Structure and expression of cDNA and genes for human interferon-beta-2, a distinct species inducible by growth-stimulatory cytokines

Exploring the landscape of synthetic IL-6-type cytokines

Interleukin-6 (IL-6)-type cytokines not only have key immunomodulatory functions that affect the pathogenesis of diseases such as autoimmune diseases, chronic inflammatory conditions, and cancer, but also fulfill important homeostatic tasks. Even though the pro-inflammatory arm has hindered the development of therapeutics based on natural-like IL-6-type cytokines to date, current synthetic trends might pave the way to overcome these limitations and eventually lead to immune-inert designer cytokines to aid type 2 diabetes and brain injuries. Those synthetic biology approaches include mutations, fusion proteins, and inter-cytokine swapping, and resulted in IL-6-type cytokines with altered receptor affinities, extended target cell profiles, and targeting of non-natural cytokine receptor complexes. Here, we survey synthetic cytokine developments within the IL-6-type cytokine family and discuss potential clinical applications.

Targeting IL-6 trans-signalling: past, present and future prospects

Interleukin-6 (IL-6) is a key immunomodulatory cytokine that affects the pathogenesis of diverse diseases, including autoimmune diseases, chronic inflammatory conditions and cancer. Classical IL-6 signalling involves the binding of IL-6 to the membrane-bound IL-6 receptor α-subunit (hereafter termed 'mIL-6R') and glycoprotein 130 (gp130) signal-transducing subunit. By contrast, in IL-6 trans-signalling, complexes of IL-6 and the soluble form of IL-6 receptor (sIL-6R) signal via membrane-bound gp130. A third mode of IL-6 signalling - known as cluster signalling - involves preformed complexes of membrane-bound IL-6-mIL-6R on one cell activating gp130 subunits on target cells. Antibodies and small molecules have been developed that block all three forms of IL-6 signalling, but in the past decade, IL-6 trans-signalling has emerged as the predominant pathway by which IL-6 promotes disease pathogenesis. The first selective inhibitor of IL-6 trans-signalling, sgp130, has shown therapeutic potential in various preclinical models of disease and olamkicept, a sgp130Fc variant, had promising results in phase II clinical studies for inflammatory bowel disease. Technological developments have already led to next-generation sgp130 variants with increased affinity and selectivity towards IL-6 trans-signalling, along with indirect strategies to block IL-6 trans-signalling. Here, we summarize our current understanding of the biological outcomes of IL-6-mediated signalling and the potential for targeting this pathway in the clinic.

The role of IL-6/JAK2/STAT3 signaling pathway in cancers

Interleukin-6 (IL-6) is a pleiotropic cytokine involved in immune regulation. It can activate janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) signaling pathway. As one of the important signal transduction pathways in cells, JAK2/STAT3 signaling pathway plays a critical role in cell proliferation and differentiation by affecting the activation state of downstream effector molecules. The activation of JAK2/STAT3 signaling pathway is involved in tumorigenesis and development. It contributes to the formation of tumor inflammatory microenvironment and is closely related to the occurrence and development of many human tumors. This article focuses on the relationship between IL-6/JAK2/STAT3 signaling pathway and liver cancer, breast cancer, colorectal cancer, gastric cancer, lung cancer, pancreatic cancer and ovarian cancer, hoping to provide references for the research of cancer treatment targeting key molecules in IL-6/JAK2/STAT3 signaling pathway.

Digital Protein Detection in Bulk Solutions

Quick and accurate molecular diagnostics in protein detection can greatly benefit medicine in disease diagnosis and lead to positive patient outcomes. However, specialized equipment used in clinical laboratories often comes with trade-offs between operation and function serving a single role for very specific needs. For example, to achieve high analytical sensitivity and specificity, instruments such as high-performance liquid chromatography and/or liquid chromatography-mass spectrometry use a complex instrument design and require thorough training of the users. On the other hand, simple tests such as protein detection in urinary tract infection using dip-stick assays provide very quick results but suffer from poor analytical sensitivity. Here, we present an application study for the 3D particle counter technology, which is based on optical confocal detection in order to scan large sample volumes (0.5-3 mL) in glass cuvettes, that aims to close the gap between analytical sensitivity and turnover assay time and simplify protein detection by adopting bead-based immunoassays. Combining the 3D particle counter technology with bead-based immunoassays, a subpicomolar limit of detection-ranging from 119 to 346 fM-was achieved within 3.5-hour assay time for recombinant mouse interleukin 6 detection. As an alternative instrument to a flow cytometer, the 3D particle counter takes advantages of bead-based immunoassays and provides unique accessibility and flexibility for users.

