Interleukin-1 and its biologically related cytokines

Interleukin-1 receptor antagonist: discovery, structure and properties

Interleukin-1 receptor antagonist (IL-1ra) is a recently-described member of the IL-1 family. This unique human protein has 30% amino acid sequence homology to IL-1 beta and binds to human types I and II IL-1 receptors without apparent cellular activation. IL-1ra blocks the in vitro stimulatory effects of IL-1 on thymocytes, fibroblasts, endothelial cells and bone cells. In addition, IL-1ra is a potent inhibitor of the inflammatory effects of IL-1 in vivo. IL-1ra represents the first naturally-occurring cytokine inhibitor and may be important in modulating IL-1 effects in both normal and abnormal physiology.

Augmentation of host defense against bacterial infection pretreated intraperitoneally with an alpha-glucan RBS in mice

Protection against Listeria monocytogenes and Escherichia coli in mice was enhanced by an intraperitoneal (i.p.) administration of polysaccharide "RBS". Peritoneal macrophages from mice administered i.p. with 30 mg/kg doses of RBS 4 days earlier exhibited increased scavenger functions as assessed by in vivo phagocytosis, in vitro intracellular killing and generation of superoxide anion. When cytokine production of the macrophages was assessed by biological assay and Northern blotting analysis, interleukin (IL)-1 production and IL-1 alpha gene expression were significantly increased in macrophages from RBS-treated mice. On the other hand, tumor necrosis factor (TNF) alpha gene was expressed in macrophages from RBS-treated mice at a much reduced level as compared with those in mice treated i.p. with Corynebacterium parvum on 4 days earlier. In correlation with expression of TNF gene in the macrophages, RBS-treated mice were less susceptible to the lethal toxicity of LPS than C.parvum-treated mice. In RBS-treated mice, in vivo elimination of bacteria was enhanced at the early phase of infection with L.monocytogenes or E.coli, resulting in augmentation of host defense against these bacterial infection. These results suggest that adequately enhanced activities of macrophages acting as scavenger phagocytes play important roles in the enhanced resistance against bacteria in mice treated i.p. with RBS.

mRNA phenotyping for studying gene expression in small numbers of cells: platelet-derived growth factor and other growth factors in wound-derived macrophages

The understanding of biologic and pathophysiologic processes in lung is aided by a technique for ascertaining the transcriptional phenotype of small numbers of cells examined in vivo. The mRNA phenotyping procedure consists of scaled-down methods for isolating mRNA from small numbers of cells, followed by reverse transcription of the RNA and specifically primed amplification of the cDNA by the polymerase chain reaction. We show an example of the use of the technique in a study of expression of platelet-derived growth factor and other growth factor genes in macrophages isolated from wound cylinders implanted in mice. With this technique, the transcriptional phenotype of purified normal lung epithelial and mesenchymal cells, macrophages, or cells obtained from lavaged lungs or punch biopsy specimens can be examined as a rapid first step in understanding molecular processes in the lung.

Transcription, not synthesis, of interleukin-1 and tumor necrosis factor by complement

Stimulation of interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF alpha) production was studied during in vitro hemodialysis (HD) of whole blood using cuprammonium (Cup) or polysulfone (PS) dialyzers. In the absence of LPS, circulation of whole blood for two hours through Cup or PS dialyzers was not sufficient to induce production of IL-1 beta or TNF alpha in peripheral blood mononuclear cells (PBMC) during subsequent 24 hour culture. However, compared to freshly isolated cells, post-HD PBMC were primed to produce more IL-1 beta and TNF alpha when subsequently stimulated with LPS. Despite the lack of spontaneous monokine synthesis after HD, we observed transcription of mRNA coding for IL-1 beta and TNF alpha after two hours of LPS-free HD. When compared to levels of mRNA induced by 5 ng/ml LPS (100%), Cup induced 27 +/- 6% whereas PS did not induce detectable transcription of IL-1 beta. In the case of TNF alpha mRNA, Cup induced 26 +/- 8% and PS 13 +/- 3%. Recombinant C5a induced mRNA for IL-1 beta in PBMC without detectable IL-1 beta protein synthesis. We conclude that transcription of mRNA for IL-1 beta and TNF alpha during HD is primarily caused by complement activation by Cup, but that LPS or other factors are required for translation of IL-1 beta and TNF alpha mRNA transcribed during HD.

