The alarmin IL-33 is a notch target in quiescent endothelial cells

IL-33 immunohistochemical pattern of expression in neoplastic and nonneoplastic peripheral lung tissues of stage 1 o 2 lung adenocarcinoma

IL-33 is a multifaceted cytokine, plays a pivotal role in various biological processes, making it a subject of extensive research and intrigue in the field of immunology. This cytokine acts as a key regulator, effectively putting the brakes on proinflammatory nuclear factor-kappa B (NF-κB), thereby modulating chromatin compaction by promoting nucleosome-to-nucleosome interactions. IL-33's influence extends to the realm of innate and acquired immunity through its binding to the membrane-bound ST2 molecule (ST2L) of the IL-33R complex, which is expressed on various immune cells, such as Th2 cells, mast cells, natural killer cells, myeloid cells, and dendritic cells. IL-33's role in inflammation is far from one-dimensional, as it has been found to have a dual role in inflammatory disorders. In the quest to understand the origins of IL-33, immunohistochemical examination of lung tissue samples from patients with adenocarcinoma could shed light on its presence in bronchial epithelial and vascular endothelial cells, in lung tissue cancerous lesions. For this reason, we conducted a pilot study about the immunohistochemical expression of IL-33 in surgical specimens of stage 1 o 2 lung adenocarcinoma received after lung resection surgery.Our results demonstrated that patients had nuclear IL-33 immunopositivity in the alveolar pneumocytes of the normal lung tissue at the periphery of lung adenocarcinoma specimen. Note the evident negativity of the neoplastic adenocarcinoma cells. Other data showed IL-33 nuclear immunoexpression in endothelial cells of intratumoral vascular structures.This finding could indicate that IL-33 might be involved in regulating blood vessel formation and maintenance within the tumor, which is a critical factor in tumor growth and progression.The presence of IL-33 in normal lung tissue and intratumoral vascular structures may be related to its physiological functions in these contexts, while its absence in neoplastic adenocarcinoma cells could indicate a potential loss of regulatory control, which might have implications for the development and progression of the tumor.

Endothelial Notch1 signaling in white adipose tissue promotes cancer cachexia

Cachexia is a major cause of morbidity and mortality in individuals with cancer and is characterized by weight loss due to adipose and muscle tissue wasting. Hallmarks of white adipose tissue (WAT) remodeling, which often precedes weight loss, are impaired lipid storage, inflammation and eventually fibrosis. Tissue wasting occurs in response to tumor-secreted factors. Considering that the continuous endothelium in WAT is the first line of contact with circulating factors, we postulated whether the endothelium itself may orchestrate tissue remodeling. Here, we show using human and mouse cancer models that during precachexia, tumors overactivate Notch1 signaling in distant WAT endothelium. Sustained endothelial Notch1 signaling induces a WAT wasting phenotype in male mice through excessive retinoic acid production. Pharmacological blockade of retinoic acid signaling was sufficient to inhibit WAT wasting in a mouse cancer cachexia model. This demonstrates that cancer manipulates the endothelium at distant sites to mediate WAT wasting by altering angiocrine signals.

Antibody blockade of Jagged1 attenuates choroidal neovascularization

Antibody-based blocking of vascular endothelial growth factor (VEGF) reduces choroidal neovascularization (CNV) and retinal edema, rescuing vision in patients with neovascular age-related macular degeneration (nAMD). However, poor response and resistance to anti-VEGF treatment occurs. We report that targeting the Notch ligand Jagged1 by a monoclonal antibody reduces neovascular lesion size, number of activated phagocytes and inflammatory markers and vascular leakage in an experimental CNV mouse model. Additionally, we demonstrate that Jagged1 is expressed in mouse and human eyes, and that Jagged1 expression is independent of VEGF signaling in human endothelial cells. When anti-Jagged1 was combined with anti-VEGF in mice, the decrease in lesion size exceeded that of either antibody alone. The therapeutic effect was solely dependent on blocking, as engineering antibodies to abolish effector functions did not impair the therapeutic effect. Targeting of Jagged1 alone or in combination with anti-VEGF may thus be an attractive strategy to attenuate CNV-bearing diseases.

Interleukin-33 Mediates Cardiomyopathy After Acute Kidney Injury by Signaling to Cardiomyocytes

BACKGROUND

Acute kidney injury (AKI) is a short-term life-threatening condition that, if survived, can lead to renal insufficiency and development of chronic kidney disease. The pathogenesis of AKI and chronic kidney disease involves direct effects on the heart and the development of hypertrophy and cardiomyopathy.

METHODS

We used mouse models of ischemia/reperfusion AKI and unilateral ureteral obstruction to investigate the role of IL-33 (interleukin-33) and its receptor-encoding gene Il1rl1 (also called ST2L [suppression of tumorigenicity 2]) in cardiac remodeling after AKI. Mice with cell type-specific genetic disruption of the IL-33/ST2L axis were used, and IL-33 monoclonal antibody, adeno-associated virus encoding IL-33 or ST2L, and recombinant IL-33, as well.

RESULTS

Mice deficient in Il33 were refractory to cardiomyopathy associated with 2 models of kidney injury. Treatment of mice with monoclonal IL-33 antibody also protected the heart after AKI. Moreover, overexpression of IL-33 or injection of recombinant IL-33 induced cardiac hypertrophy or cardiomyopathy, but not in mice lacking Il1rl1. AKI-induced cardiomyopathy was also reduced in mice with cardiac myocyte-specific deletion of Il1rl1 but not in endothelial cell- or fibroblast-specific deletion of Il1rl1. Last, overexpression of the ST2L receptor in cardiac myocytes recapitulated induction of cardiac hypertrophy.

CONCLUSIONS

These results indicate that IL-33 released from the kidney during AKI underlies cardiorenal syndrome by directly signaling to cardiac myocytes, suggesting that antagonism of IL-33/ST2 axis would be cardioprotective in patients with kidney disease.

Pro- and anti-inflammatory roles of interleukin (IL)-33, IL-36, and IL-38 in inflammatory bowel disease

Interleukin-33 (IL-33), IL-36, and IL-38 are members of the IL-1 cytokine family. The expression of each cytokine has been reported to be increased in the inflamed mucosa of patients with inflammatory bowel disease (IBD). IL-33 and IL-36 have been studied for pro- and anti-inflammatory functions, and IL-38 has been characterized as an anti-inflammatory cytokine by antagonizing the IL-36 receptor (IL-36R). IL-33 is a nuclear cytokine constitutively expressed by certain cell types such as epithelial, endothelial, and fibroblast-like cells and released on necrotic cell death. IL-33 mainly induces type 2 immune response through its receptor suppression tumorigenicity 2 (ST2) from Th2 cells and type 2 innate lymphoid cells (ILC2s), but also by stimulating Th1 cells, regulatory T cells, and CD8⁺ T cells. IL-36 cytokines consist of three agonists: IL-36α, IL-36β, and IL-36γ, and two receptor antagonists: IL-36R antagonist (IL-36Ra) and IL-38. All IL-36 cytokines bind to the IL-36R complex and exert various functions through NF-κB and mitogen-activated protein kinase (MAPK) pathways in inflammatory settings. IL-33 and IL-36 also play a crucial role in intestinal fibrosis characteristic manifestation of CD. In this review, we focused on the current understanding of the pro- and anti-inflammatory roles of IL-33, IL-36, and IL38 in experimental colitis and IBD patients.