IL-6/JAK/STAT3 Signaling in Breast Cancer Metastasis: Biology and Treatment

Breast cancer is the most commonly diagnosed cancer in women. Metastasis is the primary cause of mortality for breast cancer patients. Multiple mechanisms underlie breast cancer metastatic dissemination, including the interleukin-6 (IL-6)-mediated signaling pathway. IL-6 is a pleiotropic cytokine that plays an important role in multiple physiological processes including cell proliferation, immune surveillance, acute inflammation, metabolism, and bone remodeling. IL-6 binds to the IL-6 receptor (IL-6Rα) which subsequently binds to the glycoprotein 130 (gp130) receptor creating a signal transducing hexameric receptor complex. Janus kinases (JAKs) are recruited and activated; activated JAKs, in turn, phosphorylate signal transducer and activator of transcription 3 (STAT3) for activation, leading to gene regulation. Constitutively active IL-6/JAK/STAT3 signaling drives cancer cell proliferation and invasiveness while suppressing apoptosis, and STAT3 enhances IL-6 signaling to promote a vicious inflammatory loop. Aberrant expression of IL-6 occurs in multiple cancer types and is associated with poor clinical prognosis and metastasis. In breast cancer, the IL-6 pathway is frequently activated, which can promote breast cancer metastasis while simultaneously suppressing the anti-tumor immune response. Given these important roles in human cancers, multiple components of the IL-6 pathway are promising targets for cancer therapeutics and are currently being evaluated preclinically and clinically for breast cancer. This review covers the current biological understanding of the IL-6 signaling pathway and its impact on breast cancer metastasis, as well as, therapeutic interventions that target components of the IL-6 pathway including: IL-6, IL-6Rα, gp130 receptor, JAKs, and STAT3.

Endosomes as Signaling Platforms for IL-6 Family Cytokine Receptors

Interleukin-6 (IL-6) is the name-giving cytokine of a family of eleven members, including IL-6, CNTF, LIF, and IL-27. IL-6 was first recognized as a B-cell stimulating factor but we now know that the cytokine plays a pivotal role in the orchestration of inflammatory processes as well as in inflammation associated cancer. Moreover, IL-6 is involved in metabolic regulation and it has been shown to be involved in major neural activities such as neuroprotection, which can help to repair and to reduce brain damage. Receptor complexes of all members formed at the plasma membrane contain one or two molecules of the signaling receptor subunit GP130 and the mechanisms of signal transduction are well understood. IL-6 type cytokines can also signal from endomembranes, in particular the endosome, and situations have been reported in which endocytosis of receptor complexes are a prerequisite of intracellular signaling. Moreover, pathogenic GP130 variants were shown to interfere with spatial activation of downstream signals. We here summarize the molecular mechanisms underlying spatial regulation of IL-6 family cytokine signaling and discuss its relevance for pathogenic processes.

Therapeutic targeting of IL-6 trans-signaling

Interleukin-6 (IL-6) is a cytokine, which is involved in innate and acquired immunity, in neural cell maintenance and in metabolism. IL-6 can be synthesized by many different cells including myeloid cells, fibroblasts, endothelial cells and lymphocytes. The synthesis of IL-6 is strongly stimulated by Toll like receptors and by IL-1. Therefore, IL-6 levels in the body are high during infection and inflammatory processes. Moreover, IL-6 is a prominent growth factor of tumor cells and plays a major role in inflammation associated cancer. On target cells, IL-6 binds to an IL-6 receptor, which is not signaling competent. The complex of IL-6 and IL-6 receptor associate with a second receptor subunit, glycoprotein gp130, which dimerizes and initiates intracellular signaling. Cells, which do not express the IL-6 receptor are not responsive to IL-6. They can, however, be stimulated by the complex of IL-6 and a soluble form of the IL-6 receptor, which is generated by limited proteolysis and to a lesser extent by translation from an alternatively spliced mRNA. This process has been named IL-6 trans-signaling. This review article will explain the biology of IL-6 trans-signaling and the specific inhibition of this mode of signaling, which has been recognized to be fundamental in inflammation and cancer.

IL-6 in inflammation, autoimmunity and cancer

IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6-STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6-STAT3 axis is a critical target for treating diseases.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

Interleukin-6: Molecule in the Intersection of Cancer, Ageing and COVID-19

Interleukin-6 (IL-6) is a cytokine with multifaceted effects playing a remarkable role in the initiation of the immune response. The increased level of this cytokine in the elderly seems to be associated with the chronic inflammatory setting of the microenvironment in aged individuals. IL-6 also represents one of the main signals in communication between cancer cells and their non-malignant neighbours within the tumour niche. IL-6 also participates in the development of a premetastatic niche and in the adjustment of the metabolism in terminal-stage patients suffering from a malignant disease. IL-6 is a fundamental factor of the cytokine storm in patients with severe COVID-19, where it is responsible for the fatal outcome of the disease. A better understanding of the role of IL-6 under physiological as well as pathological conditions and the preparation of new strategies for the therapeutic control of the IL-6 axis may help to manage the problems associated with the elderly, cancer, and serious viral infections.