Interleukin 1- and tumor necrosis factor-stimulation of prostaglandin E2 synthesis in MDCK cells, and potentiation of this effect by cycloheximide

The effects of interleukin (IL)-1 alpha, IL-1 beta and TNF alpha on prostaglandin-E2 synthesis in Madin-Darby canine kidney (MDCK) cells were investigated. IL-1 beta time- and dose-dependently stimulated prostaglandin-E2 synthesis. While TNF alpha produced a comparatively small but significant stimulation of PGE2 release, coincubation of IL-1 beta with TNF alpha produced a marked synergistic stimulation of PGE2 release. The effect of IL-1 beta and of IL-1 beta and TNF alpha was apparent as early as after 2 h of incubation. The enhanced PGE2 synthesis was inhibited by indomethacin as well as actinomycin D, while cycloheximide surprisingly potentiated PGE2 synthesis in response to both IL-1 beta and TNF alpha. IL-1 alpha alone was ineffective in stimulating a significant release of PGE2 at concentrations as high as 10 nM. However, it also showed a marked synergistic interaction with TNF alpha in stimulating PGE2 release.

Interleukin 1: the first interleukin

The name 'interleukin' and the designation of interleukin 1 (IL-1) derived from the Second International Lymphokine Workshop held in Switzerland in 1979. Since then interest in the original interleukin (IL-1) has increased exponentially as measured by the numbers of publications and meetings. The main reasons for this can be seen in the accompanying centrefold. The perception of IL-1 as a biological mediator in every organ system has attracted scientists from widely different backgrounds into this area and a steady succession of important and often surprising insights into IL-1 biology has ensured that interest has been sustained at a high level. This overview of the biology of IL-1 on the tenth anniversary of its turbulent life has been compiled by Franco di Giovine and Gordon Duff. It is of necessity selective and biased towards human IL-1 and begins with some general points (mainly cautionary) as a backdrop to the centrefold.

Inflammatory bowel disease revisited: newer drugs

The development of new drug therapy is an evolutionary process progressing from clinical success with current treatments through an understanding of interactions in the immune and inflammatory events that culminate in the tissue injury of IBD. The basic immunoinflammatory response is reviewed, with identification of the recognized and potential sites of activity of current therapies. Potential sites and implications for future interventions by newer therapies are discussed as we anticipate the discovery of the etiology and eventual cure for ulcerative colitis and Crohn's disease.

Structure-function relationship of interleukin-1 giving new insights for its therapeutic potential

The pleiotropic activities of IL-1 have fostered a series of studies on the structure-function relationship in these proteins. In fact, the attempt to dissociate different biological functions of IL-1 should simplify its therapeutic use. About human IL-1 beta, which has been more extensively studied in this respect, enzymatic cleavage of the precursor protein to generate the mature polypeptide appears necessary for its full biological activity. The almost complete integrity of the mature IL-1 beta protein is also required for its ability to bind to the receptor and trigger cellular functions. However, by the use of monoclonal antibodies and recombinant or synthetic peptides, it has been possible to map some IL-1 beta regions important for different activities. Both N-terminal and C-terminal fragments are important for receptor binding. A domain around amino acids 187-204 is apparently involved in the hyperalgesic effects of IL-1 beta. Finally, the fragment in position 163-171 appears to be responsible for a restricted series of the IL-1 beta activities, mainly directed to the immune system, although irrelevant for inflammation-related effects and unable of binding to the IL-1R. It is thus possible, within the sequence of a cytokine, to isolate selectively active domains. This will give us new tools for new therapeutic approaches. Thus, IL-1 might be the prototype of a new generation of cytokines developed with the goal of stimulating specific biological activities without activating the cascade effects which are typical for many cytokines.

Mononuclear phagocytes and eicosanoids: aspects of their synthesis and biological activities

Mononuclear phagocytes convert arachidonic acid and other unsaturated fatty acids from intracellular sources to a variety of oxygenated metabolites such as prostaglandins and leukotrienes which are secreted into the surrounding medium. Other oxidative products such as hydroxylinoleic acids are reacylated into cellular constituents. The underlying metabolic pathways are activated by numerous stimuli of exogenous or endogenous origin. Depending on the state of activation and cell differentiation, the organ of origin and the nature of the stimulus used, macrophages elaborate a distinct spectrum of oxidative arachidonic acid metabolites. The contribution of these metabolites to the proinflammatory properties of macrophages is twofold: As autocrine signals they modulate the synthesis of diverse macrophage products and they influence cellular functions of other cells such as T-lymphocytes.

