IL-1 receptor accessory protein is essential for IL-33-induced activation of T lymphocytes and mast cells

Targeting alarmins in asthma: From bench to clinic

Over the past 2 decades, mechanistic studies of allergic and type 2 (T2)-mediated airway inflammation have led to multiple approved therapies for the treatment of moderate-to-severe asthma. The approval and availability of these monoclonal antibodies targeting IgE, a T2 cytokine (IL-5) and/or cytokine receptors (IL-5Rα, IL-4Rα) has been central to the progresses made in the management of moderate-to-severe asthma over this period. However, there are persistent gaps in clinician's ability to provide precise care, given that many patients with T2-high asthma do not respond to IgE- or T2 cytokine-targeting therapies and that patients with T2-low asthma have few therapeutic options. The new frontier of precision medicine in asthma, as well as in other allergic diseases, includes the targeting of epithelium-derived cytokines known as alarmins, including thymic stromal lymphopoietin, IL-25, IL-33, and their receptors. The effects of these alarmins, which can act upstream of immune cells, involve both the innate and adaptive systems and hold potential for the treatment of both T2-high and -low disease. Tezepelumab, an anti-thymic stromal lymphopoietin antibody, has already been approved for the treatment of severe asthma. In this review, we discuss our current understanding of alarmin biology with a primary focus on allergic airway diseases. We link the mechanistic corollaries to the clinical implications and advances in drug development targeting alarmins, with a particular focus on currently approved treatments, those under study, and future potential targets in alarmin signaling pathways.

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.

Implication of Immunobiological Function of Melanocytes in Dermatology

Melanocytes are essential for regulating pigmentation and providing photoprotection in human skin. Originating from neural crest cells, these cells migrate to the basal layer of the epidermis and hair follicles during embryogenesis. Melanosomes, the specialized, membrane-bound organelles are essential for melanin synthesis. Beyond their role in pigmentation, melanocytes exhibit complex immune functions, expressing a variety of immune-related markers and receptors, such as pattern recognition receptors (PRRs), major histocompatibility complex class II (MHC-II) molecules, CD40, intercellular adhesion molecule 1 (ICAM-1), and programmed death-ligand 1 (PD-L1). These receptors allow melanocytes to detect environmental signals and engage in the innate immune response. Furthermore, melanocytes release various immunomodulatory substances, including proinflammatory cytokines, chemokines, and damage-associated molecular patterns (DAMPs), contributing to immune regulation. The immune functions of melanocytes are significantly influenced by external factors such as ultraviolet radiation (UVR), the microbiome, and oxidative stress. In different skin diseases, these immune functions may vary. For example, vitiligo, a common hypopigmentary disorder, is primarily driven by an autoimmune response targeting melanocytes, giving rise to depigmentation and the appearance of white patches. In contrast, melanoma, a form of skin cancer that arises from melanocytes, is closely linked to UV exposure. This review highlights the diverse immunobiological functions of melanocytes and their implications in dermatology.

Interleukin-33 and Obesity-Related Inflammation and Cancer

Interleukin-33 (IL-33) is a cytokine belonging to the IL-1 family. It is primarily associated with type 2 immune responses. It interacts with a receptor complex on immune cells in reaction to tissue damage or cellular injury. IL-33 is crucial in immune responses and is involved in various autoimmune and inflammatory diseases. Obesity is marked by chronic inflammation and is a known risk factor for several types of cancer. Recent studies have shown that IL-33 and its receptor complex are expressed in adipose (fat) tissue, suggesting they may play a role in obesity. While inflammation connects obesity and cancer, it is not yet clear whether IL-33 contributes to cancer associated with obesity. Depending on the cellular context, inflammatory environment, expression levels, and bioactivity, IL-33 can exhibit both protumorigenic and antitumorigenic effects. This review will explore the various functions of IL-33 in the inflammation linked to obesity and its relationship with cancer.

Interleukin-33: A Double-Edged Sword in Sepsis

Despite some advances that have been made in the clinical management of sepsis, its morbidity and mortality rates remain high. The pathogenesis of systemic inflammation and organ damage leading to septic mortality is not fully understood. Interleukin-33 (IL-33), a new member of the IL-1 superfamily, can be a traditional cytokine and a nuclear factor regulating gene transcription. Due to its biological characteristics, IL-33 can act as a double-edged sword in sepsis: It not only contributes to clear bacteria and improves survival but also causes inflammation, immunosuppression, and organ damage via modulating immune response. In this review, we will summarize updated information on the dual functions of IL-33 in the host immune response to sepsis.

Novel insights: crosstalk with non-puerperal mastitis and immunity

The two primary types of non-puerperal mastitis (NPM) are granulomatous lobular mastitis (GLM) and plasma cell mastitis (PCM). Existing research indicates that immune inflammatory response is considered to be the core of the pathogenesis of GLM and PCM, and both innate and adaptive immune responses play an important role in the pathophysiology of PCM and GLM. However, the regulatory balance between various immune cells in these diseases is still unclear. Consequently, we present a comprehensive summary of the immune-related variables and recent advances in GLM and PCM.

A neutrophil elastase-generated mature form of IL-33 is a potent regulator of endothelial cell activation and proliferative retinopathy

Human interleukin-33 (IL-33) is a 270 amino acid protein that belongs to the IL-1 cytokine family and plays an important role in various inflammatory disorders. Neutrophil proteases (Cathepsin G and Elastase) and mast cell proteases (tryptase and chymase) regulate the activity of IL-33 by processing full-length IL-33 into its mature form. There is little evidence on the role of these mature forms of IL-33 in retinal endothelial cell signaling and pathological retinal angiogenesis. Here, we cloned, expressed, and purified the various mature forms of human IL-33 and then evaluated the effects of IL-3395-270, IL-3399-270, IL-33109-270, and IL-33112-270 on angiogenesis in human retinal microvascular endothelial cells (HRMVECs). We observed that IL-3395-270, IL-3399-270, IL-33109-270, and IL-33112-270 significantly induced HRMVEC migration, tube formation and sprouting angiogenesis. However, only IL-3399-270 could induce HRMVEC proliferation. We used a murine model of oxygen-induced retinopathy (OIR) to assess the role of these mature forms of IL-33 in pathological retinal neovascularization. Our 3'-mRNA sequencing and signaling studies indicated that IL-3399-270 and IL-33109-270 were more potent at inducing endothelial cell activation and angiogenesis than the other mature forms. We found that genetic deletion of IL-33 significantly reduced OIR-induced retinal neovascularization in the mouse retina and that intraperitoneal administration of mature forms of IL-33, mainly IL-3399-270 and IL-33109-270, significantly restored ischemia-induced angiogenic sprouting and tuft formation in the hypoxic retinas of IL-33-/- mice. Thus, our study results suggest that blockade or inhibition of IL-33 cleavage by neutrophil proteases could help mitigate pathological angiogenesis in proliferative retinopathies.

