Interleukin-33 in health and disease. Nat Rev Immunol. 2016;16:676-689. [PMID: 27640624 DOI: 10.1038/nri.2016.95]

Oligodendrocyte-derived IL-33 regulates self-reactive CD8+ T cells in CNS autoimmunity

In chronic inflammatory disorders of the central nervous system (CNS), tissue-resident self-reactive T cells perpetuate disease. The specific tissue factors governing the persistence and continuous differentiation of these cells remain undefined but could represent attractive therapeutic targets. In a model of chronic CNS autoimmunity, we find that oligodendrocyte-derived IL-33, an alarmin, is key for locally regulating the pathogenicity of self-reactive CD8+ T cells. The selective ablation of IL-33 from neo-self-antigen-expressing oligodendrocytes mitigates CNS disease. In this context, fewer self-reactive CD8+ T cells persist in the inflamed CNS, and the remaining cells are impaired in generating TCF-1low effector cells. Importantly, interventional IL-33 blockade by locally administered somatic gene therapy reduces T cell infiltrates and improves the disease course. Our study identifies oligodendrocyte-derived IL-33 as a druggable tissue factor regulating the differentiation and survival of self-reactive CD8+ T cells in the inflamed CNS. This finding introduces tissue factors as a novel category of immune targets for treating chronic CNS autoimmune diseases.

Role of the interleukin-33 (IL-33)/suppressor of tumorigenicity 2 (ST2) signaling in superoxide anion-triggered inflammation and pain behavior in mice

Reactive oxygen species such as superoxide anion have varied roles in inflammation and pain, which can be mimicked by potassium superoxide (KO2), the superoxide anion donor. Interleukin (IL)-33 has pleiotropic functions by activating its receptor suppression of tumorigenicity 2 (ST2). However, the role of IL-33/ST2 signaling in inflammatory pain initiated by reactive oxygen species (ROS) such as superoxide anion has not been investigated, which was the aim of the present study. IL-33 levels were assessed by enzyme-linked immunosorbent assay (ELISA). Mechanical and thermal hyperalgesia and overt pain were evaluated by electronic von Frey, hot plate, and abdominal writhing/paw flinching/licking, respectively. Edema and leukocyte recruitment (myeloperoxidase assay and total/differential cell count), antioxidant capacity, superoxide anion production and lipid peroxidation were assessed. Paw skin and spinal cord messenger ribonucleic acid (mRNA) expression of pro-inflammatory mediators and glial markers in the spinal cord were evaluated. Immunofluorescence was used to detect spinal glial and neuronal c-Fos activation. KO2 injection triggered IL-33 production in the paw skin and spinal cord of mice, induced hyperalgesia, edema, neutrophil recruitment to the paw tissue, overt pain-like behavior, and leukocyte recruitment to the peritoneum that were reduced in ST2 deficient mice. In the paw skin and spinal cord, KO2 triggered IL-33/ST2-dependent oxidative stress, and mRNA expression of inflammatory molecules, which were reduced by ST2 deficiency. KO2 induced spinal cord glial (at mRNA/protein levels) and neuronal activation in IL-33/ST2-dependent manner. IL-33/ST2 signaling mediates, at least in part, superoxide anion-induced inflammatory pain by modulating local and spinal inflammatory events.

IL-33 exerts neuroprotective effects through activation of ST2/AKT signaling axis in microglia after subarachnoid hemorrhage in rats

BACKGROUND AND PURPOSE

ST2, a member of the interleukin-1 (IL-1) receptor family, along with its ligand IL-33, plays critical roles in immune regulation and inflammatory responses. This study investigates the roles of endogenous IL-33/ST2 signaling in subarachnoid hemorrhage (SAH) and elucidates the underlying mechanisms.

METHODS

Dynamic changes in endogenous IL-33 levels were examined following SAH induction in vivo. Rats underwent the endovascular perforation model of SAH and were randomly assigned to receive either recombinant IL-33 (rIL-33) or a vehicle, administered intranasally 1 h post-SAH. ST2 siRNA or an AKT selective inhibitor was administered intraperitoneally (i.p.) 48 h prior to SAH induction to explore the potential mechanisms of IL-33-mediated neuroprotection.

RESULTS

Endogenous IL-33 and ST2 levels were elevated in in vitro models of SAH. Exogenous IL-33 significantly alleviated neuronal apoptosis, reduced brain edema, and enhanced short-term neurofunction in a dose-dependent manner following SAH in rats.

CONCLUSION

Exogenous rIL-33 alleviates SAH-induced neurological deficits by promoting M2-like polarization of microglia post-SAH. These findings suggest a potential role of the microglial ST2/AKT axis in IL-33-related neuroprotection, which warrants further investigation.

Based on the IL-33/ST2-MyD88 signaling pathway to explore the mechanism of aerobic exercise in antagonizing the inflammatory response in depressive mice

PURPOSE

This study examined how aerobic exercise affect the IL-33/ST2-MyD88 signaling pathway in mice with chronic unpredictable mild stress (CUMS) induced depression METHOD: Thirty-six C57BL/6 mice were randomly assigned t three groups: a control group (CG), a model group (MG), and an exercise group (ME). We created a depression model using chronic unpredictable mild stress, after which the ME group underwent 8 weeks of aerobic training. After exercise intervention, neurobehavioral assessment was performed. ELISA was used to detect the levels of IL-33, IL-1β and IL-10 in the serum of mice. Toluidine blue Nissl staining was used to observe the structure of hippocampal neurons. Total RNA was extracted from blood samples using magnetic beads and from hippocampal tissue or neurons using Trizol. The levels of IL-33, ST2, MyD88, IL-1β, IL-10 and NF-κB mRNA in mice were detected by RT-PCR RESULT: The number of lattice crossings and modification times were significantly reduced in MG group, the exercise time was significantly shortened, and the sugar and water preference index was significantly reduced, while the immobility time in forced swimming and tail suspension tests were significantly prolonged. The results indicated that CUMS successfully induced anhedonia and depression-like behaviors in the mice. In the ME group, there was a significant increase in the number of crossing lattices, modification times, exercise duration, and sugar and water preference index, while the immobility time in the forced swimming and tail suspension tests significantly decreased. Compared with the CG group, serum levels of inflammatory factors IL-33, IL-1β, and NF-κB significantly increased in the MG group, while these levels significantly decreased in the ME group. It decreased and IL-10 showed a very significant increase. Nissl staining results indicated that hippocampal nerve cells in MG group were sparsely arranged, with widened gaps, severe nucleus contraction, and shallow staining. The ME group had reduced neuronal vacuoles and improved nuclear shrinkage. Immunohistochemical results revealed that in MG group, the expression of pro-inflammatory factors IL-1β and MyD88 increased. In Contrast, the ME group exhibited a decrease in IL-1β and MyD88, alongside a significant increase in the anti-inflammatory factor IL-10. In the RT-PCR test results, the blood inflammation signal pathway IL-33/ST2 and its downstream factors MyD88, NF-κB, and IL-1β mRNA were significantly up-regulated, and the inhibitory factor IL-10 mRNA was up-regulated in MG group. Gene expression trends for IL-33 mRNA, ST2 mRNA, IL-1β mRNA, MyD88 mRNA and NF-κB mRNA in hippocampus tissue were similar to those in blood, all showing significant up-regulation. In contrast, IL-10 mRNA did not exhibit significant up-regulation. While IL-33/ST2 expression did not significantly decrease, other pro-inflammatory factors showed significant down-regulation, and anti-inflammatory factors demonstrated significant up-regulated. Similarly, IL-33 mRNA, ST2 mRNA and MyD88 mRNA expressions in the hippocampus of ME mice mirrored the changes observed in blood when compared to MG mice. NF-κB mRNA was significantly down-regulated, while IL-1β mRNA showed no significant change, and IL-10 mRNA was up-regulated, albeit not significantly.

CONCLUSION

Aerobic exercise may counteract the CUMS depression model in mice by regulating the IL-33/ST2-MyD88 signaling pathway. The strong correlation of inflammatory cytokines between blood and hippocampus indicated that assessing inflammatory damage in the hippocampus could be done through blood tests of the signaling pathway and related cytokine levels.

WTAP improves chondrocyte loss and dysfunctions to ameliorate osteoarthritis through mediating the mA methylation and mRNA stability of IL-33

Osteoarthritis (OA) is a multifactorial degenerative disorder entailing cartilage loss and progressive joint failure. m6A RNA methylation could impact multiple disorders, including OA. In this study, m6A methylation regulator WTAP was down-regulated in OA cartilage, accompanied by significantly lower m6A methylation levels in OA tissues. In the DMM-induced mice OA model and IL-1β- or TNF-α-stimulated chondrocytes, WTAP and m6A methylation levels were decreased, but IL-1β, IL-6, and TNF-α cytokine expressions were elevated. In vivo and in vitro, WTAP overexpression increased m6A methylation levels but reduced proinflammatory cytokine contents. Furthermore, WTAP overexpression (OE) increased chondrocyte viability and proliferation, aggrecan and collagen II protein, and decreased cell apoptosis, MMP3, MMP13, and ADAMTS5. WTAP-mediated m6A methylation of IL-33 and impaired IL-33 mRNA stability. IL-33 OE caused no changes to WTAP expression; however, IL-33 OE partially attenuated WTAP OE-induced IL-33 downregulation. IL-33 overexpression inhibited chondrocyte viability and proliferation, decreased aggrecan and collagen II but elevated MMP3, MMP13, and ADAMTS5, and increased cell apoptosis and proinflammatory cytokine contents. More importantly, IL-33 eliminated the effects of WTAP OE on chondrocytes. Therefore, WTAP is down-regulated in OA; WTAP improves chondrocyte proliferation and function, thereby ameliorating OA through mediating m6A methylation of IL-33 and impairing IL-33 mRNA stability.

