. Treg function was assessed by adoptive transfer experiments and suppression assays. The effects of AREG and IL-33 on ST2+ Tregs and ILC2s were investigated in vitro. Immune cell phenotype was analyzed by flow cytometry. Results and discussion: We identified IL-33-responsive ST2+ Tregs as an effector Treg subset in the murine liver, which was highly activated in immune-mediated hepatitis. Lack of endogenous IL-33 signaling in Il1rl1-/- mice aggravated disease pathology. This was associated with reduced Treg activation. Adoptive transfer of exogenous IL-33-activated ST2+ Tregs before induction of hepatitis suppressed inflammatory T-cell responses and ameliorated disease pathology. We further showed increased expression of AREG by hepatic ST2+ Tregs and ILC2s in immune-mediated hepatitis. Areg-/- mice developed more severe liver injury, which was associated with enhanced ILC2 activation and less ST2+ Tregs in the inflamed liver. Exogenous AREG suppressed ILC2 cytokine expression and enhanced ST2+ Treg activation in vitro. In addition, Tregs from Areg-/- mice were impaired in their capacity to suppress CD4+ T-cell activation in vitro. Moreover, application of exogenous IL-33 before disease induction did not protect Foxp3Cre+ x ST2fl/fl mice lacking ST2+ Tregs from immune-mediated hepatitis. In summary, we describe an immunoregulatory role of the ST2+ Treg/AREG axis in immune-mediated hepatitis, in which AREG suppresses the activation of hepatic ILC2s while maintaining ST2+ Tregs and reinforcing their immunosuppressive capacity in liver inflammation.

Hydrangea serrata extract attenuates PM-exacerbated airway inflammation in the CARAS model by modulating the IL-33/ST2/NF-κB signaling pathway.

Particulate matter (PM) significantly contributes to the global health crisis of respiratory diseases. It is known to induce and exacerbate conditions such as asthma and respiratory infections. Long exposure to PM can increase the risk of combined allergic rhinitis and asthma syndrome (CARAS). Although therapeutic drugs can be used to improve symptoms of respiratory diseases caused by PM, their usage is often accompanied by side effects. Therefore, many studies are being conducted to discover functional food materials that can more effectively treat respiratory diseases while minimizing the side effects of these therapeutic drugs. This study was conducted to investigate the efficacy of Hydrangea serrata extract (HSE) in airway inflammation in a mouse model of CARAS exacerbated by PM. In the CARAS mouse model worsened by PM, the airway inflammation improvement effect of HSE was evaluated by analyzing allergic nasal symptoms, changes in inflammatory cells, OVA-specific immunoglobulin (Ig) levels, cytokines, mast cell activation, and histopathological findings of both nasal mucosa and lung tissue. HSE effectively reduced OVA-specific IgE and IgG1 and inhibited the production of T helper type 2 (Th2)-related cytokines such as IL-4 and IL-5. Importantly, HSE reduced IL-33 and ST2 expression and inhibited the activation of the NF-κB signaling pathway. In addition, HSE inhibited airway hypersensitivity, mucus production, and inflammatory cell infiltration. These results suggest that HSE may inhibit airway inflammation in CARAS/PM mice by regulating the IL-33/ST2/NF-κB signaling pathway, opening avenues for considering HSE as a potential material for treating allergic airway inflammation diseases in the future.

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.

Obese visceral adipose dendritic cells downregulate regulatory T cell development through IL-33.

Regulatory T cells (Tregs) residing in visceral adipose tissue (VAT) play a pivotal role in regulating tissue inflammation and metabolic dysfunction associated with obesity. However, the specific phenotypic and functional characteristics of Tregs in obese VAT, as well as the regulatory mechanisms shaping them, remain elusive. This study demonstrates that obesity selectively reduces Tregs in VAT, characterized by restrained proliferation, heightened PD-1 expression, and diminished ST2 expression. Additionally, obese VAT displays distinctive maturation of dendritic cells (DCs), marked by elevated expressions of MHC-II, CD86, and PD-L1, which are inversely correlated with VAT Tregs. In an in vitro co-culture experiment, only obese VAT DCs, not macrophages or DCs from subcutaneous adipose tissue (SAT) and spleen, result in decreased Treg differentiation and proliferation. Furthermore, Tregs differentiated by obese VAT DCs exhibit distinct characteristics resembling those of Tregs in obese VAT, such as reduced ST2 and IL-10 expression. Mechanistically, obesity lowers IL-33 production in VAT DCs, contributing to the diminished Treg differentiation. These findings collectively underscore the critical role of VAT DCs in modulating Treg generation and shaping Treg phenotype and function during obesity, potentially contributing to the regulation of VAT Treg populations.