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.

Promoting New Approach Methodologies (NAMs) for research on skin color changes in response to environmental stress factors: tobacco and air pollution

Aging is one of the most dynamic biological processes in the human body and is known to carry significant impacts on individuals' self-esteem. Skin pigmentation is a highly heritable trait made possible by complex, strictly controlled cellular and molecular mechanisms. Genetic, environmental and endocrine factors contribute to the modulation of melanin's amount, type and distribution in the skin layers. One of the hallmarks of extrinsic skin aging induced by environmental stress factors is the alteration of the constitutive pigmentation pattern clinically defined as senile lentigines and/or melasma or other pigmentary dyschromias. The complexity of pollutants and tobacco smoke as environmental stress factors warrants a thorough understanding of the mechanisms by which they impact skin pigmentation through repeated and long-term exposure. Pre-clinical and clinical studies demonstrated that pollutants are known to induce reactive oxygen species (ROS) or inflammatory events that lead directly or indirectly to skin hyperpigmentation. Another mechanistic direction is provided by Aryl hydrocarbon Receptors (AhR) which were shown to mediate processes leading to skin hyperpigmentation in response to pollutants by regulation of melanogenic enzymes and transcription factors involved in melanin biosynthesis pathway. In this context, we will discuss a diverse range of New Approach Methodologies (NAMs) capable to provide mechanistic insights of the cellular and molecular pathways involved in the action of environmental stress factors on skin pigmentation and to support the design of raw ingredients and formulations intended to counter their impact and of any subsequently needed clinical studies.

A Deep View of the Biological Property of Interleukin-33 and Its Dysfunction in the Gut

Intestinal diseases have always posed a serious threat to human health, with inflammatory bowel disease (IBD) being one of them. IBD is an autoimmune disease characterized by chronic inflammation, including ulcerative colitis (UC) and Crohn's disease (CD). The "alarm" cytokine IL-33, which is intimately associated with Th2 immunity, is a highly potent inflammatory factor that is considered to have dual functions-operating as both a pro-inflammatory cytokine and a transcriptional regulator. IL-33 has been shown to play a crucial role in both the onset and development of IBD. Therefore, this review focuses on the pathogenesis of IBD, the major receptor cell types, and the activities of IL-33 in innate and adaptive immunity, as well as its underlying mechanisms and conflicting conclusions in IBD. We have also summarized different medicines targeted to IL-33-associated diseases. Furthermore, we have emphasized the role of IL-33 in gastrointestinal cancer and parasitic infections, giving novel prospective therapeutic utility in the future application of IL-33.

Endoplasmic reticulum stress and the inflammatory response in allergic contact dermatitis

Maintaining homeostasis is central to organismal health. Deviation is detected by a variety of sensors that react to alarm signals arising from injury, infection, and other inflammatory triggers. One important element of this alarm system is the innate immune system, which recognizes pathogen-/microbe- or damage-associated molecular patterns via pattern recognition receptors localized in the cytosol or in membranes of innate immune cells such as macrophages, dendritic cells, and mast cells but also of T cells, B cells, and epithelial cells. Activation of the innate immune system results in inflammation and is a pre-requisite for activation of the adaptive immune system. Another important element is represented by the unfolded protein response (UPR), a stress response of the endoplasmic reticulum. The UPR regulates proteostasis and also contributes to the course of inflammatory diseases such as cancer, diabetes, obesity, and neurodegenerative diseases. In addition, the UPR is instrumental in allergic contact dermatitis. This inflammatory skin disease, affecting 5-10% of the population, is caused by T cells recognizing low-molecular weight organic chemicals and metal ions. In this mini-review, we discuss the orchestration of inflammatory responses by the interplay of the innate immune system with cellular stress responses in allergic contact dermatitis, with a focus on the UPR.

Discovery of highly immunogenic spleen-resident FCGR3+CD103+ cDC1s differentiated by IL-33-primed ST2+ basophils

Recombinant interleukin-33 (IL-33) inhibits tumor growth, but the detailed immunological mechanism is still unknown. IL-33-mediated tumor suppression did not occur in Batf3-/- mice, indicating that conventional type 1 dendritic cells (cDC1s) play a key role in IL-33-mediated antitumor immunity. A population of CD103+ cDC1s, which were barely detectable in the spleens of normal mice, increased significantly in the spleens of IL-33-treated mice. The newly emerged splenic CD103+ cDC1s were distinct from conventional splenic cDC1s based on their spleen residency, robust effector T-cell priming ability, and surface expression of FCGR3. DCs and DC precursors did not express Suppressor of Tumorigenicity 2 (ST2). However, recombinant IL-33 induced spleen-resident FCGR3+CD103+ cDC1s, which were found to be differentiated from DC precursors by bystander ST2+ immune cells. Through immune cell fractionation and depletion assays, we found that IL-33-primed ST2+ basophils play a crucial role in the development of FCGR3+CD103+ cDC1s by secreting IL-33-driven extrinsic factors. Recombinant GM-CSF also induced the population of CD103+ cDC1s, but the population neither expressed FCGR3 nor induced any discernable antitumor immunity. The population of FCGR3+CD103+ cDC1s was also generated in vitro culture of Flt3L-mediated bone marrow-derived DCs (FL-BMDCs) when IL-33 was added in a pre-DC stage of culture. FL-BMDCs generated in the presence of IL-33 (FL-33-DCs) offered more potent tumor immunotherapy than control Flt3L-BMDCs (FL-DCs). Human monocyte-derived DCs were also more immunogenic when exposed to IL-33-induced factors. Our findings suggest that recombinant IL-33 or an IL-33-mediated DC vaccine could be an attractive protocol for better tumor immunotherapy.

The Role of IL-33/ST2 in COPD and Its Future as an Antibody Therapy

COPD is a leading cause of mortality and morbidity worldwide and is associated with a high socioeconomic burden. Current treatment includes the use of inhaled corticosteroids and bronchodilators, which can help to improve symptoms and reduce exacerbations; however, there is no solution for restoring lung function and the emphysema caused by loss of the alveolar tissue. Moreover, exacerbations accelerate progression and challenge even more the management of COPD. Mechanisms of inflammation in COPD have been investigated over the past years, thus opening new avenues to develop novel targeted-directed therapies. Special attention has been paid to IL-33 and its receptor ST2, as they have been found to mediate immune responses and alveolar damage, and their expression is upregulated in COPD patients, which correlates with disease progression. Here we summarize the current knowledge on the IL-33/ST2 pathway and its involvement in COPD, with a special focus on developed antibodies and the ongoing clinical trials using anti-IL-33 and anti-ST2 strategies in COPD patients.