Exercise-Induced Myokines can Explain the Importance of Physical Activity in the Elderly: An Overview

Physical activity has been found to aid the maintenance of health in the elderly. Exercise-induced skeletal muscle contractions lead to the production and secretion of many small proteins and proteoglycan peptides called myokines. Thus, studies on myokines are necessary for ensuring the maintenance of skeletal muscle health in the elderly. This review summarizes 13 myokines regulated by physical activity that are affected by aging and aims to understand their potential roles in metabolic diseases. We categorized myokines into two groups based on regulation by aerobic and anaerobic exercise. With aging, the secretion of apelin, β-aminoisobutyric acid (BAIBA), bone morphogenetic protein 7 (BMP-7), decorin, insulin-like growth factor 1 (IGF-1), interleukin-15 (IL-15), irisin, stromal cell-derived factor 1 (SDF-1), sestrin, secreted protein acidic rich in cysteine (SPARC), and vascular endothelial growth factor A (VEGF-A) decreased, while that of IL-6 and myostatin increased. Aerobic exercise upregulates apelin, BAIBA, IL-15, IL-6, irisin, SDF-1, sestrin, SPARC, and VEGF-A expression, while anaerobic exercise upregulates BMP-7, decorin, IGF-1, IL-15, IL-6, irisin, and VEGF-A expression. Myostatin is downregulated by both aerobic and anaerobic exercise. This review provides a rationale for developing exercise programs or interventions that maintain a balance between aerobic and anaerobic exercise in the elderly.

Interleukin-6 signalling in health and disease

Biochemically, interleukin-6 belongs to the class of four-helical cytokines. The cytokine can be synthesised and secreted by many cells. It acts via a cell surface-expressed interleukin-6 receptor, which is not signalling competent. This receptor, when complexed with interleukin-6, associates with the signalling receptor glycoprotein 130 kDa (gp130), which becomes dimerised and initiates intracellular signalling via the Janus kinase/signal transducer and activator of transcription and rat sarcoma proto oncogene/mitogen-activated protein kinase/phosphoinositide-3 kinase pathways. Physiologically, interleukin-6 is involved in the regulation of haematopoiesis and the coordination of the innate and acquired immune systems. Additionally, interleukin-6 plays an important role in the regulation of metabolism, in neural development and survival, and in the development and maintenance of various cancers. Although interleukin-6 is mostly regarded as a pro-inflammatory cytokine, there are numerous examples of protective and regenerative functions of this cytokine. This review will explain the molecular mechanisms of the, in part opposing, activities of the cytokine interleukin-6.

A panoramic review of IL-6: Structure, pathophysiological roles and inhibitors

Interleukin-6 (IL-6) is a pleiotropic pro-inflammatory cytokine. Its deregulation is associated with chronic inflammation, and multifactorial auto-immune disorders. It mediates its biological roles through a hexameric complex composed of IL-6 itself, its receptor IL-6R, and glycoprotein 130 (IL-6/IL-6R/gp130). This complex, in turn, activates different signaling mechanisms (classical and trans-signaling) to execute various biochemical functions. The trans-signaling mechanism activates various pathological routes, like JAK/STAT3, Ras/MAPK, PI3K-PKB/Akt, and regulation of CD4+ T cells and VEGF levels, which cause cancer, multiple sclerosis, rheumatoid arthritis, anemia, inflammatory bowel disease, Crohn's disease, and Alzheimer's disease. Involvement of IL-6 in pathophysiology of these complex diseases makes it an important target for the treatment of these diseases. Though some anti-IL-6 monoclonal antibodies are being used clinically, but their high cost, only parenteral administration, and possibility of immunogenicity have limited their use, and warranted the development of novel small non-peptide molecules as IL-6 inhibitors. In the present report, all molecules reported in literature as IL-6 inhibitors have been classified as IL-6 production, IL-6R, and IL-6 signaling inhibitors. Reports available till date are critically studied to identify important and salient structural features common in these molecules. These analyses would assist medicinal chemists to design novel and potent IL-6 production and signaling inhibitors, through knowledge- and/or computer-based approaches, for the treatment of complex multifactorial diseases.

The role of the interleukin (IL)-6/IL-6 receptor axis in cancer

Interleukin-6 (IL-6) is a pleiotropic cytokine that activates a classic signalling pathway upon binding to its membrane-bound receptor (IL-6R). Alternatively, IL-6 may 'trans-signal' in a manner that is facilitated by its binding to a soluble derivative of the IL-6 receptor (sIL-6R). Resultant signal transduction is, respectively, driven by the association of IL-6/IL-6R or IL-6/sIL-6R complex with the membrane-associated signal transducer, gp130 (Glycoprotein 130). Distinct JAK (Janus tyrosine kinase)/STAT (signal transducers and activators of transcription) and other signalling pathways are activated as a consequence. Of translational relevance, overexpression of IL-6 has been documented in several neoplastic disorders, including but not limited to colorectal, ovarian and breast cancer and several haematological malignancies. This review attempts to summarise our current understanding of the role of IL-6 in cancer development. In short, these studies have shown important roles for IL-6 signalling in tumour cell growth and survival, angiogenesis, immunomodulation of the tumour microenvironment, stromal cell activation, and ultimate disease progression. Given this background, we also consider the potential for therapeutic targeting of this system in cancer.

Interleukin-6 Family Cytokines

The interleukin (IL)-6 family cytokines is a group of cytokines consisting of IL-6, IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), oncostatin M (OSM), cardiotrophin 1 (CT-1), cardiotrophin-like cytokine (CLC), and IL-27. They are grouped into one family because the receptor complex of each cytokine contains two (IL-6 and IL-11) or one molecule (all others cytokines) of the signaling receptor subunit gp130. IL-6 family cytokines have overlapping but also distinct biologic activities and are involved among others in the regulation of the hepatic acute phase reaction, in B-cell stimulation, in the regulation of the balance between regulatory and effector T cells, in metabolic regulation, and in many neural functions. Blockade of IL-6 family cytokines has been shown to be beneficial in autoimmune diseases, but bacterial infections and metabolic side effects have been observed. Recent advances in cytokine blockade might help to minimize such side effects during therapeutic blockade.

