Purification and characterization of a 26-kDa competitive inhibitor of interleukin 1

From supernatants to cytokines: a personal view on the early history of IL-1, IL-1Ra, TNF and its inhibitor in rheumatology

Long-term cell cultures developed early in the twentieth century allowed identification in their supernatants of biological mediators subsequently defined as migration factors, interferons, lymphokines, monokines, cytokines and interleukins. In rheumatology, early in the 1930s, synovial cell cultures revealed two major distinct populations, i.e. synovial fibroblasts and monocyte-macrophages. Discovery of the interstitial collagenase (MMP-1) and its role in tissue destruction, such as in rheumatoid arthritis (RA), raised the question of the cellular source for this enzyme. My personal interest in the field was driven by the lack of understanding for the link between tissue destruction and immunology. This triggered our seminal contribution to the field, establishing in 1976-79 at the Arthritis Unit (Massachusetts General Hospital, with SM Krane) that a mononuclear factor (MCF, around 15 kDa) produced by stimulated macrophage, under direct contact with activated T cells, induced large amounts of collagenase and prostaglandin E2 (PGE2, a bone resorbing agent) in human synovial fibroblasts from RA patients. Our original "MCF" biological observations preceded cloning, and recombinant IL-1β confirmed the biological activity of the purified natural IL-1. Following my return to Geneva in 1980 and searching for a high level of IL-1 in urine and serum of patients with high fever or Still's disease, to our surprise-"a finding of absence"-we found that IL-1 was masked by a factor of approximately 17 kDa and first presented this in 1984 at the Fourth International Lymphokine Workshop. In 1987, before IL-Ra cloning, my co-worker P Seckinger and I demonstrated first-time observation in cytokine biology that the mechanism was due to the inhibition of IL-1 binding the cell surface receptor, leading to the concept of IL-1 receptor antagonist (IL-1Ra). Having reported in 1985 that TNF/cachectin also induced collagenase and PGE2 in human synovial cells, we found that IL-1Ra did not block TNF-α but was due to another inhibitor. As other investigators, we confirmed that this inhibitory factor was a soluble TNF receptor. The years between the 1970s and 1990s were probably the most exciting period in the field of cytokines and cytokine antagonists; it gave rise to two concepts in the cytokine field-one of the receptor antagonist, and the other of soluble receptor antagonists.

Is IL-1 a good therapeutic target in the treatment of arthritis?

Inflammation is an important homeostatic mechanism that limits the effects of infectious agents. However, inflammation might be self-damaging and therefore has to be tightly controlled or even abolished by the organism. Interleukin 1 (IL-1) is a crucial mediator of the inflammatory response, playing an important part in the body's natural responses and the development of pathological conditions leading to chronic inflammation. While IL-1 production may be decreased or its effects limited by so-called anti-inflammatory cytokines, in vitro IL-1 inflammatory effects are inhibited and can be abolished by one particularly powerful inhibitor, IL-1 receptor antagonist (IL-1Ra). Recent research has shown that in the processes of rheumatoid arthritis (RA) IL-1 is one of the pivotal cytokines in initiating disease, and IL-1Ra has been shown conclusively to block its effects. In laboratory and animal studies the inhibition of IL-1 by either antibodies to IL-1 or IL-1Ra proved beneficial to the outcome. Because of its beneficial effects in many animal disease models, IL-1Ra has been used as a therapeutic agent in human patients. The recombinant form of IL-1Ra, anakinra (Kineret, Amgen) failed to show beneficial effects in septic shock and displays weak effects in RA patients. However, IL-1 blockade by anakinra is dramatically effective in systemic-onset juvenile idiopathic arthritis, in adult Still's disease and in several autoinflammatory disorders, most of the latter being caused by mutations of proteins controlling IL-1beta secretion. Importantly, to be efficacious, anakinra required daily injections, suggesting that administered IL-1Ra displays very short-term effects. Better IL-1 antagonists are in the process of being developed.

The process of identifying and understanding cytokines: from basic studies to treating rheumatic diseases

This is a historical overview seen from a personal angle. It covers the insights made during the past 20 years into the destructive processes of rheumatoid arthritis (RA) related to cytokines. The biochemical knowledge of the matrix components (i.e. collagen) and enzymology (i.e. collagenase) available in the 1950s led to the identification of cells from synovial tissue producing collagenase (fibroblast-like cells) and their interaction with other immune cells, i.e. monocyte-macrophages (Mphi) and lymphocytes (1976-1979). This insight led to the isolation of soluble factors produced by Mphi, such as interleukin-1 (IL-1) and TNF, the principal cytokines inducing collagenase and PGE(2) in many target cells (i.e. synovial fibroblasts, chondrocytes, bone-derived cells) (1981-1985). Further advances resulted from observations that, in clinical conditions (i.e. leukaemia, juvenile RA), a remission of fever and inflammation may occur spontaneously and that tissue catabolism may persist despite the absence of systemic inflammation; this gave rise to the concept and identification of endogenous cytokine inhibitors (i.e. IL-1 receptor antagonist and TNF soluble receptor) (1984-1989). The fourth milestone was the observation that the production of IL-1 and TNF by Mphi was induced mainly by direct contact with lymphocytes, prompting studies of the ligands and counter-ligands on Mphi and lymphocytes as well as inhibitors involved in this cell-cell contact, some of these inhibitors being involved in lipid metabolism and acute-phase proteins (HDL-apo A-1).