The Role of the Interleukin-1 Family in Complications of Prematurity

Preterm birth is a major contributor to neonatal morbidity and mortality. Complications of prematurity such as bronchopulmonary dysplasia (BPD, affecting the lung), pulmonary hypertension associated with BPD (BPD-PH, heart), white matter injury (WMI, brain), retinopathy of prematurity (ROP, eyes), necrotizing enterocolitis (NEC, gut) and sepsis are among the major causes of long-term morbidity in infants born prematurely. Though the origins are multifactorial, inflammation and in particular the imbalance of pro- and anti-inflammatory mediators is now recognized as a key driver of the pathophysiology underlying these illnesses. Here, we review the involvement of the interleukin (IL)-1 family in perinatal inflammation and its clinical implications, with a focus on the potential of these cytokines as therapeutic targets for the development of safe and effective treatments for early life inflammatory diseases.

Chronic Myeloid Leukemia, from Pathophysiology to Treatment-Free Remission: A Narrative Literature Review

Chronic myeloid leukemia (CML) is one of the most common leukemias occurring in the adult population. The course of CML is divided into three phases: the chronic phase, the acceleration phase, and the blast phase. Pathophysiology of CML revolves around Philadelphia chromosome that constitutively activate tyrosine kinase through BCR-ABL1 oncoprotein. In the era of tyrosine kinase inhibitors (TKIs), CML patients now have a similar life expectancy to people without CML, and it is now very rare for CML patients to progress to the blast phase. Only a small proportion of CML patients have resistance to TKI, caused by BCR-ABL1 point mutations. CML patients with TKI resistance should be treated with second or third generation TKI, depending on the BCR-ABL1 mutation. Recently, many studies have shown that it is possible for CML patients who achieve a long-term deep molecular response to stop TKIs treatment and maintain remission. This review aimed to provide an overview of CML, including its pathophysiology, clinical manifestations, the role of stem cells, CML treatments, and treatment-free remission.

IL-1RAP, a Key Therapeutic Target in Cancer

Cancer is a major cause of death worldwide and especially in high- and upper-middle-income countries. Despite recent progress in cancer therapies, such as chimeric antigen receptor T (CAR-T) cells or antibody-drug conjugate (ADC), new targets expressed by the tumor cells need to be identified in order to selectively drive these innovative therapies to tumors. In this context, IL-1RAP recently showed great potential to become one of these new targets for cancer therapy. IL-1RAP is highly involved in the inflammation process through the interleukins 1, 33, and 36 (IL-1, IL-33, IL-36) signaling pathways. Inflammation is now recognized as a hallmark of carcinogenesis, suggesting that IL-1RAP could play a role in cancer development and progression. Furthermore, IL-1RAP was found overexpressed on tumor cells from several hematological and solid cancers, thus confirming its potential involvement in carcinogenesis. This review will first describe the structure and genetics of IL-1RAP as well as its role in tumor development. Finally, a focus will be made on the therapies based on IL-1RAP targeting, which are now under preclinical or clinical development.

Dual Immune Regulatory Roles of Interleukin-33 in Pathological Conditions

Interleukin-33 (IL-33), a member of the IL-1 cytokine family and a multifunctional cytokine, plays critical roles in maintaining host homeostasis and in pathological conditions, such as allergy, infectious diseases, and cancer, by acting on multiple types of immune cells and promoting type 1 and 2 immune responses. IL-33 is rapidly released by immune and non-immune cells upon stimulation by stress, acting as an “alarmin” by binding to its receptor, suppression of tumorigenicity 2 (ST2), to trigger downstream signaling pathways and activate inflammatory and immune responses. It has been recognized that IL-33 displays dual-functioning immune regulatory effects in many diseases and has both pro- and anti-tumorigenic effects, likely depending on its primary target cells, IL-33/sST2 expression levels, cellular context, and the cytokine microenvironment. Herein, we summarize our current understanding of the biological functions of IL-33 and its roles in the pathogenesis of various conditions, including inflammatory and autoimmune diseases, infections, cancers, and cases of organ transplantation. We emphasize the nature of context-dependent dual immune regulatory functions of IL-33 in many cells and diseases and review systemic studies to understand the distinct roles of IL-33 in different cells, which is essential to the development of more effective diagnoses and therapeutic approaches for IL-33-related diseases.

Heterogeneity of Group 2 Innate Lymphoid Cells Defines Their Pleiotropic Roles in Cancer, Obesity, and Cardiovascular Diseases

Group 2 innate lymphoid cells (ILC2s) are typically known for their ability to respond rapidly to parasitic infections and play a pivotal role in the development of certain allergic disorders. ILC2s produce cytokines such as Interleukin (IL)-5 and IL-13 similar to the type 2 T helper (Th2) cells. Recent findings have highlighted that ILC2s, together with IL-33 and eosinophils, participate in a considerably broad range of physiological roles such as anti-tumor immunity, metabolic regulation, and vascular disorders. Therefore, the focus of the ILC2 study has been extended from conventional Th2 responses to these unexplored areas of research. However, disease outcomes accompanied by ILC2 activities are paradoxical mostly in tumor immunity requiring further investigations. Although various environmental factors that direct the development, activation, and localization of ILC2s have been studied, IL-33/ILC2/eosinophil axis is presumably central in a multitude of inflammatory conditions and has guided the research in ILC2 biology. With a particular focus on this axis, we discuss ILC2s across different diseases.

Diverse Control Mechanisms of the Interleukin-1 Cytokine Family

The majority of interleukin-1 (IL-1) family cytokines lack amino terminal secretion signals or transmembrane domains for secretion along the conventional biosynthetic pathway. Yet, these factors must be translocated from the cytoplasm across the plasma membrane into the extracellular space in order to regulate inflammation. Recent work has identified an array of mechanisms by which IL-1 family cytokines can be released into the extracellular space, with supramolecular organizing centers known as inflammasomes serving as dominant drivers of this process. In this review, we discuss current knowledge of the mechanisms of IL-1 family cytokine synthesis, processing, and release from cells. Using this knowledge, we propose a model whereby host metabolic state dictates the route of IL-1β secretion, with implications for microbial infection and sterile inflammation.

