Nuclear IL-33 is a transcriptional regulator of NF-κB p65 and induces endothelial cell activation

Biological mechanisms and therapeutic prospects of interleukin-33 in pathogenesis and treatment of allergic disease

Allergic diseases significantly impact the quality of life of people around the world. Cytokines play a crucial role in regulating the immune system. Due to their importance in pro-inflammatory mechanisms, cytokines are used to understand pathogenesis and serve as biomarkers in many diseases. One such cytokine is interleukin-33, a member of the IL-1 family, including IL- 1α, IL-1β, and IL-18. The IL-33 receptor is a heterodimer of IL-1 receptor-like 1 and IL-1 receptor accessory protein. IL-33 plays a critical role in regulating innate and adaptive immune responses. The primary targets of IL-33 in vivo are tissue-resident immune cells, including mast cells, group 2 innate lymphoid cells, regulatory T cells, T helper 2 cells, eosinophils, basophils, dendritic cells, Th1 cells, CD8 + T cells, NK cells, iNKT cells, B cells, neutrophils, and macrophages. However, IL-33 appears to act as an alarm signal that is promptly released by producing cells under cellular damage or stress conditions. IL-33 regulates signaling and various biological functions, including induction of pro-inflammatory cytokines, regulation of cell proliferation, and involvement in tissue remodeling. IL-33 is fundamental in immune-related diseases and plays a critical role in the control of inflammation. Recently, IL-33 has been shown to significantly impact allergic diseases, primarily by inducing Th2 immune responses. IL-33 is a key regulator of mast cell function and a promising therapeutic target for treating allergic diseases. This review provides an overview of the current understanding of the role of IL-33 in allergy pathogenesis and potential clinical approaches.

REDD1 mediates HDM-induced nuclear-cytoplasmic translocation and release of IL-33 in airway epithelial cells by downregulating Nrf2

OBJECTIVE

This study aims to investigate whether REDD1 (Regulated in Development and DNA Damage Responses 1) mediates the nuclear-to-cytoplasmic translocation and release of IL-33 in airway epithelial cells induced by house dust mites (HDM).

METHODS

REDD1 expression levels in bronchial asthma patients were validated using public databases, followed by immunohistochemical analysis of REDD1 protein in airway epithelial cells from these patients. An asthma model was then established using HDM-induced 16HBE cell lines, with REDD1 gene knockout performed. The relationship between varying levels of REDD1 expression, Nrf2, and related inflammatory factors was assessed using Western blot and qPCR. To further investigate the role of the REDD1-Nrf2-IL-33 axis in the development of asthma, we employed Nrf2 activators and inhibitors to reassess the impact of REDD1 on IL-33.

RESULTS

At both mRNA and protein levels, we found that REDD1 was significantly overexpressed in samples from asthma patients (P < 0.05). In vitro, 24-hour exposure to HDM induced a notable nuclear-to-cytoplasmic translocation of IL-33 and increased its levels in the culture medium of 16HBE cells. In addition, HDM treatment significantly upregulated the expression of both REDD1 and Nrf2. Knockdown of REDD1 markedly suppressed HDM-induced IL-33 release and the expression of TNF-α, IL-6, and IL-1β, while enhancing Nrf2 expression. Moreover, treatment with the Nrf2 agonist curcumin inhibited HDM-induced nuclear-to-cytoplasmic translocation and extracellular secretion of IL-33, whereas the opposite effect was observed when using the Nrf2 antagonist ML385.

CONCLUSION

This study reveals the crucial regulatory role of the REDD1-Nrf2-IL-33 axis in the pathological process of bronchial asthma. REDD1 modulates the expression of IL-33 and other inflammatory factors through the Nrf2 signaling pathway, thereby influencing the onset and progression of asthma.

CLINICAL TRIAL NUMBER

Not applicable.

NF-κB signaling and the tumor microenvironment in osteosarcoma: implications for immune evasion and therapeutic resistance

Osteosarcoma, a highly aggressive malignancy with a generally poor prognosis, is characterized by tumor cells' ability to evade immune responses and resist treatment. The nuclear transcription factor NF-κB signaling pathway is crucial in regulating inflammatory and immune reactions. It occupies a central position in the development of the osteosarcoma tumor microenvironment. This research aimed to explore how NF-κB influences the recruitment and polarization of tumor-associated macrophages and myeloid-derived suppressor cells, both of which contribute to immunosuppression. Furthermore, NF-κB facilitates immune surveillance evasion in osteosarcoma cells by altering the expression of immune checkpoint molecules, such as PD-L1. It also enhances tumor cell resistance to chemotherapy and radiotherapy by activating anti-apoptotic signaling pathways and exacerbating treatment-induced inflammation. Potential therapeutic approaches include using NF-κB inhibitors, possibly in combination with immune checkpoint inhibitors, to overcome tumor cell resistance mechanisms and reshape antitumor immune responses. A thorough examination of NF-κB's role in osteosarcoma development is expected to yield novel clinical treatment strategies, and significantly improve patient prognosis by targeting this key signaling pathway.

The Role of Bone Marrow Stromal Cell Antigen 2 (BST2) in the Migration of Dendritic Cells to Lymph Nodes

Bone marrow stromal antigen 2 (BST2) is a host-restriction factor that plays multiple roles in the antiviral defense of innate immune responses, including the inhibition of viral particle release from virus-infected cells. BST2 may also be involved in the endothelial adhesion and migration of monocytes, but its importance in the immune system is still unclear. Immune cell adhesion and migration are closely related to the initiation of immune responses. In this study, we found that the expressions of the lymph node homing marker chemokine receptor 7 (CCR7) and an adhesion molecule intercellular adhesion molecule 1 (ICAM-1) in conventional dendritic cells (cDCs) were associated with BST2 expression. Interestingly, Bst2-/- cDCs showed lower chemotactic ability, including velocity and accumulative distance toward chemokine ligand 19 (CCL19) gradient in vitro, compared to wild-type cDCs. Bst2-/- cDCs also showed reduced migration and reduced retention capacity in draining lymph nodes in vivo. As a result, Bst2-/- cDCs as antigen-presenting cells induced lower antigen-specific B cell and T cell responses compared to Bst2+/+ cDCs. Notably, mice administered the influenza vaccine via Bst2-/- cDCs exhibited substantially inefficient virus clearance compared to mice administered the Bst2+/+ cDCs vaccine. Therefore, we propose that BST2, which plays a critical role in the effective migration and retention of cDCs, is involved in the development of optimal immunological effects in draining lymph nodes.

