The family of the interleukin-1 receptors

Structural Basis of IL-1 Family Cytokine Signaling

Interleukin-1 (IL-1) family cytokines are key signaling molecules in both the innate and adaptive immune systems, mediating inflammation in response to a wide range of stimuli. The basic mechanism of signal initiation is a stepwise process in which an agonist cytokine binds its cognate receptor. Together, this cytokine-receptor complex recruits an often-common secondary receptor. Intracellularly, the Toll/IL-1 Receptor (TIR) domains of the two receptors are brought into close proximity, initiating an NF-κB signal transduction cascade. Due to the potent inflammatory response invoked by IL-1 family cytokines, several physiological mechanisms exist to inhibit IL-1 family signaling, including antagonist cytokines and decoy receptors. The numerous cytokines and receptors in the IL-1 superfamily are further classified into four subfamilies, dependent on their distinct cognate receptors—the IL-1, IL-33, and IL-36 subfamilies share IL-1RAcP as their secondary receptor, while IL-18 subfamily utilizes a distinct secondary receptor. Here, we describe how structural biology has informed our understanding of IL-1 family cytokine signaling, with a particular focus on molecular mechanisms of signaling complex formation and antagonism at the atomic level, as well as how these findings have advanced therapeutics to treat some chronic inflammatory diseases that are the result of dysregulated IL-1 signaling.

Long intergenic non-coding RNAs regulate human lung fibroblast function: Implications for idiopathic pulmonary fibrosis

Phenotypic changes in lung fibroblasts are believed to contribute to the development of Idiopathic Pulmonary Fibrosis (IPF), a progressive and fatal lung disease. Long intergenic non-coding RNAs (lincRNAs) have been identified as novel regulators of gene expression and protein activity. In non-stimulated cells, we observed reduced proliferation and inflammation but no difference in the fibrotic response of IPF fibroblasts. These functional changes in non-stimulated cells were associated with changes in the expression of the histone marks, H3K4me1, H3K4me3 and H3K27ac indicating a possible involvement of epigenetics. Following activation with TGF-β1 and IL-1β, we demonstrated an increased fibrotic but reduced inflammatory response in IPF fibroblasts. There was no significant difference in proliferation following PDGF exposure. The lincRNAs, LINC00960 and LINC01140 were upregulated in IPF fibroblasts. Knockdown studies showed that LINC00960 and LINC01140 were positive regulators of proliferation in both control and IPF fibroblasts but had no effect upon the fibrotic response. Knockdown of LINC01140 but not LINC00960 increased the inflammatory response, which was greater in IPF compared to control fibroblasts. Overall, these studies demonstrate for the first time that lincRNAs are important regulators of proliferation and inflammation in human lung fibroblasts and that these might mediate the reduced inflammatory response observed in IPF-derived fibroblasts.

The role of interleukin 1 in the development of human diseases

Human immuno-inflammatory diseases (IID), depending on the predominant mechanisms of immune activation, are divided into two main categories: autoimmune and autoinflammatory. It is assumed that hyperproduction of "proinflammatory" and immunoregulatory cytokine-interleukin 1 (IL 1) largely determines the "intersection" between the mechanisms underlying autoimmunity and autoinflammation in many IID. This review discusses the role of IL1 in the pathogenesis of IID, primarily those associated with the activation of NLRP3-inflammasome, and therapeutic perspectives of IL1β inhibition with monoclonal antibodies to IL1β – canakinumab. The study of the IL1 role in the regulation of interactions between innate (TLR activation, inflammasome) and adaptive (Th1 – and Th17-types of immune response) immunity and the efficacy of IL1 inhibitors may be important in terms of decoding the pathogenetic mechanisms of IID and the development of new approaches to personalized therapy.