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.

Identification of Key Determinants of Cerebral Malaria Development and Inhibition Pathways

Cerebral malaria (CM), coma caused by Plasmodium falciparum-infected red blood cells (iRBCs), is the deadliest complication of malaria. The mechanisms that lead to CM development are incompletely understood. Here we report on the identification of activation and inhibition pathways leading to mouse CM with supporting evidence from the analysis of human specimens. We find that CM suppression can be induced by vascular injury when sporozoites exit the circulation to infect the liver and that CM suppression is mediated by the release of soluble factors into the circulation. Among these factors is insulin like growth factor 1 (IGF1), administration of which inhibits CM development in mice. IMPORTANCE Liver infection by Plasmodium sporozoites is a required step for infection of the organism. We found that alternate pathways of sporozoite liver infection differentially influence cerebral malaria (CM) development. CM is one of the primary causes of death following malaria infection. To date, CM research has focused on how CM phenotypes develop but no successful therapeutic treatment or prognostic biomarkers are available. Here we show for the first time that sporozoite liver invasion can trigger CM-inhibitory immune responses. Importantly, we identified a number of early-stage prognostic CM inhibitory biomarkers, many of which had never been associated with CM development. Serological markers identified using a mouse model are directly relevant to human CM.

IL-33/ST2 receptor-dependent signaling in the development of pulmonary hypertension in Sugen/hypoxia mice

Pulmonary arterial hypertension (PAH) is associated with significant morbidity and mortality. PAH is characterized by pulmonary artery remodeling, elevated right ventricular pressure (RVP) and, ultimately, cardiac failure. Pulmonary endothelial cells can sense danger or damage caused by mechanical injury or pathogens through alarmin cytokines. These cytokines can signal proliferation to restore barrier integrity or aberrant hyperproliferation and remodeling. We hypothesized that IL‐33 signals pulmonary artery endothelial cells to proliferate under hypertensive conditions during the remodeling response and rise in RVP. To test this hypothesis, pulmonary hypertension (PH) was induced in C57Bl/6J, IL‐33 receptor gene deleted (ST2^−/−) and MYD88 gene deleted (MYD88^−/−) mice by exposure to 10% O₂ and SU5416 injections (SUHX). RVP, arterial wall thickness, endothelial cell proliferation and IL‐33 levels and signaling were evaluated. In response to SUHX. RVP increased in C57Bl/6J mice in response to SUHX (49% male and 70% female; p < 0.0001) and this SUHX response was attenuated in ST2^−/− mice (29% male p = 0.003; 30% female p = 0.001) and absent in MYD88^−/− mice. Wall thickness was increased in SUHX C57Bl/6J mice (p = 0.005), but not in ST2^−/− or MYD88^−/− mice. Proliferating cells were detected in C57Bl/6J mice by flow cytometry (CD31⁺/BrDU⁺; p = 0.02) and immunofluorescence methods (Ki‐67+). IL‐33 was increased by SUHX (p = 0.03) but a genotype effect was not observed (p = 0.76). We observed that in hPAECs, IL‐33 expression is regulated by both IL‐33 and DLL4. These data suggest IL‐33/ST2 signaling is essential for the endothelial cell proliferative response in PH.

Emerging Functions of IL-33 in Homeostasis and Immunity

Our understanding of the functions of the IL-1 superfamily cytokine and damage-associated molecular pattern IL-33 continues to evolve with our understanding of homeostasis and immunity. The early findings that IL-33 is a potent driver of type 2 immune responses promoting parasite expulsion, but also inflammatory diseases like allergy and asthma, have been further supported. Yet, as the importance of a type 2 response in tissue repair and homeostasis has emerged, so has the fundamental importance of IL-33 to these processes. In this review, we outline an evolving understanding of IL-33 immunobiology, paying particular attention to how IL-33 directs a network of ST2+ regulatory T cells, reparative and regulatory macrophages, and type 2 innate lymphoid cells that are fundamental to tissue development, homeostasis, and repair.

Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

ST2 deletion accelerates inflammatory-angiogenesis and remodeling in subcutaneous implants in mice

Implantation of biomedical/synthetic devices to replace and/or repair biological tissues very often induces an adverse healing response (scarce angiogenesis, excessive collagen deposition) which is detrimental to implant functionality and integration to host tissue. Interleukin-33/ST2 axis (IL-33/ST2) has been shown to modulate angiogenic and remodeling processes in several types of injuries. However, its effects on these processes after implantation of synthetic matrix have not been reported. Using synthetic matrix of polyether-polyurethane implanted subcutaneously in mice lacking ST2 receptor (ST2/KO), we characterized neovascularization and matrix remodeling in the fibrovascular tissue induced by the implants. Tissue accumulation was increased inside and around the implants in KO implants relative to the wild type (WT). More intense proliferative activity, using CDC 47 marker, was observed in KO implants compared with that of WT implants. Angiogenesis, using two endothelial cell markers, Von Willebrand Factor (VWF) and vascular endothelial cell VE cadherin and hemoglobin content, increased in implants of KO mice relative to control WT. Remodeling of the newly formed fibrovascular tissue (soluble collagen and PicroSirius Red-stained histological sections) showed predominance of type 1 collagen in ST2-KO implants versus type 3 in control implants. The number of positive cells for caspase-3, apoptotic marker, decreased in ST2 group. Our findings evidenced a role of IL-33/ST2 axis in restraining blood vessel formation and regulating the pattern of matrix remodeling in the fibrovascular tissue induced by synthetic implants. Intervention in this cytokine complex holds potential to accelerate integration of biomaterial and host tissue by improving blood supply and matrix remodeling.

IL-33, an Alarmin of the IL-1 Family Involved in Allergic and Non Allergic Inflammation: Focus on the Mechanisms of Regulation of Its Activity

Interleukin-33 (IL-33) is a member of the interleukin-1 (IL-1) family that is expressed in the nuclei of endothelial and epithelial cells of barrier tissues, among others. It functions as an alarm signal that is released upon tissue or cellular injury. IL-33 plays a central role in the initiation and amplification of type 2 innate immune responses and allergic inflammation by activating various target cells expressing its ST2 receptor, including mast cells and type 2 innate lymphoid cells. Depending on the tissue environment, IL-33 plays a wide variety of roles in parasitic and viral host defense, tissue repair and homeostasis. IL-33 has evolved a variety of sophisticated regulatory mechanisms to control its activity, including nuclear sequestration and proteolytic processing. It is involved in many diseases, including allergic, inflammatory and infectious diseases, and is a promising therapeutic target for the treatment of severe asthma. In this review, I will summarize the literature around this fascinating pleiotropic cytokine. In the first part, I will describe the basics of IL-33, from the discovery of interleukin-33 to its function, including its expression, release and signaling pathway. The second part will be devoted to the regulation of IL-33 protein leading to its activation or inactivation.

