Cytokine Receptor Antagonists Research Articles

Treating asthma in the new millennium.

As the pathophysiologic process of asthma has become better defined, new molecular targets for treating asthma have emerged. Resident airway cells, circulating leukocytes, and various cell-derived mediators and cytokines contribute to the inflammatory events of asthma. New therapeutic approaches to moderate to severe asthma currently in clinical development include antibodies to IgE and interleukin-5, a soluble receptor that would sequester interleukin-4, cytokine and chemokine receptor antagonists, and phosphodiesterase type 4 inhibitors. Adhesion molecules, which are involved in the migration of inflammatory cells into lung tissue, are also important targets for new antiasthma therapies. Because of researchers' focus on specific pathologic processes and molecular targets, the adverse effects of new agents may be minimized. Also, the longer duration of action of some of the new agents allows weekly to monthly dosing, which may well enhance patient compliance.

The role of cytokines in rheumatoid arthritis: inhibition of cytokines in therapeutic trials.

Although the precise role(s) of cytokines in rheumatoid arthritis (RA) is still being investigated, increasing evidence implicates interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha as contributing importantly to the inflammatory, and perhaps destructive manifestations of the disease. Several natural endogenous inhibitors of IL-1 and TNF-alpha have been identified; these include interleukin-1 receptor antagonist (IL-1RA), soluble IL-1 receptors (sIL-1R), and soluble TNF-alpha receptors (sTNFR). Although increased levels of these natural inhibitors occur in sera and at sites of inflammation in patients with RA, there is an excess of IL-1 and TNF-alpha in comparison with their respective natural inhibitors that favors the proinflammatory actions of these cytokines. Therefore, a potential therapeutic maneuver for treating RA is to neutralize these implicated cytokines. Biologic agents aimed at inhibiting the proinflammatory activities of these cytokines thus far have included cytokine receptor antagonists, anticytokine monoclonal antibodies (MAbs), fusion molecules consisting of soluble cytokine receptors combined with human fusion protein (Fc) constructs or polyethylene glycol (PEG), and counterregulatory cytokines which oppose actions of the target cytokine (e.g., IL-10, IL-4 and IL-11). Inhibitors of the processing and synthesis of IL-1 and TNF-alpha are also under development. The encouraging clinical results observed in short-term trials of TNF-alpha and IL-1 inhibitors using sTNFR:Fc fusion proteins, anti-TNF MAbs and recombinant human IL-1 receptor antagonist (rhuIL-1RA) clearly warrant further studies not only to determine whether these agents are capable of modifying the destructive component of the disease, but also whether they can be administered safely for long periods. Pivotal trials with these agents have potential therapeutic applicability to other autoimmune and inflammatory disorders.

A New Type of Cytokine Receptor Antagonist Directly Targeting gp130

The interleukin-6-type family of cytokines bind to receptor complexes that share gp130 as a common signal-transducing subunit. So far, receptor antagonists for interleukin-6-type cytokines have been constructed that still bind to the specific ligand binding subunit of the receptor complex, but have lost the ability to stimulate gp130. Such receptor antagonists compete for a specific receptor of a member of the cytokine family. Interleukin-6 only binds to gp130 when complexed with the interleukin-6 receptor that exists as a membrane bound and soluble molecule. Here we have constructed fusion proteins that consist of the soluble form of the human interleukin-6 receptor covalently linked to interleukin-6 receptor antagonists. These fusion proteins directly bind to gp130. Moreover, at concentrations of 10-50 nM they completely neutralize not only the biological activity of interleukin-6 but also of other cytokines of the interleukin-6-type family that act via gp130 homodimers or gp130/LIF-R heterodimers. Therefore, these gp130 targeting cytokine antagonists might be useful therapeutic tools in disease states that are related to cytokines of the interleukin-6 family.

Molecular basis of sickness behavior.