The therapeutic potential of interleukin-1 beta in the treatment of chemotherapy- or radiation-induced myelosuppression and in tumor therapy

In vivo administration of rHuIL-1 beta selectively enhanced the recovery from granulocytopenia and thrombocytopenia caused by sublethal irradiation or 5-FU treatment. Granulopoiesis and thrombopoiesis were stimulated by rHuIL-1 beta in a dose-dependent manner at doses ranging from 0.1 to 100 micrograms/kg. In this study, we have observed IL-1 to induce at least two distinct types of hematopoietic growth factors in vivo, namely GM-CSF and a thrombopoietin-like factor. Various kinds of CSFs alone did not stimulate colony formation of primitive hematopoietic progenitor cells obtained from 5-FU treated mice. However, the pretreatment of primitive hematopoietic progenitor cells with IL-1 in vitro or in vivo for 5 days accelerated the recovery of a cell population which respond to several types of CSFs. These data suggest that IL-1 may be useful clinically to enhance the recovery of granulocytes and platelets in myelosuppressed patients. In addition, we observed that rHuIL-1 beta is directly cytostatic for certain tumor cells in vitro. Intratumoral or subcutaneous injection of rHuIL-1 beta caused regression of a subcutaneous murine sarcoma by augmenting host antitumor responses. Together with the profound effects on hematopoiesis, these results point to potentially important uses of IL-1 beta in treatment of disease.

Interleukin-1 alpha: its possible roles in cancer therapy

Our studies on recombinant human IL-1 alpha polypeptide were summarized with respect to molecular cloning, production, quantitative assay systems, antitumor activity, myelorestorative activity and augmentation of host resistance to infections. Recombinant human IL-1 alpha (18 kDa) was produced through the expression of the cloned human IL-1 alpha cDNA in Escherichia coli and purified to an endotoxin-free homogeneous polypeptide. The human IL-1 alpha inhibited dose-dependently the growth of syngeneic murine tumors transplanted in mice and completely regressed the tumors in some cases, and its antitumor activity was significantly enhanced in combination with indomethacin. The human IL-1 alpha accelerated the recovery of the numbers of peripheral leukocytes and neutrophils in a dose-dependent manner at a dose as low as 10 ng/mouse/day in myelosuppressed mouse model produced by administering anticancer chemotherapeutic drugs. The myelorestorative effect of IL-1 alpha was observed not only on leukocytes/neutrophils, but also on platelets in myelosuppressed mice. In addition, the human IL-1 alpha markedly augmented dose-dependently resistance of normal and leukopenic mice to various microbial infections. These results suggested that recombinant human IL-1 alpha might be useful for cancer therapy from the viewpoints of improving adverse effects such as myelosuppression caused by chemotherapy and/or radiation therapy and preventing infections. In addition, use of IL-1 alpha may permit more intensive chemo- and radiation therapies using higher doses. Finally, the antitumor activity of the IL-1 alpha itself may play an important role.

Multiple charge isomers of human recombinant interleukin-1 beta

Human interleukin-1 beta (rhuIL-1 beta), obtained by DNA recombinant technology, was radiolabelled. Its isoelectric properties were determined by various analytical techniques such as high-voltage ultrathin layer isoelectric focusing (IEF) and chromatofocusing. The rhuIL-1 beta molecule had a molecular mass of 18 kDa, as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. When examined by IEF on a polyacrylamide gel of 1 mm thickness in the pH range of 3.5-9.5, it was resolved into two broad bands appearing in the pH range of 6.2-5.8 and 5.5-5.2. Each of the two bands was further resolved into multiple bands when electrofocused on (i) a thinner gel of 0.5 mm thickness and (ii) a narrower pH range of 5-8. Upon chromatofocusing in a liquid column, it was possible to isolate various charged components of rhuIL-1 beta. However, all these components reacted to the antiserum to rhuIL-1 beta and displayed a molecular mass of 18 kDa suggesting the charge heterogeneity of rhuIL-1 beta.

The endogenous pyrogens in host-defense interactions

Soluble factors produced by activated macrophages serve to marshal host defenses against infection, injury, or inflammation, but they may also cause chronic inflammation or even lethal shock. Suppressing or enhancing such cytokine functions has important therapeutic potential in, respectively, chronic inflammatory and immunologically deficient states.