Excess heme orchestrates progesterone resistance in uterine endometrial cancer through macrophage polarization and the IL-33/PAX8/PGR axis

Progesterone is an important drug for hormone therapy in uterine endometrial cancer (UEC). However, the therapeutic efficacy of progestogen is often limited by resistance, and the underlying mechanism remains unknown. In this study, we observed heme metabolism is more active in progesterone-insensitive patients. Heme induced macrophages (Mφs) bias towards M2-like phenotype and downregulated the expression of IL-33, resulting in increased levels of Paired box gene 8 (PAX8). Further study showed PAX8 inhibited the transcriptional activity of PGR by binding to the PGR promoter region. In addition, PGR can also act as a transcriptional factor to regulate the transcription of autophagy-related gene 7 (ATG). Low expression of PGR decreases the transcriptional activity of ATG7 promoter, which decreases cell autophagy and promotes the progression of UEC. Overall, this study reveals the important interaction between heme metabolism, IL-33 and PGR in progesterone-insensitive UEC, and is promising to provide new therapeutic targets for overcoming progesterone resistance.

The clinicopathological implications of serum IL-33 and sST2 as cancer biomarkers: A narrative review

Background

Interleukin (IL)-33 and its receptor, soluble suppression of tumorigenicity 2 (sST2), are key players in the immune response and cancer biology. IL-33 can promote tumorigenesis by enhancing cancer cell proliferation and modulating the immune environment to support tumor growth. Conversely, it can also bolster anti-tumor immunity by recruiting and activating immune effector cells. IL-33 plays a role in multiple aspects of cancer biology, such as promoting immune evasion, tumor growth, and metastasis.

Objective

This study intends to assess the prognostic significance of serum IL-33 and sST2 in cancer and their association with clinicopathologic characteristics (CPC).

Material & methods

Scopus, PubMed electronic databases and other sources were searched and analysed from 2008-2025. The quality of the study was assessed using the Newcastle-Ottawa Quality Assessment Scale.

Results

A total of forty-four studies meeting the inclusion criteria were analyzed. These studies primarily employed an observational and analytical designs, with the majority conducted in the Southeast Asian region, particularly in China. Among the studies investigating serum IL-33 levels in cancer, 68% (26/38) reported elevated serum IL-33 levels, with the majority focusing on hepatocellular carcinoma (HCC) and non-small cell lung cancer (NSCLC), followed by breast (BC) and colon rectal cancer (CRC). Additionally, 85% (22/26) of the reports found a significant association between serum IL-33 expression in cancer and CPC. For regulating the availability and activity of IL-33, sST2, a decoy receptor that binds to IL-33, is crucial. Of the studies assessing sST2 in cancer, 55% (12/22) showed elevated sST2 levels, with most focusing on HCC, followed by BC and CRC. Furthermore, 54% (7/13) of these studies identified a significant correlation between sST2 levels and CPC.

Conclusion

The detection of increased serum IL-33 across various malignancies highlights its potential as an emerging biomarker for cancer detection and prognosis. Similarly, elevated sST2 levels have been observed in different cancers and are linked to poor prognosis, further highlighting its potential as a biomarker for tumor progression. The IL-33/ST2 signaling pathway could offer new cancer treatment strategies by enhancing immune responses while mitigating tumor-promoting effects. This study explores the roles of IL-33 and sST2 as biomarkers, their relevance in cancer diagnostics and therapeutics, and their correlation with clinical outcomes across different cancer types.

PRTN3 promotes IL33/Treg-mediated tumor immunosuppression by enhancing the M2 polarization of tumor-associated macrophages in lung adenocarcinoma

The immunosuppressive tumor microenvironment (TME) shaped by tumor-associated macrophages (TAMs) is essential for lung adenocarcinoma (LUAD) immune tolerance and tumor progression. Here, we first reported that proteinase 3 (PRTN3) promoted the alternative activation (M2) of TAMs and enhanced IL33/regulatory T cells (Tregs)-mediated tumor immunosuppression in LUAD. Firstly, clinical analysis revealed PRTN3 was highly expressed in TAMs and correlated with the tumor progression and poor prognosis in LUAD patients. Meanwhile, by using the myeloid cells-specific Prtn3-knockout mouse model, we demonstrated Prtn3 deficiency in macrophages remolded the immunosuppressive TME and suppressed tumor growth. The mechanism studies uncovered a novel signaling pathway that PRTN3 up-regulated IL33 expression in TAMs by suppressing AKT-mediated ubiquitinated degradation of FOXO1, which subsequently activated Il33 transcription. Furthermore, lack of PRTN3 or FOXO1 in macrophages greatly restrained IL33-induced Treg differentiation. Importantly, selective knockout of Prtn3 in macrophages significantly enhanced the antitumor effect of anti-PD1 therapy in the mouse model of LUAD. Thus, our work demonstrated that PRTN3 in macrophages, served as a key immunoregulator, contributed to impede the antitumor immune response through reinforcing the TAMs/Tregs crosstalk, which provided valuable insights to improve the immunotherapeutic effect by functional remodeling of TAMs to alleviate immunosuppression in LUAD.

Neutralization of IL-33 ameliorates septic myocardial injury through anti-inflammatory, anti-oxidative, and anti-apoptotic by regulating the NF-κB/STAT3/SOCS3 signaling pathway

Septic myocardial injury, a severe sepsis complication linked to high morbidity and mortality, remains a major global clinical challenge. Interleukin-33 (IL-33), a damage-associated pro-inflammatory factor, has been implicated in regulating immune responses and inflammation, but its specific role in septic myocardial injury has not been fully elucidated. This study examined IL-33's role in septic myocardial injury using Gene Expression Omnibus (GEO) database datasets, alongside in vitro and in vivo experiments. Our results indicated a significant upregulation of IL-33 in septic myocardial injury, as demonstrated in both clinical and experimental settings. Blocking IL-33 significantly enhanced cardiac function and alleviated cardiomyocyte damage. Mechanistic investigations revealed that neutralizing IL-33 mitigates inflammation, oxidative stress, and apoptosis in cardiomyocytes by regulating the nuclear factor kappa B (NF-κB)/signal transducer and activator of transcription 3 (STAT3)/suppressors of cytokine signaling 3 (SOCS3) signaling pathway. Peritoneal macrophages are recognized as a potential origin of IL-33, and targeting IL-33 derived from these cells further reduced cardiomyocyte injury. The study underscores IL-33's crucial involvement in septic myocardial injury pathogenesis, indicating that IL-33 may serve as a promising therapeutic target.

Deep insight into cytokine storm: from pathogenesis to treatment

Cytokine storm (CS) is a severe systemic inflammatory syndrome characterized by the excessive activation of immune cells and a significant increase in circulating levels of cytokines. This pathological process is implicated in the development of life-threatening conditions such as fulminant myocarditis (FM), acute respiratory distress syndrome (ARDS), primary or secondary hemophagocytic lymphohistiocytosis (HLH), cytokine release syndrome (CRS) associated with chimeric antigen receptor-modified T (CAR-T) therapy, and grade III to IV acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation. The significant involvement of the JAK-STAT pathway, Toll-like receptors, neutrophil extracellular traps, NLRP3 inflammasome, and other signaling pathways has been recognized in the pathogenesis of CS. Therapies targeting these pathways have been developed or are currently being investigated. While novel drugs have demonstrated promising therapeutic efficacy in mitigating CS, the overall mortality rate of CS resulting from underlying diseases remains high. In the clinical setting, the management of CS typically necessitates a multidisciplinary team strategy encompassing the removal of abnormal inflammatory or immune system activation, the preservation of vital organ function, the treatment of the underlying disease, and the provision of life supportive therapy. This review provides a comprehensive overview of the key signaling pathways and associated cytokines implicated in CS, elucidates the impact of dysregulated immune cell activation, and delineates the resultant organ injury associated with CS. In addition, we offer insights and current literature on the management of CS in cases of FM, ARDS, systemic inflammatory response syndrome, treatment-induced CRS, HLH, and other related conditions.

Interleukin-33 (IL-33) promotes DNA damage-resistance in lung cancer

Resistance to DNA damage is one of the primary mechanisms by which tumor cells evade the effects of standard chemotherapeutic agents and radiotherapy. Dynamic and complex interactions between the tumor microenvironment (TME) and tumor cells critically influence the DNA damage response. Interleukin-33 (IL-33) is a multifunctional cytokine secreted at high levels in response to cellular damage and stress. Recently, increasing evidence has suggested that IL-33 plays a key role in promoting the therapeutic resistance of tumors. However, the actual source of IL-33 during cancer therapy and how IL-33 contributes to a resistant TME remain incompletely understood. In this study, we found that both cancer-associated fibroblasts (CAFs) and tumor cells treated with DNA damage-inducing agents expressed and secreted high levels of IL-33, subsequently leading to enhanced DNA damage repair efficacy. Mechanistically, nuclear IL-33 primarily functions as a transcriptional co-activator of homologous recombination repair (HRR) genes, whereas the active form of IL-33 can drive the non-homologous end joining (NHEJ) pathway via the canonical IL-33/ST2 axis. Overall, we demonstrated that IL-33 plays a key role in mediating a DNA damage-resistant TME, which could represent a potential therapeutic vulnerability in chemoresistant cancer cells.

