Cloning IL-1 and the birth of a new era in cytokine biology

Polarization of Macrophages in Insects: Opening Gates for Immuno-Metabolic Research

Insulin resistance and cachexia represent severe metabolic syndromes accompanying a variety of human pathological states, from life-threatening cancer and sepsis to chronic inflammatory states, such as obesity and autoimmune disorders. Although the origin of these metabolic syndromes has not been fully comprehended yet, a growing body of evidence indicates their possible interconnection with the acute and chronic activation of an innate immune response. Current progress in insect immuno-metabolic research reveals that the induction of insulin resistance might represent an adaptive mechanism during the acute phase of bacterial infection. In Drosophila, insulin resistance is induced by signaling factors released by bactericidal macrophages as a reflection of their metabolic polarization toward aerobic glycolysis. Such metabolic adaptation enables them to combat the invading pathogens efficiently but also makes them highly nutritionally demanding. Therefore, systemic metabolism has to be adjusted upon macrophage activation to provide them with nutrients and thus support the immune function. That anticipates the involvement of macrophage-derived systemic factors mediating the inter-organ signaling between macrophages and central energy-storing organs. Although it is crucial to coordinate the macrophage cellular metabolism with systemic metabolic changes during the acute phase of bacterial infection, the action of macrophage-derived factors may become maladaptive if chronic or in case of infection by an intracellular pathogen. We hypothesize that insulin resistance evoked by macrophage-derived signaling factors represents an adaptive mechanism for the mobilization of sources and their preferential delivery toward the activated immune system. We consider here the validity of the presented model for mammals and human medicine. The adoption of aerobic glycolysis by bactericidal macrophages as well as the induction of insulin resistance by macrophage-derived factors are conserved between insects and mammals. Chronic insulin resistance is at the base of many human metabolically conditioned diseases such as non-alcoholic steatohepatitis, atherosclerosis, diabetes, and cachexia. Therefore, revealing the original biological relevance of cytokine-induced insulin resistance may help to develop a suitable strategy for treating these frequent diseases.

Apoptosis signaling pathways in osteoarthritis and possible protective role of melatonin

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive erosion of articular cartilage. As chondrocytes are the only cell type forming the articular cartilage, their gradual loss is the main cause of OA. There is a substantial body of published research that suggests reactive oxygen species (ROS) are major causative factors for chondrocyte damage and OA development. Oxidative stress elicited by ROS is capable of oxidizing and subsequently disrupting cartilage homeostasis, promoting catabolism via induction of cell death and damaging numerous components of the joint. IL-1β and TNF-α are crucial inflammatory factors that play pivotal roles in the pathogenesis of OA. In this process, the mitochondria are the major source of ROS production in cells, suggesting a role of mitochondrial dysfunction in this type of arthritis. This may also be promoted by inflammatory cytokines such as IL-1β and TNF-α which contribute to chondrocyte death. In patients with OA, the expression of endoplasmic reticulum (ER) stress-associated molecules is positively correlated with cartilage degeneration. Melatonin and its metabolites are broad-spectrum antioxidants and free radical scavengers which regulate a variety of molecular pathways such as inflammation, proliferation, apoptosis, and metastasis in different pathophysiological situations. Herein, we review the effects of melatonin on OA, focusing on its ability to regulate apoptotic processes and ER and mitochondrial activity. We also evaluate likely protective effects of melatonin on OA pathogenesis.

Generation and Characterization of Mice Expressing a Conditional Allele of the Interleukin-1 Receptor Type 1

The cytokines IL-1α and IL-1β exert powerful pro-inflammatory actions throughout the body, mediated primarily by the intracellular signaling capacity of the interleukin-1 receptor (IL-1R1). Although Il1r1 knockout mice have been informative with respect to a requirement for IL-1R1 signaling in inflammatory events, the constitutive nature of gene elimination has limited their utility in the assessment of temporal and spatial patterns of cytokine action. To pursue such questions, we have generated C57Bl/6J mice containing a floxed Il1r1 gene (Il1r1^loxP/loxP), with loxP sites positioned to flank exons 3 and 4 and thereby the ability to spatially and temporally eliminate Il1r1 expression and signaling. We found that Il1r1^loxP/loxP mice breed normally and exhibit no gross physical or behavioral phenotypes. Moreover, Il1r1^loxP/loxP mice exhibit normal IL-1R1 receptor expression in brain and spleen, as well as normal IL-1R1-dependent increases in serum IL-6 following IL-1α injections. Breeding of Il1r1^loxP/loxP mice to animals expressing a cytomegalovirus (CMV)-driven Cre recombinase afforded efficient excision at the Il1r1 locus. The Il1r1^loxP/loxP line should be a valuable tool for the assessment of contributions made by IL-1R1 signaling in diverse cell types across development.