The control of antibody production by immunomodulatory molecules

Regulation of human B cell responses is a complex process that involves the activities of a variety of cytokines. There are important differences between the regulation of human and murine B lymphocytes, especially with regard to the action of IL-2. In humans, IL-2 appears to play a central role in regulating B cell activation, proliferation, and differentiation, thereby facilitating the production of immunoglobulins of all isotypes. A wide array of additional cytokines can amplify antibody production, but none appears to be able to do this in the absence of IL-2; moreover, none appears to enhance the production of only a single isotype of immunoglobulin. Beyond the positive influences of cytokines on B cell responses, at least 2 cytokines, IL-4 and TGF beta, suppress B cell proliferation and differentiation. Inhibition by each of these cytokines can be overcome by specific cytokines that provide positive signals to B cells. Antibody production is thus regulated by a complex array of cytokines with complementary or opposing effects that may be exerted at different stages of B cell responsiveness. Whether specific subpopulations of B cells exhibit unique cytokine requirements for differentiation has not been clearly delineated, nor is it clear whether autoantibody production is uniquely regulated by cytokines. Additional information concerning the role of cytokines in the regulation of B cell function should provide further insight not only into normal antibody production, but also into potential dysregulation that leads to autoimmunity.

Characterization of a subclone (D10S) of the D10.G4.1 helper T-cell line which proliferates to attomolar concentrations of interleukin-1 in the absence of mitogens

Most studies have shown that interleukin-1 (IL-1) acts as a helper or co-stimulator in T-lymphocyte activation and proliferation by mitogens or antigens. We describe here a stable subclone (D10S) of the murine D10.G4.1 helper T-cell which proliferates to subfemtomolar (attomolar) concentrations of IL-1 beta or alpha in the absence of mitogens. D10S cells have been maintained in culture for over two years without splenic cell feeder layers nor antigen stimulation. Detection of proliferation can be made by either uptake of tritiated thymidine at 72 h or in 48 h by a colorimetric assay which measures mitochondrial dehydrogenases; the latter assay is rapid and inexpensive. D10S cells are distinct from the parent clone D10.G4., which requires mitogens for IL-1 activity. IL-1-induced proliferation is independent of the elaboration of IL-2, IL-4, or IL-6, although these cells proliferate to these lymphokines at considerably higher concentrations when compared to IL-1. The D10S cells proliferate in direct correlation to the duration of IL-1 presence in the culture. We found no evidence that IL-1 induced more IL-1 in these cells. The subclone is highly specific for IL-1: proliferation was not observed to endotoxin, human or murine interferon-gamma (IFN gamma), tumor necrosis factor (TNF), lymphotoxin, or granulocyte-macrophage colony stimulating factor (GM-CSF). There was no suppressive effect of transforming growth factor (TGF beta). Only at high concentrations (100 ng/ml) did IL-6 induce proliferation. We conclude that this stable, feeder layer-free cell line is highly sensitive to IL-1 which acts as a direct stimulant for these cells; they are also useful for bioassays as well as the study of IL-1 receptors as described in the accompanying paper.

Release of interleukin-1 beta associated with potent cytocidal action of staphylococcal alpha-toxin on human monocytes

The pathogenetic relevance of Staphylococcus aureus alpha-toxin in humans has been debated because human cells have been thought to display a natural resistance toward the cytotoxic action of this cytolysin. Following our previous demonstration that human platelets represent sensitive targets for toxin attack, we have now identified monocytes as a second, highly vulnerable human cell species that succumb to attack by low doses (20 ng/ml) of alpha-toxin. The cytotoxic action of alpha-toxin is reflected in a rapid depletion of cellular ATP that is essentially complete within 30 min. The presence of human plasma proteins affords some protection of monocytes against the action of the toxin. In 10% autologous serum, ATP depletion commences at 80 to 300 ng of toxin per ml. Subcytolytic doses stimulate the release of tumor necrosis factor alpha, a process that is slightly accentuated in the presence of 50% serum. Cytocidal toxin doses unfailingly cause the release of large amounts of interleukin-1 beta from cultured cells, with levels of this monokine generally exceeding 10 ng/ml in the cell supernatants 60 min after application of toxin. Initial evidence suggests that this is due to processing of intracellular interleukin-1 rather than to de novo synthesis of the cytokine. All noted effects are abrogated in the presence of a neutralizing monoclonal antibody against alpha-toxin. Through its capacity to provoke cytokine release from monocytes and its attack on platelets, alpha-toxin may initiate cellular events that are relevant to the pathogenesis of staphylococcal infection.