Bioinformatic analysis of cancer-associated fibroblast related gene signature as a predictive model in clinical outcomes and immune characteristics of gastric cancer

Background

Gastric cancer (GC) has a high incidence and high mortality rate among Asian countries, and distinguishing predictive prognosis biomarkers for GC are essential. Cancer-associated fibroblasts (CAFs) play a significant role in the progression, immune evasion, and therapeutic resistance of GC. Therefore, CAF-associated genes might have huge potential as prognostic biomarkers for predicting tumor progression and survival rate in GC pateints.

Methods

A sum of 1,134 GC patients from the The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD), GSE62254, and GSE84437 datasets as well as GC cohorts from Xijing hospital were included. Firstly, we performed univariate Cox regression analysis to identify CAF-associated prognostic genes. Subsequently, the Least Absolute Shrinkage and Selection Operator (LASSO) regression analysis was used to develop a CAF gene signature (CAFGS) in the TCGA-STAD training cohort. CAFGS’s predictive performance was examined in both the training and validation cohorts, and the relationship between CAFGS and the tumor microenvironment (TME) was investigated by ssGSEA, CIBERSORT, TIMER, and ESTIMATE. Finally, a nomogram of CAFGS was established.

Results

Ten CAF-associated genes (ANGPTL4, CPNE8, CST2, HTR1F, IL1RAP, NR1D1, NTAN1, OLFML2B, TMEM259, and VTN) were identified to develop CAFGS. A high CAFGS score represented a worse outcome for GC patients in four cohorts, and a strong correlation was found between CAFGS and the infiltration of immune cells. We showed that CAFs contribute to immune evasion and unfavorable prognoses of GC patients by promoting the formation of an immunosuppressive microenvironment, and a high level of CAF infiltration may attenuate the efficacy of immunotherapy. The nomogram based on CAFGS showed reasonable predictive ability and may deliver great clinical net benefits.

Conclusions

We established a CAFGS model with 10 CAF-associated genes that had a great predictive value for GC prognosis and survival rate evaluation. This study could provide a novel insight for investigating the role of CAFs in GC.

Reciprocal regulation of IL-33 receptor-mediated inflammatory response and pulmonary fibrosis by TRAF6 and USP38

Significance IL-33R mediates local inflammatory responses and plays crucial roles in the pathogenesis of immune diseases. In this study, we identified USP38, which negatively regulates IL-33-triggered signaling by mediating K27-linked deubiquitination of IL-33R at K511 and its autophagic degradation. USP38 deficiency aggravates IL-33-induced lung inflammatory response and bleomycin-induced pulmonary fibrosis. We further show that the E3 ubiquitin ligase TRAF6 catalyzes K27-linked polyubiquitination of IL-33R at K511, and that deficiency of TRAF6 inhibits IL-33-mediated signaling. Our findings reveal an important mechanism regarding how IL-33R is precisely regulated to ensure its inactivation in rest cells and proper activation following IL-33 stimulation.

Fungal mycobiome drives IL-33 secretion and type 2 immunity in pancreatic cancer

TH2 cells and innate lymphoid cells 2 (ILC2) can stimulate tumor growth by secreting pro-tumorigenic cytokines such as interleukin-4 (IL-4), IL-5, and IL-13. However, the mechanisms by which type 2 immune cells traffic to the tumor microenvironment are unknown. Here, we show that oncogenic KrasG12D increases IL-33 expression in pancreatic ductal adenocarcinoma (PDAC) cells, which recruits and activates TH2 and ILC2 cells. Correspondingly, cancer-cell-specific deletion of IL-33 reduces TH2 and ILC2 recruitment and promotes tumor regression. Unexpectedly, IL-33 secretion is dependent on the intratumoral fungal mycobiome. Genetic deletion of IL-33 or anti-fungal treatment decreases TH2 and ILC2 infiltration and increases survival. Consistently, high IL-33 expression is observed in approximately 20% of human PDAC, and expression is mainly restricted to cancer cells. These data expand our knowledge of the mechanisms driving PDAC tumor progression and identify therapeutically targetable pathways involving intratumoral mycobiome-driven secretion of IL-33.

Interleukins and Ischemic Stroke

Ischemic stroke after cerebral artery occlusion is one of the major causes of chronic disability worldwide. Interleukins (ILs) play a bidirectional role in ischemic stroke through information transmission, activation and regulation of immune cells, mediating the activation, multiplication and differentiation of T and B cells and in the inflammatory reaction. Crosstalk between different ILs in different immune cells also impact the outcome of ischemic stroke. This overview is aimed to roughly discuss the multiple roles of ILs after ischemic stroke. The roles of IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-12, IL-13, IL-15, IL-16, IL-17, IL-18, IL-19, IL-21, IL-22, IL-23, IL-32, IL-33, IL-34, IL-37, and IL-38 in ischemic stroke were discussed in this review.

Fluvastatin enhances IL-33-mediated mast cell IL-6 and TNF production

Statins are HMG-CoA reductase inhibitors prescribed for lowering cholesterol. They can also inhibit inflammatory responses by suppressing isoprenylation of small G proteins. Consistent with this, we previously found that fluvastatin suppresses IgE-mediated mast cell function. However, some studies have found that statins induced pro-inflammatory cytokines in macrophages and NK cells. In contrast to IgE signaling, we show that fluvastatin augments IL-33-induced TNF and IL-6 production by mast cells. This effect required the key mast cell growth factor, stem cell factor (SCF). Treatment of IL-33-activated mast cells with mevalonic acid or isoprenoids reduced fluvastatin effects, suggesting fluvastatin acts at least partly by reducing isoprenoid production. Fluvastatin also enhanced IL-33-induced NF-κB transcriptional activity and promoted neutrophilic peritonitis in vivo, a response requiring mast cell activation. Other statins tested did not enhance IL-33 responsiveness. Therefore, this work supports observations of unexpected pro-inflammatory effects of some statins and suggests mechanisms by which this may occur. Because statins are candidates for repurposing in inflammatory disorders, our work emphasizes the importance of understanding the pleiotropic and possible unexpected effects of these drugs.

Role of IL-33/ST2 Axis in Chronic Inflammatory Neurological Disorderss

Interleukin-33 (IL-33) is a member of IL-1 family of cytokines, produced constitutively by fibroblasts, endothelial cells, and epithelial cells. IL-33 can be released passively from cells during tissue damage and cell necrosis, suggesting that it may act as an alarmin. Function of IL-33 is mediated by its interaction with ST2 molecule that is expressed on many immune cells: Th2 lymphocytes, NK, NKT and mast cells, monocytes, dendritic cells and granulocytes. IL-33/ST2 pathway plays, often dual, roles in different physiological and inflammatory processes, mediating both, pathological immune responses and tissue repair. Expression of IL-33 in the central nervous system (CNS) is significantly enhanced during various pathological processes, indicating its important role in the pathogenesis of neurological inflammatory and degenerative diseases. In this review the biological features, expression of IL-33 and its ligand ST2 in CNS, and the role of IL- 33/ST2 pathway in development of Alzheimer’s disease and multiple sclerosis are discussed.