The saga of the discovery of IL-1 and TNF and their specific inhibitors in the pathogenesis and treatment of rheumatoid arthritis

In the seventies, the molecule subsequently termed IL-1 was among the first cytokines to attract the attention of rheumatologists due to its biological role in tissue destruction and bone resorption. In the mid-eighties, cachectin/tumor necrosis factor was found to share some of these biological activities, and a strong synergism between the two cytokines became evident. While IL-1 appeared to be more important at the local level, TNF played a more prominent part at the systemic level. In 1984, we became aware of the existence of an antagonist to IL-1 - subsequently termed IL-1Ra (interleukin-1 receptor antagonist) - in urine of febrile patients; its mechanism of action was elucidated in 1987 and the molecule cloned in 1990. The natural inhibitors of TNF were identified in 1996/97 by different investigators and proved to be soluble fragments of the TNF receptor. A concept commonly accepted at present is that disease activity and clinical outcome are controlled by the balance between agonistic and antagonistic cytokines, and at present the principal goal is to understand the underlying mechanisms. This concept is illustrated by observations in numerous animal models. The control of IL-1 and TNF is strongly dependent on the contact between activated lymphocytes and monocytes, the main source of these cytokines. Inhibiting this interaction by interfering with ligands and counter-ligands may be a useful approach if it is possible to maintain the production of the cytokine antagonist. Apolipoproteins A-I and A-II as well as beta2-integrins are molecules that block ligand/counter-ligand interaction. According to animal experiments and clinical data, blocking either IL-1 or TNF, or both, is beneficial. However, to determine not only the benefit but also the side effects of combination therapy in the human system, long-term clinical trials will be required.

Competition of IL-1 and IL-1ra determines lymphocyte response to delayed stimulation with PHA

BACKGROUND

Human peripheral blood mononuclear cells (PBMC) left in microcultures for 24h without mitogen do not respond to subsequent stimulation with PHA. They regain reactivity if the native culture medium is absorbed with other party lymphocytes or partially replaced with the medium from a PHA-stimulated culture. The observations suggest that, during the incubation, some inhibitory agent had accumulated in the culture medium.

AIM

The study was performed to determine the nature of the observed phenomenon in respect of the possible role of monocytes and their products IL-1 and IL-1 receptor antagonist (IL-1ra), and to test for immunodiagnostic purposes the significance of quantifying the lymphocyte response to delayed stimulation with PHA in patients suffering from inflammatory prosesses.

METHODS

Lymphocyte response to delayed stimulation with PHA, calculated as the lymphocyte-monokine interaction (LM) index, was determined in the microcultures of PBMC isolated from the blood of healthy donors or of patients with acute tonsilitis. The values of LM indices were compared with the ratios of IL-1ra/IL-1beta concentration estimated by enzyme-linked immunosorbent assay method in the culture supernatants. The influences of exogenous IL-1beta, IL-1ra, anti-IL1ra antibodies and antibiotic cefaclor on the monokine concentrations and on the values of LM index were tested.

RESULTS AND CONCLUSIONS

The results show that the level of lymphocyte response to delayed stimulation with PHA (LM index) is inversely proportional to the ratio of IL-1ra/IL-1beta concentration in the culture. The low LM values at high IL-1ra/IL-1beta ratios in PBMC cultures from healthy donors, reversed proportions found in patients' PBMC (acute tonsilitis), and the cefaclor-induced reduction of LM value with correlated increase of the IL-1ra/IL-1beta ratio suggest that the LM assay may prove to be useful for immunodiagnostic purposes.

Anti-interleukin-1 therapy in rheumatic diseases

Recent research has shown that in the processes of rheumatoid arthritis (RA), interleukin (IL)-1 is one of the pivotal cytokines in initiating disease, and the body's natural response, IL-1 receptor antagonist (IL-1Ra), has been shown conclusively to block its effects. In laboratory and animal studies inhibition of IL-1 by either antibodies to IL-1 or IL-1Ra proved beneficial to the outcome. To date, two large well-controlled studies in patients with RA led to the conclusion that IL-1Ra is clinically effective and that it slows progression of bone damage as measured radiographically. Being a specific, selective inhibitor of the IL-1 pathway, IL-1Ra could constitute an important new approach to treating patients with RA that significantly reduces the signs and symptoms of the disease, reduces joint destruction and up to now has proved safe and well tolerated.

Serum amyloid A, the major vertebrate acute-phase reactant

The serum amyloid A (SAA) family comprises a number of differentially expressed apolipoproteins, acute-phase SAAs (A-SAAs) and constitutive SAAs (C-SAAs). A-SAAs are major acute-phase reactants, the in vivo concentrations of which increase by as much as 1000-fold during inflammation. A-SAA mRNAs or proteins have been identified in all vertebrates investigated to date and are highly conserved. In contrast, C-SAAs are induced minimally, if at all, during the acute-phase response and have only been found in human and mouse. Although the liver is the primary site of synthesis of both A-SAA and C-SAA, extrahepatic production has been reported for most family members in most of the mammalian species studied. In vitro, the dramatic induction of A-SAA mRNA in response to pro-inflammatory stimuli is due largely to the synergistic effects of cytokine signaling pathways, principally those of the interleukin-1 and interleukin-6 type cytokines. This induction can be enhanced by glucocorticoids. Studies of the A-SAA promoters in several mammalian species have identified a range of transcription factors that are variously involved in defining both cytokine responsiveness and cell specificity. These include NF-kappaB, C/EBP, YY1, AP-2, SAF and Sp1. A-SAA is also post-transcriptionally regulated. Although the precise role of A-SAA in host defense during inflammation has not been defined, many potential clinically important functions have been proposed for individual SAA family members. These include involvement in lipid metabolism/transport, induction of extracellular-matrix-degrading enzymes, and chemotactic recruitment of inflammatory cells to sites of inflammation. A-SAA is potentially involved in the pathogenesis of several chronic inflammatory diseases: it is the precursor of the amyloid A protein deposited in amyloid A amyloidosis, and it has also been implicated in the pathogenesis of atheroscelerosis and rheumatoid arthritis.