The IL-33/ST2 Axis Affects Adipogenesis Through Regulating the TRAF6/RelA Pathway

Understanding the regulatory mechanisms of adipogenesis is essential for preventing obesity. Interleukin-33 (IL-33) has recently attracted increasing attention for its role in adipogenesis. The purpose of this study was to explore the function and regulatory mechanism of IL-33 and its receptor suppression of tumorigenicity 2 (ST2) on adipogenesis. Here, Oil Red O staining was used to detect the accumulation of intracellular lipid droplets. Molecular techniques such as qRT-PCR and Western blotting were used to detect the expression of pivotal genes and adipogenic marker genes. Gains and losses of function experiments were used to explore the potential regulatory mechanism of the IL-33/ST2 axis in adipogenesis. Functionally, IL-33 is negatively associated with adipogenesis in 3T3-L1 preadipocytes, while ST2 is positively associated with it, encompassing both the trans-membrane receptor ST2 (ST2L) and the soluble ST2 (sST2). Mechanistically, the IL-33/ST2 axis affects adipogenesis by regulating the expression of the TRAF6/RelA pathway in 3T3-L1 preadipocytes. Downregulating the expression of ST2 suppressed the activation of the IL-33/ST2 axis, which subsequently inhibits the expression of TRAF6. This further attenuates the expression of RelA, ultimately resulting in the suppression of adipogenesis in 3T3-L1 preadipocytes. This study reveals a new mechanism by which the IL-33/ST2 axis regulates the differentiation of preadipocytes and provides a new idea for improving obesity prevention.

IL-33 Signaling Inhibition Leads to a Preeclampsia-Like Phenotype in Pregnant Rats

PROBLEM

Preeclampsia (PE) is a hypertensive pregnancy disorder that is a leading cause of maternal and fetal morbidity and mortality characterized by maternal vascular dysfunction, oxidative stress, chronic immune activation, and excessive inflammation. No cure exists beyond delivery of the fetal-placental unit and the mechanisms driving pathophysiology are not fully understood. However, aberrant immune responses have been extensively characterized in clinical studies and shown to mediate PE pathophysiology in animal studies. One pathway that may mediate aberrant immune responses in PE is deficiencies in the IL-33 signaling pathway. In this study, we aim to investigate the impact of IL-33 signaling inhibition on cNK, TH17, and TReg populations, vascular function, and maternal blood pressure during pregnancy.

METHOD OF STUDY

In this study, IL-33 signaling was inhibited using two different methods: intraperitoneal administration of recombinant ST2 (which acts as a decoy receptor for IL-33) and administration of a specific IL-33 neutralizing antibody. Maternal blood pressure, uterine artery resistance index, renal and placental oxidative stress, cNK, TH17, and TReg populations, various cytokines, and pre-proendothelin-1 levels were measured.

RESULTS

IL-33 signaling inhibition increased maternal blood pressure, uterine artery resistance, placental and renal oxidative stress. IL-33 signaling inhibition also increased placental cNK and TH17 and renal TH17 cells while decreasing placental TReg populations. IL-33 neutralization increased circulating cNK and TH17s and decreased circulating TRegs in addition to increasing pre-proendothelin-1 levels.

CONCLUSIONS

Data presented in this study demonstrate a role for IL-33 signaling in controlling vascular function and maternal blood pressure during pregnancy possibly by mediating innate and adaptive immune inflammatory responses, identifying the IL-33 signaling pathway as a potential therapeutic target for managing preeclampsia.

Leishmania exploits host cAMP/EPAC/calcineurin signaling to induce an IL-33-mediated anti-inflammatory environment for the establishment of infection

Host anti-inflammatory responses are critical for the progression of visceral leishmaniasis, and the pleiotropic cytokine interleukin (IL)-33 was found to be upregulated in infection. Here, we documented that IL-33 induction is a consequence of elevated cAMP-mediated exchange protein activated by cAMP (EPAC)/calcineurin-dependent signaling and essential for the sustenance of infection. Leishmania donovani-infected macrophages showed upregulation of IL-33 and its neutralization resulted in decreased parasite survival and increased inflammatory responses. Infection-induced cAMP was involved in IL-33 production and of its downstream effectors PKA and EPAC, only the latter was responsible for elevated IL-33 level. EPAC initiated Rap-dependent phospholipase C activation, which triggered the release of intracellular calcium followed by calcium/calmodulin complex formation. Screening of calmodulin-dependent enzymes affirmed involvement of the phosphatase calcineurin in cAMP/EPAC/calcium/calmodulin signaling-induced IL-33 production and parasite survival. Activated calcineurin ensured nuclear localization of the transcription factors, nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha required for IL-33 transcription, and we further confirmed this by chromatin immunoprecipitation assay. Administering specific inhibitors of nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha in BALB/c mouse model of visceral leishmaniasis decreased liver and spleen parasite burden along with reduction in IL-33 level. Splenocyte supernatants of inhibitor-treated infected mice further documented an increase in tumor necrosis factor alpha and IL-12 level with simultaneous decrease of IL-10, thereby indicating an overall disease-escalating effect of IL-33. Thus, this study demonstrates that cAMP/EPAC/calcineurin signaling is crucial for the activation of IL-33 and in effect creates anti-inflammatory responses, essential for infection.

Immunological landscape of solid cancer: Interplay between tumor and autoimmunity

The immune system, a central player in maintaining homeostasis, emerges as a pivotal factor in the pathogenesis and progression of two seemingly disparate yet interconnected categories of diseases: autoimmunity and cancer. This chapter delves into the intricate and multifaceted role of the immune system, particularly T cells, in orchestrating responses that govern the delicate balance between immune surveillance and self-tolerance. T cells, pivotal immune system components, play a central role in both diseases. In autoimmunity, aberrant T cell activation drives damaging immune responses against normal tissues, while in cancer, T cells exhibit suppressed responses, allowing the growth of malignant tumors. Immune checkpoint receptors, example, initially explored in autoimmunity, now revolutionize cancer treatment via immune checkpoint blockade (ICB). Though effective in various tumors, ICB poses risks of immune-related adverse events (irAEs) akin to autoimmunity. This chapter underscores the importance of understanding tumor-associated antigens and their role in autoimmunity, immune checkpoint regulation, and their implications for both diseases. It also explores autoimmunity resulting from cancer immunotherapy and shared molecular pathways in solid tumors and autoimmune diseases, highlighting their interconnectedness at the molecular level. Additionally, it sheds light on common pathways and epigenetic features shared by autoimmunity and cancer, and the potential of repurposing drugs for therapeutic interventions. Delving deeper into these insights could unlock therapeutic strategies for both autoimmunity and cancer.

Probiotics mixture and taurine attenuate L-arginine-induced acute pancreatitis in rats: Impact on transient receptor potential vanilloid-1 (TRPV-1)/IL-33/NF-κB signaling and apoptosis

Acute pancreatitis (AP) is an inflammatory disorder of acinar cells. It may develop into severe chronic pancreatitis with a significant mortality rate. The current study aimed to assess the therapeutic effect of a Lactobacillus (LAB) mixture against rat AP. Six groups were created including control, taurine (300 mg/kg; i.p.) for 7 days, LAB mixture for 7 days, L-arginine (2.5 g/kg; i.p.) 2 doses with 1 h interval on 1st day, L-arginine+taurine, and L-arginine+LAB. Serum amylase and lipase activities were measured. Pancreatic tissue was used for histopathological examination, oxidative stress biomarkers including malondialdehyde (MDA) and reduced glutathione (GSH), and inflammatory biomarkers including myeloperoxidase (MPO) and interleukin (IL)-33 assessment. qRT-PCR was used for transient receptor potential vanilloid-1 (TRPV-1) investigation and Western blot analysis for measuring nuclear factor kappa-B (NF-κBp65) and the apoptosis biomarker; caspase-3. Taurine and LAB reduced lipase and significantly ameliorated induced oxidative stress by normalizing MDA and GSH contents. They counteracted inflammation by reducing MPO, IL-33, NF-κBp65, and TRPV-1. In addition, taurine and LAB counteracted apoptosis as proved by reduced caspase-3 expression. Taken together, these findings indicate that taurine and the use LAB mixture can mitigate AP by L-arginine via influencing TRPV-1/IL-33/NF-κB signaling together with exhibiting potent antioxidant and anti-inflammatory effects.