Rational Design, Synthesis and Evaluation of Oxazolo[4,5-c]-quinolinone Analogs as Novel Interleukin-33 Inhibitors

Interleukin-33 (IL-33) is an epithelial-derived cytokine that plays an important role in immune-mediated diseases such as asthma, atopic dermatitis, and rheumatoid arthritis. Although IL-33 is considered a potential target for the treatment of allergy-related diseases, no small molecule that inhibits IL-33 has been reported. Based on the structure-activity relationship and in vitro 2D NMR studies employing ¹⁵ N-labeled IL-33, we identified that the oxazolo[4,5-c]-quinolinone analog 7 c binds to the interface region of IL-33 and IL-33 receptor (ST2), an orphan receptor of the IL-1 receptor family. Compound 7 c effectively inhibited the production of IL-6 in human mast cells in a dose-dependent manner. Compound 7 c is the first low molecular weight IL-33 inhibitor and may be used as a prototype molecule for structural optimization and investigation of the IL-33/ST2 signaling pathway.

IL-33 genetics and epigenetics in immune-related diseases

Interleukin-33 (IL-33) is a 30KDa protein, which belongs to the Interleukin-1 cytokine family. It is a crucial regulator of innate and adaptive immune responses. This interleukin is additionally involved in the inflammatory reaction versus helminthic infections. Interleukin 33 acts on group 2 innate lymphoid cells and mast cells macrophages, dendritic cells and CD4 + Th2 cells eliciting a type 2 immune response. Moreover, the cytokine can activate the ST2 of Tregs, demonstrating its ability to downregulate inflammation. IL-33 has also an intracellular function by regulating transcription. The active IL-33 doesn’t have a signal peptide, so it’s not released across a normal secretory pathway; the interleukin is released when the cells are damages and acts like an “alarmin”. Its influence on immune activation could be slightly adjusted via fine epigenetic interactions involving cascade pathways and immune genes. Due to the diverse data emerged from different experimental research, we decided span literature to clarify, as much as possible, how IL-33 is influenced by and influence gene expression. The authors reported how its balance is influenced, according to the tissue considered. Fundamental for immune-related diseases, IL-33 has a key role in controlling inflammation. The understanding of the cytokine switch will be fundamental in a near future in order to block or activate some immune pathways. In fact, we could control interleukins effects not only by monoclonal antibodies but also by using siRNA or miRNAs for silencing or expressing key genes.

The interleukin-1 cytokine family members: Role in cancer pathogenesis and potential therapeutic applications in cancer immunotherapy

The interleukin-1 (IL-1) family is one of the first described cytokine families and consists of eight cytokines (IL-1β, IL-1α, IL-18, IL-33, IL-36α, IL-36β, IL-36γ and IL-37) and three receptor antagonists (IL-1Ra, IL-36Ra and IL-38). The family members are known to play an essential role in inflammation. The importance of inflammation in cancer has been well established in the past decades. This review sets out to give an overview of the role of each IL-1 family member in cancer pathogenesis and show their potential as potential anticancer drug candidates. First, the molecular structure is described. Next, both the pro- and anti-tumoral properties are highlighted. Additionally, a critical interpretation of current literature is given. To conclude, the IL-1 family is a toolbox with a collection of powerful tools that can be considered as potential drugs or drug targets.

Novel pathogenesis of atopic dermatitis from the view of cytokines in mice and humans

Type 2 immunity and inflammation underlie allergic skin disorders, such as atopic dermatitis (AD). In type 2 inflammation, IL-4, IL-13, and IL-5, which are signature type 2 cytokines, are mainly produced by type 2 helper T (Th2) cells and form the characteristic features of AD. Epithelial cell-derived cytokines such as IL-25, IL-33, and TSLP initiate type 2 inflammation by modulating various cells, including group 2 innate lymphoid cells. Moreover, IL-31, a newly identified type 2 cytokine produced mainly by Th2 cells, induces pruritus by acting on sensory neurons in the skin. Based on both basic and clinical findings, several biologics targeting Th2 cytokines have been developed and exhibited significant efficacy as therapeutic reagents for AD. We have summarized the roles of each cytokine (IL-4, 5, 13, 25, 31, and 33, and TSLP) in the development of type 2 inflammation, especially AD, from the view of basic studies in mice and clinical trials/observation in humans.

Therapeutic Opportunities of Interleukin-33 in the Central Nervous System

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is involved in various diseases. IL-33 exerts its effects via its heterodimeric receptor complex, which comprises suppression of tumorigenicity 2 (ST2) and the IL-1 receptor accessory protein (IL-1RAP). Increasing evidence has demonstrated that IL-33/ST2 signaling plays diverse but crucial roles in the homeostasis of the central nervous system (CNS) and the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infection, trauma, and ischemic stroke. In the current review, we focus on the functional roles and cellular signaling mechanisms of IL-33 in the CNS and evaluate the potential for diagnostic and therapeutic applications.

Diversified Stimuli-Induced Inflammatory Pathways Cause Skin Pigmentation

The production of melanin pigments by melanocytes and their quantity, quality, and distribution play a decisive role in determining human skin, eye, and hair color, and protect the skin from adverse effects of ultraviolet radiation (UVR) and oxidative stress from various environmental pollutants. Melanocytes reside in the basal layer of the interfollicular epidermis and are compensated by melanocyte stem cells in the follicular bulge area. Various stimuli such as eczema, microbial infection, ultraviolet light exposure, mechanical injury, and aging provoke skin inflammation. These acute or chronic inflammatory responses cause inflammatory cytokine production from epidermal keratinocytes as well as dermal fibroblasts and other cells, which in turn stimulate melanocytes, often resulting in skin pigmentation. It is confirmed by some recent studies that several interleukins (ILs) and other inflammatory mediators modulate the proliferation and differentiation of human epidermal melanocytes and also promote or inhibit expression of melanogenesis-related gene expression directly or indirectly, thereby participating in regulation of skin pigmentation. Understanding of mechanisms of skin pigmentation due to inflammation helps to elucidate the relationship between inflammation and skin pigmentation regulation and can guide development of new therapeutic pathways for treating pigmented dermatosis. This review covers the mechanistic aspects of skin pigmentation caused by inflammation.