Genetic association study of common variants in TGFB1 and IL-6 with developmental dysplasia of the hip in Han Chinese population

Developmental dysplasia of the hip (DDH) is a congenital or developmental deformation or misalignment of the hip joint that is affected by environmental and genetic factors. Recently, polymorphisms in both TGFB1 and IL-6 have been identified as being significantly associated with hip osteoarthritis in Caucasians. In this study, we conducted a case-control study involving 4,206 Han Chinese individuals to investigate the effects of TGFB1 and IL-6 on the disease status and severity of DDH. A total of 32 single-nucleotide polymorphisms (SNPs) were selected to ensure coverage of the two genetic loci. We found SNP rs1800470 in TGFB1 (OR = 1.255, P = 0.0004) and rs1800796 (OR = 0.84, P = 0.0228) in IL-6 to be significantly associated with DDH in this cohort. Further haplotype-based analysis replicated this significant result. Another SNP in IL-6, rs1800796, showed a marginally significant association with DDH. As a non-synonymous SNP, rs1800470 alters the amino acid sequence of the polypeptide encoded by TGFB1; however, bioinformatics analyses revealed that this SNP has limited functional significance. No significant results were obtained in an association study focusing on the severity of DDH and epistasis analysis. Our findings support an important role for TGFB1 in the risk of DDH. Further research is needed to validate the weak association between rs1800796 in IL-6 and DDH.

Interleukin-6 as a Multifunctional Regulator: Inflammation, Immune Response, and Fibrosis

Interleukin 6 (IL-6) is a 184-amino acid protein cytokine that is produced by many types of cells and is expressed during states of cellular stress, such as inflammation, infection, wound sites, and cancer. IL-6 levels may increase several thousand-fold in these states and may help to coordinate the response to dysregulation of tissue homeostasis. IL-6 acts through a membrane-bound IL-6 receptor (mIL-6R), which, together with a second receptor, glycoprotein 130 (gp130), leads to the initiation of intracellular signaling (classic signaling). Given that IL-6R is expressed on only a few types of cells, though all cells express gp130, direct stimulation by IL-6 is limited to cells that express mIL-6R. However, IL-6R is also produced as a soluble, secreted protein that, together with IL-6, can stimulate all gp130-expressing cells by a process termed IL-6 trans-signaling. IL-6 trans-signaling can be blocked without affecting IL-6 classic signaling through mIL-6R. IL-6 has major effects on the adaptive and innate immune system and on mesenchymal and stromal responses during inflammation. It promotes the development of pathogenic T-helper 17 T cells and the maturation of B lymphocytes. Many innate immune cells, neutrophils, and monocytes/macrophages produce and respond to IL-6, resulting in autocrine feedback loops that amplify inflammation. IL-6 has been implicated in the pathogenesis of fibrotic diseases in which IL-6 trans-signaling has been shown to stimulate the proliferation of fibroblasts and the release of procollagen and fibronectin.

Contribution of Interleukin-6 to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, manifesting in patients as tissue fibrosis, endothelial dysfunction, and inflammation. The disease is characterized by autoantibodies, a hallmark of autoimmunity. Various cytokines and growth factors are elevated in the systemic circulation and fibrotic lesions of patients with SSc. In particular, several studies over the past 2 decades have shown that interleukin-6 (IL-6) appears to be involved in the pathogenesis of SSc. Based on the association between aberrant IL-6 production and tissue fibrosis in patients with SSc, the anti-IL-6 receptor antibody, tocilizumab, is being investigated in clinical trials. This article reviews the biological features of IL-6 and the IL-6 receptor; the role of IL-6 in the pathogenesis of SSc; and the potential for IL-6 inhibition to be used in the treatment of patients with SSc.

Interleukin-10 is downregulated in mononuclear cells from endotoxin tolerant humans

It has been shown that induction of endotoxin tolerance results in a decreased potential to produce pro-inflammatory cytokines such as TNF or IL-1. The present study was carried out to examine the capacity of peripheral blood mononuclear cells (PBMC) from endotoxin tolerant humans to synthesize the anti-inflammatory cytokines IL-10 and TGFβ in response to endotoxin. Four individuals were rendered endotoxin tolerant by daily i.v. injections of endotoxin. PBMC were isolated before tolerance induction and on day 4 after the last endotoxin treatment. The cells were stimulated with endotoxin ex vivo and cytokines in culture supernatants were determined. PBMC isolated on day 4 of all of the volunteers showed decreased TNFα, IL-6 and IL-10 synthesis upon endotoxin treatment in vitro compared to pretolerant cells, while no differences occurred with regard to the amount of TGFβ formed by PBMC before and after tolerance induction. Furthermore, no changes were found in the expression of HLA-DR on PBMC after tolerance induction.

