Caspase-1-processed IL-1 family cytokines play a vital role in driving innate IL-17

The interleukin (IL)-1 cyokine family plays a vital role in inflammatory responses during infection and in autoimmune diseases. The pro-inflammatory cytokines, IL-1β and IL-18 are members of the IL-1 family that require cleavage by caspase-1 in the inflammasome to generate the mature active cytokines. Cells of the innate immune system, including γδ T cells and invariant natural killer T (iNKT) cells respond rapidly to invading pathogens by producing inflammatory cytokines, such as IFN-γ and IL-17. IL-1β or IL-18 in combination with IL-23 can induce IL-17 production by γδ T cells without T cell receptor (TCR) engagement. IL-1β and IL-23 can also synergize to induce IL-17 production by iNKT cells. Furthermore, CD4+ αβ effector memory T cells secrete IL-17 in response to IL-23 in combination with either IL-1β or IL-18, in the absence of any TCR stimulation. The early IL-17 produced by innate cells induces recruitment of neutrophils to the site of infection, stimulates local epithelial cells to secrete anti-microbial proteins, such as lipocalins and calgranulins, induces production of structural proteins important in tight junction stability, and promotes production of matrix metalloproteinases. Caspase-1 processed IL-1 family cytokines therefore play a vital role in the innate immune response and induction of IL-17 from innate immune cells which functions to fight infections and promote autoimmunity.     

C-reactive protein and coronary artery disease: influence of obesity,caloric restriction and weight loss

C reactive protein (CRP) values in blood are a good indicator of the likelihood of acute coronary and cerebral events in both healthy subjects and patients with coronary artery disease. This indicates that atherosclerotic lesions rich in inflammatory cells and cytokines are more likely to produce acute events either through vasospasm and/or thrombosis and also can be readily detected through elevations in CRP when measured using a high sensitivity assay (hsCRP). However the arterial wall is only one potential source of cytokines which induce CRP production. Fat cells also produce cytokines, in particular IL-6 which induces the synthesis of CRP by the liver. Obesity, especially abdominal obesity, is associated with elevations of hsCRP. This may be of pathogenic significance as CRP stimulates the uptake of LDL by macrophages, induces complement activation which may cause cellular damage in the artery, and enhances monocyte production of tissue factor, thus enhancing the risk of thrombosis. Caloric restriction and weight loss lowers IL-6 and CRP levels and may beneficially suppress an immune response. Whether particular dietary macronutrients or micronutrients alter IL-6 or CRP is unknown but this issue is clearly becoming more important.     

Toll-like receptor 4 and cytokine expression involved in functional immune response in an originally established porcine intestinal epitheliocyte cell line

To study the immune responses of porcine intestinal epithelial cells to gram-negative bacteria via toll-like receptors (TLRs), originally established porcine intestinal epitheliocyte (PIE) cells were treated with lipopolysaccharide (LPS) or swine-specific enterotoxigenic Escherichia coli (ETEC). Real-time quantitative PCR revealed that PIE cells expressed TLR1-9 and MD-2 mRNAs, preferentially expressed TLR4/MD-2. Immunostaining of PIE cells revealed that TLR4 was precisely expressed in PIE cells at the protein level. PIE cells treated with LPS had up-regulated expression of several TLRs (TLR2, 3, 4, 5 and 8), type 1 helper T (Th1) cytokines (interleukin (IL)-1alpha, IL-1beta, IL-6, IL-15, 18, leukemia inhibitory factor (LIF), and interferon (IFN)-beta), and chemokines (monocyte chemoattractant protein (MCP)-1 and IL-8). ETEC enhanced the expression of TLR2, Th1 type cytokines (IL-1alpha, IL-12p35 and IL-6) and chemokines (MCP-1 and IL-8). These results indicate that PIE induces inflammatory responses by up-regulating Th1 cytokines and chemokines in response to LPS or ETEC, suggesting that PIE is a useful cell line for studying inflammatory responses via TLR4/MD-2 in intestinal epithelial cells.     