Influence of a 7-day Transalpine Trail Run on cardiac biomarkers and myocardial function.

Intense physical exercise is known to increase cardiac biomarkers; however, it is unclear, whether this phenomenon is physiological, or if it indicates myocardial tissue injury. The aim of our study was to investigate the effects of seven consecutive days of excessive endurance exercise on continuous assessment of cardiac biomarkers, function, and tissue injury. During a 7-day trail-running competition (Transalpine Run, distance 267.4 km, altitude ascent/descent 15556/14450 m), daily blood samples were obtained for cardiac biomarkers (hs-TnT, NT-proBNP, and suppression of tumorigenicity-2 protein (ST2)) at baseline, after each stage and 24-48 h post-race. In addition, echocardiography was performed every second day, cardiac magnetic resonance imaging (CMR) before (n = 7) and after (n = 16) the race. Twelve (eight males) out of 17 healthy athletes finished all seven stages (average total finish time: 43 ± 8 h). Only NT-proBNP increased significantly (3.6-fold, p = 0.009) during the first stage and continued to increase during the race. Hs-TnT revealed an incremental trend during the first day (2.7-fold increase, p = 0.098) and remained within the pathological range throughout the race. ST2 levels did not change during the race. All cardiac biomarkers completely returned to physiological levels post-race. NT-proBNP kinetics correlated significantly with mild transient reductions in right ventricular function (assessed by TAPSE, tricuspid annular plane systolic function; r = -0.716; p = 0.014). No significant echocardiographic changes in LV dimensions, LV function, or relevant alterations in CMR were observed post-race. In summary, this study shows that prolonged, repetitive, high-volume exercise induced a transient, significant increase in NT-proBNP associated with right ventricular dysfunction without corresponding left ventricular functional or structural impairment.

Celecoxib attenuates interleukin 33-induced expression of vascular cell adhesion molecule-1 in human ovarian endometriotic stromal cells.

OBJECTIVE: Endometriosis is an estrogen-dependent chronic inflammatory disease in women of reproductive age. A review of the literature revealed that cytokines and inflammatory factors are associated with endometriosis-associated infertility. Interleukin 33 (IL-33) is a strong inducer of other pro-inflammatory cytokines. Vascular cell adhesion molecule-1 (VCAM-1) plays a central role in recruiting inflammatory cells, whose expression facilitates leukocyte adhesion and is rapidly induced by pro-inflammatory cytokines. Many studies have indicated that VCAM-1 expression is high in endometriosis; however, whether the expression of VCAM-1 is related to IL-33 is unclear. MATERIALS AND METHODS: Human ovarian endometriotic stromal cells (hOVEN-SCs) were treated with IL-33 to enable investigation of cell characterization, gene and protein expression, and signal pathways. Proliferation potential was measured using an MTT assay. Gene expression was analyzed using reverse transcription-polymerase chain reaction. Protein expression assay was performed using western blot analysis. RESULTS: This study investigated the effects of IL-33 on VCAM-1 and COX-2 expression in hOVEN-SCs. First, the results revealed that the IL-33/ST2/mitogen-activated protein kinase (MAPK) signaling pathway could increase the expression of VCAM-1 and COX-2 in hOVEN-SCs. Second, we discovered that COX-2 expression was essential for IL-33-induced VCAM-1 expression because the effects could be negated through NS398, a selective COX-2 inhibitor. Finally, treatment of IL-33-treated hOVEN-SCs with celecoxib significantly and dose-responsively decreased VCAM-1 expression. CONCLUSION: Taken together, these results indicate that IL-33 can upregulate VCAM-1 expression in hOVEN-SCs through the IL-33/ST2/MAPK/COX-2 signaling pathway and thereby contribute to endometriosis.

