The human IL-1 receptor antagonist gene (IL1RN) maps to chromosome 2q14-q21, in the region of the IL-1 alpha and IL-1 beta loci

Identification and gene organization of three novel members of the IL-1 family on human chromosome 2

Members of the IL-1 family of cytokines are important in mediating inflammatory responses. The genes encoding IL-1alpha, IL-beta, and the IL-1 receptor antagonist (IL-1Ra) are clustered within 450 kb on human chromosome 2q. By searching the EST databases and sequencing this region of chromosome 2, we have identified three novel genes that show homology to the IL-1 family, which we have named IL-1-related protein 1, 2, and 3 (IL-1RP1, IL-1RP2, and IL-1RP3). All three genes contain a signature motif common to the IL-1 family and appear to be more closely related to IL-1Ra. Similar to the intracellular form of IL-1Ra, these genes lack conventional hydrophobic signal sequences. The expression of these genes appears to be highly restricted to various epithelial cell populations. Our results demonstrate the existence of additional IL-1 gene family members within the previously defined IL-1 cluster and point to this region of chromosome 2 as an evolutionary hotspot for IL-1 gene duplication. These genes may prove to have an important role in inflammatory responses.

Differences in the genotypes and plasma concentrations of the INTERLEUKIN-1 receptor antagonist in black and white South African asthmatics and control subjects

The allelic frequency of a variable tandem repeat (VNTR) polymorphism in intron 2 of the IL-1 Ra gene was studied in black and white patients with asthma as well as control individuals. The plasma IL-1 Ra concentration was also determined in asthmatics and compared to control individuals. The 410-bp allele of the IL-1 Ra was significantly increased in all black subjects (90%) as compared to all white subjects (74%, P<0.0001), while the 240-bp allele was significantly reduced in all black subjects (11%) as compared to all white subjects (27%, P<0.0001). There was no difference in the frequency of the VNTR of the IL-1 Ra between black asthmatics and black controls and between white asthmatics and white controls. The IL-1 Ra levels were significantly increased in black and white patients with severe or moderate asthma as compared to patients with mild asthma. Increased plasma concentrations of the IL-1 Ra was found to be associated with disease severity in all asthmatic patients.

Interleukin-1 receptor antagonist as a treatment of HIV infection

The human immunodeficiency virus (HIV) apparently utilizes human chromosome 2, interleukin-1 (IL-1), glucocorticoid hormones, and viral Tat protein to accelerate its replication and the synthesis of all HIV proteins. HIV Tat protein binds to the long terminal repeat (LTR) ribonucleic acid, including the trans-acting responsive (TAR) sequence and the promoter region to increase HIV replication. Tat-TAR transactivation requires a factor encoded on the long arm of chromosome 2. The interaction of HIV with chromosome 2 may also cause the observed inhibition of interleukin-1 receptor antagonist (IL-1RA), thus increasing the production of IL-1. IL-1, in turn, stimulates the HIV-1 enhancer region of the LTR, thus increasing HIV gene expression and replication. IL-1 also induces glucocorticoid hormone synthesis which stimulates HIV in the virion infectivity factor (Vif) region, thus increasing HIV infectivity. It is, thus, proposed that IL-1RA not only may serve to inhibit HIV-induced IL-1, but may be the unidentified human chorionic gonadotropin-associated factor recently found to have anti-HIV and anti-Kaposi's sarcoma activity.

Interleukin 1 receptor antagonist gene polymorphism in women with vulvar vestibulitis

OBJECTIVE

Vulvar vestibulitis is a chronic inflammatory syndrome of unknown cause and pathogenesis. We examined the relation between vulvar vestibulitis and polymorphisms in the gene coding for the interleukin 1 receptor antagonist, a naturally occurring down-regulator of proinflammatory immune responses.

STUDY DESIGN

Cells from the lower genital tract of 68 women with vulvar vestibulitis, 343 women with no history of vulvodynia, and 40 women with human papillomavirus cervical infection were tested by polymerase chain reaction for the different alleles of the gene encoding for interleukin 1 receptor antagonist. The presence of human papillomavirus in the specimens was determined by polymerase chain reaction with the use of degenerate consensus primers to the conserved L1 gene.

RESULTS

Allele 2 of the gene encoding the interleukin 1 receptor antagonist was present in homozygous form in 52.9% of women with vulvar vestibulitis. In marked contrast only 8. 5% of the control women and 2.5% of women with human papillomavirus were homozygous for this allele (P </=.0001). Among the women with vulvar vestibulitis, 57.5% of those without human papillomavirus, as well as 52.2% of those with human papillomavirus, were homozygous for allele 2 of the gene encoding interleukin 1 receptor antagonist.