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.

Resident vascular endothelial progenitor definition and function: the age of reckoning

The cardiovascular system is composed around the central function of the endothelium that lines the inner surfaces of its vessels. In recent years, the existence of a progenitor population within the endothelium has been validated through the study of endothelial colony-forming cells (ECFCs) in human peripheral blood and certain vascular beds. However, our knowledge on endothelial populations in vivo that can give rise to ECFCs in culture has been limited. In this review we report and analyse recent attempts at describing progenitor populations in vivo from murine studies that reflect the self-renewal and stemness capacity observed in ECFCs. We pinpoint seminal discoveries within the field, which have phenotypically defined, and functionally scrutinised these endothelial progenitors. Furthermore, we review recent publications utilising single-cell sequencing technologies to better understand the endothelium in homeostasis and pathology.

Role of Notch in endothelial biology

The Notch signalling pathway is one of the main regulators of endothelial biology. In the last 20 years the critical function of Notch has been uncovered in the context of angiogenesis, participating in tip-stalk specification, arterial-venous differentiation, vessel stabilization, and maturation processes. Importantly, pharmacological compounds targeting distinct members of the Notch signalling pathway have been used in the clinics for cancer therapy. However, the underlying mechanisms that support the variety of outcomes triggered by Notch in apparently opposite contexts such as angiogenesis and vascular homeostasis remain unknown. In recent years, advances in -omics technologies together with mosaic analysis and high molecular, cellular and temporal resolution studies have allowed a better understanding of the mechanisms driven by the Notch signalling pathway in different endothelial contexts. In this review we will focus on the main findings that revisit the role of Notch signalling in vascular biology. We will also discuss potential future directions and technologies that will shed light on the puzzling role of Notch during endothelial growth and homeostasis. Addressing these open questions may allow the improvement and development of therapeutic strategies based on modulation of the Notch signalling pathway.

Mapping the transcriptomic changes of endothelial compartment in human hippocampus across aging and mild cognitive impairment

Compromise of the vascular system has important consequences on cognitive abilities and neurodegeneration. The identification of the main molecular signatures present in the blood vessels of human hippocampus could provide the basis to understand and tackle these pathologies. As direct vascular experimentation in hippocampus is problematic, we achieved this information by computationally disaggregating publicly available whole microarrays data of human hippocampal homogenates. Three conditions were analyzed: 'Young Adults', 'Aged', and 'aged with Mild Cognitive Impairment' (MCI). The genes identified were contrasted against two independent data-sets. Here we show that the endothelial cells from the Younger Group appeared in an 'activated stage'. In turn, in the Aged Group, the endothelial cells showed a significant loss of response to shear stress, changes in cell adhesion molecules, increased inflammation, brain-insulin resistance, lipidic alterations, and changes in the extracellular matrix. Some specific changes in the MCI group were also detected. Noticeably, in this study the features arisen from the Aged Group (high tortuosity, increased bifurcations, and smooth muscle proliferation), pose the need for further experimental verification to discern between the occurrence of arteriogenesis and/or vascular remodeling by capillary arterialization. This article has an associated First Person interview with the first author of the paper.

3D curvature-instructed endothelial flow response and tissue vascularization

Vascularization remains a long-standing challenge in engineering complex tissues. Particularly needed is recapitulating 3D vascular features, including continuous geometries with defined diameter, curvature, and torsion. Here, we developed a spiral microvessel model that allows precise control of curvature and torsion and supports homogeneous tissue perfusion at the centimeter scale. Using this system, we showed proof-of-principle modeling of tumor progression and engineered cardiac tissue vascularization. We demonstrated that 3D curvature induced rotation and mixing under laminar flow, leading to unique phenotypic and transcriptional changes in endothelial cells (ECs). Bulk and single-cell RNA-seq identified specific EC gene clusters in spiral microvessels. These mark a proinflammatory phenotype associated with vascular development and remodeling, and a unique cell cluster expressing genes regulating vascular stability and development. Our results shed light on the role of heterogeneous vascular structures in differential development and pathogenesis and provide previously unavailable tools to potentially improve tissue vascularization and regeneration.

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.

IL33 Is a Key Driver of Treatment Resistance of Cancer

Recurrence and treatment resistance are major causes of cancer-associated death. There has been a growing interest in better understanding epithelial-mesenchymal transition, stemness of cancer cells, and exhaustion and dysfunction of the immune system for which numerous genomic, proteomic, microenvironmental, and immunologic mechanisms have been demonstrated. However, practical treatments for such patients have not yet been established. Here we identified IL33 as a key driver of polyploidy, followed by rapid proliferation after treatment. IL33 induction transformed tumor cells into polyploid giant cells, showing abnormal cell cycle without cell division accompanied by Snail deregulation and p53 inactivation; small progeny cells were generated in response to treatment stress. Simultaneously, soluble IL33 was released from tumor cells, leading to expansion of receptor ST2-expressing cells including IL17RB⁺GATA3⁺ cells, which promoted tumor progression and metastasis directly and indirectly via induction of immune exhaustion and dysfunction. Blocking IL33 with a specific mAb in murine IL33⁺ metastatic tumor models abrogated negative consequences and successfully elicited antitumor efficacy induced by other combined treatments. Ex vivo assays using tumor tissues and peripheral blood mononuclear cells of patients with cancer validated the clinical relevancy of these findings. Together, these data suggest that targeting the IL33-ST2 axis is a promising strategy for diagnosis and treatment of patients likely to be resistant to treatments in the clinical settings. SIGNIFICANCE: These findings indicate that the functional role of IL33 in cancer polyploidy contributes to intrinsic and extrinsic mechanisms underlying treatment failure.

B cells with aberrant activation of Notch1 signaling promote Treg and Th2 cell-dominant T-cell responses via IL-33

The Notch-signaling pathway in a variety of mature B-cell neoplasms is often activated by gene alterations, but its role remains unclear. Here, we show that B cells harboring dysregulated activation of Notch1 signaling have an immunomodulatory effect on T cells by amplifying regulatory T (Treg) and T helper 2 (Th2) cell responses in an interleukin-33 (IL-33)-dependent manner. A conditional mouse model, in which constitutive expression of an active form of Notch1 is induced in B cells by Aicda gene promoter-driven Cre recombinase, revealed no obvious phenotypic changes in B cells; however, mice demonstrated an expansion of Treg and Th2 cell subsets and a decrease in cytokine production by Th1 and CD8⁺ T cells. The mice were susceptible to soft tissue sarcoma and defective production of CD8⁺ T cells specific for inoculated tumor cells, suggesting impaired antitumor T-cell activity. Gene-expression microarray revealed that altered T-cell responses were due to increased IL-33 production by Notch1-activated B cells. Knockout of IL33 or blockade of IL-33 by a receptor-blocking antibody abrogated the Treg and Th2 cell-dominant T-cell response triggered by B cells. Gene-expression data derived from human diffuse large B-cell lymphoma (DLBCL) samples showed that an activated Notch-signaling signature correlates positively with IL33 expression and Treg cell-rich gene-expression signatures. These findings indicate that B cells harboring dysregulated Notch signaling alter T-cell responses via IL-33, and suggest that aberrant activation of Notch signaling plays a role in fostering immune privilege in mature B-cell neoplasms.