Unpacking the complexity of nuclear IL-33 (nIL-33): a crucial regulator of transcription and signal transduction

Interleukin-33 (IL-33) (NF-HEV), a chromatin-associated nuclear cytokine, is a member of the IL-1 family. IL-33 possesses a nuclear localization signal and a homeodomain (a structure resembling a helix-turn-helix) that can bind to nuclear chromatin. Research has revealed that IL-33 can function as a nuclear factor to regulate various biological processes. This review discusses the cellular localization, functional effects, and immune regulation of full length IL-33 (FLIL-33), cytokine IL-33 (sIL-33) and nuclear IL-33 (nIL-33). In addition, the post-translational modifications of nIL-33 and the hypothesis of using nIL-33 as a treatment method were also summarized. A multidisciplinary approach is required which integrates methods and techniques from genomics, proteomics, cell biology and immunology to provide comprehensive insights into the function and therapeutic potential of nIL-33.

Flavonoid-Rich Sambucus nigra Berry Extract Enhances Nrf2/HO-1 Signaling Pathway Activation and Exerts Antiulcerative Effects In Vivo

Sambucus nigra (SN) berry extract is characterized by high antioxidant and anti-inflammatory activity. The current study aimed to investigate the effect of SN berry extract against indomethacin (IND)-induced gastric ulcer in rats and the mechanism involved. SN berry extract alleviated IND-induced gastric ulcers, as shown by assessing pathological manifestations in the gastric mucosa. These protective effects are attributed to attenuated oxidative damage to the gastric mucosa, correlated to increased activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), enhanced glutathione (GSH) levels, total antioxidant capacity (TAC), and upregulation of the Nrf2/HO-1 cascade. Moreover, oxidative stress markers, including malondialdehyde (MDA) and total oxidant status (TOS), were downregulated in SN-extract-treated animals. Furthermore, SN berry extract suppressed gastric mucosal inflammation by downregulating interleukin (IL)-33, IL-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) levels, and attenuating myeloperoxidase (MPO) activity. The protective effects of SN berry extract were similar to those exerted by esomeprazole (ESO), an acid-secretion-suppressive drug. In conclusion, SN berry extract has antiulcerative effects, alleviating oxidative stress and inflammation.

IL-33/ST2 Axis: A Potential Therapeutic Target in Neurodegenerative Diseases

Interleukin 33 (IL-33) belongs to the IL-1 family and is localized in the nucleus. IL-33 is primarily composed of three distinct domains, namely the N-terminal domain responsible for nuclear localization, the intermediate sense protease domain, and the C-terminal cytokine domain. Its specific receptor is the suppression of tumorigenicity 2 (ST2), which is detected in serum-stimulated fibroblasts and oncogenes. While most other cytokines are actively produced in cells, IL-33 is passively produced in response to tissue damage or cell necrosis, thereby suggesting its role as an alarm following cell infection, stress, or trauma. IL-33 plays a crucial role in congenital and acquired immunity, which assists in the response to environmental stress and maintains tissue homeostasis. IL-33/ST2 interaction further produces many pro-inflammatory cytokines. Moreover, IL-33 is crucial for central nervous system (CNS) homeostasis and the pathogenic mechanisms underlying CNS degenerative disorders. The present work summarizes the structure of IL-33, its fundamental activities, and its role in immunoregulation and neurodegenerative diseases. Therefore, this work proposes that IL-33 may play a role in the pathogenic mechanism of diseases and can be used in the development of treatment strategies.

Xenomake: a pipeline for processing and sorting xenograft reads from spatial transcriptomic experiments

Xenograft models are attractive models that mimic human tumor biology and permit one to perturb the tumor microenvironment and study its drug response. Spatially resolved transcriptomics (SRT) provide a powerful way to study the organization of xenograft models, but currently there is a lack of specialized pipeline for processing xenograft reads originated from SRT experiments. Xenomake is a standalone pipeline for the automated handling of spatial xenograft reads. Xenomake handles read processing, alignment, xenograft read sorting, quantification, and connects well with downstream spatial analysis packages. We additionally show that Xenomake can correctly assign organism specific reads, reduce sparsity of data by increasing gene counts, while maintaining biological relevance for 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.

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

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

IL-33-expressing microvascular endothelial cells in human esophageal squamous cell carcinoma: Implications for pathological features and prognosis

Accumulating evidence suggests that interleukin (IL)-33 plays a critical role in regulating angiogenesis and cancer progression. In this study, we characterized the pathological importance of IL-33 deployed by tumor microvascular endothelial cells (ECs) in human esophageal squamous cell carcinoma (ESCC). The expression of IL-33 in microvascular ECs in 80 cases of ESCC was examined with immunohistochemistry (IHC) and double immunofluorescence. IHC results showed that strong IL-33-immunoreactivity (IR) in microvessels, which were confirmed to be ECs by double immunofluorescence staining with IL-33/CD31 antibodies. Moreover, high proliferative activity was shown in IL-33-positive ECs, and the IL-33 functional receptor ST2 was expressed in microvascular ECs. Clinicopathological analysis revealed that IL-33-positive microvessel density (MVD) was positively correlated with node involvement in patients with ESCC. A log rank test showed a highly significant inverse correlation between the densities of IL-33-positive MVDs and overall survival rate, and patients with higher IL-33-positive MVDs tended to have a lower survival rate (both p < 0.05). Therefore, we concluded that IL-33 deployed by microvascular ECs correlates with advanced pathological features and the long-term survival rate, which provides new insights into the regulatory mechanisms of tumor angiogenesis in the tumor microenvironment and might serve as a promising target in patients with ESCC.

SUMOylated IL-33 in the nucleus stabilizes the transcription factor IRF1 in hepatocellular carcinoma cells to promote immune escape

Interleukin-33 (IL-33) functions both as a secreted cytokine and as a nuclear factor, with pleiotropic roles in cancer and immunity. Here, we explored its role in hepatocellular carcinoma (HCC) and identified that a posttranslational modification altered its nuclear activity and promoted immune escape for HCC. IL-33 abundance was overall decreased but more frequently localized to the nucleus in patient HCC tissues than in normal liver tissues. In human and mouse HCC cells in culture and in vivo, IL-33 overexpression inhibited proliferation and repressed the abundance of programmed death ligand 1 (PD-L1) at the transcriptional level by promoting the ubiquitin-dependent degradation of interferon regulatory factor 1 (IRF1). However, this interaction was disrupted by SUMOylation of IL-33 at Lys⁵⁴ mediated by the E3 ligase RanBP2. IL-33 SUMOylation correlated with its nuclear localization in HCC cells and tumors. An increase in SUMOylated IL-33 in HCC cells in cocultures and in vivo stabilized IRF1 and increased PD-L1 abundance and chemokine IL-8 secretion, which prevented the activation of cytotoxic T cells and promoted the M2 polarization of macrophages, respectively. Mutating the SUMOylation site in IL-33 reversed these effects and suppressed tumor growth. These findings indicate that SUMOylation of nuclear IL-33 in HCC cells impairs antitumor immunity.