Blocking Interleukin-33 Alleviates the Joint Inflammation and Inhibits the Development of Collagen-Induced Arthritis in Mice

Rheumatoid arthritis (RA) is considered a systemic chronic inflammatory joint disease characterized by chronic synovitis and cartilage and bone destruction. Interleukin-33 (IL-33) is a proinflammatory cytokine which is highly expressed in the synovium of RA patients and the joints of mice with collagen-induced arthritis (CIA) and exacerbates CIA in mice. However, the role of the IL-33-neutralizing antibody in the murine model of CIA remains unclear. In the present study, CIA mice were given intraperitoneally with polyclonal rabbit anti-murine IL-33 antibody (anti-IL-33) or normal rabbit IgG control after the first signs of arthritis. Administration of anti-IL-33 after the onset of disease significantly reduced the severity of CIA and joint damage compared with controls treated with normal rabbit IgG. Anti-IL-33 treatment also significantly decreased the serum levels of interferon-γ(IFN-γ),IL-6, IL-12, IL-33, and tumor necrosis factor-α (TNF-α). Moreover, anti-IL-33 treatment significantly downregulated the production of IFN-γ, IL-6, IL-12, IL-33, and TNF-α in ex vivo-stimulated spleen cells. Together, our results indicate that the IL-33-neutralizing antibody may provide a therapeutic strategy for RA by inhibiting the release of proinflammatory cytokines.

Role of Inflammation in the Development of Colorectal Cancer

Chronic inflammation can lead to the development of many diseases, including cancer. Inflammatory bowel disease (IBD) that includes both ulcerative colitis (UC) and Crohnmp's disease (CD) are risk factors for the development of colorectal cancer (CRC). Many cytokines produced primarily by the gut immune cells either during or in response to localized inflammation in the colon and rectum are known to stimulate the complex interactions between the different cell types in the gut environment resulting in acute inflammation. Subsequently, chronic inflammation, together with genetic and epigenetic changes, have been shown to lead to the development and progression of CRC. Various cell types present in the colon, such as enterocytes, Paneth cells, goblet cells, and macrophages, express receptors for inflammatory cytokines and respond to tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and other cytokines. Among the several cytokines produced, TNF-α and IL-1β are the key pro-inflammatory molecules that play critical roles in the development of CRC. The current review is intended to consolidate the published findings to focus on the role of pro-inflammatory cytokines, namely TNF-α and IL-1β, on inflammation (and the altered immune response) in the gut, to better understand the development of CRC in IBD, using various experimental model systems, preclinical and clinical studies. Moreover, this review also highlights the current therapeutic strategies available (monotherapy and combination therapy) to alleviate the symptoms or treat inflammation-associated CRC by using monoclonal antibodies or aptamers to block pro-inflammatory molecules, inhibitors of tyrosine kinases in the inflammatory signaling cascade, competitive inhibitors of pro-inflammatory molecules, and the nucleic acid drugs like small activating RNAs (saRNAs) or microRNA (miRNA) mimics to activate tumor suppressor or repress oncogene/pro-inflammatory cytokine gene expression.

Damage-associated molecular patterns in trauma

In 1994, the "danger model" argued that adaptive immune responses are driven rather by molecules released upon tissue damage than by the recognition of "strange" molecules. Thus, an alternative to the "self versus non-self recognition model" has been provided. The model, which suggests that the immune system discriminates dangerous from safe molecules, has established the basis for the future designation of damage-associated molecular patterns (DAMPs), a term that was coined by Walter G. Land, Seong, and Matzinger. The pathological importance of DAMPs is barely somewhere else evident as in the posttraumatic or post-surgical inflammation and regeneration. Since DAMPs have been identified to trigger specific immune responses and inflammation, which is not necessarily detrimental but also regenerative, it still remains difficult to describe their "friend or foe" role in the posttraumatic immunogenicity and healing process. DAMPs can be used as biomarkers to indicate and/or to monitor a disease or injury severity, but they also may serve as clinically applicable parameters for optimized indication of the timing for, i.e., secondary surgeries. While experimental studies allow the detection of these biomarkers on different levels including cellular, tissue, and circulatory milieu, this is not always easily transferable to the human situation. Thus, in this review, we focus on the recent literature dealing with the pathophysiological importance of DAMPs after traumatic injury. Since dysregulated inflammation in traumatized patients always implies disturbed resolution of inflammation, so-called model of suppressing/inhibiting inducible DAMPs (SAMPs) will be very briefly introduced. Thus, an update on this topic in the field of trauma will be provided.

Predicting Immuno-Metabolic Complications After Allogeneic Hematopoietic Cell Transplant with the Cytokine Interleukin-33 (IL-33) and its Receptor Serum-Stimulation 2 (ST2)

Patients undergoing allogeneic hematopoietic cell transplantation (HCT) are at risk for numerous acute and long-term complications from this procedure. Post-transplant diabetes mellitus (PTDM) is a common but under-recognized problem. Similar to graft-versus-host disease (GVHD), new-onset diabetes is characterized by immune dysregulation that can negatively impact transplant outcomes. This review will discuss the biology of IL-33/ST2 in acute GVHD and PTDM development, and how this cytokine axis could be leveraged for predicting and treating immuno-metabolic complications after transplant.

The IL-33-induced p38-/JNK1/2-TNFα axis is antagonized by activation of β-adrenergic-receptors in dendritic cells

IL-33, an IL-1 cytokine superfamily member, induces the activation of the canonical NF-κB signaling, and of Mitogen Activated Protein Kinases (MAPKs). In dendritic cells (DCs) IL-33 induces the production of IL-6, IL-13 and TNFα. Thereby, the production of IL-6 depends on RelA whereas the production of IL-13 depends on the p38-MK2/3 signaling module. Here, we show that in addition to p65 and the p38-MK2/3 signaling module, JNK1/2 are essential for the IL-33-induced TNFα production. The central roles of JNK1/2 and p38 in DCs are underpinned by the fact that these two MAPK pathways are controlled by activated β-adrenergic receptors resulting in a selective regulation of the IL-33-induced TNFα response in DCs.

Biological functions and therapeutic opportunities of soluble cytokine receptors

Cytokines control the immune system by regulating the proliferation, differentiation and function of immune cells. They activate their target cells through binding to specific receptors, which either are transmembrane proteins or attached to the cell-surface via a GPI-anchor. Different tissues and individual cell types have unique expression profiles of cytokine receptors, and consequently this expression pattern dictates to which cytokines a given cell can respond. Furthermore, soluble variants of several cytokine receptors exist, which are generated by different molecular mechanisms, namely differential mRNA splicing, proteolytic cleavage of the membrane-tethered precursors, and release on extracellular vesicles. These soluble receptors shape the function of cytokines in different ways: they can serve as antagonistic decoy receptors which compete with their membrane-bound counterparts for the ligand, or they can form functional receptor/cytokine complexes which act as agonists and can even activate cells that would usually not respond to the ligand alone. In this review, we focus on the IL-2 and IL-6 families of cytokines and the so-called Th2 cytokines. We summarize for each cytokine which soluble receptors exist, were they originate from, how they are generated, and what their biological functions are. Furthermore, we give an outlook on how these soluble receptors can be exploited for therapeutic purposes.