Castleman's Disease and Interleukin 6

Castleman's disease is a rare condition characterized by benign hyperplastic lymph nodes. Based on the morphological features, it has been divided into hyaline-vascular, plasma cell and intermediate types. The latter two types are frequently associated with a wide variety of clinical pictures such as fever, anemia with hypotransferrinemia, hyperimmunoglobulinemia and an increase in the concentration of C-reactive protein (CRP). Although immunological disturbances have been suggested to play important roles in the pathophysiology of Castleman's disease, the precise mechanisms for the generation of its clinical pictures are still unsettled. In this respect, we have reported a pediatric case with spontaneous production of high levels of B cell differentiation factor (BCDF) activity by the hyperplastic lymph node, and we demonstrated here the strong expression of interleukin 6 (IL-6) gene in the lymph node cells. On the other hand, recent studies have revealed that IL-6 is a multifunctional cytokine; IL-6 not only induces the immunoglobulin production but also induces the acute phase reaction, and functions as an endogeneous pyrogen. In the acute phase reaction, IL-6 may induce an increase in CRP concentration and hypotransferrinemia. These studies indicate that the overproduction of IL-6 by the hyperplastic lymph node may be closely related to the pathophysiology of Castleman's disease. Therefore, it is considered that this disease is a "disorder of IL-6 production".

The role of interleukin-6 signaling in nervous tissue

The cytokine interleukin-6 (IL-6) plays a critical role in the pathogenesis of inflammatory disorders and in the physiological homeostasis of neural tissue. Profound neuropathological changes, such as multiple sclerosis (MS), Parkinson's and Alzheimer's disease are associated with increased IL-6 expression in brain. Increased nocturnal concentrations of serum IL-6 are found in patients with impaired sleep whereas IL-6-deficient mice spend more time in rapid eye movement sleep associated with dreaming. IL-6 is crucial in the differentiation of oligodendrocytes, regeneration of peripheral nerves and acts as a neurotrophic factor. It exerts its cellular effects through two distinct pathways which include the anti-inflammatory pathway involving the membrane-bound IL-6 receptor (IL-6R) expressed on selective cells, including microglia, in a process known as classical signaling that is also critical for bacterial defense. In classical signaling binding of IL-6 to the membrane-bound IL-6R activates the β-receptor glycoprotein 130 (gp130) and subsequent down-stream signaling. The alternative, rather pro-inflammatory pathway, shown to mediate neurodegeneration in mice, termed trans-signaling, depends on a soluble form of the IL-6R that is capable of binding IL-6 to stimulate a response on distal cells that express gp130. A naturally occurring soluble form of gp130 (sgp130) has been identified that can specifically bind and neutralize the IL-6R/IL-6 complex. Thus, trans-signaling is blocked but classical signaling is completely unaffected. A modified, recombinant dimerized version of sgp130 (sgp130Fc) has successfully been used to block inflammatory processes in mice and may also be used in the clarification of IL-6 trans-signaling in neurological diseases.

Association between interleukin-6 (G174C and C572G) promoter gene polymorphisms and risk of ischemic stroke in North Indian population: a case-control study

BACKGROUND

Polymorphisms of G174C and C572G in the interleukin-6 (IL-6) promoter gene can affect both transcription and secretion of IL-6 and may be involved in inflammation related to and pathogenesis of ischemic stroke (IS). Whether these IL-6 gene polymorphisms are risk factors for IS or not, remains controversial.

OBJECTIVE

The aim of this study was to determine the association between IL-6 G174C and C572G gene polymorphisms and susceptibility to ischemic stroke in North Indian Population.

METHODS

Two hundred and fifty IS patients and 250 age- and sex-matched controls were studied. Genotyping was performed using SNaPshot method. Stroke was classified using Trial of Org 10172 in acute stroke treatment classification. Conditional logistic regression analysis was used to calculate the strength of association between IL-6 (G174C and C572G) polymorphisms and risk of IS.

RESULTS

Hypertension, diabetes, dyslipidemia, alcohol, smoking, family history of stroke, sedentary life style and low socioeconomic status were found to be associated with the risk of IS. Conditional logistic regression analysis showed a significant association of IL-6 G174C with the risk of IS under dominant model (OR, 1.61; 95%CI, 1.0-2.4; P value 0.02) and allelic model (OR, 1.5; 95%CI, 1.0-2.1; P value 0.02). For IL-6 C572G, multivariate adjusted analysis showed a significant association with the risk of IS under dominant model for overall IS (OR, 1.81; 95%CI, 1.04-3.15; P value 0.03) and small vessel disease subtype of IS (OR, 2.8; 95%CI, 1.3-6.0; P value 0.006).

CONCLUSION

Our results suggest that IL-6 (G174C) polymorphism is significantly associated with the risk of IS in North Indian population. However, IL-6 (C572G) polymorphism is found significantly associated with the risk of IS after adjusting the demographic and risk factors variables. Prospective studies with large sample size are required for independent validation. Our findings could be helpful in identifying individuals at increased risk for developing IS.

Versatile functions for IL-6 in metabolism and cancer

Owing to its abundance in inflammatory settings, interleukin IL-6 is frequently viewed as a proinflammatory cytokine, with functions that parallel those of tumor necrosis factor (TNF) and IL-1β in the context of inflammation. However, accumulating evidence points to a broader role for IL-6 in a variety of (patho)physiological conditions, including functions related to the resolution of inflammation. We review recent findings on the complex biological functions governed by IL-6 signaling, focusing on its role in inflammation-associated cancer and metabolic disorders such as obesity and type 2 diabetes mellitus (T2DM). We propose that the anti-inflammatory functions of IL-6 may extend to multiple settings and cell types, and suggest that these dimensions should be incorporated in therapeutic approaches to these diseases. Finally, we outline important areas of inquiry towards understanding this pleiotropic cytokine.