Co-localization of interleukin-1 receptor type I and interleukin-1 receptor antagonist with vasopressin in magnocellular neurons of the paraventricular and supraoptic nuclei of the rat hypothalamus

Interleukin-1 receptor type I and interleukin-1 receptor antagonist were found in magnocellular neurons of the paraventricular and supraoptic nuclei of the rat hypothalamus by immunohistochemical detection. Double-labelling experiments revealed that both proteins occurred in vasopressin-containing neurons. A similar distribution pattern was observed in a group of vasopressin-positive accessory magnocellular neurons. Axons emanating from the interleukin-1 receptor type I- and interleukin-1 receptor antagonist-immunoreactive neuronal cell bodies could be seen within the hypothalamic nuclei, and varicosities expressing interleukin-1 receptor antagonist immunoreactivity were observed in the internal zone of the median eminence, as well as in the hypothalamo-pituitary projection. The co-localization of interleukin-1 receptor type I with vasopressin is in agreement with findings that interleukin-1 has a stimulatory effect on vasopressin synthesis and release. The hypothalamic neurons may serve as a source of interleukin-1 receptor antagonist to balance the effects of interleukin-1.

The role of cytokines in the failing human heart

Despite repeated attempts to develop a unifying hypothesis that explains the clinical syndrome of heart failure, no single conceptual paradigm has withstood the test of time. In this regard, recent studies have shown that a class of biologically active molecules, generically referred to as cytokines, are overexposed in heart failure. This article will review recent clinical and experimental material that suggest proinflammatory (stress activated) cytokines such as tumor necrosis factor-alpha (TFN-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) may play a role in the pathogenesis of congestive heart failure. The scope of this article includes an overview of the biology of cytokines in the heart, as well as review of the clinical studies that have documented elevated levels of cytokines and cytokine receptors in patients with heart failure.

Evidence that interleukin-6 is produced in human skeletal muscle during prolonged running

1. This study was performed to test the hypothesis that inflammatory cytokines are produced in skeletal muscle in response to prolonged intense exercise. Muscle biopsies and blood samples were collected from runners before, immediately after, and 2 h after a marathon race. 2. The concentration of interleukin (IL)-6 protein in plasma increased from 1.5 +/- 0.7 to 94.4 +/- 12.6 pg ml-1 immediately post-exercise and to 22.1 +/- 3.8 pg ml-1 2 h post-exercise. IL-1 receptor antagonist (IL-1ra) protein in plasma increased from 123 +/- 23 to 2795 +/- 551 pg ml-1, and increased further to 4119 +/- 527 pg ml-1 2 h post-exercise. 3. The comparative polymerase chain reaction technique was used to evaluate mRNA for IL-6, IL-1ra, IL-1beta and tumour necrosis factor (TNF)-alpha in skeletal muscle and blood mononuclear cells (BMNC) (n = 8). Before exercise, mRNA for IL-6 could not be detected either in muscle or in BMNC, and was only detectable in muscle biopsies (5 out of 8) after exercise. Increased amounts of mRNA for IL-1ra were found in two muscle biopsies and five BMNC samples, and increased amounts of IL-1beta mRNA were found in one muscle and four BMNC samples after exercise. TNF-alpha mRNA was not detected in any samples. 4. This study suggests that exercise-induced destruction of muscle fibres in skeletal muscles may trigger local production of IL-6, which stimulates the production of IL-1ra from circulating BMNC.

Effects of cytokine antagonists on the hepatic acute-phase response

Endotoxin-induced hepatic acute-phase protein synthesis has been thought to be primarily regulated through cytokines such as interleukin-1 (IL-1) and interleukin-6 (IL-6). Previously, it was found that a 23-kDa murine acute-phase protein, the lipopolysaccharide (LPS)-induced protein (LIP), was synthesized following treatment of hepatocytes in vitro with LPS. Since this protein was also induced by IL-1 and IL-6, the present studies were undertaken to determine if the effect of endotoxin was mediated through these cytokines. Primary cultures of murine hepatocytes were treated with LPS, IL-1, IL-6, or an LPS-stimulated macrophage supernatant in the presence or absence of the IL-1 receptor antagonist (IL-1 RA) and/or an anti-IL-6 antibody. The cells were then radiolabeled with [35S]methionine. LIP was detected by electrophoresis and autoradiography of the secreted proteins. In vitro, IL-1 RA completely inhibited the stimulation of LIP synthesis elicited by IL-1 and the macrophage supernatant, but did not affect LPS-stimulated synthesis of this protein. The anti-IL-6 antibody inhibited IL-6-triggered synthesis of LIP, but had no effect on LPS-stimulated synthesis. Hepatocytes isolated from mice treated in vivo with both IL-1 RA and LPS synthesized LIP to the same degree as hepatocytes isolated from mice treated with LPS alone. LPS-stimulated synthesis of LIP in vitro does not require IL-1 or IL-6 as an obligatory intermediate. These results are consistent with the hypothesis that endotoxin can directly stimulate hepatocyte acute-phase protein synthesis in the absence of cytokines.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

The effects of interleukin-1 receptor antagonist protein (IRAP) infusion following spinal cord transection in rats

A laminectomy was performed at the T5-T6 vertebral level in adult, male, Sprague-Dawley rats and the spinal cord transected with a scalpel. A group of sham animals was subjected to the same surgery without the transection step. A group of unhandled control rats was also included. A subgroup of transected animals received a subcutaneous osmotic minipump that dispensed IL-1 receptor antagonist protein (IRAP) at the transection site for 7 consecutive days. Another transected subgroup received a minipump that infused the vehicle only. IRAP-treated rats displayed a significant reduction in body temperature (p < 0.05) compared with vehicle-treated rats. The IRAP-treated rats were also less active when assessed for locomotor behavior using an HVS computerized tracking system (p < 0.01). IRAP treatment had no effect on serum corticosterone, beta-endorphin levels, Con A, PHA, or LPS-induced splenocyte mitogenesis when compared with vehicle-treated animals. However, half of the IRAP-treated animals exhibited a substantive reduction in the number of reactive astrocytes near the transection site, suggesting a possible effect of IRAP on astrocyte activation.