The Interleukin-33/ST2 axis promotes glioma mesenchymal transition, stemness and TMZ resistance via JNK activation

IL-33 is an important member of the IL-1 family which has pleiotropic activities in innate and adaptive immune responses. Recently, some researchers have focused on the function of cellular immunity in the development of tumor. The biological role of IL-33 in glioma is poorly understood. In this study, we showed that glioma cells and tissues expressed higher levels of IL-33 and its receptor ST2 compared to normal brain. Clinically, IL-33 expression was associated with poor survival in patients with glioma. Administration of human IL-33 enhanced cell migration, invasion, epithelial to mesenchymal transition and stemness. Anti-ST2 blocked these effects of IL-33 on tumor. Mechanistically, IL-33 activated JNK signaling pathway via ST2 and increased the expression of key transcription factors that controlled the process of EMT and stemness. Moreover, IL-33 prevented temozolomide induced tumor apoptosis. Anti-ST2 or knockdown IL-33 increased the sensitivity of tumor to temozolomide. Thus, targeting the IL-33/ST2 axis may offer an opportunity to the treatment of glioma patients.

Roles of inflammation factors in melanogenesis (Review)

The occurrence of hyperpigmentation or hypopigmentation after inflammation is a common condition in dermatology and cosmetology. Since the exact mechanism of its occurrence is not yet known, prevention and treatment are troublesome. Previous studies have confirmed that α-melanocyte-stimulating hormone, stem cell factor and other factors can promote melanogenesis-related gene expression through the activation of signaling pathways. Recent studies have revealed that a variety of inflammatory mediators can also participate in the regulation of melanogenesis in melanocytes. In this review, we summarized that interleukin-18, interleukin-33, granulocyte-macrophage colony stimulating factor, interferon-γ, prostaglandin E2 have the effect of promoting melanogenesis, while interleukin-1, interleukin-4, interleukin-6, interleukin-17 and tumor necrosis factor can inhibit melanogenesis. Further studies have found that these inflammatory factors may activate or inhibit melanogenesis-related signaling pathways (such as protein kinase A and mitogen activated protein kinase) by binding to corresponding receptors, thereby promoting or inhibiting the expression of melanogenesis-related genes and regulating skin pigmentation processes. This suggests that the development of drugs or treatment methods from the perspective of regulating inflammation can provide new ideas and new targets for the treatment of pigmented dermatosis. This review outlines the current understanding of the inflammation factors' roles in melanogenesis.

Function and Regulation of IL-36 Signaling in Inflammatory Diseases and Cancer Development

The IL-36 subfamily of cytokines belongs to the IL-1 superfamily and consists of three pro-inflammatory agonists IL-36α, IL-36β, IL-36γ, and an IL-36 receptor (IL-36R) antagonist, IL-36Ra. These IL-36 cytokines function through a common receptor to modulate innate and adaptive immune responses. IL-36 cytokines are expressed as inactive precursors and require proteolytic processing to become fully active. Upon binding to IL-36R, IL-36 agonists augment the expression and production of inflammatory cytokines via activating signaling pathways. IL-36 is mainly expressed in epidermal, bronchial, and intestinal epithelial cells that form the barrier structures of the body and regulates the balance between pro-inflammatory and anti-inflammatory cytokine production at these tissue sites. Dysregulation of IL-36 signaling is a major etiological factor in the development of autoimmune and inflammatory diseases. Besides its critical role in inflammatory skin diseases such as psoriasis, emerging evidence suggests that aberrant IL-36 activities also promote inflammatory diseases in the lung, kidneys, and intestines, underscoring the potential of IL-36 as a therapeutic target for common inflammatory diseases. The role of IL-36 signaling in cancer development is also under investigation, with limited studies suggesting a potential anti-tumor effect. In this comprehensive review, we summarize current knowledge regarding the expression, activation, regulatory mechanisms, and biological functions of IL-36 signaling in immunity, inflammatory diseases, and cancer development.

Recombinant virus-like particles presenting IL-33 successfully modify the tumor microenvironment and facilitate antitumor immunity in a model of breast cancer

Recently, interleukin (IL)-33 has been closely associated with a variety of clinical cancers. IL-33 presents both protumorigenic, and less frequently, antitumorigenic functions depending on disease conditions. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. This study aimed to develop an effective approach to intervene in IL-33 functioning in tumors and reveal the immunotherapeutic potential of anti-IL-33 active immunization. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth in the preventive study and lung metastasis in both studies. The underlying mechanisms might include promoting tumor-specific Th1 and CTL-mediated cellular responses and the expression of the effector molecule interferon-γ (IFN-γ), suppressing T-helper type 2 (Th2) responses, and significantly reducing the infiltration of immunosuppressive Treg (regulatory T) cells and myeloid-derived suppressor cells (MDSCs) into tumor tissues in the immunized mice. In conclusion, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating the potential of this approach as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role. STATEMENT OF SIGNIFICANCE: Interleukin (IL)-33 is closely associated with a variety of clinical cancers. IL-33 signaling appears to be a possible target for the treatment of applicable tumor diseases. Recombinant truncated hepatitis B virus core antigen (HBcAg), presenting mature IL-33 molecules on the surface of virus-like particles (VLPs), was prepared and used to immunize BALB/c mice in a model of murine 4T1 breast cancer. The immunization was performed through either a preventive or therapeutic strategy in two separate studies. Anti-IL-33 immunization with VLPs elicited a persistent and highly titrated specific antibody response and significantly suppressed orthotopic tumor growth and lung metastasis in both studies. Furthermore, anti-IL-33 active immunization employing recombinant VLPs as an antigen delivery platform effectively modified the tumor microenvironment and promoted antitumor immunity, indicating its potential as a new and promising immunotherapeutic strategy for the treatment of cancers where IL-33 plays a definite protumorigenic role.