Gene of the month: Interleukin 6 (IL-6)

The Interleukin 6 (IL-6) gene encodes the classic proinflammatory cytokine IL-6. It is also known as interferon-β2 (IFN-β2), B cell stimulatory factor-2 and hybridoma/plasmacytoma growth factor. IL-6 is a multifunctional cytokine with a central role in many physiological inflammatory and immunological processes. Due to its major role in initiation as well as resolving inflammation, deregulation of IL-6 is a mainstay of chronic inflammatory and autoimmune diseases. Additionally, IL-6 has been shown to be implicated in pathogenesis of many human malignancies. Thus, a better understanding of IL-6 and its role in various pathological conditions could enable the development of strategies to use it as a therapeutic target. This short review focuses on the structure, regulation and biological activities of IL-6. In addition we discuss the role of IL-6 in diseases with inflammatory background and cancer and also the therapeutic applications of anti-IL-6 agents.

Interleukin-6 signal transduction and its role in hepatic lipid metabolic disorders

Hepatic lipid dysregulation can lead to spectrum of metabolic disease conditions including metabolic syndrome (MS), fatty liver and diabetes. Liver lipids are regulated by a complex set of extra-hepatic and intra-hepatic factors including cellular cross-talk with variety of cells, inducing various cytokines. Interleukin 6(IL-6) is a pleiotropic cytokine that exerts both pro-inflammatory and anti-inflammatory effects on hepatic system through either JNK/STAT or ERK/MAPK signaling. Although, IL-6 has shown to protect the liver from fat storage in both rodent and human models and various IL-6(-/-) studies have supported this notion yet a question remains over its deleterious pro-inflammatory effects on hepatocytes. IL-6 ability to produce reactive oxygen species (ROS) and subsequently disturb the hepatic lipid balance has created a conundrum. Furthermore, IL-6 has shown to behave differently under different disease states within hepatocytes and hence, modulating the hepatic lipids accordingly. This review deals with the role of IL-6 on hepatic lipid metabolism and analyzes various data presented on this topic.

Tocilizumab: An Updated Review of Its Use in the Treatment of Rheumatoid Arthritis and Its Application for Other Immune-Mediated Diseases

Interleukin-6 (IL-6), produced by a variety of cells, is a typical cytokine featuring redundancy and pleiotropic activity. IL-6 is promptly and transiently synthesized in response to infections or injuries, and participates in host defense by inducing immune responses, hematopoiesis, and acute-phase reactions. However, since its abnormal persistent production of mostly unknown etiology plays an important pathological role in the development of various immune-mediated diseases, a humanized anti-IL-6 receptor monoclonal antibody, tocilizumab, was developed and is now used as an innovative biologic for rheumatoid arthritis in more than 90 countries. Several factors strongly suggest that a IL-6 blockade strategy may have a broad application for the treatment of various immune-mediated diseases. These factors include favorable results of pilot or case studies with off-label use of tocilizumab, pathological analyses of the contribution of IL-6 to the development of immune-mediated diseases, and the potential capability of tocilizumab to both repair an imbalance of effector T cell subsets and to suppress pathologic autoantibody production. However, clinical trials to evaluate the efficacy and safety of tocilizumab for these diseases are essential. Furthermore, clarification of the cell source of IL-6 production and of the mechanisms through which dysregulated continuous IL-6 synthesis is induced constitutes an important issue for future studies into the pathogenesis of diseases.

Interleukin-1 activates synthesis of interleukin-6 by interfering with a KH-type splicing regulatory protein (KSRP)-dependent translational silencing mechanism

Post-transcriptional mechanisms play an important role in the control of inflammatory gene expression. The heterogeneous nuclear ribonucleoprotein K homology (KH)-type splicing regulatory protein (KSRP) triggers rapid degradation of mRNAs for various cytokines, chemokines, and other inflammation-related proteins by interacting with AU-rich elements (AREs) in the 3'-untranslated mRNA regions. In addition to destabilizing mRNAs, AU-rich elements can restrict their translation. Evidence that KSRP also participates in translational silencing was obtained in a screen comparing the polysome profiles of cells with siRNA-mediated depletion of KSRP with that of control cells. Among the group of mRNAs showing increased polysome association upon KSRP depletion are those of interleukin (IL)-6 and IL-1α as well as other ARE-containing transcripts. Redistribution of IL-6 mRNA to polysomes was associated with increased IL-6 protein secretion by the KSRP-depleted cells. Silencing of IL-6 and IL-1α mRNAs depended on their 3'-untranslated regions. The sequence essential for translational control of IL-6 mRNA and its interaction with KSRP was located to an ARE. KSRP-dependent silencing was reversed by IL-1, a strong inducer of IL-6 mRNA and protein expression. The results identify KSRP as a protein involved in ARE-mediated translational silencing. They suggest that KSRP restricts inflammatory gene expression not only by enhancing degradation of mRNAs but also by inhibiting translation, both functions that are counteracted by the proinflammatory cytokine IL-1.