Insertion of a structural domain of interleukin (IL)-1 beta confers agonist activity to the IL-1 receptor antagonist. Implications for IL-1 bioactivity

We showed previously that replacement of Lys-145 in the IL-1 receptor antagonist (IL-1ra) with Asp resulted in an analog (IL-1ra K145D) with partial agonist activity. To identify additional amino acids that affect IL-1 bioactivity, we created second site mutations in IL-1ra K145D. Substitutions of single amino acids surrounding position 145 were made; none of these substitutions increased the bioactivity of IL-1ra K145D. However, the insertion of the beta-bulge (QGEESN) of IL-1 beta at the corresponding region of IL-1ra K145D resulted in a 3-4-fold augmentation of bioactivity. An additional increase in agonist activity was observed when the beta-bulge was co-expressed with a second substitution (His-54 --> Pro) in IL-1ra K145D. We also show that the bioactivity of both IL-1ra K145D and the triple mutant IL-1ra K145D/H54P/QGEESN is dependent on interaction with the newly cloned IL-1 receptor accessory protein.

Interleukin-1 and its inhibitors: implications for disease biology and therapy

IL-1 alpha and IL-1 beta are polypeptide hormones that exhibit a broad spectrum of beneficial and harmful biologic activities. Clinical trials designed to benefit from its stimulatory effects on human hematopoiesis and from its role in improving host defenses, are being currently conducted. Other in vivo studies, using IL-1 inhibitors with an attempts to block the detrimental effects of IL-1, are underway. Because of the multifunctional effects of IL-1 in human physiology and its pathogenetic role in several diseases, the capability to control the effects of IL-1 may prove to be a useful tool in medical practice.

Blocking interleukin-1 receptors

During inflammation, injury, immunological challenge or infection, interleukin-1 appears to mediate, in part, the pathogenesis, of disease. Most studies on interleukin-1 are derived from experiments in which bacterial products, such as endotoxins from Gram-negative bacteria or exotoxins from Gram-positive organisms, are used to stimulate macrophagic cells. In general, several cytokines are induced by microbes to their products. Although cytokines are thought to play a role in the outcome of disease, only a few have been directly implicated as mediators of the pathogenic mechanisms of the host. Studies on specific inhibition of interleukin-1 activity have employed interleukin-1 receptor antagonist, interleukin-1 receptor blocking antibodies or soluble interleukin-1 receptors. Experiments in vitro, in animal models of disease and in human subjects have shed considerable light on a critical role for interleukin-1 in the pathogenesis of disease. This review focuses on interleukin-1 as a cytokine of strategic importance to the outcome of disease, particularly inflammatory and infectious diseases.

In vivo anti-inflammatory effects of the M20 IL-1 inhibitor: II. Effects on serum reactants

We have previously described an IL-1 Inhibitor derived from the M20 myelomoncytic cell line. This line also secretes several molecules of IL-1. We have shown that this factor is specific to IL-1 in vitro, as well as in vivo. In vitro IL-1 induced proliferative responses of mouse thymocytes, human T cells and fibroblasts and IL-1 stimulated PGE2 secretion from fibroblasts, were all inhibited by the M20 IL-1 Inhibitor. In vivo, the IL-1 Inhibitor reduced parameters of acute inflammation such as fever, leukocytosis and local inflammation. This study describes additional effects of the M20 IL-1 Inhibitor on inflammatory serum reactants. Levels of corticosterone and fibrinogen were increased by injection of IL-1, and decreased by the IL-1 Inhibitor. IL-1 reduced zinc and iron plasma levels and elevated copper plasma levels. The M20 IL-1 Inhibitor reversed these changes in a dose dependent manner. Similar effects produced by IL-6 and TNF were unaffected by the M20 IL-1 Inhibitor. Our results indicate that the M20 IL-1 Inhibitor acts specifically on IL-1 induced responses in vivo. Therefore we conclude that this IL-1 Inhibitor has a great potential as an anti-inflammatory agent.

In vivo anti inflammatory effects of the M20 IL-1 inhibitor: I. Effects on acute inflammatory parameters

Previous studies have described an IL-1 Inhibitor produced by a myelomonocytic line developed in our laboratory (Eur J Immunol 1986; 16: 1449). This IL-1 Inhibitor was secreted by the M20 line constitutively in addition to IL-1, from which it could be separated. We have recently shown that the M20 IL-1 Inhibitor is distinct from the IL-1ra. In vitro this factor inhibited IL-1 induced proliferative responses as well as PGE2 secretion by IL-1 induced fibroblasts. We also showed for the first time (Lymphokine Research 1988; 7(3): 268) that an IL-1 inhibitor can reduce IL-1 induced inflammatory effects. This study describes the specific effect of the M20 IL-1 Inhibitor on IL-1 induced parameters of inflammation: fever, leukocytosis and local foot pad swelling or lymph node enlargement. Purified preparations of the IL-1 Inhibitor, when injected together with IL-1, or before the IL-1, reduced fever, leukocytosis, foot pad swelling and lymph node enlargement caused by IL-1. Similar responses were obtained by injection of IL-6 or TNF, but were unaffected by the IL-1 Inhibitor, when injected together. These results indicate that the M20 IL-1 Inhibitor acts specifically on IL-1 induced responses in vivo. The potential importance of this factor as an anti-inflammatory and immune regulatory factor, is supported by the findings of this study.