Astragalus polysaccharides, chitosan and poly(I:C) obviously enhance inactivated Edwardsiella ictaluri vaccine potency in yellow catfish Pelteobagrus fulvidraco

The yellow catfish (Pelteobagrus fulvidraco) is an economically important fish in China, but Edwardsiella ictaluri, an intracellular pathogenic bacterium, causes great losses to the culture industry. Currently, vaccination is the most promising strategy to combat the infectious diseases, while adjuvant can provide effective assistant for vaccines to enhance immune responses. In the present study, inactivated E. ictaluri vaccine was prepared, then Astragalus polysaccharides (APS), chitosan and poly(I:C) were employed as adjuvants to evaluate the effect on boosting immune responses and protecting yellow catfish against E. ictaluri. The survival rate was obviously improved after vaccination with APS, chitosan or poly(I:C) respectively, in addition, these three adjuvants could clearly protect the target tissue (intestine) by pathological sections in infectious experiments. In sera, total protein levels increased throughout the immunization stages, total superoxide dismutase levels continued to raise after vaccination, and lysozyme activity levels improved at different periods, examining by the commercial kits. Moreover, checking by real time quantitative RT-PCR assays, in both spleen and head kidney tissues which were the major immune organs, mRNA expressions of inflammatory cytokine IL-1β increased in the early stage of immunity, typical Th1 immune response cytokines IL-2 and IFN-γ2 rose up in the whole immune period, and IgM significantly enhanced in the adjuvant supplementation groups. The results demonstrated the good efficiency of APS, chitosan or poly(I:C) as adjuvant, and provided more options for the fish adjuvants.

Yersinia pestis Exploits Early Activation of MyD88 for Growth in the Lungs during Pneumonic Plague

Yersinia pestis causes bubonic, pneumonic, and septicemic plague. Although no longer responsible for pandemic outbreaks, pneumonic plague continues to be a challenge for medical treatment and has been classified as a reemerging disease in some parts of the world. In the early stage of infection, inflammatory responses are believed to be suppressed by Y. pestis virulence factors in order to prevent clearance, while later, the hyperactivation of inflammation contributes to the progression of disease. In this work, we sought to identify the host factors that mediate this process and studied the role of the Toll/interleukin 1 (IL-1) receptor adapter and major inflammatory mediator myeloid differentiation primary response 88 (MyD88) in pneumonic plague. We show that pulmonary challenge of Myd88^-/- mice with wild-type (WT) Y. pestis results in significant loss of pro- and anti-inflammatory cytokines and chemokines, especially gamma interferon (IFN-γ) and KC, in the lungs compared to that in WT mice. Bacterial growth in the lungs occurred more rapidly in the WT mice, however, indicating a role for the MyD88 response in facilitating the primary lung infection. Nevertheless, Myd88^-/- mice were more sensitive to lethality from secondary septicemic plague. Together these findings indicate a central role for MyD88 during the biphasic inflammatory response to pulmonary Y. pestis infection. In the early phase, low-level MyD88-dependent chemokine expression limits initial growth but facilitates Y. pestis access to a protected replicative niche. The later hyperinflammatory phase is partially MyD88 dependent and ineffective in the lungs but controls systemic infection and reduces the progression of secondary septicemic plague.

Rapamycin ameliorates lipopolysaccharide-induced acute lung injury by inhibiting IL-1β and IL-18 production

Interleukin (IL)-1β and IL-18 play central and detrimental roles in the development of acute lung injury (ALI), and mammalian target of rapamycin (mTOR) is involved in regulating IL-1β and IL-18 production. However, it is not clear whether the mTOR specific inhibitor rapamycin can attenuate lipopolysaccharide (LPS)-induced ALI by modulating IL-1β and IL-18 production. In this study, we found that rapamycin ameliorated LPS-induced ALI by inhibiting NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated IL-1β and IL-18 secretion. Mechanistically, elevated autophagy and decreased nuclear factor (NF)-κB activation were associated with downregulated IL-1β and IL-18. Moreover, rapamycin reduced leukocyte infiltration in the lung tissue and bronchoalveolar lavage fluid (BALF), and contributed to the alleviation of LPS-induced ALI. Consistently, rapamycin also significantly inhibited IL-1β and IL-18 production by RAW264.7 cells via increased autophagy and decreased NF-κB signaling in vitro. Our results demonstrated that rapamycin protects mice against LPS-induced ALI partly by inhibiting the production and secretion of IL-1β and IL-18. mTOR and rapamycin might represent an appropriate therapeutic target and strategy for preventing ALI induced by LPS.