IL-33 is associated with alveolar dysfunction in patients with viral lower respiratory tract disease

Interleukin (IL)-33 is released following tissue damage, causing airway inflammation and remodelling via reduced IL-33 (IL-33red)/serum stimulation-2 (ST2) and oxidised IL-33 (IL-33ox)/receptor for advanced glycation end products (RAGE)/epidermal growth factor receptor (EGFR) pathways. This study aimed to identify associations of IL-33 with clinical outcomes and pathological mechanisms during viral lower respiratory tract disease (LRTD). Ultra-sensitive immunoassays were developed to measure IL-33red, IL-33ox and IL-33/sST2 complexes in samples from patients hospitalised with COVID-19. Immunohistochemistry and multiomics were used to characterise lung samples. Elevated IL-33 in the airway and IL-33/sST2 complex in the circulation correlated with poor clinical outcomes (death, need for intensive care or mechanical ventilation). IL-33 was localised to airway epithelial and endothelial barriers, whereas IL1RL1 was expressed on aerocytes, alveolar endothelial cells specialised for gaseous exchange. IL-33 increased expression of mediators of neutrophilic inflammation, immune cell infiltration, interferon signalling and coagulation in endothelial cell cultures. Endothelial IL-33 signatures were strongly related with signatures associated with viral LRTD. Increased IL-33 release following respiratory viral infections is associated with poor clinical outcomes and might contribute to alveolar dysfunction. Although this does not show a causal relationship with disease, these results provide a rationale to evaluate pathological roles for IL-33 in viral LRTD.

The Interplay Between Innate Immunity and Nonimmune Cells in Lung Damage, Inflammation, and Repair

As the site of gas exchange, the lung is critical for organismal survival. It is also subject to continual environmental insults inflicted by pathogens, particles, and toxins. Sometimes, these insults result in structural damage and the initiation of an innate immune response. Operating in parallel, the immune response aims to eliminate the threat, while the repair process ensures continual physiological function of the lung. The inflammatory response and repair processes are thus inextricably linked in time and space but are often studied in isolation. Here, we review the interplay of innate immune cells and nonimmune cells during lung insult and repair. We highlight how cellular cross talk can fine-tune the circuitry of the immune response, how innate immune cells can facilitate or antagonize proper organ repair, and the prolonged changes to lung immunity and physiology that can result from acute immune responses and repair processes.

Role and mechanism of IL-33 in bacteria infection related gastric cancer continuum: From inflammation to tumor progression

Gastric cancer, a globally prevalent malignant tumor, is characterized by low early diagnosis rate, high metastasis rate, and poor prognosis, particularly in East Asia, Eastern Europe, and South America. Helicobacter pylori (H. pylori) is recognized as the primary risk factor for gastric cancer. However, the fact that fewer than 3 % of infected individuals develop cancer suggests that other bacteria may also influence gastric carcinogenesis. A diverse community of microorganisms may interact with H. pylori, thereby driving disease progression. Here, the role of the cytokine IL-33, a member of the IL-1 family, is scrutinized. Its production can be induced by H. pylori through the activation of specific signaling pathways, and it contributes to the inflammatory environment by promoting the release of pro-inflammatory cytokines. This article reviews the conflicting evidence regarding IL-33's role in the progression from gastritis to gastric cancer and discusses the potential therapeutic implications of targeting the IL-33/ST2 axis, with various antibodies and inhibitors in development or undergoing clinical trials for inflammatory diseases. However, the role of IL-33 in gastric cancer treatment remains to be fully elucidated, with its effects potentially dependent on the cellular context and stage of cancer progression. In summary, this review provides a comprehensive overview of the intricate relationship between gastric microbiota, IL-33, and gastritis - gastric cancer transition, offering insights into potential therapeutic targets and the development of novel treatment strategies.

The role of ILC2s in asthma combined with atopic dermatitis: bridging the gap from research to clinical practice

Asthma, a complex and heterogeneous respiratory disease, is often accompanied by various comorbidities, notably atopic dermatitis (AD). AD characterized by recurrent eczematous lesions and severe itching, can trigger or exacerbate asthma. Individuals with AD are 2.16 times more likely to develop asthma compared to the reference population. Furthermore, asthmatics with AD experience more severe and frequent emergency department visits and hospital admissions compared to patients with asthma alone. The close connection between asthma and AD indicates there are overlap pathophysiologic mechanisms. It is well-known that dysregulated type 2 (T2) immune inflammation is pivotal in the development of both AD and asthma, traditionally attributed to CD4+ type 2 helper T (Th2) cells. Over the past decade, group 2 innate lymphoid cells (ILC2s), as potent innate immune cells, have been demonstrated to be the key drivers of T2 inflammation, playing a crucial role in the pathogenesis of both asthma and AD. ILC2s not only trigger T2 immune-inflammation but also coordinate the recruitment and activation of innate and adaptive immune cells, thereby intensifying the inflammatory response. They are rapidly activated by epithelium alarmins producing copious amounts of T2 cytokines such as interleukin (IL) -5 and IL-13 that mediate the airway inflammation, hyperresponsiveness, and cutaneous inflammation in asthma and AD, respectively. The promising efficiency of targeted ILC2s in asthma and AD has further proven their essential roles in the pathogenesis of both conditions. However, to the best of our knowledge, there is currently no review article specifically exploring the role of ILC2s in asthma combined with AD and their potential as future therapeutic targets. Hence, we hypothesize that ILC2s may play a role in the pathogenesis of asthma combined with AD, and targeting ILC2s could be a promising therapeutic approach for this complex condition in the future. In this review, we discuss recent insights in ILC2s biology, focus on the current knowledge of ILC2s in asthma, AD, particularly in asthma combined with AD, and suggest how this knowledge might be used for improved treatments of asthma combined with AD.

Keloids and inflammation: the crucial role of IL-33 in epidermal changes

Introduction

Keloids are benign fibroproliferative disorders characterized by excessive collagen deposition and inflammation that extend beyond the original wound boundaries. IL-33 is an alarmin cytokine released upon cellular damage or stress. Dysregulation of IL-33 in epidermal keratinocytes compromises the skin barrier and triggers chronic inflammation.

Method

In this study, we first noticed an increased expression of IL-33 in the keratinocytes of keloid epidermis through histological staining. Then, an increased expression of IL-33 receptor (ST2) in the lymphocytes infiltrating the superficial dermis of keloid scars were identified through histological staining and flow cytometry analysis. The IFN-γ-IL-33 loop between lymphocytes and keratinocytes were further revealed by flow cytometry and Western blotting analysis. The abnormal keratinocyte differentiation in epiderm is mediated by IFN-γ-IL-33 loop were confirmed by in vitro studies in HaCaT cells via Western blotting analysis and immunofluorescence staining. Finally, the IFN-γ-IL-33 loop were also verified in cocultured peripheral blood mononuclear cells and HaCaT through ELISA analysis.

Results

Our results demonstrate that IL-33 levels are significantly elevated in the epidermis of keloid tissues, where it functions as an alarmin, promoting a chronic inflammatory response. We further reveal a feedback loop between IL-33 and interferon-gamma (IFN-γ), whereby IL-33 induces IFN-g production in lymphocytes, which in turn stimulates keratinocytes to produce more IL-33. This loop contributes to impaired keratinocyte differentiation and skin barrier dysfunction, exacerbating the inflammatory environment.

Discussion

By elucidating the role of the IL-33/ST2 axis in keloid formation, this research provides valuable insights into potential therapeutic targets for managing this challenging condition.

From Edmonton to Lantidra and beyond: immunoengineering islet transplantation to cure type 1 diabetes

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of insulin-producing β cells within pancreatic islets, the specialized endocrine cell clusters of the pancreas. Islet transplantation has emerged as a β cell replacement therapy, involving the infusion of cadaveric islets into a patient's liver through the portal vein. This procedure offers individuals with T1D the potential to restore glucose control, reducing or even eliminating the need for exogenous insulin therapy. However, it does not address the underlying autoimmune condition responsible for T1D. The need for systemic immunosuppression remains the primary barrier to making islet transplantation a more widespread therapy for patients with T1D. Here, we review recent progress in addressing the key limitations of islet transplantation as a viable treatment for T1D. Concerns over systemic immunosuppression arise from its potential to cause severe side effects, including opportunistic infections, malignancies, and toxicity to transplanted islets. Recognizing the risks, the Edmonton protocol (2000) marked a shift away from glucocorticoids to prevent β cell damage specifically. This transition led to the development of combination immunosuppressive therapies and the emergence of less toxic immunosuppressive and anti-inflammatory drugs. More recent advances in islet transplantation derive from islet encapsulation devices, biomaterial platforms releasing immunomodulatory compounds or surface-modified with immune regulating ligands, islet engineering and co-transplantation with accessory cells. While most of the highlighted studies in this review remain at the preclinical stage using mouse and non-human primate models, they hold significant potential for clinical translation if a transdisciplinary research approach is prioritized.

IL-33-Induced TREM2+ Macrophages Promote Pathological New Bone Formation Through CREG1-IGF2R Axis in Ankylosing Spondylitis

Pathological new bone formation is the main cause of disability in ankylosing spondylitis (AS), and so far, it lacks a targeted therapy. Macrophages are central orchestrators of inflammation progression and tissue remodeling, but their contribution to pathological new bone formation has largely not been explored. Here, it is identified that TREM2+ macrophages predominated within the sites of new bone formation and adjacent to osteogenic precursor cells. In vivo, both depletion of macrophages and knockout of Trem2 significantly reduced pathological new bone formation in a collagen antibody-induced arthritis (CAIA) model. Specifically, TREM2+ macrophages promoted osteogenic differentiation of ligament-derived progenitor cells (LDPCs) by secreting CREG1, a secretory glycoprotein involved in cell differentiation and normal physiology. CREG1-IGF2R-PI3K-AKT signaling pathway is involved in TREM2+ macrophage-mediated pathological new bone formation. In addition, it is found that IL-33 promoted TREM2+ macrophage differentiation through phosphorylation of STAT6. Targeting the above signalings alleviated new bone formation in the CAIA model. The findings highlight the critical role of IL-33-induced TREM2+ macrophages in pathological new bone formation and provide potential therapeutic targets for halting spinal ankylosis in AS.