The role of cytokines in the pathogenesis and staging of Trypanosoma brucei rhodesiense sleeping sickness

Human African trypanosomiasis due to Trypanosoma brucei rhodesiense is invariably fatal if untreated with up to 12.3 million people at a risk of developing the disease in Sub-Saharan Africa. The disease is characterized by a wide spectrum of clinical presentation coupled with differences in disease progression and severity. While the factors determining this varied response have not been clearly characterized, inflammatory cytokines have been partially implicated as key players. In this review, we consolidate available literature on the role of specific cytokines in the pathogenesis of T. b. rhodesiense sleeping sickness and further discuss their potential as stage biomarkers. Such information would guide upcoming research on the immunology of sleeping sickness and further assist in the selection and evaluation of cytokines as disease stage or diagnostic biomarkers.

Statins as Pleiotropic Modifiers of Vascular Oxidative Stress and Inflammation

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the industrialized world and in the future is expected to be the number one killer worldwide. The main cause underlying CVD is atherosclerosis. A key event in atherosclerosis initiation and progression is oxidative stress through the production of reactive oxygen species as well as endothelial dysfunction. Several pro- inflammatory and anti-inflammatory cytokines and proteins are involved in this process, complemented by activation of adhesion molecules that promote leukocyte rolling, tethering and infiltration into the sub-endothelial space. Statins represent the agent of choice since numerous clinical trials have verified that their pharmacological action extends beyond lipid lowering. Statins demonstrate direct anti-oxidant effects by scavenging free radicals and stimulating anti-oxidant enzymes while acting as regulators for cytokine, protein and adhesion molecule expression, all of which are involved in the atherosclerotic process. Statin use is considered one of the most efficient currently used interventions in managing CVD with the likely hood of remaining so in the near future.

Interleukin-1 beta enhances human multipotent mesenchymal stromal cell proliferative potential and their ability to maintain hematopoietic precursor cells

Multipotent mesenchymal stromal cells (MMSCs) have been demonstrated to produce mature stromal cells and maintain hematopoietic progenitor cells (HPC). It was previously demonstrated that interleukin-1 beta (IL-1 beta) stimulates the growth of the stromal microenvironment in vivo. The aim of this study was to investigate the effect of IL-1 beta treatment of human MMSCs on their proliferative potential, gene expression, immunomodulating properties, and their ability to support HPCs in vitro. Human bone marrow-derived MMSCs were cultivated in standard conditions or with IL-1 beta. The cumulative cell production was assessed for five passages. After withdrawal of IL-1 beta, MMSC clonal efficiency was investigated, and the maintenance of HPCs on top of MMSCs layers was estimated using cobblestone area forming cell (CAFC) and long-term culture initiating cell (LTC-IC) assays. The effect of untreated MMSCs or MMSCs pretreated with IL-1 beta on lymphocyte proliferation was studied by CFSE staining. The relative expression level of various genes by MMSCs was analyzed using RT-qPCR. The administration of IL-1 beta elevated MMSCs clonal efficiency and total cell production but did not affect lymphocyte proliferation. MMSCs pretreatment with IL-1 beta enhanced their ability to maintain HPCs, as detected by CAFC assay, and it altered the expression levels of genes participating in HPC regulation by stromal cells, e.g., adhesion molecules (ICAM1) and growth factors (SDF1). This study revealed the ability of IL-1 beta to stimulate MMSCs proliferation and enhance their potential to maintain HPCs. MMSCs are considered a stromal niche component in vitro. The combined in vitro and previous in vivo data suggest that IL-1 beta is a systemic regulator of the stromal microenvironment.