Circulating levels of IL-1 family cytokines and receptors in Alzheimer's disease: new markers of disease progression?

Background

Although the mechanisms underlying AD neurodegeneration are not fully understood, it is now recognised that inflammation could play a crucial role in the initiation and progression of AD neurodegeneration. A neuro-inflammatory network, based on the anomalous activation of microglial cells, includes the production of a number of inflammatory cytokines both locally and systemically. These may serve as diagnostic markers or therapeutic targets for AD neurodegeneration.

Methods

We have measured the levels of the inflammation-related cytokines and receptors of the IL-1 family in serum of subjects with AD, compared to mild cognitive impairment (MCI), subjective memory complaints (SMC), and normal healthy subjects (NHS). Using a custom-made multiplex ELISA array, we examined ten factors of the IL-1 family, the inflammation-related cytokines IL-1α, IL-1β, IL-18, and IL-33, the natural inhibitors IL-1Ra and IL-18BP, and the soluble receptors sIL-1R1, sIL-1R2, sIL-1R3, and sIL-1R4.

Results

The inflammatory cytokines IL-1α and IL-1β, their antagonist IL-1Ra, and their soluble receptor sIL-1R1 were increased in AD. The decoy IL-1 receptor sIL-1R2 was only increased in MCI. IL-33 and its soluble receptor sIL-1R4 were also significantly higher in AD. The soluble form of the accessory receptor for both IL-1 and IL-33 receptor complexes, sIL-1R3, was increased in SMC and even more in AD. Total IL-18 levels were unchanged, whereas the inhibitor IL-18BP was significantly reduced in MCI and SMC, and highly increased in AD. The levels of free IL-18 were significantly higher in MCI.

Conclusions

AD is characterised by a significant alteration in the circulating levels of the cytokines and receptors of the IL-1 family. The elevation of sIL-1R4 in AD is in agreement with findings in other diseases and can be considered a marker of ongoing inflammation. Increased levels of IL-1Ra, sIL-1R1, sIL-1R4, and IL-18BP distinguished AD from MCI and SMC, and from other inflammatory diseases. Importantly, sIL-1R1, sIL-1R3, sIL-1R4, and IL-18BP negatively correlated with cognitive impairment. A significant elevation of circulating sIL-1R2 and free IL-18, not present in SMC, is characteristic of MCI and disappears in AD, making them additional interesting markers for evaluating progression from MCI to AD.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1376-1) contains supplementary material, which is available to authorized users.

Death, TIR, and RHIM: Self-assembling domains involved in innate immunity and cell-death signaling

The innate immune system consists of pattern recognition receptors (PRRs) that detect pathogen- and endogenous danger-associated molecular patterns (PAMPs and DAMPs), initiating signaling pathways that lead to the induction of cytokine expression, processing of pro-inflammatory cytokines, and induction of cell-death responses. An emerging concept in these pathways and associated processes is signaling by cooperative assembly formation (SCAF), which involves formation of higher order oligomeric complexes, and enables rapid and strongly amplified signaling responses to minute amounts of stimulus. Many of these signalosomes assemble through homotypic interactions of members of the death-fold (DF) superfamily, Toll/IL-1 receptor (TIR) domains, or the RIP homotypic interaction motifs (RHIM). We review the current understanding of the structure and function of these domains and their molecular interactions with a particular focus on higher order assemblies.

The Role of Interleukin-1 in the Pathogenesis of Cancer and its Potential as a Therapeutic Target in Clinical Practice

Interleukin-1 (IL-1) has long been known to be a key mediator of immunity and inflammation. Its dysregulation has been implicated in recent years in tumorigenesis and tumor progression, and its upregulation is thought to be associated with many tumors. Overexpression of the IL-1 agonists IL-1α and IL-1β has been shown to promote tumor invasiveness and metastasis by inducing the expression of angiogenic genes and growth factors. IL-1 blockers such as anakinra and canakinumab are already approved and widely used for the treatment of some autoimmune and autoinflammatory diseases and are currently being tested in preclinical and human clinical trials for cancer therapy. In this paper we review the most recent discoveries regarding the association between IL-1 dysregulation and cancer and present the novel IL-1 blockers currently being tested in cancer therapy and their corresponding clinical trials.