Viral interleukin-6: role in Kaposi's sarcoma-associated herpesvirus: associated malignancies

Viral interleukin-6 (vIL-6) is a product of Kaposi's sarcoma-associated herpesvirus (KSHV) expressed in latently infected cells and to a higher degree during viral replication. A distinctive feature of vIL-6 is the ability to directly bind and activate gp130 signaling in the absence of other receptor subunits. Secretion of vIL-6 is generally poor, but vIL-6 can activate gp130 from inside the cell. Due to the wide cell distribution of gp130, vIL-6 has the potential to induce a wide range of biological effects. Expression of vIL-6 is variable in KSHV-associated Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD), and in a newly described MCD-like systemic inflammatory syndrome observed in human immunodeficiency virus-positive patients. PEL effusions usually contain vIL-6 at high concentrations; since vIL-6 induces vascular endothelial growth factor, vIL-6 likely contributes to vascular permeability and formation of PEL effusions. Lymph nodes affected with MCD contain vIL-6-positive cells, and vIL-6 levels rise in conjunction with flares of the disease and likely contribute to symptoms of inflammation. The development of vIL-6 inhibitors is a potentially important advance in the treatment of KSHV-associated malignancies where vIL-6 is expressed.

Interleukin-6, a mental cytokine

Almost a quarter of a century ago, interleukin-6 (IL-6) was discovered as an inflammatory cytokine involved in B cell differentiation. Today, IL-6 is recognized to be a highly versatile cytokine, with pleiotropic actions not only in immune cells, but also in other cell types, such as cells of the central nervous system (CNS). The first evidence implicating IL-6 in brain-related processes originated from its dysregulated expression in several neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. In addition, IL-6 was shown to be involved in multiple physiological CNS processes such as neuron homeostasis, astrogliogenesis and neuronal differentiation. The molecular mechanisms underlying IL-6 functions in the brain have only recently started to emerge. In this review, an overview of the latest discoveries concerning the actions of IL-6 in the nervous system is provided. The central position of IL-6 in the neuroinflammatory reaction pattern, and more specifically, the role of IL-6 in specific neurodegenerative processes, which accompany Alzheimer's disease, multiple sclerosis and excitotoxicity, are discussed. It is evident that IL-6 has a dichotomic action in the CNS, displaying neurotrophic properties on the one hand, and detrimental actions on the other. This is in agreement with its central role in neuroinflammation, which evolved as a beneficial process, aimed at maintaining tissue homeostasis, but which can become malignant when exaggerated. In this perspective, it is not surprising that 'well-meant' actions of IL-6 are often causing harm instead of leading to recovery.

Human cell toxicogenomic analysis of bromoacetic acid: a regulated drinking water disinfection by-product

The disinfection of drinking water is a major achievement in protecting the public health. However, current disinfection methods also generate disinfection by-products (DBPs). Many DBPs are cytotoxic, genotoxic, teratogenic, and carcinogenic and represent an important class of environmentally hazardous chemicals that may carry long-term human health implications. The objective of this research was to integrate in vitro toxicology with focused toxicogenomic analysis of the regulated DBP, bromoacetic acid (BAA) and to evaluate modulation of gene expression involved in DNA damage/repair and toxic responses, with nontransformed human cells. We generated transcriptome profiles for 168 genes with 30 min and 4 hr exposure times that did not induce acute cytotoxicity. Using qRT-PCR gene arrays, the levels of 25 transcripts were modulated to a statistically significant degree in response to a 30 min treatment with BAA (16 transcripts upregulated and nine downregulated). The largest changes were observed for RAD9A and BRCA1. The majority of the altered transcript profiles are genes involved in DNA repair, especially the repair of double strand DNA breaks, and in cell cycle regulation. With 4 hr of treatment the expression of 28 genes was modulated (12 upregulated and 16 downregulated); the largest fold changes were in HMOX1 and FMO1. This work represents the first nontransformed human cell toxicogenomic study with a regulated drinking water disinfection by-product. These data implicate double strand DNA breaks as a feature of BAA exposure. Future toxicogenomic studies of DBPs will further strengthen our limited knowledge in this growing area of drinking water research.

Interleukin 6 in autoimmune and inflammatory diseases: a personal memoir

In this review, the author discusses the research that led to the identification and characterization of interleukin 6 (IL-6), including his own experience isolating IL-6, and the roles this cytokine has on autoimmune and inflammatory diseases. The cDNAs encoding B-cell stimulatory factor 2 (BSF-2), interferon (IFN)-beta2 and a 26-kDa protein were independently cloned in 1986, which in turn led to the identification of each. To resolve the confusing nomenclature, these identical molecules were named IL-6. Characterization of IL-6 revealed a multifunctional cytokine that is involved in not only immune responses but also hematopoiesis, inflammation, and bone metabolism. Moreover, IL-6 makes significant contributions to such autoimmune and inflammatory diseases as rheumatoid arthritis (RA).IL-6 activates both the STAT3 and SHP2/Gab/MAPK signaling pathways via the gp130 signal transducer. F759 mice, which contain a single amino-acid substitution in gp130 (Y759F) and show enhanced STAT3 activation, spontaneously develop a RA-like arthritis as they age. F759 arthritis is dependent on CD4(+) T cells, IL-6, and IL-17A, and is enhanced by the pX gene product from human T cell leukemia virus 1 (HTLV-1). Arthritis development in these mice requires that the F759 mutation is present in nonhematopoietic cells, but not in immune cells, highlighting the important role of the interaction between nonimmune tissues and the immune system in this disease. Furthermore, this interaction is mediated by the IL-6 amplifier through STAT3 and NF-kappaB. Ultimately, this model may represent a general etiologic process underlying other autoimmune and inflammatory diseases. More importantly, the understanding of IL-6 has paved the way for new therapeutic approaches for RA and other autoimmune and inflammatory diseases.