IL-10 Differentially Promotes Mast Cell Responsiveness to IL-33, Resulting in Enhancement of Type 2 Inflammation and Suppression of Neutrophilia.

Mast cells (MCs) play critical roles in the establishment of allergic diseases. We recently demonstrated an unexpected, proinflammatory role for IL-10 in regulating MC responses. IL-10 enhanced MC activation and promoted IgE-dependent responses during food allergy. However, whether these effects extend to IgE-independent stimuli is not clear. In this article, we demonstrate that IL-10 plays a critical role in driving IL-33-mediated MC responses. IL-10 stimulation enhanced MC expansion and degranulation, ST2 expression, IL-13 production, and phospho-relA upregulation in IL-33-treated cells while suppressing TNF-α. These effects were partly dependent on endogenous IL-10 and further amplified in MCs coactivated with both IL-33 and IgE/Ag. IL-10's divergent effects also extended in vivo. In a MC-dependent model of IL-33-induced neutrophilia, IL-10 treatment enhanced MC responsiveness, leading to suppression of neutrophils and decreased TNF-α. In contrast, during IL-33-induced type 2 inflammation, IL-10 priming exacerbated MC activity, resulting in MC recruitment to various tissues, enhanced ST2 expression, induction of hypothermia, recruitment of eosinophils, and increased MCPT-1 and IL-13 levels. Our data elucidate an important role for IL-10 as an augmenter of IL-33-mediated MC responses, with implications during both allergic diseases and other MC-dependent disorders. IL-10 induction is routinely used as a prognostic marker of disease improvement. Our data suggest instead that IL-10 can enhance ST2 responsiveness in IL-33-activated MCs, with the potential to both aggravate or suppress disease severity depending on the inflammatory context.

Epithelial overexpression of IL-33 induces eosinophilic esophagitis dependent on IL-13.

BACKGROUND: Eosinophilic esophagitis (EoE) is an increasingly common inflammatory condition of the esophagus; however, the underlying immunologic mechanisms remain poorly understood. The epithelium-derived cytokine IL-33 is associated with type 2 immune responses and elevated in esophageal biopsy specimens from patients with EoE. OBJECTIVE: We hypothesized that overexpression of IL-33 by the esophageal epithelium would promote the immunopathology of EoE. METHODS: We evaluated the functional consequences of esophageal epithelial overexpression of a secreted and active form of IL-33 in a novel transgenic mouse, EoE33. EoE33 mice were analyzed for clinical and immunologic phenotypes. Esophageal contractility was assessed. Epithelial cytokine responses were analyzed in three-dimensional organoids. EoE33 phenotypes were further characterized in ST2-/-, eosinophil-deficient, and IL-13-/- mice. Finally, EoE33 mice were treated with dexamethasone. RESULTS: EoE33 mice displayed ST2-dependent, EoE-like pathology and failed to thrive. Esophageal tissue remodeling and inflammation included basal zone hyperplasia, eosinophilia, mast cells, and TH2 cells. Marked increases in levels of type 2 cytokines, including IL-13, and molecules associated with immune responses and tissue remodeling were observed. Esophageal organoids suggested reactive epithelial changes. Genetic deletion of IL-13 in EoE33 mice abrogated pathologic changes in vivo. EoE33 mice were responsive to steroids. CONCLUSIONS: IL-33 overexpression by the esophageal epithelium generated immunopathology and clinical phenotypes resembling human EoE. IL-33 may play a pivotal role in the etiology of EoE by activating the IL-13 pathway. EoE33 mice are a robust experimental platform for mechanistic investigation and translational discovery.

Ultrasmall Nanoparticles Regulate Immune Microenvironment by Activating IL-33/ST2 to Alleviate Renal Ischemia-Reperfusion Injury.