Remifentanil upregulates hepatic IL-18 binding protein (IL-18BP) expression through transcriptional control

Interleukin (IL)-18 plays an important role in liver ischemia/reperfusion (I/R) injury. We have previously demonstrated that remifentanil protects against liver I/R injury by upregulating the hepatic expression of IL-18-binding protein (IL-18BP), a natural IL-18 inhibitor. The current study was performed to further clarify the effects of remifentanil on IL-18BP expression in the liver as well as investigate the underlying mechanisms. In Sprague-Dawley (SD) rats, we demonstrated that remifentanil significantly increased the expression of IL-18BP in normal rat liver tissue over a 24-h time period with maximal expression at 24 h after treatment. The upregulation of remifentanil on IL-18BP expression displayed similar trends in in vitro cellular studies, including mouse primary hepatocytes, normal human hepatocyte LO2, and mouse hepatoma cells Hep1-6. In LO2 cells, preexposure of the cells to remifentanil significantly inhibited IL-18-activated p65 NF-κB phosphorylation, and the inhibition was absent when the cells were transfected with IL-18BP siRNA, indicating the functional effects of IL-18BP induced by remifentanil. Pretreatment with actinomycin D abolished remifentanil-induced upregulation of IL-18BP mRNA, suggesting that the induction occurred at the transcriptional level. This was further supported by the luciferase reporter assay, which demonstrated that remifentanil treatment significantly increased transcription of the IL-18BP promoter. Both western blot analysis and ChIP assays showed that STAT1 and C/EBP β were activated by remifentanil. Furthermore, remifentanil failed to upregulate IL-18BP expression after silencing STAT1 or C/EBP β gene expression. These findings demonstrate that remifentanil could upregulate hepatic IL-18BP expression through transcriptional activation of the IL-18BP promoter, and STAT1 and C/EBP β are two key transcriptional factors involved in this process.

A novel ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases

Pancreatic ribonuclease is known to participate in host defense system against pathogens, such as parasites, bacteria, and virus, which results in innate immune response. Nevertheless, its potential impact to host cells remains unclear. Of interest, several ribonucleases do not act as catalytically competent enzymes, suggesting that ribonucleases may be associated with certain intrinsic functions other than their ribonucleolytic activities. Most recently, human pancreatic ribonuclease 5 (hRNase5; also named angiogenin; hereinafter referred to as hRNase5/ANG), which belongs to the human ribonuclease A superfamily, has been demonstrated to function as a ligand of epidermal growth factor receptor (EGFR), a member of the receptor tyrosine kinase family. As a newly identified EGFR ligand, hRNase5/ANG associates with EGFR and stimulates EGFR and the downstream signaling in a catalytic-independent manner. Notably, hRNase5/ANG, whose level in sera of pancreatic cancer patients, serves as a non-invasive serum biomarker to stratify patients for predicting the sensitivity to EGFR-targeted therapy. Here, we describe the hRNase5/ANG-EGFR pair as an example to highlight a ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases, which are thought as two unrelated protein families associated with distinct biological functions. The notion of serum biomarker-guided EGFR-targeted therapies will also be discussed. Furthering our understanding of this novel ligand-receptor interaction will shed new light on the search of ligands for their cognate receptors, especially those orphan receptors without known ligands, and deepen our knowledge of the fundamental research in membrane receptor biology and the translational application toward the development of precision medicine.

Potential roles of IL-1 subfamily members in glycolysis in disease

The interleukin-(IL)-1 subfamily consists of IL-1α, IL-1β, IL-1 receptor antagonist IL-1Ra and IL-33. These cytokines are the main members of the IL-1 family and have been widely recognized as having significant roles in pro-inflammatory and immunomodulatory actions. Mounting evidence has revealed that these cytokines also play key roles in the regulation of glycolysis, which is an important metabolic pathway in most organisms that provides energy. Dysregulation of glycolysis is associated with various diseases, including type 2 diabetes, rheumatoid arthritis (RA) and cancer. We reviewed studies addressing the important roles of IL-1 subfamily cytokines, with particular focus on their ability to regulate glycolysis in disease states. In this review, we summarize the potential roles of IL-1 subfamily members in glycolysis in disease states and address the underlying mechanisms. Furthermore, we discuss the potential of these cytokines as therapeutic targets in clinical applications to provide insight into possible therapeutic strategies for treatment, especially for cancers.