Initial and ongoing tobacco smoking elicits vascular damage and distinct inflammatory response linked to neurodegeneration

Tobacco smoking is strongly linked to vascular damage contributing to the development of hypertension, atherosclerosis, as well as increasing the risk for neurodegeneration. Still, the involvement of the innate immune system in the development of vascular damage upon chronic tobacco use before the onset of clinical symptoms is not fully characterized. Our data provide evidence that a single acute exposure to tobacco elicits the secretion of extracellular vesicles expressing CD105 and CD49e from endothelial cells, granting further recognition of early preclinical biomarkers of vascular damage. Furthermore, we investigated the effects of smoking on the immune system of healthy asymptomatic chronic smokers compared to never-smokers, focusing on the innate immune system. Our data reveal a distinct immune landscape representative for early stages of vascular damage in clinically asymptomatic chronic smokers, before tobacco smoking related diseases develop. These results indicate a dysregulated immuno-vascular axis in chronic tobacco smokers that are otherwise considered as healthy individuals. The distinct alterations are characterized by increased CD36 expression by the blood monocyte subsets, neutrophilia and increased plasma IL-18 and reduced levels of IL-33, IL-10 and IL-8. Additionally, reduced levels of circulating BDNF and elevated sTREM2, which are associated with neurodegeneration, suggest a considerable impact of tobacco smoking on CNS function in clinically healthy individuals. These findings provide profound insight into the initial and ongoing effects of tobacco smoking and the potential vascular damage contributing to neurodegenerative disorders, specifically cerebrovascular dysfunction and dementia.

Molecular Mechanisms Underlying IL-33-Mediated Inflammation in Inflammatory Bowel Disease

Interleukin-33 (IL-33) is a cytokine defined by its pleiotropic function, acting either as a typical extracellular cytokine or as a nuclear transcription factor. IL-33 and its receptor, suppression of tumorigenicity 2 (ST2), interact with both innate and adaptive immunity and are considered critical regulators of inflammatory disorders. The IL-33/ST2 axis is involved in the maintenance of intestinal homeostasis; on the basis of their role as pro- or anti-inflammatory mediators of first-line innate immunity, their expression is of great importance in regard to mucosal defenses. Mucosal immunity commonly presents an imbalance in inflammatory bowel disease (IBD). This review summarizes the main cellular and molecular aspects of IL-33 and ST2, mainly focusing on the current evidence of the pro- and anti-inflammatory effects of the IL-33/ST2 axis in the course of ulcerative colitis and Crohn's disease, as well as the molecular mechanisms underlying the association of IL-33/ST2 signaling in IBD pathogenesis. Although IL-33 modulates and impacts the development, course, and recurrence of the inflammatory response, the exact role of this molecule is elusive, and it seems to be associated with the subtype of the disease or the disease stage. Unraveling of IL-33/ST2-mediated mechanisms involved in IBD pathology shows great potential for clinical application as therapeutic targets in IBD treatment.

Interleukin (IL)-33 immunobiology in asthma and airway inflammatory diseases

OBJECTIVE

Identify key features of IL-33 immunobiology important in allergic and nonallergic airway inflammatory diseases and potential therapeutic strategies to reduce disease burden.

DATA SOURCES

PubMed, clinicaltrials.gov.

STUDY SELECTIONS

A systematic and focused literature search was conducted of PubMed from March 2021 to December 2021 using keywords to either PubMed or BioMed Explorer including IL-33/ST2, genetic polymorphisms, transcription, translation, post-translation modification, nuclear protein, allergy, asthma, and lung disease. Clinical trial information on IL-33 was extracted from clinicaltrials.gov in August 2021.

RESULTS

In total, 72 publications with relevance to IL-33 immunobiology and/or clinical lung disease were identified (allergic airway inflammation/allergic asthma n = 26, non-allergic airway inflammation n = 9, COPD n = 8, lung fibrosis n = 10). IL-33 levels were higher in serum, BALF and/or lungs across inflammatory lung diseases. Eight studies described viral infections and IL-33 and 4 studies related to COVID-19. Mechanistic studies (n = 39) including transcript variants and post-translational modifications related to the immunobiology of IL-33. Single nucleotide polymorphism in IL-33 or ST2 were described in 9 studies (asthma n = 5, inflammatory bowel disease n = 1, mycosis fungoides n = 1, ankylosing spondylitis n = 1, coronary artery disease n = 1). Clinicaltrials.gov search yielded 84 studies of which 17 were related to therapeutic or biomarker relevance in lung disease.

CONCLUSION

An integral role of IL-33 in the pathogenesis of allergic and nonallergic airway inflammatory disease is evident with several emerging clinical trials investigating therapeutic approaches. Current data support a critical role of IL-33 in damage signaling, repair and regeneration of lungs.

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.

IL-33 biology in cancer: An update and future perspectives

Interleukin-33 (IL-33) is a member of the IL-1 family of cytokines that is constitutively expressed in the nucleus of epithelial, endothelial and fibroblast-like cells. Upon cell stress, damage or necrosis, IL-33 is released into the cytoplasm to exert its prime role as an alarmin by binding to its specific receptor moiety, ST2. IL-33 exhibits pleiotropic function in inflammatory diseases and particularly in cancer. IL-33 may play a dual role as both a pro-tumorigenic and anti-tumorigenic cytokine, dependent on tumor and cellular context, expression levels, bioactivity and the nature of the inflammatory environment. In this review, we discuss the differential contribution of IL-33 to malignant or inflammatory conditions, its multifaceted effects on the tumor microenvironment, while providing possible explanations for the discrepant findings described in the literature. Additionally, we examine the emerging and divergent functions of IL-33 in the nucleus, and aspects of IL-33 biology that are currently under-addressed.

Insights Into the Properties, Biological Functions, and Regulation of USP21

Deubiquitylating enzymes (DUBs) antagonize ubiquitination by removing ubiquitin from their substrates. The role of DUBs in controlling various physiological and pathological processes has been extensively studied, and some members of DUBs have been identified as potential therapeutic targets in diseases ranging from tumors to neurodegeneration. Ubiquitin-specific protease 21 (USP21) is a member of the ubiquitin-specific protease family, the largest subfamily of DUBs. Although USP21 was discovered late and early research progress was slow, numerous studies in the last decade have gradually revealed the importance of USP21 in a wide variety of biological processes. In particular, the pro-carcinogenic effect of USP21 has been well elucidated in the last 2 years. In the present review, we provide a comprehensive overview of the current knowledge on USP21, including its properties, biological functions, pathophysiological roles, and cellular regulation. Limited pharmacological interventions for USP21 have also been introduced, highlighting the importance of developing novel and specific inhibitors targeting USP21.