Early Origins of Asthma and Allergies: Clues From Studies in China

Asthma and allergies have emerged as some of the most common chronic diseases, particularly in developed countries. Epidemiological studies have consistently demonstrated that children growing up in farming/rural environments are less likely to develop these conditions. Over the past three decades, China has experienced unprecedented economic development and urbanisation, accompanied by a rapid rise in the prevalence of allergic disorders. Despite the substantial number of affected individuals, allergy management in China remains inconsistent and often inadequate, compounded by variations in diagnostic criteria and limited healthcare access in less developed regions. Furthermore, the vast population, regional disparities, and methodological inconsistencies in data collection have hindered the acquisition of comprehensive, large-scale epidemiological data. This review examines the factors contributing to asthma and allergies from their early origins, focusing on modifiable factors from a specific perspective of China. Factors related to traditional lifestyle, such as early-life exposure to agricultural farming and poultry, diverse dietary patterns, and early introduction of allergenic foods, appear to offer protection against allergies. Conversely, exposure to open-fire cooking, incense burning, tobacco smoke, as well as early-life antibiotic use and perinatal factors like Caesarean section delivery and prematurity may represent potential risks. A clear understanding of the role of these factors would pave the way for developing effective interventions to mitigate the substantial health and socioeconomic burdens associated with asthma and allergies.

Prognostic implications and characterization of tumor-associated tertiary lymphoid structures genes in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is among the most aggressive cancers, with rising incidence and limited responsiveness to immunotherapy due to its highly suppressive tumor microenvironment (TME). Tertiary lymphoid structures (TLS), ectopic formation structures of immune cells, are linked to better prognosis and improved immunotherapy responses in PDAC. Understanding TLS's role in PDAC could enhance immunotherapy effectiveness.

METHODS

This study integrated transcriptomic and clinical data from 310 PDAC patients in GEO database. We performed consensus clustering using tumor-associated TLS (TA-TLS) genes, identifying three distinct molecular subtypes. Single-sample gene set enrichment analysis (ssGSEA) was then employed to calculate a TLS score for each patient, allowing for TLS-based evaluation. Key prognostic genes were identified using an iterative LASSO method, leading to the construction of a risk assessment model, which was validated across independent cohorts. We further analyzed the TLS score using single-cell RNA sequencing (scRNA-seq), visualized key gene expression, and validated protein expression through immunohistochemistry (IHC). Additionally, we explored the effects of DNASE1L3 on cell proliferation and migration, and its immune-related functions using Gene Set Enrichment Analysis (GSEA) and multiplex cytokine analysis.

RESULTS

Consensus clustering revealed three PDAC molecular subtypes with significant differences in prognosis, TA-TLS gene expression, and TME features. The TLS score effectively stratified patients into high and low groups, correlating with survival outcomes and TME characteristics. Our risk model, validated across cohorts, reliably predicted patient outcomes. Validation studies showed lower expression of DNASE1L3 and IL33 in tumor tissues. scRNA-seq confirmed TLS score associations with immune cells. DNASE1L3 overexpression inhibited PDAC cell proliferation and migration, with cytokine analysis indicating increased immune activity.

CONCLUSIONS

This study elucidated the expression profile of TA-TLS genes in PDAC, constructed a TLS gene-based scoring system, and developed a related risk model. We also explored the functions and potential antitumor mechanisms of key genes, providing evidence and new insights for enhancing TLS-targeted immunotherapy strategies in PDAC.

Involvement of lncRNA MIR205HG in idiopathic pulmonary fibrosis and IL-33 regulation via Alu elements

Idiopathic pulmonary fibrosis (IPF) causes remodeling of the distal lung. Pulmonary remodeling is histologically characterized by fibrosis, as well as appearance of basal cells; however, the involvement of basal cells in IPF remains unclear. Here, we focus on the long noncoding RNA MIR205HG, which is highly expressed in basal cells, using RNA sequencing. Through RNA sequencing of genetic manipulations using primary cells and organoids, we discovered that MIR205HG regulates IL-33 expression. Mechanistically, the AluJb element of MIR205HG plays a key role in IL-33 expression. Additionally, we identified a small molecule that targets the AluJb element, leading to decreased IL-33 expression. IL-33 is known to induce type 2 innate lymphoid cells (ILC2s), and we observed that MIR205HG expression was positively correlated with the number of ILC2s in patients with IPF. Collectively, these findings provide insights into the mechanisms by which basal cells contribute to IPF and suggest potential therapeutic targets.

HSP70 chaperones IL-33 in chronic airway disease

RATIONALE

IL-33 is a key driver of type 2 inflammation relevant to airway epithelial biology. However, the mechanisms for IL-33 secretion and regulation in the context of chronic airway disease is poorly understood.

OBJECTIVES

We sought to define how a disease associated isoform IL-33d34 that escapes nuclear sequestration and is tonically secreted from epithelial cells can be recruited to non-canonical secretory pathways.

METHODS

IL-33d34 interaction with HSP70 was assessed and validated by affinity purification, mass-spectrometry and miniTurboID proximity labeling. Secretion and activity reporter assays were used to probe the effect of HSP70 on epithelial IL-33d34 secretion and receptor binding. Human airway disease biospecimens were analyzed for dysregulation of heat shock pathways revealing modulation of TCP1 complex intermediates.

MEASUREMENTS AND MAIN RESULTS

We confirmed that HSP70 interacts directly with IL-33d34, recruits the cytokine to a vesicular compartment and enhances stability upon secretion. IL-33, HSP70 and other key mediators of proteostasis were found to be dysregulated in airway disease biospecimens and secreted extracellular vesicles. The IL-33d34 interactome was characterized and novel secretion modulators were identified.

CONCLUSIONS

This study confirms a role for HSP70 in non-canonical IL-33d34 secretion and function that may be amenable for therapeutic targeting in airway diseases.

Immune-privileged cord blood-derived endothelial colony-forming cells: advancing immunomodulation and vascular regeneration

Cord blood-derived endothelial colony-forming cells (CB-ECFCs) hold significant promise for regenerative medicine due to their unique vasculogenic and immunomodulatory properties. These cells exhibit a superior proliferative capacity, robust ability to form vascular networks, and lower immunogenicity compared to adult and embryonic stem cell-derived counterparts. The immune-privileged characteristics of CB-ECFCs, including reduced expression of pro-inflammatory mediators and tolerance-inducing molecules such as HLA-G, further enhance their therapeutic potential. Their low immunogenicity minimizes the risk of immune rejection, making them suitable for allogenic cell therapies. Their application extends to complex tissue engineering and organ revascularization, where their ability to integrate into three-dimensional scaffolds and support vascular tree formation represents a significant advancement. Moreover, CB-ECFCs' capability to adapt to inflammatory stimuli and retain immunological memory highlights their functional versatility in dynamic microenvironments. This review highlights the remarkable ontogeny of ECFCs while unveiling the unparalleled potential of CB-ECFCs in revolutionizing regenerative medicine. From pre-vascularizing engineered tissues and organoids to pioneering cell-based therapies for cardiovascular, dermatological, and degenerative diseases, CB-ECFCs stand at the forefront of cutting-edge biomedical advancements, offering unprecedented opportunities for therapeutic innovation. By leveraging their vasculogenic, immune-regulatory, and regenerative capacities, CB-ECFCs offer a robust alternative for addressing the challenges of vascular repair and organ engineering. Future research should focus on unraveling their transcriptomic and functional profiles to optimize clinical applications and advance the field of regenerative medicine.

Myeloid-derived IL-33 drives γδ T cell-dependent resistance against cutaneous infection by Strongyloides ratti

Interleukin 33 (IL-33) is a pleiotropic cytokine released from diverse cell types that regulate both pro- and anti-inflammatory responses during pathogen infection. However, it remains unclear whether IL-33 controls key aspects of cutaneous immunity against skin-penetrating parasites. In this study, mice percutaneously infected with the parasitic helminth Strongyloides ratti were investigated to understand mechanisms of anamnestic immunity at the skin barrier. Surprisingly, mice lacking the Type 2 transcription factor STAT6 (signal transducer and activator of transcription 6) had no defects in secondary resistance to infection, whereas IL-33 gene deficiency or local blockade of IL-33 receptor (ST2) signaling abrogated host resistance. Depletion of CD4+ T cells or type 2 innate lymphoid cells had only a moderate impact on protection, but the loss of γδ T cells completely ablated cutaneous immunity against rechallenge. We identified a CD62Lhi IL-33 receptor (ST2)-expressing γδ T cell population that accumulated in the skin of protected mice that was dependent upon IL-33 expression in myeloid lineage antigen-presenting cells. This work suggests a previously unrecognized mechanism wherein noncanonical type 2 immunity operates through myeloid antigen-presenting cells and skin γδ T cells to adaptively repel skin-penetrating helminth larvae.

Εosinophilic Chronic Obstructive Pulmonary Disease. What Do We Know So Far?