CONCLUSION

The unique distribution of interleukin 1 receptor antagonist alleles among women with vulvar vestibulitis suggests that polymorphism in this gene may be a factor influencing susceptibility to this syndrome, severity of symptoms, or both.

Human interleukin-1 receptor antagonist: large-scale expression in Bacillus brevis 47-5Q

Interleukin-1 receptor antagonist (IL-1RA) has been used as a tool to study the biologic activity of IL-1 and as a possible therapeutic substance for inflammatory disease. To perform in vivo study, however, large quantities of IL-1RA are required. Bacillus brevis strains secrete large amounts of protein but little protease into the medium. Using B. brevis 47-5Q, we developed a large-scale expression system of human IL-1RA (HuIL-1RA). The bacteria secreted HuIL-1RA into the culture medium at very high levels, approximately 200 mg/L. The protein was isolated in one-step purification with monoclonal antibody (mAb) against HuIL-1RA. The IL-1RA molecule was determined to be functionally active by the inhibiting assay of HuIL-1-induced cell proliferation in a mouse T cell line, D10N4M.

Dynamic regulation of the proinflammatory cytokine, interleukin-1beta: molecular biology for non-molecular biologists

Interleukin-1beta (IL-1beta) is a key mediator and modulator of a wide array of physiological responses important for survival. It is created by a variety of cell types, including immune cells, glia, and neurons. It is a very potent biological molecule, acting both at the periphery as well as within the central nervous system. The production and release of IL-1beta is tightly regulated by far more complex processes than previously thought. An appreciation of this complexity is necessary for proper interpretation of apparent contradictions in the literature where different aspects of IL-1beta expression are measured. Given that many researchers are not molecular biologists by training, yet need an appreciation of the controls that regulate the function of key proteins such as IL-1beta, this review is aimed at both: (a) clarifying the multiple levels at which IL-1beta production is modulated and (b) using IL-1beta regulation to explain the dynamics of gene regulation to non-molecular biologists. Three major topics will be discussed. First, regulation of IL-1beta production will be examined at every level from extracellular signals that trigger gene activation through release of active protein into the extracellular fluid. Second, regulation of IL-1beta bioavailability and bioactivity will be discussed. This section examines the fact that even after IL-1beta is released, it may or may not be able to exert a biological action due to multiple modulatory factors. Last is the introduction of the idea that IL-1beta regulation is, at times, beyond the direct control of host; that is, when IL-1beta production becomes dysregulated by pathogens.

Interleukin-1beta, interleukin-1 receptor antagonist, interleukin-4, and interleukin-10 gene polymorphisms: relationship to occurrence and severity of rheumatoid arthritis

OBJECTIVE

To test if interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL-1Ra), IL-4, or IL-10 gene polymorphisms could be used as markers of susceptibility or severity in rheumatoid arthritis (RA).

METHODS

The study included 108 patients with early RA followed up for 2 years and 128 healthy controls. From genomic DNA, 6 polymorphisms in genes for IL-1beta, IL-1Ra, IL-10, and IL-4 were typed. Allelic frequencies and carriage rates were compared between RA patients and controls, between patients with erosive and nonerosive RA, and between patients with or without sustained remission.

RESULTS

The RP1 allele of the IL-4 gene was found with a significantly higher frequency in RA patients compared with controls. The combination of an RA-related HLA-DR allele expressing shared epitope and the presence of allele E2 in IL-1beta exon 5 was found to expose patients to an increased risk of erosive disease, with an odds ratio of 8.20 (95% confidence interval 2.59-25.84, P < 0.0001). No significant association was observed between polymorphisms and the occurrence of sustained remission.

CONCLUSION

This report, for the first time, indicates an association between RA and a polymorphic IL-4 gene sequence located in 5q31-33. In addition, the results show the prognostic value of a polymorphism in IL-1beta exon 5, which allowed prediction of erosive disease with a specificity of 91.8% in 42.1% of patients. Although these observations are very interesting, they have to be considered preliminary and will need to be confirmed.