IL-33 enhances Jagged1 mediated NOTCH1 intracellular domain (NICD) deubiquitination and pathological angiogenesis in proliferative retinopathy

Pathological retinal neovascularization (NV) is a clinical manifestation of various proliferative retinopathies, and treatment of NV using anti-VEGF therapies is not selective, as it also impairs normal retinal vascular growth and function. Here, we show that genetic deletion or siRNA-mediated downregulation of IL-33 reduces pathological NV in a murine model of oxygen-induced retinopathy (OIR) with no effect on the normal retinal repair. Furthermore, our fluorescent activated cell sorting (FACS) data reveals that the increase in IL-33 expression is in endothelial cells (ECs) of the hypoxic retina and conditional genetic deletion of IL-33 in retinal ECs reduces pathological NV. In vitro studies using human retinal microvascular endothelial cells (HRMVECs) show that IL-33 induces sprouting angiogenesis and requires NFkappaB-mediated Jagged1 expression and Notch1 activation. Our data also suggest that IL-33 enhances de-ubiquitination and stabilization of Notch1 intracellular domain via its interaction with BRCA1-associated protein 1 (BAP1) and Numb in HRMVECs and a murine model of OIR.

The Merkel Cell Polyomavirus T-Antigens and IL-33/ST2-IL1RAcP Axis: Possible Role in Merkel Cell Carcinoma

Merkel cell polyomavirus (MCPyV) is a causal factor in Merkel cell carcinoma (MCC). The oncogenic potential is mediated through its viral oncoproteins large T-antigen (LT) and small T-antigen (sT). Cytokines produced by tumor cells play an important role in cancer pathogenesis, and viruses affect their expression. Therefore, we compared human cytokine and receptor transcript levels in virus positive (V+) and virus negative (V−) MCC cell lines. Increased expression of IL-33, a potent modulator of tumor microenvironment, was observed in V+ MCC cell lines when compared to V− MCC-13 cells. Transient transfection studies with luciferase reporter plasmids demonstrated that LT and sT stimulated IL-33, ST2/IL1RL1 and IL1RAcP promoter activity. The induction of IL-33 expression was confirmed by transfecting MCC-13 cells with MCPyV LT. Furthermore, recombinant human cytokine domain IL-33 induced activation of MAP kinase and NF-κB pathways, which could be blocked by a ST2 receptor antibody. Immunohistochemical analysis demonstrated a significantly stronger IL-33, ST2, and IL1RAcP expression in MCC tissues compared to normal skin. Of interest, significantly higher IL-33 and IL1RAcP protein levels were observed in MCC patient plasma compared to plasma from healthy controls. Previous studies have demonstrated the implication of the IL-33/STL2 pathway in cancer. Because our results revealed a T-antigens-dependent induction of the IL-33/ST2 axis, IL-33/ST2 may play a role in the tumorigenesis of MCPyV-positive MCC. Therefore, neutralizing the IL-33/ST2 axis may present a novel therapeutic approach for MCC patients.

Galectin-1 as the new player in staging and prognosis of COVID-19

A new virus from the group of coronaviruses was identified as the cause of atypical pneumonia and called Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and disease called Corona Virus Disease (COVID-19). During the cytokine storm, the main cause of the death, proinflammatory cytokines are released which stimulate further tissue destruction. Galectin-1 (Gal-1) is a pleiotropic cytokine involved in many immune and inflammatory processes and its role in COVID-19 is still unknown. The aim of this study was to determine systemic values of Gal-1 and correlations between Gal-1 and proinflammatory cytokines and clinical parameters during COVID-19 progression. This is observational and cross-sectional study. 210 COVID-19 patients were included and divided into mild, severe or critical group according to COVID-19 severity. Serum levels of IL-1β, IL-6, IL-10, IL-23, IL-33 and Gal-1 were measured using sensitive enzyme-linked immunosorbent assay (ELISA) kits. Systemic levels of IL-1β, IL-6, IL-10, IL-23, IL-33 and Gal-1 were significantly higher in stage III of COVID-19 patients compared to stage I and II. There were no significant differences in the ratio between Gal-1 and IL-10 with proinflammatory cytokines. Positive correlation was detected between Gal-1 and IL-1β, IL6, IL-10, IL-23 and IL-33. Gal-1 positively correlated with chest radiographic finding, dry cough and headache and negatively correlated with normal breathing sound. Linear regression model and ROC curve analysis point on Gal-1 as significant predictor for COVID-19 severity. Presented results implicate on Gal-1 and IL-10 dependent immunomodulation. The precise mechanism of Gal-1 effect in COVID-19 and its potential as a stage marker of disease severity is still to be clarified.

Decreased intracellular IL-33 impairs endometrial receptivity in women with adenomyosis

Adenomyosis is a common benign uterine lesion that is associated with female infertility, reduced clinical pregnancy rate and high miscarriage risk. While it has been known that the impaired endometrial receptivity is implicated in infertility in patients with adenomyosis, the underlying mechanism remains unclear. In the present study, we showed that intracellular protein level of IL-33 was downregulated in the endometrium of patients with adenomyosis, and IL-33 expression status was shown to be positively correlated with that of HOXA10, an endometrial receptivity marker. The subsequent analysis indicated IL-33 overexpression led to the increase of HOXA10 expression and enhancement of embryo implantation in vitro, which was accompanied with induction of STAT3 phosphorylation. Meanwhile, cryptotanshinone, a potent STAT3 inhibitor, was found to significantly suppress the increase of HOXA10 expression and embryo implantation caused by IL-33 overexpression in vitro, revealing the critical role of STAT3 activity. Consistently, the positive relationship between IL33 and HOXA10 expression in the endometrium was verified in the analysis of adenomyosis mouse model.

Temporal Quantitative Phosphoproteomics Profiling of Interleukin-33 Signaling Network Reveals Unique Modulators of Monocyte Activation

Interleukin-33 (IL-33), a member of the IL-1 superfamily cytokines, is an endogenous danger signal and a nuclear-associated cytokine. It is one of the essential mediators of both innate and adaptive immune responses. Aberrant IL-33 signaling has been demonstrated to play a defensive role against various infectious and inflammatory diseases. Although the signaling responses mediated by IL-33 have been previously reported, the temporal signaling dynamics are yet to be explored. To this end, we applied quantitative temporal phosphoproteomics analysis to elucidate pathways and proteins induced by IL-33 in THP-1 monocytes. Employing a TMT labeling-based quantitation and titanium dioxide (TiO₂)-based phosphopeptide enrichment strategy followed by mass spectrometry analysis, we identified and quantified 9448 unique phosphopeptides corresponding to 3392 proteins that showed differential regulation. Of these, 171 protein kinases, 60 phosphatases and 178 transcription factors were regulated at different phases of IL-33 signaling. In addition to the confirmed activation of canonical signaling modules including MAPK, NFκB, PI3K/AKT modules, pathway analysis of the time-dependent phosphorylation dynamics revealed enrichment of several cellular processes, including leukocyte adhesion, response to reactive oxygen species, cell cycle checkpoints, DNA damage and repair pathways. The detailed quantitative phosphoproteomic map of IL-33 signaling will serve as a potentially useful resource to study its function in the context of inflammatory and pathological conditions.