Essential roles of IL-6 trans-signaling in colonic epithelial cells, induced by the IL-6/soluble-IL-6 receptor derived from lamina propria macrophages, on the development of colitis-associated premalignant cancer in a murine model

Activation of the IL-6/Stat3 via IL-6 trans-signaling plays an important role in the pathogenesis of inflammatory bowel disease. Colitis-associated cancer (CAC) is a large bowel cancer and occurs with long-standing inflammatory bowel disease. The role of the IL-6/Stat3 in the development of CAC has not been fully understood. We investigate whether IL-6 trans-signaling contributes to the development of CAC using a mouse colitis-associated premalignant cancer (CApC) model. Chronic colitis (CC) was induced in BALB/c mice using dextran sodium sulfate. CApC was induced by dextran sodium sulfate treatment to CC-affected mice. IL-6 expression was determined by quantitative RT-PCR and immunofluorescence staining in colon. Phospho-Stat3 expression was examined by Western blotting and immunofluorescence analysis. The expression of IL-6 receptors (i.e., the IL-6R alpha-chain and gp130) and tumor necrosis factor-alpha converting enzyme in the colon was examined by laser-capture microdissection and immunofluorescence staining. Soluble IL-6R alpha (sIL-6R alpha) was examined by Western blotting of epithelial cell-depleted colonic tissues. We also investigated whether a soluble gp130-Fc fusion protein could prevent CApC. IL-6 expression was increased in the colon of CC- and CApC-affected mice and was restricted to lamina propria-macrophages. The expression of IL-6R alpha and tumor necrosis factor-alpha converting enzyme was increased in the lamina propria CD11b-macrophages of CC-affected mice. sIL-6R alpha expression was also increased in these tissues. Reduced levels of IL-6R alpha generation were observed in the colonic epithelial cells of CC- and CApC-affected mice and were associated with the increased expression of gp130 and phospho-Stat3. Treatment with soluble gp130Fc significantly reduced the CApC. IL-6 trans-signaling in epithelial cells induced by macrophage-derived IL-6/sIL-6R alpha plays a crucial role in the development of CAC.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Zinc-gene interaction related to inflammatory/immune response in ageing

The pivotal role played by zinc-gene interaction in affecting some relevant cytokines (IL-6 and TNF-alpha) and heat shock proteins (HSP70-2) in ageing, successful ageing (nonagenarians) and the most common age-related diseases, such as atherosclerosis and infections, is now recognized. The polymorphisms of genes codifying proteins related to the inflammation are predictive on one hand in longevity, on the other hand they are associated with atherosclerosis or severe infections. Since the health life-span has a strong genetic component, which in turn also affected by nutritional factors like zinc, the association of these polymorphisms with innate immune response, zinc ion bioavailability and Metallothioneins (MT) homeostasis is an useful tool to unravel the role played by zinc-gene interactions in longevity, especially due to the inability of MT in zinc release in ageing and chronic inflammation. In ageing, this last fact leads to depressed innate immune response for host defence. In contrast, in very old age the inflammation is lower with subsequent more zinc ion bioavailability, less MT gene expression and satisfactory innate immunity. Therefore, the zinc-gene (IL-6, TNF-alpha, Hsp70-2) interactions, via MT homeostasis, are crucial to achieve successful ageing.

The molecular regulators of macrophage and granulocyte development. Role of MGI-2/IL-6

The development of a cell culture system for the in vitro cloning and clonal differentiation of normal hematopoietic cells made it possible to identify the proteins that regulate growth and differentiation of different hematopoietic cell lineages and the change in normal controls that produce leukemia. A model system with myeloid cells has identified different myeloid cell colony-inducing proteins, which we called MGI-1 (= CSF, including IL-3). There is another protein that we first described in 1976 and called MGI-2 in 1980 that induces differentiation of myeloid cells to macrophages or granulocytes without inducing the clonal growth of myeloid cells. The four CSF proteins and IL-1 induce the production of MGI-2 in myeloid cells and MGI-2 induces the production of GM-CSF. This shows the participation of MGI-2 in the network of interactions with different myeloid regulatory proteins. Using a monoclonal antibody to MGI-2, amino acid sequencing, and recombinant protein, we have shown in collaboration with the Genetics Institute that the major form of MGI-2 (MGI-2A) is IL-6. This shows that IL-6 is a myeloid cell differentiation inducing protein. The results also suggest new clinical potentials for MGI-2/IL-6.