De Novo Transcriptome Sequencing Analysis of Goose (Anser anser) Embryonic Skin and the Identification of Genes Related to Feather Follicle Morphogenesis at Three Stages of Development

The objective of this study was to evaluate the changes in the goose embryo transcriptome during feather development. RNA-Sequencing (RNA-Seq) was used to find the transcriptome profiles of feather follicles from three stages of embryonic dorsal skin at embryonic day 13, 18, and 28 (E13, E18, E28). The results showed that 3001, 6634, and 13,780 genes were differently expressed in three stages. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that differentially expressed genes (DEGs) in E13 vs. E18 were significantly mapped into the GO term of extracellular structure organization and the pathway of extracellular matrix (ECM)-receptor interaction. In E18 vs. E28, the top significantly mapped into GO term was the single-organism developmental process; the pathway was also the ECM-receptor interaction. DEGs in E13 vs. E28 were significantly mapped into the GO term of the multicellular organismal process and the pathway of cell adhesion molecules. Subsequently, the union of DEGs was categorized by succession cluster into eight profiles, which were then grouped into four ideal profiles. Lastly, the seven genes spatio-temporal expression pattern was confirmed by real-time PCR. Our findings advocate that interleukin 20 receptor subunit alpha (IL20RA), interleukin 6 receptor (IL6R), interleukin 1 receptor type 1 (IL-1R1), Wnt family member 3A (WNT3A), insulin-like growth factor binding protein 3 (IGFBP3), bone morphogenetic protein 7 (BMP7), and secreted-frizzled related protein 2 (SFRP2) might possibly play vital roles in skin and feather follicle development and growth processes.

Interleukin-1β signaling in osteoarthritis - chondrocytes in focus

Osteoarthritis (OA) can be regarded as a chronic, painful and degenerative disease that affects all tissues of a joint and one of the major endpoints being loss of articular cartilage. In most cases, OA is associated with a variable degree of synovial inflammation. A variety of different cell types including chondrocytes, synovial fibroblasts, adipocytes, osteoblasts and osteoclasts as well as stem and immune cells are involved in catabolic and inflammatory processes but also in attempts to counteract the cartilage loss. At the molecular level, these changes are regulated by a complex network of proteolytic enzymes, chemokines and cytokines (for review: [1]). Here, interleukin-1 signaling (IL-1) plays a central role and its effects on the different cell types involved in OA are discussed in this review with a special focus on the chondrocyte.

Regulation of IL-1 signaling by the decoy receptor IL-1R2

The pleiotropic cytokine IL-1 mediates its biological functions via association with the signaling receptor IL-1R1. Despite an apparent simplicity in IL-1 signaling activation, multiple negative regulators have been identified. The decoy receptor IL-1R2 (also known as CD121b) can suppress IL-1 maturation, sequester its active forms or hinder the signaling complex assembly. IL-1R2 is differentially expressed among numerous cell types and displays cis- and trans- modes of action. In this review, we link different forms of IL-1R2 (membrane-bound (mIL-1R2), secreted (sIL-1R2), shedded (shIL-1R2), cytoplasmic, and intracellular domain (IL-1R2^ICD) restricted) with their ability to interfere with IL-1, thereby regulating immune responses. We also discuss the intriguing possible function of IL-1R2 as a transcriptional regulator. Finally, we summarize the known impact of IL-1R2 in disease pathogenesis and discuss its potential role in treatment of inflammatory conditions.