Intracellular Delivery of Lipopolysaccharide Induces Effective Th1-Immune Responses Independent of IL-12

Lipopolysaccharide (LPS) is responsible for many of the inflammatory responses and pathogenic effects of Gram-negative bacteria, however, it also induces protective immune responses. LPS induces the production of inflammatory cytokines such as TNF-α, IL-6, and IL-12 from dendritic cells (DCs) and macrophages. It is thought that IL-12 is required for one of the protective immune responses induced by LPS, the T helper 1 (Th1)-immune response, which include the production of IFN-γ from Th1cells and IgG2c class switching. Here, we clearly demonstrate that intracellular delivery of LPS by LPS-formulated liposomes (LPS-liposomes) does not induce the production of inflammatory cytokines from DCs, but enhances Th1-immune responses via type-I IFNs, independent of IL-12. Collectively, our results strongly suggest that LPS-liposomes can effectively induce Th1-immune responses without inducing unnecessary inflammation, and may be useful as an immune adjuvant to induce protective immunity.     

Ciliary neurotrophic factor induces acute-phase protein expression in hepatocytes.

During inflammatory states, hepatocytes are induced to synthesize and secrete a group of proteins called acute-phase proteins. It has recently been shown that besides interleukin-6 (IL-6), related cytokines such as leukemia inhibitory factor, oncostation M and interleukin-11 are also mediators of the hepatic acute-phase response. All these mediators belong to the hematopoietic family of alpha-helical cytokines. Here we show that an additional member of this cytokine family, ciliary neurotrophic factor (CNTF), induces the hepatic acute-phase protein genes haptoglobin, alpha 1-antichymotrypsin, alpha 2-macroglobulin and beta-fibrinogen in human hepatoma cells (HepG2) and in primary rat hepatocytes with a time course and dose-response comparable with that of IL-6. Our next aim was to define the receptor components used by CNTF on hepatic cells. Using a cell-free binding assay we exclude that CNTF binds to the 80 kDa IL-6 receptor, a protein with significant homology to the CNTF receptor which has recently been cloned from neuroblastoma cells. In human hepatoma cells (Hep3B) which lack the leukemia inhibitory factor receptor, CNTF was not able to induce acute-phase protein synthesis, indicating that this receptor protein may be part of the functional CNTF receptor on hepatic cells.     

Identification of anaplastic lymphoma kinase as a receptor for the growth factor pleiotrophin

Pleiotrophin (PTN) is a secreted growth factor that induces neurite outgrowth and is mitogenic for fibroblasts, epithelial, and endothelial cells. During tumor growth PTN can serve as an angiogenic factor and drive tumor invasion and metastasis. To identify a receptor for PTN, we panned a phage display human cDNA library against immobilized PTN protein as a bait. From this we isolated a phage insert that was homologous to an amino acid sequence stretch in the extracellular domain (ECD) of the orphan receptor tyrosine kinase anaplastic lymphoma kinase (ALK). In parallel with PTN, ALK is highly expressed during perinatal development of the nervous system and down-modulated in the adult. Here we show in cell-free assays as well as in radioligand receptor binding studies in intact cells that PTN binds to the ALK ECD with an apparent Kd of 32 +/- 9 pm. This receptor binding is inhibited by an excess of PTN, by the ALK ECD, and by anti-PTN and anti-ECD antibodies. PTN added to ALK-expressing cells induces phosphorylation of both ALK and of the downstream effector molecules IRS-1, Shc, phospholipase C-gamma, and phosphatidylinositol 3-kinase. Furthermore, the growth stimulatory effect of PTN on different cell lines in culture coincides with the endogenous expression of ALK mRNA, and the effect of PTN is enhanced by ALK overexpression. From this we conclude that ALK is a receptor that transduces PTN-mediated signals and propose that the PTN-ALK axis can play a significant role during development and during disease processes.     

IL-8 expression in malignant melanoma: implications in growth and metastasis

This review article has described briefly studies supporting the concept that IL-8 expression and its regulation by inflammatory cytokines like IL-1 may play an important role in controlling the phenotypes associated with melanoma progression and metastasis. It is clear from the experiments presented here that IL-8 is an important autocrine multifunctional cytokine that modulates melanoma/cell proliferation, migration by induction of extracellular matrix degradation enzymes and induces neovascularization, all of which are critical for melanoma growth and metastasis. In addition, their expression in melanoma tumor specimens suggests an association between IL-8 expression and tumor aggressiveness. Further, inflammatory cytokines produced by either tumor cells or stromal cells may regulate IL-8 expression, which can control melanoma growth and enhance our current knowledge regarding melanoma progression and metastasis. Understanding these events and their significance will allow us to design novel therapeutic approaches for treatment of melanoma.     