Peripheral and central injections of lipopolysaccharide (LPS), a cytokine inducer, and recombinant proinflammatory cytokines such as interleukin-1 beta (IL-1 beta) induce sickness behavior in the form of reduced food intake and decreased social activities. Mechanisms of the behavioral effects of cytokines have been the subject of much investigation during the last 3 years. At the behavioral level, the profound depressing effects of cytokines on behavior are the expression of a highly organized motivational state. At the molecular level, sickness behavior is mediated by an inducible brain cytokine compartment that is activated by peripheral cytokines via neural afferent pathways. Centrally produced cytokines act on brain cytokine receptors that are similar to those characterized on peripheral immune and nonimmune cells, as demonstrated by pharmacologic experiments using cytokine receptor antagonists, neutralizing antibodies to specific subtypes of cytokine receptors, and gene targeting techniques. Evidence exists that different components of sickness behavior are mediated by different cytokines and that the relative importance of these cytokines is not the same in the peripheral and central cytokine compartments.

Monoclonal antibodies to the common gamma-chain as cytokine receptor antagonists in vivo: effect on intrathymic and intestinal intraepithelial T lymphocyte development.

Mice lacking a functional gamma c subunit of cytokine receptors exhibit profound defects in the development of multiple lymphoid lineages. To investigate the role of gamma c-dependent cytokines in T cell development, the phenotype of developing T cells was compared in interleukin (IL)-7Ralpha-deficient mice and anti-gamma c mAb-treated chimeric mice reconstituted with adult bone marrow cells or subsets of pro-T cells. These studies indicate that gamma c contributes to T cell development at multiple stages of pro-T cell maturation and that IL-7/IL-7R is the primary cytokine for thymic-dependent T cell development. However, our data also implicate other gamma c-dependent cytokines during thymic T cell development. By contrast, substantial intestinal intraepithelial lymphocytes (IEL) development was observed in the intestinal intraepithelium in both types of mice. Analysis of IL-7Ralpha-deficient mice indicates that the IL-7/IL-7R system is critical only for the development of TCR gammadelta+ IEL. However, the inhibitory activity of the anti-deltac mAb in the chimeric mouse model suggests that additional gamma cutilizing cytokines regulate the development of the remaining subsets of IEL.

Cytokines in rheumatoid arthritis. Potential targets for pharmacological intervention.

The ingress of inflammatory leucocytes into the synovium is a crucial step in the pathogenesis of rheumatoid arthritis (RA). Cytokines are mediators involved in the inflammatory events, adhesive mechanisms, angiogenesis and osteopenia associated with RA. Pro- and anti-inflammatory cytokines, growth factors and chemokines all have an important role in these processes. Because the efficacy of currently used antirheumatic therapy is often limited, there is a need for more specific intervention strategies. Anticytokine therapy may include the use of monoclonal antibodies, antagonistic cytokines, soluble cytokine receptors, cytokine receptor antagonists, somatic gene transfer or other approaches. Hopefully, the study of cytokines and their interactions will lead to the development of new immunomodulatory strategies that will benefit patients with RA.

Cytokines and the hepatic acute phase response

The acute phase response is an orchestrated response to tissue injury, infection or inflammation. A prominent feature of this response is the induction of acute phase proteins, which are involved in the restoration of homeostasis. Cytokines are important mediators of the acute phase response. Uncontrolled and prolonged action of cytokines is potentially harmful, therefore mechanisms exist which limit the activity of cytokines; these include soluble cytokine receptors and receptor antagonists. The cytokine signal is transmitted into the cell via membrane-bound receptors. Different intracellular signalling pathways are activated by different cytokine-receptor interactions. Eventually, cytokine-inducible transcription factors interact with their response elements in the promotor region of acute phase genes and transcription is induced. Systemic inflammation results in a systemic acute phase response. However, local inflammatory or injurious processes in the liver may also induce an acute phase response, for example after partial hepatectomy and during hepatic fibrosis. The acute phase proteins induced in these conditions probably act to limit proteolytic and/or fibrogenic activity and tissue damage. The possible function of the acute phase protein alpha 2-macroglobulin in hepatic fibrosis is discussed in some detail.

New therapeutic approaches in inflammatory bowel disease

This article surveys the current thrust of the `new therapeutics' of inflammatory bowel disease. It defines the potential targets of therapy—enhancing the mucosal barrier between mucosa and lumen, altering the antigen challenge from the lumen, and inhibiting the processes leading to amplification and recruitment of pro-inflammatory mechanisms. Approaches based on current understanding of the molecular aspects of inflammation are emphasised, including the use of monoclonal antibodies, cytokine receptor antagonists, and rapidly metabolised corticosteroids.