The latest advances in asthma treatment have highlighted the significance of eosinophilia and the possible role of some pro-eosinophilic mediators, like interleukins (IL) IL-5, IL-4/IL-13, and IL-33 in the disease's pathogenesis. Considering that a subgroup of patients with chronic obstructive pulmonary disease (COPD) may have blood eosinophilia akin to that seen in asthma, numerous studies in the last decade have suggested that eosinophilic COPD is a separate entity. While the exact role of blood eosinophils in the pathophysiology of COPD remains unclear, eosinophilia seems to increase the effectiveness of corticosteroid therapy. Currently, monoclonal antibodies targeting the interleukins (IL-5, IL-4, IL-13, and IL-33) or their receptors are being investigated in patients with COPD belonging in T2-high endotype. This review focuses on the mechanisms of eosinophilia in COPD, the effects of eosinophilia on disease outcome, and examines the most recent data on the use of peripheral blood eosinophilia in treating patients with COPD. Finally, we emphasize the current implication of monoclonal antibodies in COPD in the context of eosinophilic airway inflammation.

Type 2 immunity in allergic diseases

Significant advancements have been made in understanding the cellular and molecular mechanisms of type 2 immunity in allergic diseases such as asthma, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis (EoE), food and drug allergies, and atopic dermatitis (AD). Type 2 immunity has evolved to protect against parasitic diseases and toxins, plays a role in the expulsion of parasites and larvae from inner tissues to the lumen and outside the body, maintains microbe-rich skin and mucosal epithelial barriers and counterbalances the type 1 immune response and its destructive effects. During the development of a type 2 immune response, an innate immune response initiates starting from epithelial cells and innate lymphoid cells (ILCs), including dendritic cells and macrophages, and translates to adaptive T and B-cell immunity, particularly IgE antibody production. Eosinophils, mast cells and basophils have effects on effector functions. Cytokines from ILC2s and CD4+ helper type 2 (Th2) cells, CD8 + T cells, and NK-T cells, along with myeloid cells, including IL-4, IL-5, IL-9, and IL-13, initiate and sustain allergic inflammation via T cell cells, eosinophils, and ILC2s; promote IgE class switching; and open the epithelial barrier. Epithelial cell activation, alarmin release and barrier dysfunction are key in the development of not only allergic diseases but also many other systemic diseases. Recent biologics targeting the pathways and effector functions of IL4/IL13, IL-5, and IgE have shown promising results for almost all ages, although some patients with severe allergic diseases do not respond to these therapies, highlighting the unmet need for a more detailed and personalized approach.

Exosomes from adipose-derived stem cells accelerate wound healing by increasing the release of IL-33 from macrophages

BACKGROUND

Mesenchymal stem cell (MSC) -derived exosomes, especially adipose-derived mesenchymal stem cell exosomes (ADSC-Exos), have emerged as a promising alternative for skin damage repair with anti-inflammatory, angiogenic and cell proliferation effects while overcoming some of the limitations of MSC. However, the mechanism by which ADSC-Exos regulates inflammatory cells during wound healing remains unclear. This study investigated how ADSC-Exos regulate macrophages to promote wound healing.

METHODS

ADSC-Exos were isolated using ultracentrifugation, with subsequent quantification of exosomes particle number. To investigate their role in wound healing, the effects of ADSC-Exos on inflammation, angiogenesis, collagen deposition and macrophage polarization were evaluated through immunohistochemical staining, immunofluorescence and western blotting. Changes in gene expression associated with ADSC-Exos-induced macrophage polarization were analyzed using qPCR. RNA sequencing was performed to identify differentially expressed genes affected by ADSC-Exos. The critical role of IL-33 in the wound healing process was further confirmed using Il33-/- mice. Additionally, co-culture experiments were conducted to explore the effects of IL-33 on keratinocyte proliferation, collagen deposition and epithelialization.

RESULTS

ADSC-Exos inhibited the expression of TNF-α and IL-6, induced M2 macrophage polarization, promoted collagen deposition and angiogenesis, and accelerated wound healing. RNA sequencing identified IL-33 as a key mediator in this process. In Il33-/- mice, impaired wound healing and decreased M2 macrophage polarization were observed. The co-culture experiments showed that IL-33 enhanced keratinocyte function through activation of the Wnt/β-catenin signaling pathway. These findings highlight the therapeutic potential of ADSC-Exos in wound healing by modulating IL-33.

CONCLUSIONS

ADSC-Exos promote wound healing by regulating macrophage polarization and enhancing IL-33 release which drives keratinocyte proliferation, collagen deposition and epithelialization via the Wnt/β-catenin signaling pathway. These findings provide a mechanistic basis for the therapeutic potential of ADSC-Exos in tissue repair and regeneration.

Endogenous IL-33 inhibits apoptosis in non-small cell lung cancer cells by regulating BCL2/BAX via the ERK1/2 pathway

Lung cancer remains a leading cause of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) accounting for 85% of cases. Although targeted therapies have improved treatment outcomes, drug resistance poses a significant challenge, underscoring the need for novel therapeutic strategies. Interleukin-33 (IL-33), a member of the IL-1 superfamily, functions both as a nuclear protein and a cytokine, binding to its receptor, ST2. While IL-33 is known to promote tumour cell migration and metastasis, its role in regulating apoptosis remains incompletely understood. In this study, we focused on endogenous IL-33, employing lentiviral transfection to overexpress both the full-length and mature forms of IL-33 in lung cancer cells. We examined its effects on apoptosis in vitro and investigated the underlying molecular mechanisms. Our findings reveal that endogenous IL-33 inhibits apoptosis in lung cancer cells by modulating the expression of BCL2 and BAX via the ERK1/2 pathway in an autocrine manner. These results uncover a novel mechanism of IL-33-mediated tumour survival and provide a foundation for the development of IL-33/ST2-targeted therapies in NSCLC.

Proteomic meta-analysis unveils new frontiers for biomarkers research in pancreatic carcinoma

Pancreatic carcinoma (PC) is the sixth leading cause of cancer death in both sexes in 2022, responsible for almost 5% of all cancer deaths worldwide; it is characterized by a poor prognosis since most patients present with an unresectable and metastatic tumor. To date, the decreasing trend in mortality rates related to the most common cancers has contributed to making pancreatic cancer a serious public health problem. In the last few years, scientific research has led to many advances in diagnostic approaches, perioperative management, radiotherapy techniques, and systemic therapies for advanced disease, but only with modest incremental progress in PC patient outcomes. Most of the causes of this high mortality are, unfortunately, late diagnosis and an important therapeutic resistance; for this reason, the most recent high-throughput proteomics technologies focus on the identification of novel biomarkers and molecular profiling to generate new insights in the study of PC, to improve diagnosis and prognosis and to monitor the therapies progress. In this work, we present and discuss the integration of results from different revised studies on protein biomarkers in a global proteomic meta-analysis to understand which path to pursue scientific research. In particular, cancer signaling, inflammatory response, and cell migration and signaling have emerged as the main pathways described in PC, as well as scavenging of free radicals and metabolic alteration concurrently highlighted new research insights on this disease. Interestingly, from the study of upstream regulators, some were found to be shared by collecting data relating to both biological fluid and tissue biomarkers, side by side: specifically, TNF, LPS, p38-MAPK, AGT, miR-323-5p, and miR-34a-5p. By integrating many biological components with their interactions and environmental relationships, it's possible to achieve an in-depth description of the pathological condition in PC and define correlations between concomitant symptoms and tumor genesis and progression. In conclusion, our work may represent a strategy to combine the results from different studies on various biological samples in a more comprehensive way.

Diabetes exacerbates periodontitis by disrupting IL-33-mediated interaction between periodontal ligament fibroblasts and macrophages

Tissue-resident fibroblasts with immunomodulatory properties have recently been identified as key players in inflammation. However, their roles within the periodontal niche in diabetes-associated periodontitis remain unclear. Interleukin (IL)-33, known as an "alarmin" in inflammatory responses, has recently emerged as a potential contributor to periodontitis. Herein, we show that IL-33 levels are reduced in periodontal ligament fibroblasts (PDLFs) in the in vivo models of diabetes-associated periodontitis and in vitro models of diabetic inflammation. In the in vitro co-culture model, overexpression of IL-33 in PDLFs promotes M2 macrophage polarization, while knockdown of IL-33 in PDLFs instigates M1 macrophage polarization. Notably, supplementation with IL-33 in vivosignificantly alleviates periodontal tissue destruction and enhances M2 macrophage infiltration, whereas targeting the IL-33/ST2 axis exacerbates tissue damage and promotes M1 macrophage polarization in diabetes-associated periodontitis. Additionally, theCUT&RUN assay confirms the direct regulation of IL-33 by Yes-associated protein (YAP). These findings demonstrate that IL-33 deficiency in PDLFs favors M1 macrophage polarization, thereby exacerbating the pathogenesis of diabetes-associated periodontitis. Our study underscores the essential immunomodulatory role of PDLFs in creating an inflammatory niche and unveils a novel interaction axis between PDLFs and macrophages in diabetes-associated periodontitis.

The role of IL-19, IL-24, IL-21 and IL-33 in intestinal mucosa of inflammatory bowel disease: A narrative review

Interleukins are potential therapeutic targets that can alter the prognosis and progression of inflammatory bowel disease (IBD). The roles of IL-6, IL-10, IL-17, and IL-23 have been extensively studied, setting the stage for the development of novel treatments for patients with IBD. Other cytokines have been less extensively studied. Members of the IL-20 family, mainly IL-19 and IL-24, are involved in the pathogenesis of IBD, but their exact role remains unclear. Similarly, IL-33, a newly identified cytokine, has been shown to control the Th1 effector response and the action of colonic Tregs in animal models of colitis and patients with IBD. IL-21 is involved in the Th1, Th2, and Th17 responses. Data support a promising future use of these interleukins as biomarkers of severe diseases and as potential therapeutic targets for novel monoclonal antibodies. This review aims to summarize the existing studies involving animal models of colitis and patients with IBD to clarify their role in the intestinal mucosa.