The Paradigm Change of IL-33 in Vascular Biology

In this review, we focus on the actual understanding of the role of IL-33 in vascular biology in the context of the historical development since the description of IL-33 as a member of IL-1 superfamily and the ligand for ST2 receptor in 2005. We summarize recent data on the biology, structure and signaling of this dual-function factor with both nuclear and extracellular cytokine properties. We describe cellular sources of IL-33, particularly within vascular wall, changes in its expression in different cardio-vascular conditions and mechanisms of IL-33 release. Additionally, we summarize the regulators of IL-33 expression as well as the effects of IL-33 itself in cells of the vasculature and in monocytes/macrophages in vitro combined with the consequences of IL-33 modulation in models of vascular diseases in vivo. Described in murine atherosclerosis models as well as in macrophages as an atheroprotective cytokine, extracellular IL-33 induces proinflammatory, prothrombotic and proangiogenic activation of human endothelial cells, which are processes known to be involved in the development and progression of atherosclerosis. We, therefore, discuss that IL-33 can possess both protective and harmful effects in experimental models of vascular pathologies depending on experimental conditions, type and dose of administration or method of modulation.

IL 33 Correlates With COVID-19 Severity, Radiographic and Clinical Finding

Objective: The increased level of interleukin (IL)-33 is considered as a predictor of severe coronavirus disease 2019 (COVID-19) infection, but its role at different stages of the disease is still unclear. Our goal was to analyze the correlation of IL-33 and other innate immunity cytokines with disease severity. Methods: In this study, 220 patients with COVID-19 were included and divided into two groups, mild/moderate and severe/critical. The value of the cytokines, clinical, biochemical, radiographic data was collected and their correlation with disease severity was analyzed. Results: Most patients in the severe/critical group were male (81.8%) and older (over 64.5 years). We found a statistically significant difference (p < 0.05) in these two groups between clinical features (dyspnea, dry cough, fatigue, and auscultatory findings); laboratory [(neutrophil count, lymphocyte count, monocyte count, hemoglobin, plasma glucose, urea, creatinine, total bilirubin (TBIL), direct bilirubin (DBIL), aspartate aminotransferase (AST), albumin (ALB), lactate dehydrogenase (LDH), creatinine kinase (CK), D-dimer, C-reactive protein (CRP), procalcitonin (PCT), Fe, and Ferritin)], arterial blood gases (oxygen saturation-Sa02, partial pressure of oxygen -p02), and chest X-rays (CXR) lung findings (p = 0.000). We found a significantly higher serum concentration (p < 0.05) of TNF-α, IL-1β, IL-6, IL-12, IL-23, and IL-33 in patients with COVID-19 with severe disease. In the milder stage of COVID-19, a positive correlation was detected between IL-33 and IL-1β, IL-12 and IL-23, while a stronger positive correlation between the serum values of IL-33 and TNF-α, IL-1β, IL-6, and IL-12 and IL-23 was detected in patients with COVID-19 with severe disease. A weak negative correlation (p < 0.05) between pO2 and serum IL-1β, IL-12, and IL-33 and between SaO2 and serum IL-33 was noted. The positive relation (p < 0.05) between the serum values of IL-33 and IL-12, IL-33 and IL-6, and IL-6 and IL-12 is proven. Conclusion: In a more progressive stage of COVID-19, increased IL-33 facilitates lung inflammation by inducing the production of various innate proinflammatory cytokines (IL-1β, IL-6, TNF-α, IL-12, and IL-23) in several target cells leading to the most severe forms of the disease. IL-33 correlates with clinical parameters of COVID-19 and might represent a promising marker as well as a therapeutic target in COVID-19.

IL-1 family cytokines as drivers and inhibitors of trained immunity

Trained immunity is the long-term memory of innate immune cells, characterised by increased pro-inflammatory responses towards homo- and heterologous secondary stimuli. Interleukin (IL)-1 signalling plays an essential role in the induction of trained immunity, also called innate immune memory. As such, certain anti-inflammatory members of the IL-1 family of cytokines (IL-1F) which interfere with the inflammatory process have the potential to regulate the induction of a trained phenotype. The aim of this review is to provide an update on the role of IL-1F members in the context of trained immunity, emphasising the role of anti-inflammatory cytokines from the IL-1F to inhibit the induction of trained immunity, and touching upon their potential as therapeutics in IL-1-driven inflammatory disorders.

The role of MerTK in promoting cell migration is enhanced by the oncogenic Ras/IL-33 signaling axis

Ras genes are frequently mutated in many cancer types; however, there are currently no conclusively effective anticancer drugs against Ras-induced cancer. Therefore, the downstream effectors of Ras signaling need to be identified for the development of promising novel therapeutic approaches. We previously reported that oncogenic Ras induced the expression of NF-HEV/IL-33, a member of the interleukin-1 family, and showed that intracellular IL-33 was required for oncogenic Ras-induced cellular transformation. In the present study, we demonstrated that the c-Mer proto-oncogene tyrosine kinase (MerTK), a receptor tyrosine kinase, played essential roles in oncogenic Ras/IL-33 signaling. The expression of MerTK was enhanced in transformed NIH-3T3 cells by the expression of oncogenic Ras, H-Ras (G12V), in an IL-33-dependent manner. In human colorectal cancer tissues, MerTK expression also correlated with IL-33 expression. The knockdown of IL-33 or MerTK effectively attenuated the migration of NIH-3T3 cells transformed by H-Ras (G12V) and A549, LoVo, and HCT116 cells harboring an oncogenic K-Ras mutation. Furthermore, the suppression of Ras-induced cell migration by the knockdown of IL-33 was rescued by the enforced expression of MerTK. The present results also revealed that MerTK was effectively phosphorylated in NIH-3T3 cells transformed by Ras (G12V). Ras signaling was essential for the tyrosine phosphorylation of MerTK, and the kinase activity of MerTK was indispensable for accelerating cell migration. Collectively, the present results reveal a novel role for MerTK in cancer malignancy, which may be utilized to develop novel therapeutic strategies that target Ras-transformed cells.

Host-Viral Interactions in the Pathogenesis of Ulcerative Colitis

Ulcerative colitis is characterized by relapsing and remitting colonic mucosal inflammation. During the early stages of viral infection, innate immune defenses are activated, leading to the rapid release of cytokines and the subsequent initiation of downstream responses including inflammation. Previously, intestinal viruses were thought to be either detrimental or neutral to the host. However, persisting viruses may have a role as resident commensals and confer protective immunity during inflammation. On the other hand, the dysregulation of gut mucosal immune responses to viruses can trigger excessive, pathogenic inflammation. The purpose of this review is to discuss virus-induced innate immune responses that are at play in ulcerative colitis.