Renal ischemia-reperfusion injury (IRI) is a common disease with high morbidity and mortality. Renal IRI can cause the disorder of immune microenvironment and reprograming the immune microenvironment to alleviate excessive inflammatory response is crucial for its treatment. Cytokine IL-33 can improve the immune inflammatory microenvironment by modulating both innate and adaptive immune cells, and serve as an important target for modulating immune microenvironment of renal IRI. Herein, we report that bilobetin-functionalized ultrasmall Cu2- xSe nanoparticles (i.e., CSPB NPs) can activate the PKA/p-CREB/IL-33/ST2 signaling pathway to regulate innate and adaptive immune cells for reprograming the immune microenvironment of IRI-induced acute kidney injury. The biocompatible CSPB NPs can promote the polarization of M1-like macrophages into M2-like macrophages, and the expansion of ILC2 and Treg cells by activating IL-33/ST2 to modulate the excessive immune inflammatory response of renal IRI. More importantly, they can rapidly accumulate at the injured kidney to significantly alleviate IRI. This work demonstrates that modulating the expression of cytokines to reprogram immune microenvironment has great potential in the treatment of renal IRI and other ischemic diseases.

Promoting (and targeting) alternative expression.

Lineage-specific effects of upstream promoters affect ST2 expression and effector function in TH1cells.

Interleukin-33/ST2 axis involvement in atrial remodeling and arrhythmogenesis.

Interleukin (IL)-33, a cytokine involved in immune responses, can activate its receptor, suppression of tumorigenicity 2 (ST2), is elevated during atrial fibrillation (AF). However, the role of IL-33/ST2 signaling in atrial arrhythmia is unclear. This study explored the pathological effects of the IL-33/ST2 axis on atrial remodeling and arrhythmogenesis. Patch clamping, confocal microscopy, and Western blotting were used to analyze the electrical characteristics of and protein activity in atrial myocytes (HL-1) treated with recombinant IL-33 protein and/or ST2-neutralizing antibodies for 48 hrs. Telemetric electrocardiographic recordings, Masson's trichrome staining, and immunohistochemistry staining of the atrium were performed in mice receiving tail vein injections with nonspecific immunoglobulin (control), IL-33, and IL-33 combined with anti-ST2 antibody for 2 weeks. IL-33-treated HL-1 cells had a reduced action potential duration, lower L-type Ca2+ current, greater sarcoplasmic reticulum (SR) Ca2+ content, increased Na+/Ca2+ exchanger (NCX) current, elevation of K+ currents, and increased intracellular calcium transient. IL-33-treated HL-1 myocytes had greater activation of the calcium-calmodulin-dependent protein kinase II (CaMKII)/ryanodine receptor 2 (RyR2) axis and nuclear factor kappa B (NF-κB) / NLR family pyrin domain containing 3 (NLRP3) signaling than did control cells. IL-33 treated cells also had greater expression of Nav1.5, Kv1.5, NCX, and NLRP3 than did control cells. Pretreatment with neutralizing anti-ST2 antibody attenuated IL-33-mediated activation of CaMKII/RyR2 and NF-κB/NLRP3 signaling. IL-33-injected mice had more atrial ectopic beats and increased AF episodes, greater atrial fibrosis, and elevation of NF-κB/NLRP3 signaling than did controls or mice treated with IL-33 combined with anti-ST2 antibody. Thus, IL-33 recombinant protein treatment promotes atrial remodeling through ST2 signaling. Blocking the IL-33/ST2 axis might be an innovative therapeutic approach for patients with atrial arrhythmia and elevated serum IL-33.

A type 1 immunity-restricted promoter of the IL-33 receptor gene directs antiviral T-cell responses.

The pleiotropic alarmin interleukin-33 (IL-33) drives type 1, type 2 and regulatory T-cell responses via its receptor ST2. Subset-specific differences in ST2 expression intensity and dynamics suggest that transcriptional regulation is key in orchestrating the context-dependent activity of IL-33-ST2 signaling in T-cell immunity. Here, we identify a previously unrecognized alternative promoter in mice and humans that is located far upstream of the curated ST2-coding gene and drives ST2 expression in type 1 immunity. Mice lacking this promoter exhibit a selective loss of ST2 expression in type 1- but not type 2-biased T cells, resulting in impaired expansion of cytotoxic T cells (CTLs) and T-helper 1 cells upon viral infection. T-cell-intrinsic IL-33 signaling via type 1 promoter-driven ST2 is critical to generate a clonally diverse population of antiviral short-lived effector CTLs. Thus, lineage-specific alternative promoter usage directs alarmin responsiveness in T-cell subsets and offers opportunities for immune cell-specific targeting of the IL-33-ST2 axis in infections and inflammatory diseases.