Inhibition of growth by pro-inflammatory cytokines: an integrated view.

In response to antigenic stimuli, a variety of cells, including activated macrophages, secrete cytokines that are responsible for altering the host's metabolism. Three of these cytokines (tumor necrosis factor alpha [TNF-alpha], interleukin-1 [IL-1], and interleukin-6 [IL-6]) have profound behavioral, neuroendocrine, and metabolic effects. There is evidence that cytokines and their cognate receptors are present in the neuroendocrine system and brain. Moreover, in laboratory animal species, IL-1, IL-6, and TNF-alpha have been found to modulate intermediary metabolism of carbohydrate, fat, and protein substrates, regulate hypothalamic-pituitary outflow, and act in the brain to reduce food intake. Finally, many of the systemic acute-phase responses to inflammatory stimuli such as lipopolysaccharide are inhibited by treatment with cytokine receptor antagonists. In short, many findings converge to suggest that a major component of the growth inhibition observed in immunologically challenged animals is mediated by pro-inflammatory cytokines. The goal of this article is to provide an integrated view of how cytokines act systemically on disparate tissues to alter growth.

Sepsis and cytokines: current status

Sepsis is a constellation of clinical signs and symptoms resulting from excessive systemic host inflammatory response to infection. This inflammatory response is largely mediated by cytokines, which are released into the systemic circulation. Plasma concentrations of specific cytokines, TNF alpha, IL-1 beta, IL-6 and IL-8 are frequently elevated in human sepsis and cytokine concentrations correlate with severity and outcome of sepsis. In addition to pro-inflammatory cytokines, soluble cytokine receptors, cytokine receptor antagonists and counter-inflammatory cytokines are also produced in large quantities in patients with sepsis; however, the specific role of these molecules in sepsis remains undefined. A complex interaction of cytokines and cytokine-neutralizing molecules probably determines the clinical presentation and course of sepsis. Intervening in this sequence of events to modify the host inflammatory responses may prove to be a beneficial treatment strategy for sepsis, but currently tested anticytokine therapies have been largely unsuccessful.

The production and characterization of a modified recombinant interleukin-1 receptor antagonist.

The increasingly complex cytokine network involves both positive and negative regulatory pathways. Natural inhibitors of cytokines are of great importance both as analytical tools and as potential therapeutic agents. Interleukin-1 (IL-1) inhibitory bioactivity including a specific receptor antagonist of IL-I (IL-1ra) has been described both in cultured cell supernatants and in human body fluids. In the current studies, the cDNA of IL-1ra from human monocytes was obtained by the techniques of mRNA isolation and reverse transcription/polymerase chain reaction (RT/PCR). The IL-1ra cDNA/pET-15b was transfected into DE3 cells and the recombinant protein expressed. The purified protein was demonstrated as a single band with molecular mass of 20 KD by SDS-PAGE; it had strong IL-1 inhibitory activity. This IL-1 inhibitor competed with IL-1 for their receptor as assessed by flow cytometer. The existence of this naturally occurring specific cytokine receptor antagonist may lead to a different perspective of the cytokine network. The availability of this recombinant IL-1 receptor antagonist allows us to test its role on the cytokine network, and on possible disease modification.

The effect of an interleukin receptor antagonist (IL‐1ra) on colonocyte eicosanoid release

We investigated whether an interleukin 1 receptor antagonist (IL-1ra) altered cellular release of prostanoids and leukotrienes in a transformed colonic cell line (CACO-2) in the presence of proinflammatory stimuli. Cellular inflammation was induced by treatment with lipopolysaccharide (LPS) or the cytokine, interleukin 1 beta (IL-1β). In a separate set of experiments, cells were pretreated with IL-1ra prior to exposure to LPS or IL-1β. Prostaglandin E2 and leukotriene B4 (LTB4) levels were quantified by ELISA assays. Both LPS and IL-1β exposure were noted to stimulate cellular PGE2 release, a response which was significantly inhibited by IL-1ra treatment. Either stimulant when administered alone failed to stimulate release of LTB4. When administered after IL-1ra pretreatment however, both stimuli caused a significant increase in LTB4 release. These results suggest that a cytokine receptor antagonist can selectively influence eicosanoid production in this cell line. Furthermore, this study suggests that a IL-1ra may have a future clinical role in the treatment of inflammatory disorders of the colon which are intimately linked to enhanced eicosanoid synthesis.