IL-1 Family Cytokine Regulation of Vascular Permeability and Angiogenesis

The IL-1 family of cytokines are well-known for their primary role in initiating inflammatory responses both in response to and acting as danger signals. It has long been established that IL-1 is capable of simultaneously regulating inflammation and angiogenesis, indeed one of IL-1's earliest names was haemopoeitn-1 due to its pro-angiogenic effects. Other IL-1 family cytokines are also known to have roles in mediating angiogenesis, either directly or indirectly via induction of proangiogenic factors such as VEGF. Of note, some of these family members appear to have directly opposing effects in different tissues and pathologies. Here we will review what is known about how the various IL-1 family members regulate vascular permeability and angiogenic function in a range of different tissues, and describe some of the mechanisms employed to achieve these effects.

Divergent Roles for the IL-1 Family in Gastrointestinal Homeostasis and Inflammation

Inflammatory disorders of the gastro-intestinal tract are a major cause of morbidity and significant burden from a health and economic perspective in industrialized countries. While the incidence of such conditions has a strong environmental component, in particular dietary composition, epidemiological studies have identified specific hereditary mutations which result in disequilibrium between pro- and anti-inflammatory factors. The IL-1 super-family of cytokines and receptors is highly pleiotropic and plays a fundamental role in the pathogenesis of several auto-inflammatory conditions including rheumatoid arthritis, multiple sclerosis and psoriasis. However, the role of this super-family in the etiology of inflammatory bowel diseases remains incompletely resolved despite extensive research. Herein, we highlight the currently accepted paradigms as they pertain to specific IL-1 family members and focus on some recently described non-classical roles for these pathways in the gastrointestinal tract. Finally, we address some of the shortcomings and sources of variance in the field which to date have yielded several conflicting results from similar studies and discuss the potential effect of these factors on data interpretation.

Endothelial Sox17 promotes allergic airway inflammation

BACKGROUND

IL-33, levels of which are known to be increased in patients with eosinophilic asthma and which is suggested as a therapeutic target for it, activates endothelial cells in which Sry-related high-mobility-group box (Sox) 17, an endothelium-specific transcription factor, was upregulated.

OBJECTIVE

We investigated the relationship between Sox17 and IL-33 and the possible role of Sox17 in the pathogenesis of asthma using a mouse model of airway inflammation.

METHODS

We used ovalbumin (OVA) to induce airway inflammation in endothelium-specific Sox17 null mutant mice and used IL-33 neutralizing antibody to evaluate the interplay between IL-33 and Sox17. We evaluated airway inflammation and measured levels of various cytokines, chemokines, and adhesion molecules. We also carried out loss- or gain-of-function experiments for Sox17 in human endothelial cells.

RESULTS

Levels of IL-33 and Sox17 were significantly increased in the lungs of OVA-challenged mice. Anti-IL-33 neutralizing antibody treatment attenuated not only OVA-induced airway inflammation but also Sox17 expression in pulmonary endothelial cells. Importantly, endothelium-specific deletion of Sox17 resulted in significant alleviation of various clinical features of asthma, including airway inflammation, immune cell infiltration, cytokine/chemokine production, and airway hyperresponsiveness. Sox17 deletion also resulted in decreased densities of Ly6c^high monocytes and inflammatory dendritic cells in the lungs. In IL-33-stimulated human endothelial cells, Sox17 showed positive correlation with CCL2 and intercellular adhesion molecule 1 levels. Lastly, Sox17 promoted monocyte adhesion to endothelial cells and upregulated the extracellular signal-regulated kinase-signal transducer and activator of transcription 3 pathway.

CONCLUSION

Sox17 was regulated by IL-33, and its genetic ablation in endothelial cells resulted in alleviation of asthma-related pathophysiologic features. Sox17 might be a potential target for asthma management.

MicroRNA-regulated pathways of flow-stimulated angiogenesis and vascular remodeling in vivo

BACKGROUND

Vascular shear stress promotes endothelial cell sprouting in vitro. The impact of hemodynamic forces on microRNA (miRNA) and gene expression within growing vascular networks in vivo, however, remain poorly investigated. Arteriovenous (AV) shunts are an established model for induction of neoangiogenesis in vivo and can serve as a tool for analysis of hemodynamic effects on miRNA and gene expression profiles over time.

METHODS

AV shunts were microsurgically created in rats and explanted on postoperative days 5, 10 and 15. Neoangiogenesis was confirmed by histologic analysis and micro-computed tomography. MiRNA and gene expression profiles were determined in tissue specimens from AV shunts by microarray analysis and quantitative real-time polymerase chain reaction and compared with sham-operated veins by bioinformatics analysis. Changes in protein expression within AV shunt endothelial cells were determined by immunohistochemistry.

RESULTS

Samples from AV shunts exhibited a strong overexpression of proangiogenic cytokines, oxygenation-associated genes (HIF1A, HMOX1), and angiopoetic growth factors. Significant inverse correlations of the expressions of miR-223-3p, miR-130b-3p, miR-19b-3p, miR-449a-5p, and miR-511-3p which were up-regulated in AV shunts, and miR-27b-3p, miR-10b-5p, let-7b-5p, and let-7c-5p, which were down-regulated in AV shunts, with their predicted interacting targets C-X-C chemokine receptor 2 (CXCR2), interleukin-1 alpha (IL1A), ephrin receptor kinase 2 (EPHA2), synaptojanin-2 binding protein (SYNJ2BP), forkhead box C1 (FOXC1) were present. CXCL2 and IL1A overexpression in AV shunt endothelium was confirmed at the protein level by immunohistochemistry.

CONCLUSIONS

Our data indicate that flow-stimulated angiogenesis is determined by an upregulation of cytokines, oxygenation associated genes and miRNA-dependent regulation of FOXC1, EPHA2 and SYNJ2BP.

Notch-1 signaling activation sustains overexpression of interleukin 33 in the epithelium of nasal polyps

BACKGROUND

Alterations in the nasal epithelial barrier homeostasis and increased interleukin 33 (IL-33) expression contribute to the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP).

AIMS

As Notch-1 signaling is crucial in repair processes of mucosa, the current study assessed Notch-1/Jagged-1 signaling and IL-33 in the epithelium of nasal polyps biopsies from allergic (A-CRSwNP; n = 9) and not allergic (NA-CRSwNP; n = 9) subjects by immunohistochemistry. We also assessed, in a model of nasal epithelial cells, the effects of stimulation of Notch-1 with Jagged-1 on the expression of IL-33 (by flow cytometry, immunofluorescence, and immunocytochemistry), Jagged-1 (by flow cytometry), and p-CREB transcription factor (by western blot analysis).