Antibodies to cachectin/tumor necrosis factor reduce interleukin 1 beta and interleukin 6 appearance during lethal bacteremia

Cytokines secreted in response to invading micro-organisms are important mediators of detrimental hemodynamic and metabolic changes in the host. To test whether cachectin/TNF plays a role in triggering release of other cytokines in the setting of infection, anesthetized baboons were passively immunized against systemic cachectin/TNF before infusion of a LD100 dose of live Escherichia coli. Bacteremia led to significant increases in circulating levels of cachectin/TNF, IL-1 beta, and IL-6. Although bacterial endotoxin/lipopolysaccharide is a potent stimulus for the synthesis and release of IL-1 and IL-6 in vitro, specific neutralization of cachectin/TNF in vivo with mAb pretreatment significantly attenuated both the IL-1 beta and the IL-6 responses despite fulminant overwhelming bacteremia. These data suggest that cachectin/TNF is essential for the initiation or amplification of IL-1 and IL-6 release during lethal gram-negative septic shock syndrome.

Studies on IL-1 receptors on D10S T-helper cells: demonstration of two molecularly and antigenically distinct IL-1 binding proteins

Receptor binding studies were performed on the interleukin-1 (IL-1) sensitive T-helper cell line D10S, a stable line which proliferates to subfemtomolar concentrations of IL-1 in the absence of mitogens. IL-1 binds in a specific and saturable manner and Scatchard analysis at 4 degrees C reveals one class of binding affinity. On D10S cells, the Kd for IL-1 is 227 pM +/- 80, with 11,000 (range 3,300 to 23,800) sites per cell. EL4.6.1 cells, which are less sensitive to IL-1, bind with a single class of high affinity sites (55 pM; 4,000 sites). D10S cells incubated 18 h with IL-1 display reduced IL-1 receptor (IL-1R) numbers and affinities, consistent with reduced (75%, p less than 0.005) proliferation to subsequent IL-1; preincubation with IL-4 increases the number of IL-1R which is associated with increased (200%, p less than 0.001) proliferation to IL-1. The molecular mass of the major (80 kD) IL-1R binding [125I]IL-1 alpha on D10S cells was consistently observed at 73 kD as compared to the 80 kD molecule on the EL4 cells. On the other hand, crosslinking studies with [125I]IL-1 beta on D10S cells revealed a novel 46 kD band on gradient SDS-PAGE corresponding to a binding protein of 29 to 30 kD, which is antigenically distinct from the 80 kD IL-1R. Crosslinking of D10S or EL4 cells at 4 degrees C in the presence of phytohemagglutinin (PHA) and labeled IL-1 enhanced the appearance of the 30 kD IL-1 binding protein. The findings are consistent with a two-chain model for the IL-1R, although Scatchard analysis did not consistently indicate two classes of affinities. IL-1 binding to the 80 kD protein may form a heteroduplex with the 30 kD IL-1R which could account for the presence of the 120 to 130 kD IL-1 crosslinked proteins observed by several investigators.

Interleukin-1-induced anorexia in the rat. Influence of prostaglandins

The anorexia associated with acute and chronic inflammatory or infectious conditions is poorly understood. Our objectives were to explore the anorexigenic effects of interleukin-1 (IL-1) in the rat. Recombinant human (rh) IL-1 beta, murine (rm) IL-1 alpha and to a lesser extent rhIL-1 alpha significantly reduced food intake at greater than or equal to 4.0 micrograms/kg i.p. but not at lower doses, in young (200-250 g) meal-fed rats on chow diets. The anorexic effect appears to be mediated by prostaglandins since pretreatment with ibuprofen completely blocked it, and a fish oil based diet abolished it, in comparison to corn oil or chow diets. Fish oil feeding also decreased basal and IL-1 stimulated prostaglandin E2 production by tissues in vitro (liver, brain, peritoneal macrophages) and in the whole body. Constant intravenous infusions of lower doses of IL-1 also diminished food intake, though intravenous boluses did not (reflecting rapid renal clearance). Chronic daily administration of IL-1 caused persistent inhibition of food intake for 7-17 d in chow and corn oil fed rats, but had no effect in fish oil fed rats. There was an attenuation of the effect (tachyphylaxis) after 7 d in corn oil and chow fed rats, but slowed weight gain and lower final weights were observed after 17-32 d of daily IL-1. Old (18-20 mo Fisher 344) rats showed less sensitivity to IL-1 induced anorexia. In conclusion, IL-1 is anorexigenic in the rat, but this is influenced by the structural form of IL-1, the route and chronicity of administration, the source of dietary fat, and the age of the animal. The ability of prior fat intake to influence the anorexic response to IL-1 represents a novel nutrient-nutrient interaction with potential therapeutic implications.