Regulation of the inflammatory response in asthma by mast cell products

In airways, mast cells lie adjacent to nerves, blood vessels and lymphatics, which highlights their pivotal importance in regulating allergic inflammatory processes. In asthma, mast cells are predominantly activated by IgE receptor cross linking. In response to activation, preformed mediators that are stored bound to proteoglycans, for example, TNF-alpha, IL-4, IL-13, histamine, tryptase and chymase, are released. New synthesis of arachidonic acid metabolites (leukotriene C4 (LTC4), leukotriene B4 (LTB4) and prostaglandin D2 (PGD2)) and further cytokines is stimulated. Mediators from degranulating mast cells are critical to the pathology of the asthmatic lung. Mast cell proteases stimulate tissue remodelling, neuropeptide inactivation and enhanced mucus secretion. Histamine stimulates smooth muscle cell contraction, vasodilatation and increased venular permeability and further mucus secretion. Histamine induces IL-16 production by CD8+ cells and airway epithelial cells; IL-16 is an important early chemotactic factor for CD4+ lymphocytes. LTC4, LTB4 and PGD2 affect venular permeability and can regulate the activation of immune cells. The best characterized mast cell cytokine in asthmatic inflammation is TNF-alpha, which induces adhesion molecules on endothelial cells and subsequent transmigration of inflammatory leucocytes. IL-13 is critical to development of allergic asthma, although its mode of action is less clear.     

IL-26 Is Overexpressed in Rheumatoid Arthritis and Induces Proinflammatory Cytokine Production and Th17 Cell Generation

Interleukin-26 (IL-26), a member of the IL-10 cytokine family, induces the production of proinflammatory cytokines by epithelial cells. IL-26 has been also reported overexpressed in Crohn''s disease, suggesting that it may be involved in the physiopathology of chronic inflammatory disorders. Here, we have analyzed the expression and role of IL-26 in rheumatoid arthritis (RA), a chronic inflammatory disorder characterized by joint synovial inflammation. We report that the concentrations of IL-26 are higher in the serums of RA patients than of healthy subjects and dramatically elevated in RA synovial fluids compared to RA serums. Immunohistochemistry reveals that synoviolin⁺ fibroblast-like synoviocytes and CD68⁺ macrophage-like synoviocytes are the main IL-26-producing cells in RA joints. Fibroblast-like synoviocytes from RA patients constitutively produce IL-26 and this production is upregulated by IL-1-beta and IL-17A. We have therefore investigated the role of IL-26 in the inflammatory process. Results show that IL-26 induces the production of the proinflammatory cytokines IL-1-beta, IL-6, and tumor necrosis factor (TNF)-alpha by human monocytes and also upregulates the expression of numerous chemokines (mainly CCL20). Interestingly, IL-26-stimulated monocytes selectively promote the generation of RORgamma t⁺ Th17 cells, through IL-1-beta secretion by monocytes. More precisely, IL-26-stimulated monocytes switch non-Th17 committed (IL-23R⁻ or CCR6⁻ CD161⁻) CD4⁺ memory T cells into Th17 cells. Finally, synovial fluids from RA patients also induce Th17 cell generation and this effect is reduced after IL-26 depletion. These findings show that IL-26 is constitutively produced by RA synoviocytes, induces proinflammatory cytokine secretion by myeloid cells, and favors Th17 cell generation. IL-26 thereby appears as a novel proinflammatory cytokine, located upstream of the proinflammatory cascade, that may constitute a promising target to treat RA and chronic inflammatory disorders.     

Anti-apoptotic signaling of pleiotrophin through its receptor,anaplastic lymphoma kinase

The secreted growth factor pleiotrophin (PTN) can induce mitogenesis in cells that express the receptor for this growth factor, anaplastic lymphoma kinase (ALK). Here we examine the ability of PTN to produce anti-apoptotic signals. We demonstrate that PTN is a survival factor for SW-13 epithelial cells and show that ribozyme-mediated depletion of ALK from SW-13 cells abolishes this effect of PTN. Furthermore, in serum-starved NIH3T3 fibroblasts PTN prevents apoptosis (measured by annexin V staining) with an EC(50) of 0.2 ng/ml and induces cell growth at higher concentrations of PTN. A polyclonal antibody against the PTN ligand-binding domain of the ALK receptor (alpha-LBD) was a partial agonist for ALK in NIH3T3 cells. This alpha-LBD antibody showed high agonist activity for anti-apoptosis (56 +/- 9% relative to PTN), low agonist activity for cell growth (21 +/- 1% relative to PTN), and was an antagonist of PTN-induced cell growth (61 +/- 2% inhibition). Both MAP kinase and phosphatidylinositol (PI) 3-kinase cascades in NIH3T3 cells were activated by PTN, and this effect persisted for up to 3 h. Surprisingly, the anti-apoptotic effect of PTN was completely blocked by the MAP kinase inhibitor UO126, but was not affected by the PI 3-kinase inhibitor LY294002. In contrast, PTN-dependent cell growth required both MAPK and PI 3-kinase activity. We conclude that anti-apoptotic signaling of PTN through ALK in NIH3T3 fibroblasts is via the MAP kinase pathway.     