Interplay of IL-33 and IL-35 Modulates Th2/Th17 Responses in Cigarette Smoke Exposure HDM-Induced Asthma.

Cigarette smoke (CS) facilitates adverse effects on the airway inflammation and treatment of asthma. Here, we investigated the mechanisms by which CS exacerbates asthma. The roles of IL-33 and IL-35 in asthma development were examined by treatment with IL-33 knockout (IL-33 KO) or transfection of adenovirus encoding IL-35 (Ad-IL-35) in a murine model of cigarette smoke-exposure asthma. Furthermore, the involvement of IL-33 and IL-35 in regulating DCs and Th2/Th17 cells was examined in a coculture system of DCs with CD4+ T cells. Additionally, we observed the effect of CpG-ODNs on the balance of IL-33 and IL-35. We show that CS and house dust mite (HDM) exposure induced IL-33 and suppressed IL-35 levels in cigarette smoke-exposure asthma in vivo and in vitro. Treatment with IL-33 KO or Ad-IL-35 significantly attenuated airway hyperreactivity, goblet hyperplasia, airway remodelling, and eosinophil and neutrophil infiltration in the lung tissues from asthmatic mice. Furthermore, we demonstrated reciprocal regulation between CS and HDM-modulated IL-33 and IL-35. Mechanistically, IL-33 KO (or anti-ST2) and Ad-IL-35 attenuated Th2- and Th17-associated inflammation by downregulating TSLP-DC signalling. Finally, administration of CpG-ODNs suppressed the expression of IL-33/ST2 and elevated the levels of IL-35, which is mainly derived from CD4+Foxp+ Tregs, to alleviate Th2- and Th17-associated inflammation by inhibiting the activation of BMDCs. Taken together, the IL-33/ST2 pathway drives the DC-Th2 and Th17 responses of cigarette smoke-exposure asthma, while IL-35 has the opposite effect. CpG-ODNs represent a potential therapeutic strategy for modulating the balance of IL-33 and IL-35 to suppress allergic airway inflammation.

Electroacupuncture prevents the development or establishment of chronic pain via IL-33/ST2 signaling in hyperalgesic priming model rats.

BACKGROUND: Chronic pain is acomplexhealth issue. Compared to acute pain, which has a protective value, chronic pain is defined as persistent pain after tissue injury. Few clinical advances have been made to prevent the transition from acute to chronic pain. Electroacupuncture (EA), the most common form of acupuncture, is widely used in clinical practice to relieve pain. METHODS: The hyperalgesic priming model, established via a carrageenan injection followed by a prostaglandin E2 injection, was used to investigate the development or establishment of chronic pain. We observed the hyperalgesic effect of EA on rats and investigated the expression p38 mitogen-activated protein kinase, interleukin-33 (IL-33), and its receptor ST2 in astrocytes in the L4-L6 spinal cord dorsal horns (SDHs) after EA. The IL-33/ST2 signaling pathway in SDH is associated with the development of chronic pain. RESULTS: EA can reverse the pain threshold in hyperalgesic priming model rats and regulates the expression of phosphorylated p38, IL-33, and ST2 in astrocytes in the L4-L6 SDHs. We discovered that EA raises the pain threshold. This suggests that EA can prevent the development or establishment of chronic pain by inhibiting IL-33/ST2 signaling in the lower central nervous system. CONCLUSIONS: EA can alleviate the development or establishment of chronic pain by modulating IL-33/ST2 signaling in SDHs. Our findings will help clinicians understand the mechanisms of EA analgesia.

Role of IL-33-ST2 pathway in regulating inflammation: current evidence and future perspectives.