IL-33-activated ILC2s induce tertiary lymphoid structures in pancreatic cancer

Tertiary lymphoid structures (TLSs) are de novo ectopic lymphoid aggregates that regulate immunity in chronically inflamed tissues, including tumours. Although TLSs form due to inflammation-triggered activation of the lymphotoxin (LT)-LTβ receptor (LTβR) pathway1, the inflammatory signals and cells that induce TLSs remain incompletely identified. Here we show that interleukin-33 (IL-33), the alarmin released by inflamed tissues2, induces TLSs. In mice, Il33 deficiency severely attenuates inflammation- and LTβR-activation-induced TLSs in models of colitis and pancreatic ductal adenocarcinoma (PDAC). In PDAC, the alarmin domain of IL-33 activates group 2 innate lymphoid cells (ILC2s) expressing LT that engage putative LTβR+ myeloid organizer cells to initiate tertiary lymphoneogenesis. Notably, lymphoneogenic ILC2s migrate to PDACs from the gut, can be mobilized to PDACs in different tissues and are modulated by gut microbiota. Furthermore, we detect putative lymphoneogenic ILC2s and IL-33-expressing cells within TLSs in human PDAC that correlate with improved prognosis. To harness this lymphoneogenic pathway for immunotherapy, we engineer a recombinant human IL-33 protein that expands intratumoural lymphoneogenic ILC2s and TLSs and demonstrates enhanced anti-tumour activity in PDAC mice. In summary, we identify the molecules and cells of a druggable pathway that induces inflammation-triggered TLSs. More broadly, we reveal a lymphoneogenic function for alarmins and ILC2s.

Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxic respiratory failure caused by diffuse lung inflammation and edema. ARDS can be precipitated by intrapulmonary factors or extrapulmonary factors, which can lead to severe hypoxemia. Patients suffering from ARDS have high mortality rates, including a 28-day mortality rate of 34.8% and an overall in-hospital mortality rate of 40.0%. The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of systemic inflammation and coagulation, including the respiratory system, circulatory system, and immune system. In general, the treatment of inflammatory injuries is a coordinated process that involves the downregulation of proinflammatory pathways and the upregulation of anti-inflammatory pathways. Given the complexity of the underlying disease, treatment needs to be tailored to the problem. Hence, we discuss the pathogenesis and treatment methods of affected organs, including 2019 coronavirus disease (COVID-19)-related pneumonia, drowning, trauma, blood transfusion, severe acute pancreatitis, and sepsis. This review is intended to provide a new perspective concerning ARDS and offer novel insight into future therapeutic interventions.

Exploring the causal relationship between inflammatory cytokines, metabolites, and Behcet's syndrome: Mendelian randomization

INTRODUCTION

Behcet's syndrome, as a vasculitic disease involving multiple systems, often induces oral mucosal ulcers. However, levels of inflammatory cytokines and metabolites are unknown for the probability of developing the disease. This study aims to reveal the causal relationship between the cytokines and metabolites and Behcet's syndrome through Mendelian randomization analysis.

MATERIALS AND METHODS

The instrumental variable single nucleotide polymorphisms (SNPs) were used in the study, which showed associations between 91 cytokines and 553 metabolites, respectively. To explore the causal relationship between these exposure factors and Behcet's syndrome, the random effects inverse variance weighting method was adopted. In addition, sensitivity analysis was carried out using Cochran's Q test, heterogeneity test, horizontal pleotropy test and MR-Egger intercept test to evaluate the robustness and validity of our research results.

RESULTS

A total of five substances were identified as causally related to Behcet's syndrome, namely, the cellular factors Interleukin 12 subunit beta(IL-12B) and Interleukin-33(IL-33), the metabolite mannitol, X-12728, and Ratio of Bisallylic groups to double bonds. Furthermore, no significant evidence suggesting heterogeneity or pleiotropy was observed.

CONCLUSION

Our study adds to current knowledge on the role of specific inflammatory cytokines and metabolites in aetiology of Behcet's syndrome. The identified cytokines and metabolites might be used as markers for clinical screening and prevention of Behcet's syndrome, as well as candidate molecules for future mechanism exploration and drug target selection. Further validation is needed to assess the potential of these cytokines and metabolites as pharmacological targets for Behcet's syndrome prevention.

Dermal White Adipose Tissue-Derived Il-33 Regulates Il-4/13 Expression in Myeloid Cells during Inflammation

Effective tissue response to infection and injury essentially relies on the fine-tuned induction and subsequent resolution of inflammation. Recent research highlighted multiple functions of dermal white adipose tissue (dWAT) beyond its traditional role as an energy reservoir. However, in contrast to other fat depots, there are only limited data about putative immune-regulatory functions of dWAT. Therefore, we investigated the impact of dWAT in the control of an acute skin inflammation. Skin inflammation triggers the activation of dWAT. In turn, soluble mediators of activated dWAT stimulate the expression of numerous genes controlling skin inflammation, including the T helper 2 cell cytokines Il4 and Il13, in myeloid cells in vitro. Consistently, myeloid cells isolated from inflamed skin showed a significant upregulation of Il-4/13 expression compared with those isolated from healthy skin. Mechanistically, we demonstrate that IL-33 released from activated dWAT is responsible for IL-4/13 stimulation in myeloid cells. Interestingly, obesity attenuates IL-33 secretion in dWAT during inflammation, resulting in decreased Il-4 and Il-13 expressions in myeloid cells. Our data reveal an IL-33-IL-4/13 signaling cascade initiated from dWAT in a T helper 2-independent context of inflammation that may contribute to limitation of inflammation. This cascade seems to be disturbed in individuals with obesity with prolonged inflammation.

IL-33 released during challenge phase regulates allergic asthma in an age-dependent way

Epithelial-derived cytokines, especially type 2 alarmins (TSLP, IL-25, and IL-33), have emerged as critical mediators of type 2 inflammation. IL-33 attracts more interest for its strong association with allergic asthma, especially in childhood asthma. However, the age-dependent role of IL-33 to the development of allergic asthma remains elusive. Here, using OVA-induced allergic asthma model in neonatal and adult mice, we report that IL-33 is the most important alarmin in neonatal lung both at steady state or inflammation. The deficiency of IL-33/ST2 abrogated the development of allergic asthma only in neonates, whereas in adults the effect was limited. Interestingly, the deficiency of IL-33/ST2 equally dampened the ILC2 responses in both neonatal and adult models. However, the effect of IL-33/ST2 deficiency on Th2 responses is age-dependent, which is only blocked in neonates. Furthermore, IL-33/ST2 signaling is dispensable for OVA sensitization. Following OVA challenge in adults, the deficiency of IL-33/ST2 results in compensational more TSLP, which in turn recruits and activates lung DCs and boosts Th2 responses. The enriched γδ T17 cells in IL-33/ST2 deficient neonatal lung suppress the expression of type 2 alarmins, CCL20 and GM-CSF via IL-17A, thus might confer the inhibition of allergic asthma. Finally, on the basis of IL-33 deficiency, the additive protective effects of TSLP blocking is much more pronounced than IL-25 blocking in adults. Our studies demonstrate that the role of IL-33 for ILC2 and Th2 responses varies among ages in OVA models and indicate that the factor of age should be considered for intervention of asthma.

IL-33/ST2 axis in diverse diseases: regulatory mechanisms and therapeutic potential

Interleukin-33 (IL-33) is a nuclear factor and member of the IL-1 cytokine family. IL-33 is mainly expressed by epithelial and endothelial cells and exerts its function through interaction with various immune cells, and binding to its receptor can form the IL-33/Suppression of tumorigenicity 2 (ST2) signaling pathway. While most cytokines are actively synthesized within cells, IL-33 is produced passively in response to tissue damage or cell necrosis, indicating its role as a signaling molecule following cellular infection, stress, or trauma. IL-33/ST2 signaling pathway has been proved to play diverse role in the pathological process of central nervous system disorders, cancer, fibrosis, autoimmune diseases, etc. Although research on the IL-33/ST2 signaling pathway has deepened recently, relevant treatment strategies have been proposed, and even targeted drugs are in the preclinical stage; further research on the effect of the IL-33/ST2 signaling pathway in different diseases is still necessary, to provide a clearer understanding of the different roles of IL-33/ST2 in disease progression and to develop new drugs and treatment strategies. Because IL-33/ST2 plays an important role in the occurrence and progression of diseases, the study of therapeutic drugs targeting this pathway is also necessary. This review focused on recent studies on the positive or negative role of IL-33/ST2 in different diseases, as well as the current related drugs targeting IL-33/ST2 in the preclinical and clinical stage. The mechanism of IL-33/ST2 in different diseases and its mediating effect on different immune cells have been summarized, as well as the antibody drugs targeting IL-33 or ST2, natural compounds with a mediating effect, and small molecule substances targeting relative pathway. We aim to provide new ideas and treatment strategies for IL-33/ST2-related drugs to treat different diseases.

Inhibition of BRD4 attenuated IFNγ-induced apoptosis in colorectal cancer organoids

BACKGROUND

This study aimed to analyze the functional role of Brd4 in colorectal cancer (CRC) organoids. Brd4 was identified as a CRC-related gene by our previous Sleeping Beauty mutagenesis transposon screening in mice. Brd4 is a transcriptional regulator that recognizes acetylated histones and is known to be involved in inflammatory responses. The role of Brd4 in CRC development remains largely unknown.