RESULTS

Ex vivo (a) in normal epithelium, the expression of Notch-1 and IL-33 were higher in NA-CRSwNP than in A-CRSwNP; (b) in metaplastic epithelium, the expression of Notch-1, Jagged-1, and IL-33 were higher in NA-CRSwNP than in A-CRSwNP; (c) in hyperplastic epithelium, the expression of Notch-1, Jagged-1, and IL-33 were higher in A-CRSwNP than in NA-CRSwNP; and (d) in basal epithelial cells, no differences were observed in the expression of Jagged-1, IL-33, and Notch-1. The expression of Notch-1 significantly correlated with the expression of IL-33. In vitro, stimulation of Notch-1 with Jagged-1 induced the expression of (a) Jagged-1; (b) IL-33; and (c) p-CREB transcription factor. The inhibitor of Notch-1, DAPT, reduced all the effects of Jagged-1 on nasal epithelial cells.

CONCLUSIONS

The data herein provided support, for the first time, a putative role of Notch-1/Jagged-1 signaling in the overexpression of IL-33 in the epithelium of nasal polyps from patients with CRSwNP.

A network map of IL-33 signaling pathway

Interleukin-33 (IL-33) is a member of the IL-1 family of cytokines that play a central role in the regulation of immune responses. Its release from epithelial and endothelial cells is mediated by pro-inflammatory cytokines, cell damage and by recognition of pathogen-associated molecular patterns (PAMPs). The activity of IL-33 is mediated by binding to the IL-33 receptor complex (IL-33R) and activation of NF-κB signaling via the classical MyD88/IRAK/TRAF6 module. IL-33 also induces the phosphorylation and activation of ERK1/2, JNK, p38 and PI3K/AKT signaling modules resulting in the production and release of pro-inflammatory cytokines. Aberrant signaling by IL-33 has been implicated in the pathogenesis of several acute and chronic inflammatory diseases, including asthma, atopic dermatitis, rheumatoid arthritis and ulcerative colitis among others. Considering the biomedical importance of IL-33, we developed a pathway resource of signaling events mediated by IL-33/IL-33R in this study. Using data mined from the published literature, we describe an integrated pathway reaction map of IL-33/IL-33R consisting of 681 proteins and 765 reactions. These include information pertaining to 19 physical interaction events, 740 enzyme catalysis events, 6 protein translocation events, 4 activation/inhibition events, 9 transcriptional regulators and 2492 gene regulation events. The pathway map is publicly available through NetPath ( http://www.netpath.org /), a resource of human signaling pathways developed previously by our group. This resource will provide a platform to the scientific community in facilitating identification of novel therapeutic targets for diseases associated with dysregulated IL-33 signaling. Database URL: http://www.netpath.org/pathways?path_id=NetPath_120 .

IL-33 is induced in undifferentiated, non-dividing esophageal epithelial cells in eosinophilic esophagitis

The molecular and cellular etiology of eosinophilic esophagitis (EoE), an emerging tissue-specific allergic disease, involves dysregulated gene expression in esophageal epithelial cells. Herein, we assessed the esophageal expression of IL-33, an epithelium-derived alarmin cytokine, in patients with EoE. IL-33 protein was markedly overexpressed within the nuclei of a subpopulation of basal layer esophageal epithelial cells in patients with active EoE compared to control individuals. IL-33 exhibited dynamic expression as levels normalized upon EoE remission. IL-33–positive basal epithelial cells expressed E-cadherin and the undifferentiated epithelial cell markers keratin 5 and 14 but not the differentiation marker keratin 4. Moreover, the IL-33–positive epithelial cells expressed the epithelial progenitor markers p75 and p63 and lacked the proliferation markers Ki67 and phospho-histone H3. Additionally, the IL-33–positive cells had low expression of PCNA. IL-33 expression was detected in ex vivo–cultured primary esophageal epithelial cells in a subpopulation of cells lacking expression of proliferation markers. Collectively, we report that IL-33 expression is induced in an undifferentiated, non-dividing esophageal epithelial cell population in patients with active EoE.

The Notch pathway inhibitor stapled α-helical peptide derived from mastermind-like 1 (SAHM1) abrogates the hallmarks of allergic asthma

BACKGROUND

The Notch signaling pathway has been implicated in the pathogenesis of allergic airway inflammation. Targeting the active Notch transactivation complex by using the cell-permeable, hydrocarbon-stapled synthetic peptide stapled α-helical peptide derived from mastermind-like 1 (SAHM1) resulted in genome-wide suppression of Notch-activated genes in leukemic cells and other models. However, the efficacy of SAHM1 in allergic asthma models has remained unexplored.

OBJECTIVE

We aimed to investigate the therapeutic efficacy of SAHM1 in a house dust mite (HDM)-driven asthma model.

METHODS

Topical therapeutic intervention with SAHM1 or a control peptide was performed during sensitization, challenge, or both with HDM in mice. Airway inflammation was assessed by using multicolor flow cytometry, and bronchial hyperreactivity was studied. Additionally, SAHM1 therapy was investigated in mice with established allergic airway inflammation and in a model in which we neutralized IFN-γ during HDM challenge to support the T_H2 response and exacerbate asthma.

RESULTS

SAHM1 treatment during the challenge phase led to a marked reduction of eosinophil and T cell numbers in bronchoalveolar lavage fluid compared with those in diluent-treated or control peptide-treated mice. Likewise, T-cell cytokine content and bronchial hyperreactivity were reduced. SAHM1 treatment dampened T_H2 inflammation during ongoing HDM challenge and enhanced recovery after established asthma. Additionally, in the presence of anti-IFN-γ antibodies, SAHM1 downregulated expression of the key T_H2 transcription factor GATA3 and intracellular IL-4 in bronchoalveolar lavage fluid T cells, but expression of the T_H17 transcription factor retinoic acid-related orphan receptor γt or intracellular IL-17 was not affected. SAHM1 therapy also reduced serum IgE levels.

CONCLUSIONS

Therapeutic intervention of Notch signaling by SAHM1 inhibits allergic airway inflammation in mice and is therefore an interesting new topical treatment opportunity in asthmatic patients.

IL-33 and the intestine: The good, the bad, and the inflammatory

Interleukin-33 (IL-33) is a member of the IL-1 cytokine family that has been widely studied since its discovery in 2005 for its dichotomous functions in homeostasis and inflammation. IL-33, along with its receptor suppression of tumorigenicity 2 (ST2), has been shown to modulate both the innate and adaptive immune system. Originally, the IL-33/ST2 signaling axis was studied in the context of inducing type 2 immune responses with the expression of ST2 by T helper 2 (T_H2) cells. However, the role of IL-33 is not limited to T_H2 responses. Rather, IL-33 is a potent activator of T_H1 cells, group 2 innate lymphoid cells (ILC2s), regulatory T (Treg) cells, and CD8⁺ T cells. The intestine is uniquely important in this discussion, as the intestinal epithelium is distinctively positioned to interact with both pathogens and the immune cells housed in the mucosa. In the intestine, IL-33 is expressed by the pericryptal fibroblasts and its expression is increased particularly in disease states. Moreover, IL-33/ST2 signaling aberrancy is implicated in the pathogenesis of inflammatory bowel disease (IBD). Accordingly, for this review, we will focus on the role of IL-33 in the regulation of intestinal immunity, involvement in intestinal disease, and implication in potential therapeutics.