Interleukin-1 receptor antagonist: role in biology

The interleukin-1 receptor antagonist (IL-1Ra) is a member of the IL-1 family that binds to IL-1 receptors but does not induce any intracellular response. Two structural variants of IL-1Ra have previously been described: a 17-kDa form that is secreted from monocytes, macrophages, neutrophils, and other cells (sIL-1Ra) and an 18-kDa form that remains in the cytoplasm of keratinocytes and other epithelial cells, monocytes, and fibroblasts (icIL-1Ra). An additional 16-kDa intracellular isoform of IL-1Ra has recently been described in neutrophils, monocytes, and hepatic cells. Both of the major isoforms of IL-1Ra are transcribed from the same gene through the use of alternative first exons. The two promoters regulating transcription of the secreted and intracellular forms have been cloned, and some of the functional cis-acting DNA regions have been characterized. The production of IL-1Ra is stimulated by many substances including adherent IgG, other cytokines, and bacterial or viral components. The tissue distribution of IL-1Ra in mice indicates that sIL-1Ra is found predominantly in peripheral blood cells, lungs, spleen, and liver, while icIL-1Ra is found in large amounts in skin. Studies in transgenic and knockout mice indicate that IL-1Ra is important in host defense against endotoxin-induced injury. IL-1Ra is produced by hepatic cells with the characteristics of an acute phase protein. Endogenous IL-1Ra is produced in numerous experimental animal models of disease as well as in human autoimmune and chronic inflammatory diseases. The use of neutralizing anti-IL-1Ra antibodies has demonstrated that endogenous IL-1Ra is an important natural antiinflammatory protein in arthritis, colitis, and granulomatous pulmonary disease. Treatment of human diseases with recombinant human IL-1Ra showed an absence of benefit in sepsis syndrome. However, patients with rheumatoid arthritis treated with IL-1Ra for six months exhibited improvements in clinical parameters and in radiographic evidence of joint damage.

Regulation of inhibitory pathways of the interleukin-1 system

The IL-1 system includes two agonists, converting enzymes, antagonists, and two receptors (R). New elements and functions in the system will be discussed, including (a) cloning of a new isoform of the receptor antagonist; (b) further analysis of the type II IL-1-binding molecule as a decoy R. The modulation of IL-1R by chemotactic signals was recently investigated. It was found that chemoattractants cause rapid release of the type II decoy R from myelomonocytic cells with a t1/2 of 30 sec. Induction of decoy R release represents an early event in the multistep process of recruitment. It may serve to block the systemic action of IL-1 leaking from sites of inflammation, while preserving responsiveness in situ. We recently cloned the first long pentraxin, PTX3 (human and mouse, cDNA and genomic) as an IL-1-inducible gene. The structural and functional features of this molecule as well as initial evidence of involvement in human pathology will be discussed.

Induction of interleukin-1 and glucocorticoid hormones by HIV promotes viral replication and links human chromosome 2 to AIDS pathogenesis: genetic mechanisms and therapeutic implications

Human immunodeficiency virus may regulate its replication by stimulating the synthesis of interleukin-1. Interleukin-1, in turn, has the ability to stimulate the human immunodeficiency virus enhancer region. The human genes responsible for interleukin-1 and interleukin-1 receptor antagonist synthesis are located on the long arm of chromosome 2. Coincidentally, the trans-activation responsive ribonucleic acid element in the R region of the long terminal repeat of human immunodeficiency virus-1 has been found to interact directly with a factor present on the long arm of chromosome 2 to facilitate transactivation by the human immunodeficiency virus Tat protein. The human CD26 gene is also located on the long arm of chromosome 2. CD26 is a lymphocyte cell surface antigen that is stimulated by interleukin-1 and serves with CD4 as a coreceptor that interacts with the V3 loop in gp120 of human immunodeficiency virus. The human immunodeficiency virus-induced interleukin-1 excess, thus, serves human immunodeficiency virus by enhancing replication, and by increasing human immunodeficiency virus infectivity via activation of CD26. IL-1 also adversely affects acquired immune deficiency syndrome-related Kaposi's sarcoma. Several genetic treatments for human immunodeficiency virus infection are proposed.

An association between type 1 diabetes and the interleukin-1 receptor type 1 gene. The DiMe Study Group. Childhood Diabetes in Finland

The polygenic susceptibility to type 1 diabetes is well established and recent studies have demonstrated linkage of a further locus on chromosome 2q to disease. We have studied a polymorphism of the interleukin-1 receptor type 1 gene (IL1R1) on chromosome 2q in type 1 diabetic and control subjects from Finland, the United Kingdom, South India: three populations in which the risk of disease varies from very high to very low. In the medium-risk U.K. population we find a very strong association of IL1R1 with type 1 diabetes (p = 0.0002) but we find no overall association in either the high-risk Finnish or low-risk South-Indian populations. However, we do find heterogeneity of risk at IL1R1 amongst Finnish diabetic subjects according to the possession of HLA-DR associated susceptibility (p = 0.0001); there is an association with IL1R1 in only those Finnish diabetic subjects who do not possess high-risk HLA-DR4 or DR3 haplotypes (p = 0.006), as recently demonstrated for the insulin gene region in this population. We find no such heterogeneity of risk in either the U.K. or South-Indian populations. This study further demonstrates the genetic heterogeneity of disease susceptibility between and within populations and also supports the hypothesis of an interaction of the IL1R1 locus with genes within the HLA and insulin gene regions in the susceptibility to type 1 diabetes.