Interleukin-1 receptor antagonist expression in sarcoidosis

Sarcoidosis is a systemic granulomatous disease with a marked propensity for involvement of the pulmonary parenchyma and thoracic lymphatic system. This granulomatous process is characterized by aggregations of mononuclear cells, multinucleated giant cells, and variable degrees of fibrosis. The agent(s) responsible for the initiation of the inflammatory granulomatous process remain unknown. Interleukin-1 beta (IL-1) is a cytokine that has been shown to possess potent proinflammatory properties and is likely to play a role in mediating many of the immunopathologic events observed in sarcoidosis. Despite the degree of granulomatous inflammation, both the pulmonary and systemic pathogenic changes associated with sarcoidosis have a remarkable propensity for spontaneous resolution. The interleukin-1 receptor antagonist (IRAP), an endogenous inhibitor of IL-1 bioactivity, may have a critical role as an in vivo immunomodulator of IL-1-dependent granulomatous inflammation of sarcoidosis. In this study we demonstrate constitutive expression of IRAP mRNA and antigen from bronchoalveolar lavage fluid cells and cell-free fluid, respectively, obtained from both normal subjects and patients with sarcoidosis. However, immunolocalization of IRAP was found to be significantly localized to the sarcoid granuloma as compared with the uninvolved lung interstitium. Our findings indicate that IRAP expression is compartmentalized (granuloma) within the interstitium of patients with sarcoidosis. Thus, IRAP may function as an important in vivo immunomodulator of granulomatous inflammation.

Role of interleukin-1 inhibitory molecules in therapy of acute and chronic myelogenous leukemia

The poor outcome of conventional therapy of acute and chronic myelogenous leukemias (AML and CML) has prompted several groups to investigate new therapeutic directions. Data from various laboratories, including our own, indicate that both normal and leukemia precursors proliferate in response to growth factors. Furthermore, it has been shown that AML blasts, low-density cells from CML patients with advanced disease, and cultured bone marrow-adherent layers from CML blast crisis patients produce interleukin 1 (IL-1); this molecule may play a pivotal role in driving leukemia cell proliferation through autocrine or paracrine pathways. We have therefore hypothesized that interruption of the IL-1-mediated growth-stimulatory mechanism may suppress leukemia precursor multiplication. In searching for IL-1-inhibitory molecules that may be used clinically, we have investigated the in vitro effects of various IL-1 inhibitors including IL-1 receptor antagonist, soluble IL-1 receptors, and interleukin 4. Our studies suggest that IL-1 inhibitors can suppress clonogenic growth of cultured AML and CML progenitors and may hence be exploitable in clinical trials.

The synthesis of IL-1 receptor antagonist (IL-1ra) by synovial fibroblasts is markedly increased by the cytokines TNF-alpha and IL-1

The regulation of inhibitors which block the action of IL-1 has significant implications in the control of inflammation. Different modulators of cellular metabolism were studied for their effect on the synthesis of IL-1 receptor antagonist (IL-1ra). Among the different growth factors and cytokines studied, only the inflammatory mediators IL-1 and TNF-alpha and one growth factor, PDGF-BB, were found to significantly increase, in an additive manner, the synthesis and secretion of IL-1ra.

Interleukin-1 receptor antagonist

IL-1ra is the first described naturally occurring receptor antagonist of any cytokine or hormone-like molecule. IL-1ra is a member of the IL-1 family by three criteria: amino acid sequence homology of 26 to 30% to IL-1 beta and 19% to IL-1 alpha; similarities in gene structure; and common gene localization to human chromosome 2q14. Two structural variants of IL-1ra exist: sIL-1ra, a secretory molecule produced by monocytes, macrophages, neutrophils, fibroblasts, and other cells; and icIL-1ra, an intracellular molecule produced by keratinocytes and other epithelial cells, macrophages, and fibroblasts. IL-1ra production by monocytes, macrophages, and neutrophils may be regulated in a differential fashion with IL-1 beta. Human IL-1ra binds to both human IL-1RIs and IL-1RIIs on cell surfaces, although with 100-fold greater avidity to IL-1RIs. IL-1ra may bind preferentially to soluble IL-1RIs and not at all to soluble IL-1RIIs. IL-1ra competitively inhibits binding of both IL-1 alpha and IL-1 beta to cell surface receptors without inducing any discernible intracellular responses. All three forms of IL-1 may bind to IL-1 receptors in a similar fashion but IL-1ra may lack the secondary interactions necessary to trigger cell responses. A 100-fold or greater excess of IL-1ra over IL-1 may be necessary to inhibit biological responses to IL-1 both in vitro and in vivo. The roles of sIL-1ra and icIL-1ra in normal physiology or in host defense mechanisms remain unclear. The administration of IL-1ra blocks the effects of IL-1 in some animal models of septic shock, inflammatory arthritis, graft-versus-host disease, and inflammatory bowel disease. The preliminary results of clinical trials in humans indicate possible efficacy of IL-1ra in sepsis syndrome, rheumatoid arthritis, and GVHD.