Endothelial IL-33 Expression Is Augmented by Adenoviral Activation of the DNA Damage Machinery

IL-33, required for viral clearance by cytotoxic T cells, is generally expressed in vascular endothelial cells in healthy human tissues. We discovered that endothelial IL-33 expression was stimulated as a response to adenoviral transduction. This response was dependent on MRE11, a sensor of DNA damage that can also be activated by adenoviral DNA, and on IRF1, a transcriptional regulator of cellular responses to viral invasion and DNA damage. Accordingly, we observed that endothelial cells responded to adenoviral DNA by phosphorylation of ATM and CHK2 and that depletion or inhibition of MRE11, but not depletion of ATM, abrogated IL-33 stimulation. In conclusion, we show that adenoviral transduction stimulates IL-33 expression in endothelial cells in a manner that is dependent on the DNA-binding protein MRE11 and the antiviral factor IRF1 but not on downstream DNA damage response signaling.

Notch Inhibition Enhances Cardiac Reprogramming by Increasing MEF2C Transcriptional Activity

Conversion of fibroblasts into functional cardiomyocytes represents a potential means of restoring cardiac function after myocardial infarction, but so far this process remains inefficient and little is known about its molecular mechanisms. Here we show that DAPT, a classical Notch inhibitor, enhances the conversion of mouse fibroblasts into induced cardiac-like myocytes by the transcription factors GATA4, HAND2, MEF2C, and TBX5. DAPT cooperates with AKT kinase to further augment this process, resulting in up to 70% conversion efficiency. Moreover, DAPT promotes the acquisition of specific cardiomyocyte features, substantially increasing calcium flux, sarcomere structure, and the number of spontaneously beating cells. Transcriptome analysis shows that DAPT induces genetic programs related to muscle development, differentiation, and excitation-contraction coupling. Mechanistically, DAPT increases binding of the transcription factor MEF2C to the promoter regions of cardiac structural genes. These findings provide mechanistic insights into the reprogramming process and may have important implications for cardiac regeneration therapies.

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Notch activation is a barrier for GHMT-induced cardiac cell reprogramming

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Notch blockade by DAPT improves GHMT-induced cardiac reprogramming

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DAPT increases sarcomere organization, calcium flux, and beating in GHMT reprogramming

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DAPT enhances transcriptional activity of MEF2C in GHMT reprogramming

The Notch pathway promotes the cancer stem cell characteristics of CD90+ cells in hepatocellular carcinoma

CD90 has been identified as a marker for liver cancer stem cells (CSCs) that are responsible for tumorigenic activity, but it is not known how CD90⁺ cells contribute to tumor initiation and progression. Our data demonstrated that high expression of CD90 in Hepatocellular Carcinoma (HCC) tissues correlated with venous filtration in HCC patients. CD90⁺ cells isolated from HCC cell lines exhibited increased tumorigenicity, chemoresistance, tumor invasion and metastasis. Notch pathway was activated in CD90⁺ cells and we found that inhibition of Notch pathway in CD90⁺ CSCs decreased tumorigenicity, cell invasion, migration and expression of stem cell related genes. Activation of Notch pathway in CD90⁻ cells induced self-renewal, invasion and migration. Furthermore, we observed that cancer stem cell features were facilitated by stimulating G1-S transition in the cell cycle phase and inhibiting apoptosis mediated by Notch pathway. Our findings suggested CD90 could be used as a potential biomarker for HCC CSCs, and that cancer stem cell activity was elevated through up activated Notch pathway in CD90⁺ CSCs.

Matricellular protein SPARCL1 regulates tumor microenvironment-dependent endothelial cell heterogeneity in colorectal carcinoma

Different tumor microenvironments (TMEs) induce stromal cell plasticity that affects tumorigenesis. The impact of TME-dependent heterogeneity of tumor endothelial cells (TECs) on tumorigenesis is unclear. Here, we isolated pure TECs from human colorectal carcinomas (CRCs) that exhibited TMEs with either improved (Th1-TME CRCs) or worse clinical prognosis (control-TME CRCs). Transcriptome analyses identified markedly different gene clusters that reflected the tumorigenic and angiogenic activities of the respective TMEs. The gene encoding the matricellular protein SPARCL1 was most strongly upregulated in Th1-TME TECs. It was also highly expressed in ECs in healthy colon tissues and Th1-TME CRCs but low in control-TME CRCs. In vitro, SPARCL1 expression was induced in confluent, quiescent ECs and functionally contributed to EC quiescence by inhibiting proliferation, migration, and sprouting, whereas siRNA-mediated knockdown increased sprouting. In human CRC tissues and mouse models, vessels with SPARCL1 expression were larger and more densely covered by mural cells. SPARCL1 secretion from quiescent ECs inhibited mural cell migration, which likely led to stabilized mural cell coverage of mature vessels. Together, these findings demonstrate TME-dependent intertumoral TEC heterogeneity in CRC. They further indicate that TEC heterogeneity is regulated by SPARCL1, which promotes the cell quiescence and vessel homeostasis contributing to the favorable prognoses associated with Th1-TME CRCs.

Loss of interleukin 33 expression in colonic crypts - a potential marker for disease remission in ulcerative colitis

Interleukin 33 (IL-33) is a cytokine preferentially elevated in acute ulcerative colitis (UC), inferring a role in its pathogenesis. The role of IL-33 in intestinal inflammation is incompletely understood, with both pro-inflammatory and regulatory properties described. There are also conflicting reports on cellular sources and subcellular location of IL-33 in the colonic mucosa, justifying a closer look at IL-33 expression in well-defined clinical stages of UC. A total of 50 study participants (29 UC patients and 21 healthy controls) were included from a prospective cohort of inflammatory bowel disease patients treated to disease remission with infliximab, a tumour necrosis factor alpha (TNF) inhibitor. To our knowledge this is the first study examining mucosal IL-33 expression before and after anti-TNF therapy. In colonic mucosal biopsies we found a 3-fold increase in IL-33 gene expression comparing acute UC to healthy controls (p < 0.01). A significant reduction of IL33 between acute UC and disease remission was observed when TNF normalised in the mucosa (p = 0.02). Immunostaining revealed IL-33 in the nuclei of epithelial cells of scattered colonic crypts in acute disease, while at disease remission, IL-33 was undetectable, a novel finding suggesting that enterocyte-derived IL-33 is induced and maintained by inflammatory mediators.

Wounds that heal and wounds that don't - The role of the IL-33/ST2 pathway in tissue repair and tumorigenesis

IL-33 is a member of the IL-1 family of cytokines. IL-33 is predominantly located within the nucleus of cells where it plays a role in gene regulation. Given the right combination of signals and cellular damage, stored IL-33 is released from the cell where it can interact with its receptor ST2, triggering danger-associated responses and act as a cellular "alarmin". Whilst IL-33/ST2 signalling has been shown to induce potent pro-inflammatory responses that can be detrimental in certain disease states, a dichotomous, protective role of IL-33 in promoting wound healing has also emerged in multiple tissues types. This review will explore the current literature concerning this homeostatic role of IL-33/ST2 in tissue repair and also review its role in uncontrolled wound responses as seen in both fibrosis and tumorigenesis.