IL-33/ST2 Axis Plays a Protective Effect in Streptococcus pyogenes Infection through Strengthening of the Innate Immunity

Group A Streptococcus (GAS) causes invasive human diseases with the cytokine storm. Interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) axis is known to drive TH2 response, while its effect on GAS infection is unclear. We used an air pouch model to examine the effect of the IL-33/ST2 axis on GAS-induced necrotizing fasciitis. GAS infection induced IL-33 expression in wild-type (WT) C57BL/6 mice, whereas the IL-33- and ST2-knockout mice had higher mortality rates, more severe skin lesions and higher bacterial loads in the air pouches than those of WT mice after infection. Surveys of infiltrating cells in the air pouch of GAS-infected mice at the early stage found that the number and cell viability of infiltrating cells in both gene knockout mice were lower than those of WT mice. The predominant effector cells in GAS-infected air pouches were neutrophils. Absence of the IL-33/ST2 axis enhanced the expression of inflammatory cytokines, but not TH1 or TH2 cytokines, in the air pouch after infection. Using in vitro assays, we found that the IL-33/ST2 axis not only enhanced neutrophil migration but also strengthened the bactericidal activity of both sera and neutrophils. These results suggest that the IL-33/ST2 axis provided the protective effect on GAS infection through enhancing the innate immunity.

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.

IL-33 activates mTORC1 and modulates glycolytic metabolism in CD8+ T cells

Interleukin (IL)-33, a member in the IL-1 family, plays a central role in innate and adaptive immunity; however, how IL-33 mediates cytotoxic T-cell regulation and the downstream signals remain elusive. In this study, we found increased mouse IL-33 expression in CD8⁺ T cells following cell activation via anti-CD3/CD28 stimulation in vitro or lymphocytic choriomeningitis virus (LCMV) infection in vivo. Our cell adoptive transfer experiment demonstrated that extracellular, but not nuclear, IL-33 contributed to the activation and proliferation of CD8⁺ , but not CD4⁺ T effector cells in LCMV infection. Importantly, IL-33 induced mTORC1 activation in CD8⁺ T cells as evidenced by increased phosphorylated S6 ribosomal protein (p-S6) levels both in vitro and in vivo. Meanwhile, this IL-33-induced CD8⁺ T-cell activation was suppressed by mTORC1 inhibitors. Furthermore, IL-33 elevated glucose uptake and lactate production in CD8⁺ T cells in both dose- and time-dependent manners. The results of glycolytic rate assay demonstrated the increased glycolytic capacity of IL-33-treated CD8⁺ T cells compared with that of control cells. Our mechanistic study further revealed the capacity of IL-33 in promoting the expression of glucose transporter 1 (Glut1) and glycolytic enzymes via mTORC1, leading to accelerated aerobic glucose metabolism Warburg effect and increased effector T-cell activation. Together, our data provide new insights into IL-33-mediated regulation of CD8⁺ T cells, which might be beneficial for therapeutic strategies of inflammatory and infectious diseases in the future.

Anemia of inflammation in patients with colorectal cancer: Correlation with Interleukin-1, Interleukin-33 and Galectin-1

Background

Patients with colorectal cancer (CRC) have anemia often present as a consequence of chronic bleeding from tumor. The exact role of lL-33, Galectin-l and IL-l in the pathological genesis of anemia in colorectal cancer patients has not been elucidated yet. The main goal of this research was to analyze Gal-l, IL-l and lL-33 systemic values in anemic and non-anemic CRC patients.

Methods

Concentrations of IL-33, Galectin-1 and IL-1 have been studied in blood samples of 55 CRC patients (27 without anemia and 28 with anemia).

Results

CRC patients with anemia had more severe and local advanced disease compared to CRC non-anemic patients. Anemia positively correlated with higher nuclear grade, lymph and blood vessel invasion, as well as with higher TNM stage, detectable metastatic lesions in lung and liver and peritoneal carcinomatosis. Significantly higher IL-33, Gal-1 and IL-1 concentration have been found in sera of patients with CRC and detected anemia. CRC patients mostly had microcytic anemia, while ferritin values were in normal range. Analysis revealed positive mutual correlation between serum values of galectin-1, IL-1 and IL-33 in CRC patients. Level of hemoglobin negatively correlated with serum IL-33, Gal-1 and IL-1. We have analyzed the Receiver Operating Characteristic (ROC) curves of serum IL-33, Gal-1 and IL-1 showed that these cytokines can be treated as additional markers for anemia of inflammation in CRC patients.

Conclusions

Predomination of Galectin-1, IL-1 and IL-33 in anemic CRC patients implicates on their potential role in anemia genesis and further development.

IL-33 Is Involved in the Anti-Inflammatory Effects of Butyrate and Propionate on TNFα-Activated Endothelial Cells

Short-chain fatty acids (e.g., butyrate and propionate) are able to diminish endothelial cell activation. The aim of this study was to investigate whether intracellular IL-33 mediates the effects of butyrate and propionate on TNFα-induced IL-8 production and vascular cell adhesion molecule-1 (VCAM-1) expression. In addition, it was investigated whether regulating NF-κB and MAPK signaling pathways are involved. Intracellular IL-33 was measured in human endothelial cells (HUVECs) pre-incubated for 24 h with butyrate (0.1 mM or 5 mM), propionate (0.3 mM or 10 mM), or trichostatin A (TSA, 0.5 μM) prior to TNFα (1 ng/mL) stimulation (24 h). The effects of butyrate, propionate, and TSA on TNFα-induced IL-8, vascular cell adhesion molecule-1 (VCAM-1), NF-κB, and MAPK signaling pathways in normal HUVECs and IL-33 siRNA (siIL-33)-transfected HUVECs were compared to study the role of IL-33 in the protective effects of butyrate and propionate. Endogenous IL-33 was highly expressed in the perinuclear in HUVECs, which was significantly reduced by TNFα stimulation. The TNFα-induced reduction in IL-33 was prevented by pre-incubation with butyrate or propionate. Butyrate (0.1 mM), propionate (0.3 mM), and TSA inhibited the IL-8 production and activation of NF-κB. Interestingly, this effect was not observed in siIL-33-transfected HUVECs. The effects of butyrate (5 mM), propionate (10 mM), and TSA (0.5 μM) on VCAM-1 expression and activation of MAPK signaling pathways were not affected by siIL-33 transfection. In conclusion, we showed that the inhibitory effects of butyrate and propionate on TNFα-induced IL-8 production were mediated by the HDACs/IL-33/NF-κB pathway, while their effects on VCAM-1 expression might be associated with the HDACs/MAPK signaling pathway, independently of IL-33.