The M20 IL-1 inhibitor prevents onset of adjuvant arthritis

Cytokines, specifically IL-1 and TNF, have been implicated as important mediators of joint destruction in rheumatoid arthritis (RA). Elevated levels of IL-1 in the joint fluid of patients with RA have been reported, as well as the presence of IL-1 inhibitory activity. We have reported the characterization of an inhibitor derived from a myelomonocytic cell line cloned in our laboratory which is specific for IL-1. This IL-1 inhibitor is protein in nature which specifically inhibits activity in vitro and in vivo. Previous studies showed that the inhibitor reduced acute inflammatory reactions associated with IL-1 (fever, leukocytosis, local foot pad swelling, lymph node enlargement and acute phase reactants). Thus it was of interest to study whether the M20 IL-1 inhibitor could modify adjuvant-induced chronic inflammation in rats, which is often used as a model for human RA. Administration of complete Freund's adjuvant (CFA) into Lewis rats, resulted in a severe adjuvant arthritis (AA) which reached peak severity after 14 days. Daily administration of IL-1 inhibitor, beginning after injection of CFA, abolished the appearance of AA. The parameters investigated were: joint swelling (the increase in diameter of joints), peri-articular erythema, limping of the rats and histological examination. The effect of the M20 IL-1 inhibitor was shown to be dose dependent and the IL-1 inhibitor alone had no adverse effects. These results indicate that the M20 IL-1 inhibitor may have a role in the treatment of AA and may be used to reduce pathological processes in joint inflammation.

The M20 IL-1 inhibitor. II. Biological characterization

Interleukin-1 (IL-1) is an important mediator in inflammation and immunological processes. The findings of native IL-1 inhibitors suggest a negative feedback mechanism to down-regulate IL-1 mediated acute inflammation. IL-1 inhibitors were also found elevated in disease states associated with high IL-1 levels. We have previously described one such IL-1 inhibitor derived from the human M20 myelomonocytic cell line. In this paper we present several biological and biochemical characteristics of the M20 IL-1 inhibitor. Various in vitro activities of the inhibitor are described and its IL-1 specificity in these assays is demonstrated. Purification of the inhibitor was performed by DEAE-high performance liquid chromatography, isoelectric focusing, gel filtration and dye ligand chromatography column. This protein factor has a MW of 52 +/- 4 kDa and a pI of 4.15 +/- 0.1. The inhibitor has no cross-reactivity against a panel of known cytokines (IL-1 alpha, IL-1 beta, IL-2, sIL-2R, IL-6, tumor necrosis factor (TNF), interferon-gamma (IFN-gamma)) and is distinct from the IL-1 receptor antagonist (IL-1ra). The purified IL-1 inhibitor was destroyed by trypsin, 2-mercaptoethanol, sodium dodecyl sulfate and extremes in pH and in temperature. Only IL-1 induced (but not the IL-2, IL-6 or TNF induced) thymocyte proliferation and PGE2 production by fibroblasts were inhibited by the inhibitor, thus showing specificity to IL-1 in these assays.

Serum tumor necrosis factor and interleukin 1 in leprosy and during lepra reactions

Tumor necrosis factor--alpha (TNF), one of the mediators of septic shock, has a role in the immunopathological complications of several infections. However, its role in leprosy is yet unclear. In this study, serum TNF and IL-1 levels in 64 patients spread over the spectrum of leprosy [lepromatous leprosy (LL), 30; borderline lepromatous, 12; borderline borderline, 8; and borderline tuberculoid-tuberculoid leprosy, 14] were measured at the time of admission. Elevated levels of TNF ranging from 15 to 4500 pg/ml were detected in lepromatous leprosy cases (399 +/- 189) and low levels ranging from 15 to 160 pg/ml were detected in the tuberculoid form of leprosy. Patients undergoing type 1 and type 2 lepra reactions also exhibited high TNF levels of 15-2100 pg/ml. Of the 14 clinically healthy individuals studied, 3 showed TNF levels of 15, 50, and 58 pg/ml. Interleukin 1-beta (IL-1) levels were found to be significantly higher in LL cases (70-5000 pg/ml) (328 +/- 184) in comparison to other groups or normal controls (9 +/- 3). The coefficient of correlation between TNF and IL-1 levels was statistically significant in LL and reaction cases (r = 0.96, P less than 0.001). These patients were followed up as outpatients for a period of 1 year. It was observed that 4 out of 8 patients with TNF levels greater than 100 pg/ml went into lepra reactions between 2 and 6 months after entry into the study, whereas only 5 out of 56 with less than 100 pg/ml went into mild lepra reactions (chi 2 = 9.7, P less than 0.01). Determination of TNF and IL-1 levels thus seems to have a prognostic significance in terms of lepra reaction in patients.

Psoriatic skin reveals the in vivo presence of an epidermal IL-1 inhibitor

Production of inhibitor(s) of IL-1 activity can be induced in keratinocytes by exposure to UVB. We describe in this study the characterization of an endogenous constitutively expressed IL-1 inhibitor which is present in extracts of human psoriatic epidermal keratome biopsies. Size-fractionated extracts of normal human epidermis did not reveal IL-1 inhibitory factor(s) activity in normal epidermis. Psoriatic epidermal extracts, however, contained virtually no IL-1 bioactivity and inhibited the activity of recombinant human IL-1 beta. This IL-1 inhibitor has a molecular weight of approximately 30 kDa and a pI of 5.3, as revealed by fast protein liquid chromatography size fractionation and chromatofocusing of psoriatic epidermal extracts. IL-1 inhibitory activity was not blocked by neutralizing anti-TGF beta monoclonal antibody. It did not have any inhibitory effect upon normal cellular proliferation but could block the IL-1 induction of IL-2 production by LBRM.33 cells as late as 4 h after exposure of LBRM.33 cells to IL-1. Thus, in vivo human psoriatic epidermis expresses an IL-1 inhibitor that specifically inhibits IL-1 activity but which appears distinct from previously described UV-induced epidermal IL-1 inhibitory activity or TGF beta.