Concise Review: Functional Definition of Endothelial Progenitor Cells: A Molecular Perspective

: Since the discovery of endothelial progenitor cells (EPCs) almost 2 decades ago, there has been great hope in their use in treating chronic ischemic disease. Unfortunately, to date, many of the clinical trials using EPCs have been hampered by the lack of clear definition of this cell population. Attributes of a progenitor population are self-renewal and multipotentiality. Major progress has been achieved moving from a definition of EPCs based on a candidate cell surface molecule to a functional definition based essentially on self-renewal hierarchy of endothelial colony-forming cells (ECFCs). More recent work has seized on this functional characterization to associate gene expression signatures with the self-renewal capacity of ECFCs. In particular, Notch signaling driving the quiescence of progenitors has been shown to be central to progenitor self-renewal. This new molecular definition has tremendous translational consequences, because progenitors have been shown to display greater vasculogenic potential. Also, this molecular definition of EPC self-renewal allows assessment of the quality of presumed EPC preparations. This promises to be the initial stage in progressing EPCs further into mainstream clinical use.

SIGNIFICANCE

The development of a therapy using endothelial progenitor cells provides great hope for patients in treating cardiovascular diseases going forward. For continual development of this therapy toward the clinical, further understanding of the fundamental biology of these cells is required. This will enable a greater understanding of their stemness capacity and provide insight into their ability to differentiate and drive tissue regeneration when injected into a host.

IL-33 mediates reactive eosinophilopoiesis in response to airborne allergen exposure

BACKGROUND

Exposure to aeroallergens induces eosinophilic airway inflammation in patients with asthma and allergic airway diseases. The circulating number of eosinophils in peripheral blood is relatively small, leading us to hypothesize that bone marrow needs to be engaged quickly to meet the demands of the tissues.

METHODS

To investigate the communication between the lungs and bone marrow, we used acute allergen exposure and airway inflammation models in mice. Gene-deficient mice and cytokine reporter mice as well as in vitro cell culture models were used to dissect the mechanisms.

RESULTS

Naïve BALB/c mice produced increased numbers of eosinophil precursors and mature eosinophils in the bone marrow when their airways were exposed to a common fungal allergen, Alternaria alternata. Expression of IL-5 and IL-33 increased rapidly in the lungs, but not in the bone marrow. Sera from allergen-exposed mice promoted eosinophilopoiesis in bone marrow cells from naïve mice, which was blocked by anti-IL-5 antibody. Mice deficient in the IL-33 receptor ST2 (i.e., Il1rl1(-/-) mice) were unable to increase their serum levels of IL-5 and allergen-induced eosinophilopoiesis in the bone marrow after allergen exposure. Finally, group 2 innate lymphoid cells (ILC2s) in the lungs showed robust expression of IL-5 after Alternaria exposure.

CONCLUSIONS

These finding suggests that lung IL-33, through innate activation of ILC2s and their production of IL-5, plays a key role in promoting acute reactive eosinophilopoiesis in the bone marrow when naïve animals are exposed to airborne allergens. Therefore, bone marrow eosinophilopoiesis may be affected by atmospheric environmental conditions.

Programming of Intestinal Epithelial Differentiation by IL-33 Derived from Pericryptal Fibroblasts in Response to Systemic Infection

The intestinal epithelium constitutes an efficient barrier against the microbial flora. Here, we demonstrate an unexpected function of IL-33 as a regulator of epithelial barrier functions. Mice lacking IL-33 showed decreased Paneth cell numbers and lethal systemic infection in response to Salmonella typhimurium. IL-33 was produced upon microbial challenge by a distinct population of pericryptal fibroblasts neighboring the intestinal stem cell niche. IL-33 programmed the differentiation of epithelial progenitors toward secretory IEC including Paneth and goblet cells. Finally, IL-33 suppressed Notch signaling in epithelial cells and induced expression of transcription factors governing differentiation into secretory IEC. In summary, we demonstrate that gut pericryptal fibroblasts release IL-33 to translate bacterial infection into an epithelial response to promote antimicrobial defense.

Self-Renewal and High Proliferative Colony Forming Capacity of Late-Outgrowth Endothelial Progenitors Is Regulated by Cyclin-Dependent Kinase Inhibitors Driven by Notch Signaling

Since the discovery of endothelial colony forming cells (ECFC), there has been significant interest in their therapeutic potential to treat vascular injuries. ECFC cultures display significant heterogeneity and a hierarchy among cells able to give rise to high proliferative versus low proliferative colonies. Here we aimed to define molecularly this in vitro hierarchy. Based on flow cytometry, CD34 expression levels distinguished two populations. Only CD34 + ECFC had the capacity to reproduce high proliferative potential (HPP) colonies on replating, whereas CD34- ECFCs formed only small clusters. CD34 + ECFCs were the only ones to self-renew in stringent single-cell cultures and gave rise to both CD34 + and CD34- cells. Upon replating, CD34 + ECFCs were always found at the centre of HPP colonies and were more likely in G0/1 phase of cell cycling. Functionally, CD34 + ECFC were superior at restoring perfusion and better engrafted when injected into ischemic hind limbs. Transcriptomic analysis identified cyclin-dependent kinase (CDK) cell cycle inhibiting genes (p16, p21, and p57), the Notch signaling pathway (dll1, dll4, hes1, and hey1), and the endothelial cytokine il33 as highly expressed in CD34 + ECFC. Blocking the Notch pathway using a γ-secretase inhibitor (DAPT) led to reduced expression of cell cycle inhibitors, increased cell proliferation followed by a loss of self-renewal, and HPP colony formation capacity reflecting progenitor exhaustion. Similarly shRNA knockdown of p57 strongly affected self-renewal of ECFC colonies. ECFC hierarchy is defined by Notch signalling driving cell cycle regulators, progenitor quiescence and self-renewal potential.

The Protective Role of Interleukin-33 in Myocardial Ischemia and Reperfusion Is Associated with Decreased HMGB1 Expression and Up-Regulation of the P38 MAPK Signaling Pathway

Interleukin-33 (IL-33) plays a protective role in myocardial ischemia and reperfusion (I/R) injury, but the underlying mechanism was not fully elucidated. The present study was designed to investigate whether IL-33 protects against myocardial I/R injury by regulating both P38 mitogen-activated-protein kinase (P38 MAPK), which is involved in one of the downstream signaling pathways of IL-33, and high mobility group box protein 1 (HMGB1), a late pro-inflammatory cytokine. Myocardial I/R injury increased the level of IL-33 and its induced receptor (sST) in myocardial tissue. Compared with the I/R group, the IL-33 group had significantly lower cardiac injury (lower serum creatine kinase (CK), lactate dehydrogenase (LDH), and cTnI levels and myocardial infarct size), a suppressed inflammatory response in myocardial tissue (lower expression of HMGB1, IL-6, TNF-α and INF-γ) and less myocardial apoptosis (much higher Bcl-2/Bax ratio and lower cleaved caspase-3 expression). Moreover, IL-33 activated the P38 MAPK signaling pathway (up-regulating P-P38 expression) in myocardial tissue, and SB230580 partially attenuated the anti-inflammatory and anti-apoptosis effects of IL-33. These findings indicated that IL-33 protects against myocardial I/R injury by inhibiting inflammatory responses and myocardial apoptosis, which may be associated with the HMGB1 and P38 MAPK signaling pathways.