The structural pathway of interleukin 1 (IL-1) initiated signaling reveals mechanisms of oncogenic mutations and SNPs in inflammation and cancer

Interleukin-1 (IL-1) is a large cytokine family closely related to innate immunity and inflammation. IL-1 proteins are key players in signaling pathways such as apoptosis, TLR, MAPK, NLR and NF-κB. The IL-1 pathway is also associated with cancer, and chronic inflammation increases the risk of tumor development via oncogenic mutations. Here we illustrate that the structures of interfaces between proteins in this pathway bearing the mutations may reveal how. Proteins are frequently regulated via their interactions, which can turn them ON or OFF. We show that oncogenic mutations are significantly at or adjoining interface regions, and can abolish (or enhance) the protein-protein interaction, making the protein constitutively active (or inactive, if it is a repressor). We combine known structures of protein-protein complexes and those that we have predicted for the IL-1 pathway, and integrate them with literature information. In the reconstructed pathway there are 104 interactions between proteins whose three dimensional structures are experimentally identified; only 15 have experimentally-determined structures of the interacting complexes. By predicting the protein-protein complexes throughout the pathway via the PRISM algorithm, the structural coverage increases from 15% to 71%. In silico mutagenesis and comparison of the predicted binding energies reveal the mechanisms of how oncogenic and single nucleotide polymorphism (SNP) mutations can abrogate the interactions or increase the binding affinity of the mutant to the native partner. Computational mapping of mutations on the interface of the predicted complexes may constitute a powerful strategy to explain the mechanisms of activation/inhibition. It can also help explain how an oncogenic mutation or SNP works.

Interleukin-1 beta is an irradiation-induced stromal growth factor

Gamma irradiation of tissues and organs leads to many pathological consequences due to the formation of reactive oxygen species, DNA damage and the subsequent massive death of cells. The therapeutic use of gamma irradiation in the treatment of cancer is based on its penetrating power and damaging effects on tumor cells. Other effects from the irradiation are unnoticeable in comparison. Moreover, the long-term consequences of gamma irradiation are still poorly understood. When a donor bone marrow plug is implanted under the renal capsule of a syngeneic animal, а hematopoietic ectopic focus is formed. The size of the focus is increased in mice that received irradiation compared to non-irradiated ones, regardless of the amount of time between irradiation and bone marrow plug implantation. Long-term repetitive injections of blood serum from irradiated mice given to syngeneic non-irradiated recipients of bone marrow plugs also lead to the formation of enlarged foci. Hence, the blood of irradiated animals must contain an activity that induces the growth of a hematopoietic microenvironment. It was previously shown that the bones of irradiated animals secrete a growth factor required to create stromal microenvironments. The identity of this factor has, until now, been difficult to obtain. We demonstrated that interleukin 1 beta (IL-1) stimulates the growth of murine bone marrow stromal cells in vitro and in vivo. It was shown that the expression of the Il1b gene and the secretion of its product, IL-1, were activated in bone cells long after total body gamma irradiation. Hence, IL-1, or proteins regulated by this cytokine, appears to be the same stromal growth factor previously observed in the serum of irradiated animals. Our data demonstrate several non-canonical functions of IL-1. In addition, the presence of up-regulated levels of IL-1 long after irradiation points to an unknown mechanism governing its gene expression.

Interleukin-1 (IL-1) pathway

The interleukin-1 (IL-1) family of cytokines comprises 11 proteins (IL-1F1 to IL-1F11) encoded by 11 distinct genes in humans and mice. IL-1-type cytokines are major mediators of innate immune reactions, and blockade of the founding members IL-1alpha or IL-1beta by the interleukin-1 receptor antagonist (IL-1RA) has demonstrated a central role of IL-1 in a number of human autoinflammatory diseases. IL-1alpha or IL-1beta rapidly increase messenger RNA expression of hundreds of genes in multiple different cell types. The potent proinflammatory activities of IL-1alpha and IL-1beta are restricted at three major levels: (i) synthesis and release, (ii) membrane receptors, and (iii) intracellular signal transduction. This pathway summarizes extracellular and intracellular signaling of IL-1alpha or IL-1beta, including positive- and negative-feedback mechanisms that amplify or terminate the IL-1 response. In response to ligand binding of the receptor, a complex sequence of combinatorial phosphorylation and ubiquitination events results in activation of nuclear factor kappaB signaling and the JNK and p38 mitogen-activated protein kinase pathways, which, cooperatively, induce the expression of canonical IL-1 target genes (such as IL-6, IL-8, MCP-1, COX-2, IkappaBalpha, IL-1alpha, IL-1beta, MKP-1) by transcriptional and posttranscriptional mechanisms. Of note, most intracellular components that participate in the cellular response to IL-1 also mediate responses to other cytokines (IL-18 and IL-33), Toll-like-receptors (TLRs), and many forms of cytotoxic stresses.