Characterization of IL-1 inhibitory factor released from human alveolar macrophages as IL-1 receptor antagonist

IL-1 possesses pleiotropic properties on various cells and its activity may be stringently regulated in several ways. We have previously reported that both IL-1 and its inhibitory factor are concomitantly released from alveolar macrophages in both healthy subjects and patients with chronic inflammatory lung diseases. An increase in IL-1 activities and a decrease in inhibitory activities are characteristics found in both healthy smokers and patients with interstitial lung diseases. In this study, we further examined the biological properties of IL-1 inhibitory factor. The inhibitor exhibited a dose-dependent specific inhibition of an augmentation by IL-1 of PHA-induced murine thymocyte proliferation, while no inhibition of the augmentation by IL-2, IL-4, IL-6, or tumour necrosis factor (TNF) was found. 125I-labelled IL-1 alpha binding on PHA-stimulated murine thymocytes revealed two types of IL-1 binding sites, 44 sites/cell with a Kd of 2.7 x 10(-10) M and 230 sites/cell with a Kd of 2.5 x 10(-9) M. Alveolar macrophage culture supernatants blocked the binding of labelled IL-1 to the IL-1 receptor in a dose-dependent fashion. Scatchard plot analysis revealed that the inhibitory factor in the supernatants blocked the binding competitively. These results indicate that alveolar macrophages produce a specific IL-1 inhibitory factor, functioning as an IL-1 receptor antagonist.

Flare-up of experimental arthritis in mice with murine recombinant IL-1

Intra-articular injections of murine recombinant IL-1 (mrIL-1) during the chronic phase of antigen-induced arthritis (AIA) induced a flare-up of the smouldering inflammation. The exacerbation was characterized by acute and transient joint swelling and this coincided with the extravascular accumulation of neutrophils. IL-1 injected into arthritic joints of neutropenic mice demonstrated that joint swelling was independent of the neutrophil influx into the joint. Both phenomena were absent when IL-1 was injected into a naive joint. The IL-1-induced flare-up was not T cell mediated as in the antigen-induced flare-up, and suggestive evidence is presented that IL-1 sensitivity depended on the resident macrophage population. This explained why the hypersensitivity is not restricted to the immunologically mediated arthritis but reflects a more general hypersensitivity of previously injured joints, e.g. zymosan-induced arthritis and IL-1-affected joints. In addition, IL-1 could also potentiate the antigen-specific flare-up of chronic AIA and prolongs the duration of the exacerbation. Our data indicate that joints bearing a chronic infiltrate are at risk from exacerbations in two ways: a T cell mediated rechallenge with antigen, and a non-specific reactivation by systemic and local IL-1 generation.

Cytokines, receptors, and inhibitors

Cytokines are endogenous mediators in inflammatory and immunologic host defense reactions. In various diseases cytokines produced in excess cause systemic or local toxic effects. Cytokines therefore are tightly controlled by regulation of their biosynthesis and release and by counteracting mechanisms which limit their activities. Two new cytokine inhibitory mechanisms have recently been discovered. First, the generation of soluble receptors which compete with cellular receptors for cytokine binding has been recognized as a general phenomenon. Second, a receptor antagonist polypeptide binding to the receptor but not eliciting biological activity has been discovered in the IL-1 system. These polypeptides, when expressed in various recombinant forms, are not only research tools but may find also direct clinical use.

Inflammatory cytokines: interleukin-1 and tumor necrosis factor as effector molecules in autoimmune diseases

The nature of the events that precipitate autoimmune diseases varies. Interleukin-1 and tumor necrosis factor do not precipitate autoimmune diseases but rather act as effector molecules. They induce eicosanoid and nitric oxide synthesis, stimulate collagenases and collagen synthesis, and trigger the genes for other cytokines, namely interleukin-2, interleukin-6 and interleukin-8. The ability to block interleukin-1 with the receptor antagonist, and tumor necrosis factor with soluble receptors, has given investigators specific tools to test the role of these two cytokines in the pathological processes of autoimmune disease.

Interleukin 1 receptor antagonist. A new member of the interleukin 1 family

This review has summarized recent information derived from many laboratories on the discovery, characteristics, and properties of a new member of the IL-1 family, IL-1 receptor antagonist. In addition to information, an emphasis has been placed on unanswered questions and new concepts. The existence of this first-described naturally occurring specific cytokine receptor antagonist may lead to a different perspective on the cytokine network. A major unanswered question emphasized throughout this review, that now can be addressed more directly, concerns what are the physiological roles of members of the IL-1 family. Although IL-1 beta is presumed to function primarily as an extracellular cytokine, this molecule lacks a leader peptide, is synthesized and handled by the cells in a manner suggestive of a cytoplasmic (not secretory) protein, and may only be released after cellular injury. Furthermore, although IL-1ra possesses a leader sequence, 50% or more of this protein remains cell associated. Do these observations suggest that members of the IL-1 family possess important intracellular functions, as yet undetermined? IL-1 alpha may play an intracellular role in regulating senescence; an IL-1 alpha antisense oligodeoxynucleotide was shown to prolong the life span of cultured human endothelial cells. Whether intracellular IL-1ra plays a role in influencing life span has not been determined. The discovery of IL-1ra has led to a first level of assumptions that this molecule may be functioning in vivo to regulate the pleiotropic extracellular effects of IL-1 in physiological or pathophysiological processes. Although enticing, these assumptions have not yet been proven to be true. Perhaps we need to look beyond, or within, and consider that IL-1ra and other members of the IL-1 family may have additional roles in normal or abnormal cell growth and development.