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.     

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.     

Coordination between TLR9 signaling in macrophages and CD3 signaling in T cells induces robust expression of IL-30

IL-30, the p28 subunit of IL-27, interacts with EBV-induced gene 3 to form IL-27, which modulates both proinflammatory and anti-inflammatory responses during autoimmune or infectious disease. It also acts as a natural antagonist of gp130, thereby attenuating the signals of other gp130-associated cytokines. IL-30 regulation via LPS has been reported by others, but the intercellular communication that induces IL-30 expression is unknown. In this study, we show that treatment with anti-CD3/CD28 Abs plus CpG oligodeoxynucleotides induces robust expression of IL-30, whereas either treatment alone induces only low expression of IL-30. This observation in vitro mirrors the murine model in which administration of CpG under inflammatory conditions in vivo induces IL-30 expression. This robust induction of IL-30 occurs through the coordination of helper CD4(+) T cells and innate immune cells (e.g., macrophages) and, to a lesser degree, B cells via the CD40/CD154 signaling pathway. These findings reveal a previously unrecognized mechanism that integrates signaling pathways from T cells and macrophages at the cellular level to induce IL-30 expression.     

IL-1, IL-6, and PDGF mRNA expression in alveolar cells following stimulation with a tobacco-derived antigen.

To test the hypothesis that inflammatory cytokine production might be an early event in the development of the disease associated with smoking, we used alveolar cells from healthy nonsmokers stimulated with TGP as a model system. TGP, a phenol-rich glycoprotein which is present in tobacco leaves and cigarette smoke condensate, activates the immune system. It stimulates polyclonal B cell differentiation, induces primarily an IgE response, and activates human leukocytes to produce IL-1. Using in situ nucleic acid hybridization we show that the steady-state levels of IL-1 alpha, IL-1 beta, IL-6, platelet-derived growth factor (PDGF)-A, and PDGF-B mRNAs are consistently elevated in the alveolar cells of all donors following TGP stimulation. The kinetics of mRNA expression suggest that IL-1 alpha and IL-1 beta mRNAs are independently regulated in alveolar cells, while the regulation of PDGF-A and PDGF-B mRNA seems to be similar. The activated cells also synthesize elevated levels of IL-1 and IL-6. These findings lend support to the suggestion that some clinical consequences of smoking might be initiated and enhanced by the production of inflammatory cytokines. Moreover, IL-6 could also activate a polyclonal B cell response, which could lead to the synthesis of autoantibodies and thus cause immune-mediated tissue injury.     

Interleukin-25 Expressed by Brain Capillary Endothelial Cells Maintains Blood-Brain Barrier Function in a Protein Kinase C?-dependent Manner

Interleukin (IL)-25, a member of the IL-17 family of cytokines, is expressed in the brains of normal mice. However, the cellular source of IL-25 and its function in the brain remain to be elucidated. Here, we show that IL-25 plays an important role in preventing infiltration of the inflammatory cells into the central nervous system. Brain capillary endothelial cells (BCECs) express IL-25. However, it is down-regulated by inflammatory cytokines, including tumor necrosis factor (TNF)-α, IL-17, interferon-γ, IL-1β, and IL-6 in vitro, and is also reduced in active multiple sclerosis (MS) lesions and in the inflamed spinal cord of experimental autoimmune encephalomyelitis, an animal model of MS. Furthermore, IL-25 restores the reduced expression of tight junction proteins, occludin, junction adhesion molecule, and claudin-5, induced by TNF-α in BCECs and consequently repairs TNF-α-induced blood-brain barrier (BBB) permeability. IL-25 induces protein kinase Cϵ (PKCϵ) phosphorylation, and up-regulation of claudin-5 is suppressed by PKCϵ inhibitor peptide in the IL-25-stimulated BCECs. These results suggest that IL-25 is produced by BCECs and protects against inflammatory cytokine-induced excessive BBB collapse through a PKCϵ-dependent pathway. These novel functions of IL-25 in maintaining BBB integrity may help us understand the pathophysiology of inflammatory brain diseases such as MS.