Is interleukin-1 a good or bad 'guy' in tumor immunobiology and immunotherapy?

The interleukin-1 (IL-1) family consists of two major agonistic proteins, IL-1alpha and IL-1beta, which are pleiotropic and affect mainly inflammation, immunity, and hemopoiesis. The IL-1 receptor antagonist (IL-1Ra) is a physiological inhibitor of pre-formed IL-1. In their secreted form, IL-1alpha and IL-1beta bind to the same receptors and induce the same biological functions. However, the IL-1 molecules differ in their compartmentalization within the producing cell or the microenvironment. Thus, IL-1beta is solely active in its secreted form, whereas IL-1alpha is mainly active in cell-associated forms (intracellular precursor and membrane-bound IL-1) and only rarely as a secreted cytokine, mainly by macrophages/monocytes. IL-1 is abundant at tumor sites, being produced by cellular elements of the tumor microenvironment or by the malignant cells, and it affects not only various phases of the malignant process, such as carcinogenesis, tumor growth, and invasiveness, but also patterns of interactions between malignant cells and the host's immune system. Hence, the effects of the IL-1 molecules on the malignant process are complex and are often of an opposing nature. Comparative studies on the differential roles of malignant cell- or host-derived IL-1alpha and IL-1beta in different stages of the malignant process can subsequently open new avenues for manipulation of IL-1 expression and function in cancer immunotherapy.

Primer: inflammasomes and interleukin 1beta in inflammatory disorders

Inflammasomes are large, multimeric protein complexes that link the sensing of microbial products and metabolic stress to the proteolytic processing of prointerleukin (pro-IL)-1beta to its active form. NALP1 and NALP2 are founding members of the Nod-like receptor family. Other Nod-like receptors, including NALP3 and NOD2, which are associated with inflammatory disorders, have also been described. The NALP1 and NALP3 inflammasomes are located in the cytoplasm and can, therefore, detect intracellular infection through recognition of microbial pathogen-associated molecular patterns. The inflammasome pathways cooperate with Toll-like receptor pathways to mediate a rapid and appropriate response to pathogens and genotoxic stress. Mutations in both pyrin and NALP3 components of inflammasomes are associated with innate-immune-mediated diseases (familial Mediterranean fever and the 'cryopyrinopathies'), and aberrant IL-1beta processing has been reported in several autoinflammatory conditions, including Muckle-Wells syndrome, chronic infantile neurologic, cutaneous and articular syndrome/neonatal onset multisystem inflammatory disease, and gout. The effectiveness of IL-1beta blockade in treating many of these conditions has transformed the understanding and management of these disorders and also highlighted the role of aberrant IL-1beta signaling in other conditions, such as adult-onset Still's disease and systemic juvenile idiopathic arthritis.

Historical insights into cytokines

Cytokines affect nearly every biological process; these include embryonic development, disease pathogenesis, non-specific response to infection, specific response to antigen, changes in cognitive functions and progression of the degenerative processes of aging. In addition, cytokines are part of stem cell differentiation, vaccine efficacy and allograft rejection. This short insight focuses on the milestones in cytokine biology and how the various and often contradictory activities of these small, non-structural proteins affected the fields of inflammation and immunology. Multiple biological properties or pleiotropism is the hallmark of a cytokine. Today, the term "cytokine" encompasses interferons, the interleukins, the chemokine family, mesenchymal growth factors, the tumor necrosis factor family and adipokines. As of this writing, 33 cytokines are called interleukins, but many are part of families of related but distinct gene products. There are certainly over 100 separate genes coding for cytokine-like activities, many with overlapping functions and many still unexplored. Also discussed in this overview are the failures and successes of cytokines as therapeutic targets. A recent advance in the field has been that of differential cytokine production, which can be used to classify human disease as being "autoimmune" or "autoinflammatory" thus impacting on therapeutic interventions.