The curious case of IL-33 in homeostasis and infection

The importance of interleukin (IL)‐33 in promoting effective antiviral immune responses is evident, yet the critical cellular sources of IL‐33 in homeostasis and infection are largely unknown. In this issue of the European Journal of Immunology, Aparicio‐Domingo et al. [Eur. J. Immunol. 2021. 51: 76–90] explore the main source of IL‐33 expression in lymph nodes (LNs) and dissect its role in LN homeostasis and antiviral adaptive immune response. The authors reveal that fibroblastic reticular cells and lymphatic endothelial cells are both producing IL‐33 in steady‐state LNs. Remarkably, however, by using cell‐type specific deletion approaches, the authors demonstrate that exclusively fibroblastic reticular cells, and not lymphatic endothelial cells, are the critical cellular source for promoting antiviral CD8⁺ T‐cell responses upon infection. These findings provide an important insight into the role of specific LN stromal cell subsets as potent modulators of antiviral immunity.

Glioma-derived IL-33 orchestrates an inflammatory brain tumor microenvironment that accelerates glioma progression

Despite a deeper molecular understanding, human glioblastoma remains one of the most treatment refractory and fatal cancers. It is known that the presence of macrophages and microglia impact glioblastoma tumorigenesis and prevent durable response. Herein we identify the dual function cytokine IL-33 as an orchestrator of the glioblastoma microenvironment that contributes to tumorigenesis. We find that IL-33 expression in a large subset of human glioma specimens and murine models correlates with increased tumor-associated macrophages/monocytes/microglia. In addition, nuclear and secreted functions of IL-33 regulate chemokines that collectively recruit and activate circulating and resident innate immune cells creating a pro-tumorigenic environment. Conversely, loss of nuclear IL-33 cripples recruitment, dramatically suppresses glioma growth, and increases survival. Our data supports the paradigm that recruitment and activation of immune cells, when instructed appropriately, offer a therapeutic strategy that switches the focus from the cancer cell alone to one that includes the normal host environment.

Contributions of IL-33 in Non-hematopoietic Lung Cells to Obstructive Lung Disease

Interleukin (IL)-33 plays important roles in pulmonary immune responses and lung diseases including asthma and chronic obstructive pulmonary disease (COPD). There is substantial interest in identifying and characterizing cellular sources vs. targets of IL-33, and downstream signaling pathways involved in disease pathophysiology. While epithelial and immune cells have largely been the focus, in this review, we summarize current knowledge of expression, induction, and function of IL-33 and its receptor ST2 in non-hematopoietic lung cells in the context of health and disease. Under basal conditions, epithelial cells and endothelial cells are thought to be the primary resident cell types that express high levels of IL-33 and serve as ligand sources compared to mesenchymal cells (smooth muscle cells and fibroblasts). Under inflammatory conditions, IL-33 expression is increased in most non-hematopoietic lung cells, including epithelial, endothelial, and mesenchymal cells. In comparison to its ligand, the receptor ST2 shows low expression levels at baseline but similar to IL-33, ST2 expression is upregulated by inflammation in these non-hematopoietic lung cells which may then participate in chronic inflammation both as sources and autocrine/paracrine targets of IL-33. Downstream effects of IL-33 may occur via direct receptor activation or indirect interactions with the immune system, overall contributing to lung inflammation, airway hyper-responsiveness and remodeling (proliferation and fibrosis). Accordingly from a therapeutic perspective, targeting IL-33 and/or its receptor in non-hematopoietic lung cells becomes relevant.

Fibroblast-derived IL-33 is dispensable for lymph node homeostasis but critical for CD8 T-cell responses to acute and chronic viral infection

Upon viral infection, stressed or damaged cells can release alarmins like IL-33 that act as endogenous danger signals alerting innate and adaptive immune cells. IL-33 coming from nonhematopoietic cells has been identified as important factor triggering the expansion of antiviral CD8⁺ T cells. In LN the critical cellular source of IL-33 is unknown, as is its potential cell-intrinsic function as a chromatin-associated factor. Using IL-33-GFP reporter mice, we identify fibroblastic reticular cells (FRC) and lymphatic endothelial cells (LEC) as the main IL-33 source. In homeostasis, IL-33 is dispensable as a transcriptional regulator in FRC, indicating it functions mainly as released cytokine. Early during infection with lymphocytic choriomeningitis virus (LCMV) clone 13, both FRC and LEC lose IL-33 protein expression suggesting cytokine release, correlating timewise with IL-33 receptor expression by reactive CD8⁺ T cells and their greatly augmented expansion in WT versus ll33^-/- mice. Using mice lacking IL-33 selectively in FRC versus LEC, we identify FRC as key IL-33 source driving acute and chronic antiviral T-cell responses. Collectively, these findings show that LN T-zone FRC not only regulate the homeostasis of naïve T cells but also their expansion and differentiation several days into an antiviral response.

The IL-33/ST2 Axis in Immune Responses Against Parasitic Disease: Potential Therapeutic Applications

Parasitic infections pose a wide and varying threat globally, impacting over 25% of the global population with many more at risk of infection. These infections are comprised of, but not limited to, toxoplasmosis, malaria, leishmaniasis and any one of a wide variety of helminthic infections. While a great deal is understood about the adaptive immune response to each of these parasites, there remains a need to further elucidate the early innate immune response. Interleukin-33 is being revealed as one of the earliest players in the cytokine milieu responding to parasitic invasion, and as such has been given the name "alarmin." A nuclear cytokine, interleukin-33 is housed primarily within epithelial and fibroblastic tissues and is released upon cellular damage or death. Evidence has shown that interleukin-33 seems to play a crucial role in priming the immune system toward a strong T helper type 2 immune response, necessary in the clearance of some parasites, while disease exacerbating in the context of others. With the possibility of being a double-edged sword, a great deal remains to be seen in how interleukin-33 and its receptor ST2 are involved in the immune response different parasites elicit, and how those parasites may manipulate or evade this host mechanism. In this review article we compile the current cutting-edge research into the interleukin-33 response to toxoplasmosis, malaria, leishmania, and helminthic infection. Furthermore, we provide insight into directions interleukin-33 research may take in the future, potential immunotherapeutic applications of interleukin-33 modulation and how a better clarity of early innate immune system responses involving interleukin-33/ST2 signaling may be applied in development of much needed treatment options against parasitic invaders.

An intrinsic role of IL-33 in Treg cell-mediated tumor immunoevasion

Regulatory T (T_reg) cells accumulate into tumors hindering the success of cancer immunotherapy. Yet, therapeutic targeting of T_reg cells shows limited efficacy or leads to autoimmunity. The molecular mechanisms that guide T_reg cell stability in tumors, remain elusive. Herein, we identify a cell-intrinsic role of the alarmin IL-33 in the functional stability of T_reg cells. Specifically, IL-33-deficient T_reg cells demonstrated attenuated suppressive properties in vivo and facilitated tumor regression in an ST2 (IL-33 receptor)-independent fashion. Upon activation, Il33^–/– T_reg cells exhibited epigenetic reprogramming with increased chromatin accessibility of the Ifng locus leading to elevated interferon-γ (IFN-γ) production in an NF-κB–T-bet-dependent manner. IFN-γ was essential for T_reg cell defective function since its ablation restored Il33^–/– T_reg cell suppressive properties. Importantly, genetic ablation of Il33 potentiated the therapeutic effect of immunotherapy. Our findings reveal a novel and therapeutically important intrinsic role of IL-33 in T_reg cell stability in cancer.