Interleukin (IL)-33 is an alarmin of the IL-1 superfamily localized to the nucleus of expressing cells, such as endothelial cells, epithelial cells, and fibroblasts. In response to cellular damage or stress, IL-33 is released and activates innate immune responses in some immune and structural cells via its receptor interleukin-1 receptor like-1 (IL-1RL1 or ST2). Recently, IL-33 has become a hot topic of research because of its role in pulmonary inflammation. The IL-33-ST2 signaling pathway plays a pro-inflammatory role by activating the type 2 inflammatory response, producing type 2 cytokines and chemokines. Elevated levels of IL-33 and ST2 have been observed in chronic pulmonary obstructive disease (COPD). Notably, IL-33 is present in COPD induced by cigarette smoke or acute inflammations. The role of IL-33 in sepsis is becoming increasingly prominent, and understanding its significance in the treatment of sepsis associated with high mortality is critical. In addition to its pro-inflammatory effects, the IL-33-ST2 axis appears to play a role in bacterial clearance and tissue repair. In this review, we focused on the role of the IL-33-ST2 axis in sepsis, asthma, and COPD and summarized the therapeutic targets associated with this axis, providing a basis for future treatment.

Moxibustion influences hippocampal microglia polarization via IL-33/ST2 pathway in Alzheimer's disease mice. / è‰¾ç¸é€šè¿‡ç™½ç»†èƒžä»‹ç´ -33/ç”Ÿé•¿åˆºæ¿€è¡¨è¾¾åŸºå› 2è›‹ç™½é€šè·¯å½±å“é˜¿å°”èŒ¨æµ·é»˜ç— å°é¼ æµ·é©¬å°èƒ¶è´¨ç»†èƒžæžåŒ–.

OBJECTIVES: To observe the effect of moxibustion on the polarization of microglia towards M2 direction in Alzheimer's disease (AD) mice through the interleukin-33 (IL-33)/growth stimulating gene 2 protein (ST2) signaling pathway. METHODS: Five-month-old APP/PS1 male mice were randomly divided into model and moxibustion (Moxi) groups, and C57BL/6J mice of the same age were as the control group, with 9 mice in each group. In the Moxi group, moxibustion was applied at "Baihui" (GV20) and "Yongquan" (KI1) for 30 min, once a day, 5 days a week for 4 weeks. The spatial learning memory ability was observed by the Morris water maze test. The relative expressions of IL-33 and ST2 in hippocampus were detected by Western blot. The positive expression of amyloid-ß (Aß), phosphorylated Tau (p-Tau), IL-33/ionized calcium binding adapter molecule 1(Iba-1), ST2/Iba-1, arginase 1 (Arg1)/Iba-1 and indu-cible nitric oxide synthase (iNOS)/Iba-1 in hippocampal CA1 region were detected by immunofluorescence. RESULTS: Compared with the control group, the escape latency of the mice in the model group was prolonged (P<0.001, P<0.01), the number of times to enter the effective area and the percentage of target quadrant swimming time were reduced (P<0.001), the positive expression of both Aß and p-Tau, the positive expression of iNOS/Iba-1 in the hippocampal CA1 region was increased (P<0.001), while the expression of IL-33 and ST2 protein in hippocampal tissue, the positive expression levels of IL-33/Iba-1, ST2/Iba-1 and Arg1/Iba-1 in hippocampal CA1 region were all decreased (P<0.05, P<0.001). After treatment, compared with the model group, the escape latency of the mice in the moxibustion group was shortened (P<0.001, P<0.01), the number of entries into the effective area and the percentage of target quadrant swimming time were increased (P<0.001), the positive expression of Aß and p-Tau in the hippocampal CA1 region, and the positive expression of iNOS/Iba-1 were decreased (P<0.001), while the expression of IL-33 and ST2 protein in the hippocampal tissue, the positive expression of IL-33/Iba-1, ST2/Iba-1 and Arg1/Iba-1 in hippocampal CA1 region were all increased (P<0.05, P<0.01, P<0.001). CONCLUSIONS: Moxibustion can improve the spatial learning and memory abilities, reduce the pathological deposition of Aß and p-Tau in APP/PS1 mice, which may be related to its function in up-regulating the IL-33/ST2 signaling pathway to regulate the polarization of microglia towards M2 direction.