Cutting Edge: IL-1R1 Mediates Host Resistance to Mycobacterium tuberculosis by Trans-Protection of Infected Cells

IL-1R1 deficiency in mice causes severe susceptibility to Mycobacterium tuberculosis Mice and macrophage cultures lacking IL-1R1 display increased bacterial growth, suggesting that phagocytes may require IL-1R1-dependent antimicrobial signals to limit intracellular M. tuberculosis replication directly. However, the myeloid-cell-intrinsic versus -extrinsic requirements for IL-1R1 to control M. tuberculosis infection in mice have not been directly addressed. Using single-cell analysis of infected cells, competitive mixed bone marrow chimeras, and IL-1R1 conditional mutant mice, we show in this article that IL-1R1 expression by pulmonary phagocytes is uncoupled from their ability to control intracellular M. tuberculosis growth. Importantly, IL-1R1-dependent control was provided to infected cells in trans by both nonhematopoietic and hematopoietic cells. Thus, IL-1R1-mediated host resistance to M. tuberculosis infection does not involve mechanisms of cell-autonomous antimicrobicidal effector functions in phagocytes but requires the cooperation between infected cells and other cells of hematopoietic or nonhematopoietic origin to promote bacterial containment and control of infection.

Interleukin-1 Beta-A Friend or Foe in Malignancies?

Interleukin-1 beta (IL-1β) is induced by inflammatory signals in a broad number of immune cell types. IL-1β (and IL-18) are the only cytokines which are processed by caspase-1 after inflammasome-mediated activation. This review aims to summarize current knowledge about parameters of regulation of IL-1β expression and its multi-facetted role in pathophysiological conditions. IL-1 signaling activates innate immune cells including antigen presenting cells, and drives polarization of CD4+ T cells towards T helper type (Th) 1 and Th17 cells. Therefore, IL-1β has been attributed a largely beneficial role in resolving acute inflammations, and by initiating adaptive anti-tumor responses. However, IL-1β generated in the course of chronic inflammation supports tumor development. Furthermore, IL-1β generated within the tumor microenvironment predominantly by tumor-infiltrating macrophages promotes tumor growth and metastasis via different mechanisms. These include the expression of IL-1 targets which promote neoangiogenesis and of soluble mediators in cancer-associated fibroblasts that evoke antiapoptotic signaling in tumor cells. Moreover, IL-1 promotes the propagation of myeloid-derived suppressor cells. Using genetic mouse models as well as agents for pharmacological inhibition of IL-1 signaling therapeutically applied for treatment of IL-1 associated autoimmune diseases indicate that IL-1β is a driver of tumor induction and development.

From macrophage to osteoclast - How metabolism determines function and activity

Osteoclasts are specialised cells that resorb bone and develop from the monocyte/macrophage lineage. While there is a wealth of information on the regulation of macrophage function through metabolic activity, the connection between osteoclast differentiation and metabolism is less well understood. Recent data show that mitochondria participate in switching macrophages from an inflammatory phenotype towards differentiation into osteoclasts. Additionally, it was found that reactive oxygen species (ROS) actively take place in osteoclast differentiation by acting as secondary signalling molecules. Bone resorption is an energy demanding process and differentiating osteoclasts triggers the biogenesis of mitochondria. In addition, the activity of specific OXPHOS components of macrophages and osteoclasts is differentially regulated. This review summarises our knowledge on macrophage-mediated inflammation, its impact on a cell's metabolic activity and its effect on osteoclast differentiation.

Trial Watch: Immunostimulation with recombinant cytokines for cancer therapy

Cytokines regulate virtually aspects of innate and adaptive immunity, including the initiation, execution and extinction of tumor-targeting immune responses. Over the past three decades, the possibility of using recombinant cytokines as a means to elicit or boost clinically relevant anticancer immune responses has attracted considerable attention. However, only three cytokines have been approved so far by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, namely, recombinant interleukin (IL)-2 and two variants of recombinant interferon alpha 2 (IFN-α2a and IFN-α2b). Moreover, the use of these cytokines in the clinics is steadily decreasing, mostly as a consequence of: (1) the elevated pleiotropism of IL-2, IFN-α2a and IFN-α2b, resulting in multiple unwarranted effects; and (2) the development of highly effective immunostimulatory therapeutics, such as immune checkpoint blockers. Despite this and other obstacles, research in the field continues as alternative cytokines with restricted effects on specific cell populations are being evaluated. Here, we summarize research preclinical and clinical developments on the use of recombinant cytokines for immunostimulation in cancer patients.