Interleukin-33 in Tissue Homeostasis, Injury, and Inflammation

Interleukin-33 (IL-33) is a nuclear-associated cytokine of the IL-1 family originally described as a potent inducer of allergic type 2 immunity. IL-33 signals via the receptor ST2, which is highly expressed on group 2 innate lymphoid cells (ILC2s) and T helper 2 (Th2) cells, thus underpinning its association with helminth infection and allergic pathology. Recent studies have revealed ST2 expression on subsets of regulatory T cells, and for a role for IL-33 in tissue homeostasis and repair that suggests previously unrecognized interactions within these cellular networks. IL-33 can participate in pathologic fibrotic reactions, or, in the setting of microbial invasion, can cooperate with inflammatory cytokines to promote responses by cytotoxic NK cells, Th1 cells, and CD8(+) T cells. Here, we highlight the regulation and function of IL-33 and ST2 and review their roles in homeostasis, damage, and inflammation, suggesting a conceptual framework for future studies.

Increased levels of soluble ST2 in patients with active newly diagnosed ANCA-associated vasculitis

OBJECTIVE

ST2, a member of the interleukin-1 receptor family, is selectively expressed on Th2 cells and mediates important Th2 functions. IL-33 is a specific ligand of ST2. The aim of the study was to determine whether serum levels of soluble ST2 (sST2) or IL-33 predict activity of the disease in patients with ANCA-associated vasculitides (AAV).

METHODS

139 AAV patients and 62 controls were studied. IL-33 and sST2 in the blood were measured with a commercially available ELISA.

RESULTS

Newly diagnosed AAV patients had higher sST2 levels than controls (P < 0.01). Levels of sST2 were significantly higher in active newly diagnosed AAV patients than in patients with remission (P < 0.001). IL-33 levels were higher in AAV patients than in the control groups (P = 0.002). However, serum IL-33 levels were not increased in patients with active AAV compared to patients in remission. IL-33 levels were higher in patients with granulomatosis with polyangiitis than in patients with microscopic polyangiitis (P = 0.012).

CONCLUSIONS

Serum sST2, but not serum IL-33, may be a marker of activity in AAV patients.

Increased IL-33 expression in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung disease characterized by inflammatory cell activation and the release of inflammatory mediators. Interleukin-33 (IL-33) plays a critical role in various inflammatory and immunological pathologies, but evidence for its role in COPD is lacking. This study aimed to investigate the expression of IL-33 in COPD and to determine whether IL-33 participates in the initiation and progression of COPD. Levels of serum IL-33 and its receptors were measured by ELISA, and serum levels of IL-33, ST2, and IL-1 receptor accessory protein were elevated in patients with COPD compared with control subjects. Flow cytometry analysis further demonstrated an increase in peripheral blood lymphocytes (PBLs) expressing IL-33 in patients with COPD. Immunofluorescence analysis revealed that the main cellular source of IL-33 in lung tissue was human bronchial epithelial cells (HBEs). Cigarette smoke extract and lipopolysaccharide could enhance the ability of PBLs and HBEs to express IL-33. Furthermore, PBLs from patients with COPD showed greater IL-33 release in response to the stimulus. Collectively, these findings suggest that IL-33 expression levels are increased in COPD and related to airway and systemic inflammation. Therefore, IL-33 might contribute to the pathogenesis and progression of this disease.

Actual position of interleukin(IL)-33 in atherosclerosis and heart failure: Great Expectations or En attendant Godot?

Atherosclerosis has been recognized as an inflammatory/autoimmune disease. The long-standing low-grade inflammation which fuels its development is primarily focused on the components of the vessel wall. Originally, inflammation in atherogenesis was supposed to be driven by the pro-inflammatory Th1 cellular and cytokine immune response. On the basis of accumulating evidence, this view has been re-evaluated to include the Th17/Th1 axis which is shared by most diseases of sterile inflammation. The anti-inflammatory Th2 cellular and cytokine immune response is initiated concomitantly with the former two, the latter dampening their harmful reactions which culminate in full-blown atherosclerosis. Interleukin-33, a novel member of the IL-1 cytokine superfamily, was suggested to take part in the anti-atherogenic response by mediating the Th1-to-Th2 switch of the immune reactions. However, IL-33 is a multifaceted mediator with both pro- and anti-inflammatory activities, also called a “dual factor” or a “Janus face” interleukin. IL-33 occurs both in an extracellular (cytokine-like) and in a nuclear-bound (transcription factor-like) form, each of them performing distinct activities of their own. This review article presents the latest data relevant to IL-33’s role in atherosclerosis and cardiac diseases as perceived by a cardiologist and a cardiac surgeon.

The role of IL-33 in host response to Candida albicans

BACKGROUND

Interleukin (IL) 33 is a recently identified pleiotropic cytokine that influences the activity of multiple cell types and orchestrates complex innate and adaptive immune responses.

METHODS

We performed an extensive review of the literature published between 2005 and 2013 on IL-33 and related cytokines, their functions, and their regulation of the immune system following Candida albicans colonization. Our literature review included cross-references from retrieved articles and specific data from our own studies.

RESULTS

IL-33 (IL-1F11) is a recently identified member of the IL-1 family of cytokines. Accumulating evidence suggests a pivotal role of the IL-33/ST2 axis in host immune defense against fungal pathogens, including C. albicans. IL-33 induces a Th2-type inflammatory response and activates both innate and adaptive immunity. Studies in animal models have shown that Th2 inflammatory responses have a beneficial role in immunity against gastrointestinal and systemic infections by Candida spp.

CONCLUSIONS

This review summarizes the most important clinical studies and case reports describing the beneficial role of IL-33 in immunity and host defense mechanisms against pathogenic fungi. The finding that the IL-33/ST2 axis is involved in therapeutic target has implications for the prevention and treatment of inflammatory diseases, including acute or chronic candidiasis.

Role of IL-33 and its receptor in T cell-mediated autoimmune diseases

Interleukin-33 (IL-33) is a new cytokine of interleukin-1 family, whose specific receptor is ST2. IL-33 exerts its functions via its target cells and plays different roles in diseases. ST2 deletion and exclusion of IL-33/ST2 axis are accompanied by enhanced susceptibility to dominantly T cell-mediated organ-specific autoimmune diseases. It has been reported that IL-33/ST2 pathway plays a key role in host defense and immune regulation in inflammatory and infectious diseases. This review focuses on new findings in the roles of IL-33 and ST2 in several kinds of T cell-mediated autoimmune diseases.