Negative regulators of the interleukin-1 system: receptor antagonists and a decoy receptor

The IL-1 system includes 2 agonists, alpha and beta, processing and transport molecules, receptor antagonists, signalling receptor, a decoy receptor and an accessory molecule. Negative pathways of regulation include the antagonists, of which 3 isoforms have been cloned and the type II "decoy" receptor. Molecules that regulate inflammation and immunity coordinatively affect different components of the system. The complexity of the system and the existence of unique pathways of negative regulation, the antagonists and the decoy receptor, emphasize the need for a tight control of the production and action of IL-1.

Biologic control of the tumor necrosis factor and interleukin-1 signaling cascade

It is clear that activation of the proinflammatory cytokine cascade is both the cause and the consequence of renal injury. Recently, it has been appreciated that a rich network of signaling pathways contributes to modulation of tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) bioactivity, both in vitro and in vivo. Insight into the checks and balances that intervene or temper endogenous cytokine effector mechanisms has arisen from an explosion of new information on the cell biology of proinflammatory cytokines. Novel mechanisms of cytokine regulation are currently being described and hold promise for therapeutic potential: soluble cytokine receptors, endogenous receptor antagonists, and anti-inflammatory cytokines such as IL-4, IL-10, and IL-13.

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.

Severity of alopecia areata is associated with a polymorphism in the interleukin-1 receptor antagonist gene

One of the most potent pro-inflammatory mediators is the early-acting cytokine interleukin-1. Its actions are regulated by a structurally related anti-inflammatory cytokine known as the interleukin-1 receptor antagonist. We have previously characterized a DNA polymorphism in this gene (IL-1rn) and have found associations between allele 2 and several chronic inflammatory diseases. In the present study, we tested the frequency of allele 2 of the IL-1rn gene in 90 patients with alopecia areata compared with 261 healthy controls. There was a significant association between allele 2 of the polymorphism and the severity of alopecia areata. The frequency of allele 2 increased from 24.1% in the control population to 25.9% in patchy alopecia areata, 36.1% in alopecia totalis, and 47.2% in alopecia universalis (p = 0.005). This severity association is similar to that found in other epithelial-related diseases, including inflammatory bowel disease, lichen sclerosus, and systemic lupus erythematosus.

The mouse interleukin 1 receptor antagonist protein: gene structure and regulation in vitro

The interleukin 1 receptor antagonist (IL-1ra) protein is an inhibitor of the pro-inflammatory cytokine interleukin 1. We have sequenced the mouse gene encoding the monocyte form of IL-1ra (IL-1rn) and compared it with the sequence of the human homologue. In addition to high levels of similarity between the coding regions of the two genes, portions of the introns show surprisingly high levels of identity. In order to develop an in vitro model system to investigate the regulation of IL-1ra induction, three differently responding mouse macrophage cell lines were stimulated with lipopolysaccharide. The kinetics and magnitude of IL-1ra mRNA accumulation was cell-line specific indicating that IL-1ra synthesis in response to inducing agents varies according to the phenotype of the cell. Analysis of the relative transcription rate and the half life of the mouse IL-1ra mRNA indicate that IL-1ra mRNA accumulation in macrophages following LPS treatment is due primarily to an increase in transcription rate rather than to increased stability.

Chromosomal mapping of the human interleukin-1 receptor antagonist gene (IL-1RN) and isolation of specific YAC clones

Using a panel of somatic rodent-human cell hybrids, we show that the interleukin-1 receptor antagonist gene (IL-1RN) maps to the long arm of human chromosome 2. Linkage studies permitted the regional localization of this gene to band q14-21. This is the same region in which the IL-1 alpha and IL-1 beta genes are localized. Three yeast artificial chromosome (YAC) clones containing the IL-1RN gene were isolated, and these will be used for further characterization of this chromosome 2 region.

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.

Human interleukin-1 receptor antagonist. High yield expression in E. coli and examination of cysteine residues

The human IL-1 receptor antagonist (IL-1ra) was produced in a high yield E. coli expression system, and was purified in a rapid two-step purification. This recombinant IL-1ra molecule possessed full binding activity to the IL-1 receptor (type I) and totally inhibited IL-1-induced PGE2 production by human dermal fibroblasts. Radioalkylation and analysis of V8-derived IL-1ra peptides indicate that the four cysteines present in the IL-1ra are not disulphide-linked.

Human interleukin-1 receptor antagonist is expressed in liver

Using PCR and Northern blot analysis, an IL-1 receptor antagonist specific transcript was amplified from HepG2- and liver mRNA. cDNA clones coding for IL-1 receptor antagonist were isolated from a liver cDNA library and sequence comparison revealed complete identity with the secreted, monocytic form of IL-1 receptor antagonist.