Soluble Cytokine Receptors and Receptor Antagonists Are Sequentially Released after Trauma

Cytokine receptors and receptor antagonists (RAs) have been identified in trauma patients. We hypothesized that after traumatic injury, a sequential release of soluble cytokine receptors and RAs may exist that mirrors the release of the primary cytokines themselves. Twenty-two patients were included in the study: 14 males and 8 females. The mean age was 30.1 +/- 12.5 (range, 19 to 71), and the mean Injury Severity Score was 28.7 +/- 12.6 (range, 4 to 57). There were 15 survivors and 7 nonsurvivors. Samples were collected on arrival to the emergency department and at serial intervals for up to 7 days. Monoclonal antibody enzyme-linked immunosorbent assay kits to tumor necrosis factor (TNF), soluble TNF-receptor (sTNF-R) 55 kd and 75 kd, interleukin (IL)-1 and IL-1 RA, and IL-2 and IL-2r were used. Sera from 22 healthy individuals were used as normal controls. No TNF, IL-1, or IL-2 could be detected in any patient sera after injury. Control levels for the soluble cytokine receptors and RAs were as follows: sTNF-R 55 kd, 607 +/- 89 pg/mL; sTNF-R 75 kd, 2,141 +/- 169 pg/mL; IL-1 RA, 291 +/- 35 pg/mL; and IL-2r, 426 +/- 53 U/mL. In trauma patients, both 55 kd and 75 kd sTNF-R were significantly elevated on arrival to the emergency department, with values of 2,441 +/- 506 pg/mL (p < 0.001) and 4,736 +/- 537 pg/mL (p < 0.001), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Soluble cytokine receptors and the low 3,5,3'-triiodothyronine syndrome in patients with nonthyroidal disease.

Cytokines have been implicated in the pathogenesis of the low T3 syndrome during illness. This is supported by our recent observation of a strong negative relationship between serum T3 and serum interleukin-6 (IL-6) in nonthyroidal illness (NTI). In the last few years, soluble cytokine receptors and cytokine receptor antagonists have been discovered in human serum. These proteins have the potential to further regulate cytokine activity. Therefore, we now studied the association between serum T3 and serum levels of soluble tumor necrosis factor-alpha (sTNF alpha R p55 and sTNF alpha R p75), soluble interleukin-2 receptor (sIL-2R), and the interleukin-1 receptor antagonist (IL-1RA) in 100 consecutive hospital admissions with a wide variety of nonthyroidal diseases. Patients were divided into group A (T3, > or = 1.30 nmol/L; T4, > or = 75 nmol/L; n = 41), group B (T3, < 1.30 nmol/L; T4, > or = 75 nmol/L; n = 46), and group C (T3, < 1.30 nmol/L; T4, < 75 nmol/L; n = 13). Serum sTNF alpha R p55, sTNF alpha R p75, sIL-2R, and IL-1RA were lower in group A than in groups B and C [median values; sTNF alpha R p55, 1.25, 2.25, and 3.55 ng/mL (P < 0.001); sTNF alpha R p75, 2.02, 4.56, and 7.00 ng/mL (P < 0.001); sIL-2R, 184, 259, and 272 U/mL (P = 0.0004), respectively]. Serum IL-1RA levels were not different in the three groups (median values, 122, 193, and 258 pg/mL, respectively). Taking all patients together, a significant negative relation was found among serum T3 and sTNF alpha p55 (r = -0.59; P < 0.0001), sTNF alpha R p75 (r = -0.55; P < 0.0001), sIL-2R (r = -0.54; P < 0.0001), IL-1RA (r = -0.38; P = 0.001), and IL-6 (r = -0.56; P < 0.0001). A remarkable high correlation (r = -0.70; P < 0.0001) was found between serum T3 and a newly designed total score based on the summation of serum levels of IL-6 and the four soluble cytokine receptor proteins. IL-6 and the four cytokine receptor proteins were all significantly related to each other. Stepwise multiple regression indicated IL-6 and sTNF alpha R p75 as independent determinants of T3 [serum T3 = 2.09-0.32ln (sTNF alpha R p75) -0.15ln (IL-6); r = 0.70]. The variability in serum T3 was accounted for 35% by changes in ln (sTNF alpha R p75) and 14% by changes in ln (IL-6).(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin-1 receptor antagonist.