METHODS

We knocked out Brd4 in tumor organoids carrying mutations in Apc and Kras to generate Brd4KO organoids, and performed RNA-seq. The response of Brd4KO organoids to IFNγ was analyzed via a cell viability assay, an apoptosis assay, and RNAseq. The results were validated by pharmacological inhibition experiments with JQ1 in human CRC organoids.

RESULTS

In Brd4KO organoids, the IFNγ signaling genes Il33 and Myc target genes were downregulated. The addition of IFNγ to the colon organoids induced apoptosis, but IFNγ-induced apoptosis was attenuated in the Brd4KO organoids compared with the control organoids (two-sided t-test, P < 0.05). Similar results were obtained from pharmacological inhibition with JQ1 in human CRC organoids; IL33 expression was decreased, and IFNγ-induced apoptosis was attenuated in the presence of JQ1.

CONCLUSIONS

Our results showed that the inhibition of Brd4 suppressed IFNγ-induced cytotoxicity by modulating the Jak-Stat pathway. These data suggested that the inhibition of Brd4 could increase cell viability in the cancer microenvironment where IFNγ is abundant, revealing a new aspect of the molecular mechanism of CRC development. Our results may help in evaluating the application of Bet inhibitors in treating CRC. Additionally, our RNA-seq data sets will be helpful for clarifying the relationship between Brd4 and immunomodulators, such as Il33, or for studying the responses of colonic epithelial cells to IFNγ.

IL-33, a neutrophil extracellular trap-related gene involved in the progression of diabetic kidney disease

BACKGROUND

Chronic inflammation is well recognized as a key factor related to renal function deterioration in patients with diabetic kidney disease (DKD). Neutrophil extracellular traps (NETs) play an important role in amplifying inflammation. With respect to NET-related genes, the aim of this study was to explore the mechanism of DKD progression and therefore identify potential intervention targets.

METHODS

Hub NET-related DEGs were screened via differential expression analysis and three machine learning methods, namely, LASSO, SVM-RFE and random forest. Consensus clustering was performed to analyze NET-related subtypes in DKD patients. KEGG enrichment analysis, GSEA, GSVA, ssGSEA and ESTIMATE were conducted to explore the molecular features of DKD patient subtypes. Leveraging single-nucleus RNA-seq datasets, the "scissor" and "bisqueRNA" algorithms were applied to identify the composition of renal cell types in DKD patient subtypes. Soft clustering analysis was performed to obtain gene groups with similar expression patterns during the development and progression of DKD. The correlations between hub NET-related DEGs and clinical parameters were mined from the Nephroseq V5 database. The core gene among the hub NET-related DEGs was selected by calculating semantic similarity. "Cellchat" algorithm, immunostaining, ELISA and flow cytometry were performed to explore the expression and function of the core gene. The Drug-Gene Interaction Database (DGIdb) was searched to identify candidate drugs.

RESULTS

Six hub NET-related DEGs, namely, ACTN1, ITGB2, IL33, HRG, NFIL3 and CLEC4E, were identified. On the basis of these 6 genes, DKD patients were classified into 2 clusters. Cluster 1 patients, with higher NET scores, were evidently more immune-activating than those of cluster 2. Markedly increased numbers of immune cells, fibroblasts and proinflammatory proximal tubular cells were observed in cluster 1 but not in cluster 2. Cluster 1 also represented a more clinically advanced disease state. Among the 6 hub NET-related DEGs, the mRNA expression of ACTN1, ITGB2, IL33 and HRG was correlated with the eGFR. By semantic similarity analysis, IL33 was considered a central gene among the 6 genes. Cell-cell communication analysis further indicated that intercellular interactions via IL-33 were enhanced in DKD. Serum IL-33 concentration was negatively correlated with eGFR. IHC staining revealed that IL-33 expression was upregulated in the tubular epithelium in DKD patients. Supernatants from inflammatory tubular epithelial cells can increase MPO in neutrophils, whereas addition of anti-IL-33 antibody attenuated this phenotype.

CONCLUSIONS

We identified 2 distinct NET-related subtypes in DKD patients, in which one subgroup was apparently more inflammatory and associated with a more severe clinical state. A significantly increased level of IL-33 in this inflammatory patient subgroup may play a role in aggravating inflammation via the IL-33-ST2 axis.

Optimization of seizure prevention by cannabidiol (CBD)

Objective

Cannabidiol (CBD) is one of the most prominent non-psychotropic cannabinoids with known therapeutic potentials. Based on its anti-seizure efficacy, the first cannabis derived pharmaceutical grade CBD-based medication was approved in the USA in 2018 for the treatment of seizures in patients 2 years and older. Despite the effectiveness in reducing seizures, there remain several major questions on the optimization of CBD therapy for epilepsy such as the optimal dosage, composition, and route of delivery, which are the main objective of this current study.

Methods

We evaluated the antiseizure effects of CBD through different compositions, routes of delivery, and dosages in a pre-clinical model. We used a kainic acid-induced epilepsy model in C57BL/6 mice, treated them with placebo and/or CBD through inhalation, oral, and injection (intraperitoneal) routes. We used CBD broad spectrum (inhaled and intraperitoneal) vs CBD isolate formulations. We employed the Racine scaling system to evaluate the severity of the seizures, flow cytometry for measuring immune biomarkers and neurotrophic factors, and histologic analysis to examine and compare the groups.

Results

Our findings showed that all forms of CBD reduced seizures severity. Among the combination of CBD tested, CBD broad spectrum via inhalation was the most effective in the treatment of epileptic seizures (p < 0.05) compared to other forms of CBD treatments.

Conclusion

Our data suggest that route and CBD formulations affect its efficacy in the prevention of epileptic seizures. Inhaled broad spectrum CBD showed a potential superior effect compared to other delivery routes and CBD formulations in the prevention of epileptic seizures, which warrants further research.

Fibroblast-derived IL-33 exacerbates orofacial neuropathic pain via the activation of TRPA1 in trigeminal ganglion neurons

Damage to the peripheral nerves of trigeminal ganglion (TG) neurons leads to intractable orofacial neuropathic pain through the induction of neuroinflammation. However, the details of this process are not yet fully understood. Here, we found that fibroblast-derived interleukin (IL)-33 was required for the development of mechanical allodynia in whisker pad skin following infraorbital nerve injury (IONI). The amount of IL-33 in the TG increased after IONI when the mice exhibited mechanical allodynia. Neutralization of IL-33 in the TG inhibited the development of IONI-induced mechanical allodynia. Conversely, intra-TG administration of recombinant human IL-33 (rhIL-33) elicited mechanical allodynia in naïve mice. IL-33 and its receptor were exclusively expressed in fibroblasts and neurons, respectively, in the TG. Fibroblast ablation caused the loss of IL-33 in the TG and delayed the development of mechanical allodynia after IONI. rhIL-33 elicited an increase in intracellular Ca2+ concentration and subsequent enhancement of Ca2+ influx via transient receptor potential ankyrin 1 (TRPA1) in primary cultured TG neurons. Additionally, rhIL-33 facilitated membrane translocation of TRPA1 in the TG. Mechanical allodynia caused by intra-TG administration of rhIL-33 was significantly inhibited by pharmacological blockade or gene silencing of TRPA1 in the TG. Inhibition of protein kinase A abrogated TRPA1 membrane translocation and delayed mechanical allodynia after IONI. Substance P stimulation caused upregulation of IL-33 expression in primary cultured fibroblasts. Preemptive administration of a neurokinin-1 receptor antagonist in the TG attenuated mechanical allodynia and IL-33 expression following IONI. Taken together, these results indicate that fibroblast-derived IL-33 exacerbates TG neuronal excitability via suppression of tumorigenicity 2 (ST2)-TRPA1 signaling, ultimately leading to orofacial neuropathic pain.

Dynamics of tissue repair regulatory T cells and damage in acute Trypanosoma cruzi infection

Tissue-repair regulatory T cells (trTregs) comprise a specialized cell subset essential for tissue homeostasis and repair. While well-studied in sterile injury models, their role in infection-induced tissue damage and antimicrobial immunity is less understood. We investigated trTreg dynamics during acute Trypanosoma cruzi infection, marked by extensive tissue damage and strong CD8+ immunity. Unlike sterile injury models, trTregs significantly declined in secondary lymphoid organs and non-lymphoid target tissues during infection, correlating with systemic and local tissue damage, and downregulation of function-associated genes in skeletal muscle. This decline was linked to decreased systemic IL-33 levels, a key trTreg growth factor, and promoted by the Th1 cytokine IFN-γ. Early recombinant IL-33 treatment increased trTregs, type 2 innate lymphoid cells, and parasite-specific CD8+ cells at specific time points after infection, leading to reduced tissue damage, lower parasite burden, and improved disease outcome. Our findings not only provide novel insights into trTregs during infection but also highlight the potential of optimizing immune balance by modulating trTreg responses to promote tissue repair while maintaining effective pathogen control during infection-induced injury.

Lack of ST2 aggravates glioma invasiveness, vascular abnormality, and immune suppression

Background

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, characterized by aggressive growth and a dismal prognosis. Interleukin-33 (IL-33) and its receptor ST2 have emerged as regulators of glioma growth, but their exact function in tumorigenesis has not been deciphered. Indeed, previous studies on IL-33 in cancer have yielded somewhat opposing results as to whether it is pro- or anti-tumorigenic.

Methods

IL-33 expression was assessed in a GBM tissue microarray and public databases. As in vivo models we used orthotopic xenografts of patient-derived GBM cells, and syngenic models with grafted mouse glioma cells.