IL-33 Is a Cell-Intrinsic Regulator of Fitness during Early B Cell Development

IL-33 is an IL-1 family member protein that is a potent driver of inflammatory responses in both allergic and nonallergic disease. This proinflammatory effect is mediated primarily by extracellular release of IL-33 from stromal cells and binding of the C-terminal domain of IL-33 to its receptor ST2 on targets such as CD4+ Th2 cells, ILC2, and mast cells. Notably, IL-33 has a distinct N-terminal domain that mediates nuclear localization and chromatin binding. However, a defined in vivo cell-intrinsic role for IL-33 has not been established. We identified IL-33 expression in the nucleus of progenitor B (pro-B) and large precursor B cells in the bone marrow, an expression pattern unique to B cells among developing lymphocytes. The IL-33 receptor ST2 was not expressed within the developing B cell lineage at either the transcript or protein level. RNA sequencing analysis of wild-type and IL-33-deficient pro-B and large precursor B cells revealed a unique, IL-33-dependent transcriptional profile wherein IL-33 deficiency led to an increase in E2F targets, cell cycle genes, and DNA replication and a decrease in the p53 pathway. Using mixed bone marrow chimeric mice, we demonstrated that IL-33 deficiency resulted in an increased frequency of developing B cells via a cell-intrinsic mechanism starting at the pro-B cell stage paralleling IL-33 expression. Finally, IL-33 was detectable during early B cell development in humans and IL33 mRNA expression was decreased in B cell chronic lymphocytic leukemia samples compared with healthy controls. Collectively, these data establish a cell-intrinsic, ST2-independent role for IL-33 in early B cell development.

Alteration of the IL-33-sST2 pathway in hypertensive patients and a mouse model

Inflammatory cells play an important role in the occurrence of hypertension. Recent studies have demonstrated that interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) signaling plays a critical role in the pathogenesis of several cardiovascular diseases. We aimed to evaluate the association of IL-33 and its receptor levels with the occurrence of hypertension in angiotensin II (Ang II)-infused mice using microarray analysis and validated our results in human specimens. Male wild-type mice were infused with Ang II (1500 ng/kg/min) for 1, 3 and 7 days. Patients with essential hypertension (EH) (n = 166) and healthy control subjects (n = 306) were enrolled. Levels of IL-33 and ST2 mRNAs in serum and peripheral blood mononuclear cells (PBMCs) were analyzed by Luminex assay or ELISA and qPCR analysis. We found that IL-33 expression was significantly increased in the aortas of mice receiving Ang II infusion compared with that of control mice. In contrast, the levels of IL-33 in serum and PBMCs were not significantly different between hypertensive patients and normal controls. However, the levels of soluble ST2 (sST2) in serum and PBMCs were markedly higher in hypertensive patients than in controls (P < 0.001 and P = 0.014, respectively). In addition, the ST2L level in PBMCs was also significantly decreased in hypertensive patients (P = 0.028). Further, logistic analysis showed that the odds ratios of having hypertension based on sST2 levels in serum and PBMCs were 9.714 and 2.244 (P = 0.013 and P = 0.024, respectively) compared with the control group. Above all, sST2 acted as a risk factor for the occurrence of hypertension and may be a promising novel predictive marker for EH.

Molecular mechanisms regulating immune responses in thromboangiitis obliterans: A comprehensive review

Thromboangiitis obliterans (TAO) is a thrombotic-occlusive as well as an inflammatory peripheral vascular disease with unknown etiology. Recent evidence has supported the immunopathogenesis of the disease, however, the factors contributing to the altered immune function and vascular tissue inflammation are still unclear. This review was intended to collate the more current knowledge on the regulatory molecules involved in TAO from an immunoreactive perspective. The homeostasis of the immune system as well as a variety of progenitor cell populations appear to be affected during TAO and these alterations are associated with intrinsic signaling defects that are directing to an improved understanding of the crosstalk between angiogenesis and the immune system, as well as the potential of new co-targeting strategies applying both immunotherapy and angiogenic therapy.

ST2 and the ST2/IL-33 signalling pathway-biochemistry and pathophysiology in animal models and humans

ST2 is an interleukin (IL)-1 receptor family member with transmembrane (ST2L) and soluble (sST2) isoforms. Structurally, the ST2 gene products are very similar in mice and humans. In humans and in mice, alternative promoter activation and splicing produce ST2L and sST2. ST2L represents the longest transcript, whereas sST2 is the truncated, soluble isoform. ST2L is the biological receptor for IL-33, a member of the IL-1 family. IL-33 is the functional ligand of ST2L and signals the presence of tissue damage to local immune cells. IL-33/ST2L signalling leads to the production of inflammatory cytokines/chemokines and to the induction of the immune response. Conversely, sST2 functions as a decoy receptor for IL-33, inhibiting the effects of IL-33/ST2L signalling. Animal studies have allowed the investigation of ST2 and the IL-33/ST2L signalling pathway at multiple levels. However, clinical studies have mainly focused on the determination of sST2 in the circulation. In humans, plasma concentrations of sST2 increase in several diseases, such as heart disease, pulmonary disease, burn injury and graft-versus-host disease. Consequently, increased plasma concentrations of sST2 are not specific for a single disorder in humans and are thus of limited value for diagnostic purposes. However, increased plasma concentrations of sST2 have been linked to a worse prognosis in numerous diseases. Nevertheless, the major source of circulating sST2 in healthy and diseased humans is currently not fully established. In addition, whether the downregulation of sST2 can improve the outcome of patients in the clinical setting has not been elucidated. The aim of the present review was to provide an update on the findings regarding the biochemistry and pathophysiology of ST2 and the sST2 signalling pathway in humans and experimental models.

Emerging therapeutic potential of group 2 innate lymphoid cells in acute kidney injury

Acute kidney injury (AKI) remains a global challenge and, despite the availability of dialysis and transplantation, can be fatal. Those that survive an AKI are at increased risk of developing chronic kidney disease and end stage renal failure. Understanding the fundamental mechanisms underpinning the pathophysiology of AKI is critical for developing novel strategies for diagnosis and treatment. A growing body of evidence indicates that amplifying type 2 immunity may have therapeutic potential in kidney injury and disease. Of particular interest are the recently described subset of innate immune cells, termed group 2 innate lymphoid cells (ILCs). Group 2 ILCs are crucial tissue-resident immune cells that maintain homeostasis and regulate tissue repair at multiple organ sites, including the kidney. They are critical mediators of type 2 immune responses following infection and injury. The existing literature suggests that activation of group 2 ILCs and production of a local type 2 immune milieu is protective against renal injury and associated pathology. In this review, we describe the emerging role for group 2 ILCs in renal homeostasis and repair. We provide an in-depth discussion of the most recent literature that use preclinical models of AKI and assess the therapeutic effect of modulating group 2 ILC function. We debate the potential for targeting these cells as novel cellular therapies in AKI and discuss the implications for future studies and translation. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.