The interleukin-1 receptor antagonist (IL-1ra) is unusual in that it is the only known naturally occurring, cytokine receptor antagonist with no apparent agonist function. Over the last 5 years, since the cloning of the IL-1ra cDNA sequence, there has been intensive research on the genetics, regulation, and potential therapeutic value of this protein. The later discovery of a second form of IL-1ra in 1991 has complicated the picture. Whereas the originally described IL-1ra is predominantly glycosylated and secreted (sIL-1ra), the alternative isoform is unglycosylated and intracellular (icIL-1ra). Although the biological roles of the two forms are still open to question, IL-1ra is likely to be of great importance in the pathogenesis of both acute and chronic inflammatory diseases. A large body of evidence for this conclusion has come from animal models of inflammatory disease that respond well to administration of exogenous IL-1ra. A role for recombinant IL-1ra in the management of human disease is still under investigation. The two forms of IL-1ra are encoded by a single gene by alternative usage of two first exons. Expression of sIL-1ra and icIl-1ra is regulated by two promoters. In this review I explore the genetics of the gene encoding IL-1ra (IL-1RN) and the mechanisms of IL-1ra gene activation to produce sIL-1ra and icIL-1ra. Also, possible biological roles for these immunomodulators in health and disease are discussed.

Multiple Organ Dysfunction Syndrome (MODS) Following Multiple Trauma: Rationale and Concept of Therapeutic Approach

The multiple organ dysfunction syndrome (MODS) represents the number one cause of death in surgical intensive care units. It is divided into a primary and a secondary MODS based on time of manifestation and pathophysiologic events which attribute to it. The therapy of the primary MODS includes sufficient and quick resuscitation, adequate oxygen delivery and early enteral nutrition to reduce or avoid the incidence of bacterial translocation. In addition, a reduction of the "antigenic load" by control of hemorrhage, radical wound debridement, decompression, and fixation of long bone fractures appears to be effective in reducing the occurrence of MODS. The treatment of the secondary MODS remains supportive and its prevention is essential. Further studies are necessary to evaluate the clinical significance of new therapeutic agents such as monoclonal antibodies or cytokine receptor antagonists.

Cytokine Reduction in the Treatment of Joint Conditions

The destruction of joints caused by rheumatoid arthritis and osteoarthritis is characterized by an imbalance of enzyme catalysed cartilage breakdown and regeneration. A complex cytokine network perpetuates joint conditions by direct regulation of metalloproteases, by indirect recruitment of cells that secrete degradative enzymes, and by inhibition of reparative processes. The destructive action of cytokines such as interleukin-1, interleukin-6 and tumour necrosis factor-α can be modulated at multiple points associated either with cytokine production or with cytokine action. Potential agents for cytokine reduction include selective anti-cytokine antibodies, anticytokine receptor antibodies, cytokine receptor antagonist proteins, and soluble and chimeric cytokine receptor molecules. Pharmacologic regulation of IL-1 and TNFα remain primary targets for treatment of arthritis, and results of early clinical trials are promising. However, the results of long-term clinical trials will be required to support the value of anti-cytokine therapy in treatment of arthritis.

Scar wars strategies. Target collagen.

Hypertrophic scarring and keloid formation are clinical problems with effectively limited solutions. Although numerous methods have been devised to combat them, this article focuses on promising pharmacologic strategies that target collagen metabolism. Laboratory investigations of amino-acid analogs, procollagen peptides, D-penicillamine, and pentoxifylline have demonstrated them to be effective inhibitors of collagen synthesis in cultured cells and/or in animal models. Clinical trials of intralesional administration of interferons have shown impressive reductions in the size and collagen production of keloids. Furthermore, interference of extracellular matrix-enhancing cytokines, such as TGF-beta, may be an effective solution to keloids and hypertrophic scars. Additional research of soluble cytokine receptors, autoantibodies to cytokines, cytokine receptor antagonists, and cytokine-binding molecules may lead to the development of better therapeutic agents.

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.