Results

We analyzed the role of IL-33 and its receptor ST2 in nonmalignant cells of the glioma microenvironment and found that IL-33 levels are increased in cells surrounding the tumor. Protein complexes of IL-33 and ST2 are mainly found outside of the tumor core. The IL-33-producing cells consist primarily of oligodendrocytes. To determine the function of IL-33 in the tumor microenvironment, we used mice lacking the ST2 receptor. When glioma cells were grafted to ST2-deficient mouse brains, the resulting tumors exhibited a more invasive growth pattern, and are associated with poorer survival, compared to wild-type mice. Tumors in ST2-deficient hosts are more invasive, with increased expression of extracellular matrix remodeling enzymes and enhanced tumor angiogenesis. Furthermore, the absence of ST2 leads to a more immunosuppressive environment.

Conclusions

Our findings reveal that glia-derived IL-33 and its receptor ST2 participate in modulating tumor invasiveness, tumor vasculature, and immunosuppression in glioma.

Prognostic value and clinical significance of IL-33 expression in patients with uterine corpus endometrial carcinoma

Uterine corpus endometrial carcinoma (UCEC) is one of the most common malignant tumours of the female genital tract. In the occurrence, progression and prognosis of UCEC, chronic inflammation plays an important role, making it pivotal to identify inflammatory response-related endometrial diseases. The cytokine interleukin-33 (IL-33) plays significant roles in immune responses, and has been associated with inappropriate allergic reactions, autoimmune diseases, and cancer pathology. In the past decade, studies have begun to uncover the pivotal roles of IL-33 in shaping tumour microenvironment (TME), where it may promote or inhibit tumorigenesis and development depending on the specific tumour types. However, the association between IL-33 expression and UCEC remains unclear. Here we investigated the expression profiles of IL-33 in pan-cancer based on TCGA database. Then, differential gene expression analysis and correlation analysis of IL-33 was investigated in UCEC. In addition, functional enrichment analysis and Kaplan-Meier survival analysis were performed to predict the potential function of IL-33 and its role in the prognosis of UCEC patients. Also, a nomogram model was constructed to predict the prognosis of UCEC. The expression of the inflammatory factor NF-κB p65 and the IL-33, along with its receptor ST2, was analyzed in UCEC tumour tissues and normal tissues of clinical specimens through immunohistochemical staining. Meanwhile, we used toluidine blue staining and methanol Congo red staining to observe the infiltration of mast cells and eosinophils in the endometrial tissue. The results of Kaplan-Meier plotter data indicated that patients with lower IL-33 expression had poorer progression-free interval than those with higher expression. Based on the results of multifactor Cox regression, a nomogram was generated to predict UCEC occurrence risk and prognosis. Clinical specimen characteristics also confirmed a negative correlation between IL-33 expression and UCEC staging and grading. This comprehensive analysis of IL-33, based on bioinformatics and immunohistochemistry, revealed that IL-33 has the function of inhibiting UCEC occurrence and progression and can be served as a beneficial prognostic marker in the clinic.

Interleukin-33: Expression, regulation and function in adipose tissues

Interleukin-33 (IL-33) is a pleiotropic cytokine of the IL-1 family that plays a key role in innate and adaptive immune responses and contributes to tissue homeostasis. Its role in adipose tissue function has been extensively studied, as adipose tissue serves as an important mediator of metabolic dysfunction. In adipose tissue, IL-33 is primarily produced by stromal cells. Its production is regulated by factors, such as androgens, aging, sympathetic innervation, and various inflammatory stimuli that affect the proliferation and differentiation of IL-33-producing stromal cells. Many studies have elucidated the mechanisms by which IL-33 interacts with the immune system components, local nerve fibers, and adipocytes to influence energy balance, with important consequences in obesity, cold-induced thermogenesis, and aging-related metabolic dysfunction. Here, we detail our current understanding of the molecular events that regulate the production of IL-33 within adipose tissue and discuss its role in regulating adipose function.

Interleukin-33 induces angiogenesis after myocardial infarction via AKT/eNOS signaling pathway

Myocardial infarction (MI) is one of the leading causes of mortality and morbidity worldwide. MI-damaged vascular structures are difficult to completely restore due to the heart's low regenerative capacity. Given interleukin-33 (IL-33) as a potent endothelial activator promoting angiogenesis, this study investigated the role of IL-33 in angiogenesis and cardiac repair after MI. A mouse model of MI was established. IL-33 improved cardiac function and induced an increase in vascular density after MI. Besides, IL-33 promoted human endothelial cells proliferation, migration, and differentiation under both normoxic and hypoxic conditions, consistently with increased angiogenesis in vivo. Mechanistic studies demonstrated that IL-33 could promote angiogenesis by activating eNOS and AKT, and stimulating NO production in vivo and in vitro. Given that injection of exogenous IL-33 induced an inflammatory response, we employed a multifunctional biomimetic nanoparticle drug delivery system to deliver IL-33, thereby enhancing its targeting to the heart for fibrotic therapy and reducing inflammation. In conclusion, our results indicate that IL-33 promotes endothelial angiogenesis after MI through AKT/eNOS/NO signaling pathway. PM&EM/IL-33 nanoparticles may hold promising therapeutic potential for protecting cardiac ischemic injury and mitigating inflammation.

Exploring the Impact of IL-33 Gene Polymorphism (rs1929992) on Susceptibility to Chronic Spontaneous Urticaria and Its Association with Serum Interleukin-33 Levels

Urticaria is a debilitating skin condition affecting up to 20% of the global population, characterized by erythematous, maculopapular lesions and significant quality of life impairment. This study focused on the role of interleukin 33 (IL-33) and its polymorphisms, particularly SNP rs1929992, in chronic spontaneous urticaria (CSU). Using demographic, clinical, and laboratory data from CSU patients and controls, we estimated allele and genotype frequencies, Hardy-Weinberg equilibrium condition, and serum IL-33 levels, using unconditional binomial logistic regression for association analysis. Results revealed that CSU patients had significantly higher frequencies of the minor allele of IL-33 rs1929992 compared to controls (31.25% vs. 17.35%, p = 0.024), and carriers of the GA genotype exhibited increased odds of CSU (adjusted OR = 2.208, p ≤ 0.001). Additionally, serum IL-33 levels were markedly elevated in CSU patients, particularly those with the GA genotype. The findings suggest that the IL-33 SNP is associated with an increased susceptibility to CSU, emphasizing its potential as a diagnostic and therapeutic biomarker. This study underscores the genetic and immunological underpinnings of CSU, paving the way for personalized treatment approaches.

The Presence and Pathogenic Roles of M(IL-33 + IL-2) Macrophages in Allergic Airway Inflammation

BACKGROUND

Macrophages, one of the most abundant immune cells in the lung, have drawn great attention in allergic asthma. Currently, most studies emphasize alternative activated (M2) polarization bias. However, macrophage function in allergic asthma is still controversial. Interleukin (IL)-9 contributes to the development and pathogenesis of allergic airway inflammation. We sought to investigate the IL-9-producing macrophage and its role in allergic asthma.

METHODS

The model of ovalbumin (OVA)-induced allergic airway inflammation was employed to evaluate IL-9 production in macrophages of lung tissues. We used 22 cytokines or stimuli to screen for IL-9-producing mouse macrophage subset in vitro. Real-time PCR, flow cytometry, ELISA, and RNA-seq to explore the subset. Conditional IL-33 receptor knockout (Lyz-ST2KO) mice and cellular adoptive transfer experiment were used to characterize the potential roles of M(IL-33 + IL-2) in allergic asthma.

RESULTS

We identified a unique pathogenic IL-9-producing macrophage in OVA-induced allergic airway inflammation. We found that only IL-33 significantly induced IL-9 production in mouse macrophages, and IL-2 collaborated with IL-33 to promote IL-9 production, referred to as M(IL-33 + IL-2). Importantly, human monocyte-derived macrophages produced IL-9 after IL-33 and IL-2 stimulation. Using Lyz-ST2KO mice and adoptive transfer of M(IL-33 + IL-2), we found that M(IL-33 + IL-2) significantly promoted pathogenesis in OVA-induced allergic airway inflammation. M(IL-33 + IL-2) has a distinctive gene expression profile with high expression of IL-9, IL-5, and IL-13 and its polarization is dependent on JAK2-STAT3-IRF1 pathway.

CONCLUSIONS

The identification of M(IL-33 + IL-2) subset extends the diversity and heterogeneity of macrophage subsets and may offer novel therapeutic strategies for the treatment of allergic inflammation.

Interleukin-33-activated basophils promote asthma by regulating Th2 cell entry into lung tissue

Asthma is characterized by lung eosinophilia, remodeling, and mucus plugging, controlled by adaptive Th2 effector cells secreting IL-4, IL-5, and IL-13. Inhaled house dust mite (HDM) causes the release of barrier epithelial cytokines that activate various innate immune cells like DCs and basophils that can promote Th2 adaptive immunity directly or indirectly. Here, we show that basophils play a crucial role in the development of type 2 immunity and eosinophilic inflammation, mucus production, and bronchial hyperreactivity in response to HDM inhalation in C57Bl/6 mice. Interestingly, conditional depletion of basophils during sensitization did not reduce Th2 priming or asthma inception, whereas depletion during allergen challenge did. During the challenge of sensitized mice, basophil-intrinsic IL-33/ST2 signaling, and not FcεRI engagement, promoted basophil IL-4 production and subsequent Th2 cell recruitment to the lungs via vascular integrin expression. Basophil-intrinsic loss of the ubiquitin modifying molecule Tnfaip3, involved in dampening IL-33 signaling, enhanced key asthma features. Thus, IL-33-activated basophils are gatekeepers that boost allergic airway inflammation by controlling Th2 tissue entry.