Selective and early increase of IL-1 inhibitors, IL-6 and cortisol after elective surgery

After trauma, inflammatory, immunological and hormonal changes are well documented. Surgical intervention is a form of programmed trauma. Through the study of surgical patients, changes in early endogenous mediators of inflammation, immune response and tissue repair can be investigated. Here we analysed changes in serum levels of IL-1 inhibitors, IL-1 beta, IL-6, tumour necrosis factor-alpha (TNF-alpha) and cortisol in patients undergoing elective surgery. C-reactive protein (CRP) was measured as a marker of the acute-phase response. Rises in serum levels of IL-1 inhibitors, IL-6 and cortisol were detected as early as 1 h after the intervention. Peak levels were reached between 2 and 5 h. Serum levels of IL-6 and cortisol remained elevated for several days implying a persistent production. Serum levels of IL-1 and TNF did not change after the intervention. CRP levels peaked on day 2. The communication system sustained by endogenous mediators is activated after surgery as shown by selective changes in IL-1 inhibitors, IL-6 and cortisol. These mediators have different kinetics in serum and IL-6 is not the only early mediator detected. Some IL-1 inhibitors might be involved in the immunological depression observed after major surgery, in the regulation of the inflammatory response or in tissue repair. IL-6 and cortisol seem to act synergistically to activate the acute-phase response. A systemic role for IL-1 and TNF is not evident, even if the possibility that these lymphokines may act locally is not ruled out.

Immunomodulation: Suppression, enhancement and autoimmunity

Recent reports highlight new approaches to immunointervention (suppression or enhancement) based on the known roles of lymphocyte populations, cytokines and their receptors, and adhesion molecules in immune responses. Considerable interest over the past year has focused on immunophilins (cyclophilin and the FK506-binding protein) which appear to play key roles in signal transduction within activated T cells and provide a molecular basis for new advances in immunosuppressive drug therapy.

Conversion of the interleukin 1 receptor antagonist into an agonist by site-specific mutagenesis

Interleukin 1 (IL-1) receptor antagonist (IL-1ra) is a naturally occurring protein that binds to the IL-1 receptor present on T cells, fibroblasts, and other cell types and acts to block IL-1-induced responses. IL-1ra is a pure antagonist and has no agonist activity in in vitro or in vivo systems. By site-specific mutagenesis, an analog of IL-1ra was created that contained a substitution of a single amino acid, Lys-145----Asp. This analog, IL-1ra K145D, exhibited partial agonist activity in the D10.G4.1 cell proliferation assay. The newly acquired agonist activity could not be neutralized by antisera to IL-1 alpha or IL-1 beta, but it could be blocked by a monoclonal antibody to the T-cell IL-1 receptor. The analog also showed agonist activity as assayed by increased prostaglandin E2 synthesis from CHO cells expressing recombinant mouse IL-1 receptor. These results with IL-1ra K145D demonstrate the importance of the region surrounding the corresponding Asp-145 residue in IL-1 beta for triggering the biological response to IL-1.

Killing of Plasmodium falciparum by cytokine activated effector cells (neutrophils and macrophages)

Macrophages display natural antibody independent killing of asexual blood stages of Plasmodium falciparum in vitro. In contrast, the neutrophil killing of P. falciparum requires the presence of antibodies. Cytokines such as TNF alpha have very little effect on the macrophage-induced antiplasmodial activity, but significantly increase the damage of parasites by neutrophils. Cytokines, TNF alpha, IFN-gamma and TNF beta at very high concentrations were not toxic to P. falciparum in culture. It is postulated that the basis for cytokine modulated antiplasmodial activity of leukocytes is increased expression of Fc and complement receptors, which leads to a more efficient interaction between the parasite and neutrophils. It is also postulated that the parasite evades natural macrophage killing mechanisms by inducing factors which suppress this macrophage activity. Cytokine inhibitors may be induced during the course of a malarial infection. These could be involved in attempts to attain a balance between the host and the parasite, by protecting the parasite from the damaging effect of the immune system and protecting the host from the deleterious effects of cytokines.

Production of a 26,000-dalton interleukin 1 inhibitor by human monocytes is regulated by granulocyte-macrophage colony-stimulating factor

An interleukin 1 (IL 1) inhibitor is secreted into culture medium by a human promyelocytic cell line, H-161, upon stimulation with (PMA) and recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF). Since the morphological characteristics of this cell line were macrophage-like, human monocytes were tested for their ability to produce similar activity using the same induction conditions. Upon induction of adherent peripheral blood monocytes with rhGM-CSF and/or PMA, an IL 1 antagonistic activity was found in the cell supernatants, as determined by IL 1 receptor binding assay, using the murine EL-4.6.1C10 cell line as the cell target. Most of the inhibition of IL 1 binding induced by PMA or by PMA/rhGM-CSF was shown to be caused by IL 1, since it was neutralized by a mixture of anti-IL 1 alpha/beta antibodies and was active in the murine thymocyte proliferation assay (LAF). The activity induced by GM-CSF alone was not neutralized by anti-IL 1 alpha/beta antibodies and showed no LAF activity. The IL 1 inhibitor activity was induced by rhGM-CSF with a D50 around 40 pg/ml. The activity was produced for more than 3 wk in the presence of GM-CSF; removal of GM-CSF was followed by a rapid decrease of IL 1 antagonistic activity. The specific binding of biosynthetically labeled IL 1 inhibitor to target cells (EL-4.6.1C10) showed a protein of 26 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This molecule shares biological and physical characteristics with the urinary IL 1 inhibitor and the promyelocytic H-161-derived IL 1 inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)